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authorKartik K. Agaram <vc@akkartik.com>2016-01-26 23:47:23 -0800
committerKartik K. Agaram <vc@akkartik.com>2016-01-26 23:47:23 -0800
commitd009e158803956c76adbf8f58a62884c3e7affb3 (patch)
treeb88198e28d15cd1fc064f5300365a190decc4c50 /html
parent2da43c9462c7b7c1bb78d2f2826b3b97b4874973 (diff)
downloadmu-d009e158803956c76adbf8f58a62884c3e7affb3.tar.gz
2605
Diffstat (limited to 'html')
-rw-r--r--html/003trace.cc.html12
-rw-r--r--html/003trace.test.cc.html6
-rw-r--r--html/010vm.cc.html15
-rw-r--r--html/011load.cc.html7
-rw-r--r--html/020run.cc.html8
-rw-r--r--html/021check_instruction.cc.html8
-rw-r--r--html/022arithmetic.cc.html7
-rw-r--r--html/029tools.cc.html2
-rw-r--r--html/030container.cc.html15
-rw-r--r--html/031address.cc.html18
-rw-r--r--html/032array.cc.html18
-rw-r--r--html/033exclusive_container.cc.html54
-rw-r--r--html/034call.cc.html6
-rw-r--r--html/035call_ingredient.cc.html3
-rw-r--r--html/036call_reply.cc.html6
-rw-r--r--html/037recipe.cc.html59
-rw-r--r--html/038new.cc.html (renamed from html/043new.cc.html)323
-rw-r--r--html/042name.cc.html20
-rw-r--r--html/043space.cc.html (renamed from html/044space.cc.html)142
-rw-r--r--html/044space_surround.cc.html (renamed from html/045space_surround.cc.html)37
-rw-r--r--html/045closure_name.cc.html (renamed from html/046closure_name.cc.html)28
-rw-r--r--html/046global.cc.html (renamed from html/047global.cc.html)35
-rw-r--r--html/047check_type_by_name.cc.html (renamed from html/048check_type_by_name.cc.html)14
-rw-r--r--html/050scenario.cc.html17
-rw-r--r--html/052tangle.cc.html8
-rw-r--r--html/053rewrite_stash.cc.html2
-rw-r--r--html/054dilated_reagent.cc.html19
-rw-r--r--html/055parse_tree.cc.html9
-rw-r--r--html/056recipe_header.cc.html135
-rw-r--r--html/057static_dispatch.cc.html98
-rw-r--r--html/059shape_shifting_recipe.cc.html44
-rw-r--r--html/060immutable.cc.html72
-rw-r--r--html/061abandon_checks.cc.html159
-rw-r--r--html/061recipe.cc.html235
-rw-r--r--html/062scheduler.cc.html (renamed from html/038scheduler.cc.html)58
-rw-r--r--html/063wait.cc.html (renamed from html/039wait.cc.html)6
-rw-r--r--html/070text.mu.html463
-rw-r--r--html/071channel.mu.html134
-rw-r--r--html/072array.mu.html8
-rw-r--r--html/073list.mu.html52
-rw-r--r--html/075duplex_list.mu.html386
-rw-r--r--html/076stream.mu.html18
-rw-r--r--html/080display.cc.html2
-rw-r--r--html/081print.mu.html296
-rw-r--r--html/082scenario_screen.cc.html39
-rw-r--r--html/083scenario_screen_test.mu.html10
-rw-r--r--html/084console.mu.html22
-rw-r--r--html/085scenario_console.cc.html38
-rw-r--r--html/086scenario_console_test.mu.html8
-rw-r--r--html/091run_interactive.cc.html63
-rw-r--r--html/channel.mu.html14
-rw-r--r--html/chessboard.mu.html126
-rw-r--r--html/counters.mu.html10
-rw-r--r--html/edit/001-editor.mu.html102
-rw-r--r--html/edit/002-typing.mu.html272
-rw-r--r--html/edit/003-shortcuts.mu.html816
-rw-r--r--html/edit/004-programming-environment.mu.html157
-rw-r--r--html/edit/005-sandbox.mu.html729
-rw-r--r--html/edit/006-sandbox-edit.mu.html176
-rw-r--r--html/edit/007-sandbox-delete.mu.html241
-rw-r--r--html/edit/008-sandbox-test.mu.html39
-rw-r--r--html/edit/009-sandbox-trace.mu.html61
-rw-r--r--html/edit/010-warnings.mu.html310
-rw-r--r--html/edit/011-editor-undo.mu.html738
-rw-r--r--html/fork.mu.html4
-rw-r--r--html/global.mu.html4
-rw-r--r--html/screen.mu.html6
67 files changed, 4229 insertions, 2820 deletions
diff --git a/html/003trace.cc.html b/html/003trace.cc.html
index a1c0be03..c19044fb 100644
--- a/html/003trace.cc.html
+++ b/html/003trace.cc.html
@@ -287,7 +287,7 @@ int trace_count<span class="Delimiter">(</span>string label<span class="Delimite
   long result = <span class="Constant">0</span><span class="Delimiter">;</span>
   for <span class="Delimiter">(</span>vector&lt;trace_line&gt;::iterator p = Trace_stream<span class="Delimiter">-&gt;</span>past_lines<span class="Delimiter">.</span>begin<span class="Delimiter">();</span> p != Trace_stream<span class="Delimiter">-&gt;</span>past_lines<span class="Delimiter">.</span>end<span class="Delimiter">();</span> ++p<span class="Delimiter">)</span> <span class="Delimiter">{</span>
     if <span class="Delimiter">(</span>label == p<span class="Delimiter">-&gt;</span>label<span class="Delimiter">)</span> <span class="Delimiter">{</span>
-      if <span class="Delimiter">(</span>line == <span class="Constant">&quot;&quot;</span> || line == trim<span class="Delimiter">(</span>p<span class="Delimiter">-&gt;</span>contents<span class="Delimiter">))</span>
+      if <span class="Delimiter">(</span>line == <span class="Constant">&quot;&quot;</span> || trim<span class="Delimiter">(</span>line<span class="Delimiter">)</span> == trim<span class="Delimiter">(</span>p<span class="Delimiter">-&gt;</span>contents<span class="Delimiter">))</span>
         ++result<span class="Delimiter">;</span>
     <span class="Delimiter">}</span>
   <span class="Delimiter">}</span>
@@ -304,6 +304,16 @@ int trace_count<span class="Delimiter">(</span>string label<span class="Delimite
 <span class="PreProc">    </span><span class="Identifier">return</span><span class="Delimiter">;</span><span class="PreProc"> \</span>
 <span class="PreProc">  </span><span class="Delimiter">}</span>
 
+<span class="PreProc">#define CHECK_TRACE_COUNT(label</span><span class="Delimiter">,</span><span class="PreProc"> count) \</span>
+<span class="PreProc">  </span>if<span class="PreProc"> (trace_count(label) != (count)) </span><span class="Delimiter">{</span><span class="PreProc"> \</span>
+<span class="PreProc">    ++Num_failures</span><span class="Delimiter">;</span><span class="PreProc"> \</span>
+<span class="PreProc">    cerr &lt;&lt; </span><span class="Constant">&quot;</span><span class="cSpecial">\n</span><span class="Constant">F - &quot;</span><span class="PreProc"> &lt;&lt; __FUNCTION__ &lt;&lt; </span><span class="Constant">&quot;(&quot;</span><span class="PreProc"> &lt;&lt; </span><span class="Constant">__FILE__</span><span class="PreProc"> &lt;&lt; </span><span class="Constant">&quot;:&quot;</span><span class="PreProc"> &lt;&lt; </span><span class="Constant">__LINE__</span><span class="PreProc"> &lt;&lt; </span><span class="Constant">&quot;): trace_count of &quot;</span><span class="PreProc"> &lt;&lt; label &lt;&lt; </span><span class="Constant">&quot; should be &quot;</span><span class="PreProc"> &lt;&lt; count &lt;&lt; </span><span class="cSpecial">'\n'</span><span class="Delimiter">;</span><span class="PreProc"> \</span>
+<span class="PreProc">    cerr &lt;&lt; </span><span class="Constant">&quot;  got &quot;</span><span class="PreProc"> &lt;&lt; trace_count(label) &lt;&lt; </span><span class="cSpecial">'\n'</span><span class="Delimiter">;</span><span class="PreProc">  </span><span class="Comment">/*</span><span class="Comment"> multiple eval </span><span class="Comment">*/</span><span class="PreProc"> \</span>
+<span class="PreProc">    DUMP(label)</span><span class="Delimiter">;</span><span class="PreProc"> \</span>
+<span class="PreProc">    Passed = </span><span class="Constant">false</span><span class="Delimiter">;</span><span class="PreProc"> \</span>
+<span class="PreProc">    </span><span class="Identifier">return</span><span class="Delimiter">;</span><span class="PreProc">  </span><span class="Comment">/*</span><span class="Comment"> Currently we stop at the very first failure. </span><span class="Comment">*/</span><span class="PreProc"> \</span>
+<span class="PreProc">  </span><span class="Delimiter">}</span>
+
 bool trace_doesnt_contain<span class="Delimiter">(</span>string label<span class="Delimiter">,</span> string line<span class="Delimiter">)</span> <span class="Delimiter">{</span>
   <span class="Identifier">return</span> trace_count<span class="Delimiter">(</span>label<span class="Delimiter">,</span> line<span class="Delimiter">)</span> == <span class="Constant">0</span><span class="Delimiter">;</span>
 <span class="Delimiter">}</span>
diff --git a/html/003trace.test.cc.html b/html/003trace.test.cc.html
index 963493e4..b5768fc6 100644
--- a/html/003trace.test.cc.html
+++ b/html/003trace.test.cc.html
@@ -40,6 +40,12 @@ void test_trace_check_ignores_other_layers<span class="Delimiter">()</span> <spa
   CHECK_TRACE_DOESNT_CONTAIN<span class="Delimiter">(</span><span class="Constant">&quot;test layer 2: foo&quot;</span><span class="Delimiter">);</span>
 <span class="Delimiter">}</span>
 
+void test_trace_check_ignores_leading_whitespace<span class="Delimiter">()</span> <span class="Delimiter">{</span>
+  trace<span class="Delimiter">(</span><span class="Constant">&quot;test layer 1&quot;</span><span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot; foo&quot;</span> &lt;&lt; end<span class="Delimiter">();</span>
+  CHECK<span class="Delimiter">(</span>trace_count<span class="Delimiter">(</span><span class="Constant">&quot;test layer 1&quot;</span><span class="Delimiter">,</span> <span class="Comment">/*</span><span class="Comment">too little whitespace</span><span class="Comment">*/</span><span class="Constant">&quot;foo&quot;</span><span class="Delimiter">)</span> == <span class="Constant">1</span><span class="Delimiter">);</span>
+  CHECK<span class="Delimiter">(</span>trace_count<span class="Delimiter">(</span><span class="Constant">&quot;test layer 1&quot;</span><span class="Delimiter">,</span> <span class="Comment">/*</span><span class="Comment">too much whitespace</span><span class="Comment">*/</span><span class="Constant">&quot;  foo&quot;</span><span class="Delimiter">)</span> == <span class="Constant">1</span><span class="Delimiter">);</span>
+<span class="Delimiter">}</span>
+
 void test_trace_check_ignores_other_lines<span class="Delimiter">()</span> <span class="Delimiter">{</span>
   trace<span class="Delimiter">(</span><span class="Constant">&quot;test layer 1&quot;</span><span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;foo&quot;</span> &lt;&lt; end<span class="Delimiter">();</span>
   trace<span class="Delimiter">(</span><span class="Constant">&quot;test layer 1&quot;</span><span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;bar&quot;</span> &lt;&lt; end<span class="Delimiter">();</span>
diff --git a/html/010vm.cc.html b/html/010vm.cc.html
index 69d5dec0..40ae0c5e 100644
--- a/html/010vm.cc.html
+++ b/html/010vm.cc.html
@@ -282,14 +282,14 @@ reagent::reagent<span class="Delimiter">(</span>string s<span class="Delimiter">
   name = properties<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">).</span>first<span class="Delimiter">;</span>
   type = new_type_tree<span class="Delimiter">(</span>properties<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">).</span>second<span class="Delimiter">);</span>
   if <span class="Delimiter">(</span>is_integer<span class="Delimiter">(</span>name<span class="Delimiter">)</span> &amp;&amp; type == <span class="Constant">NULL</span><span class="Delimiter">)</span> <span class="Delimiter">{</span>
-    type = new type_tree<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">);</span>
     assert<span class="Delimiter">(</span>!properties<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">).</span>second<span class="Delimiter">);</span>
     properties<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">).</span>second = new string_tree<span class="Delimiter">(</span><span class="Constant">&quot;literal&quot;</span><span class="Delimiter">);</span>
+    type = new type_tree<span class="Delimiter">(</span>get<span class="Delimiter">(</span>Type_ordinal<span class="Delimiter">,</span> <span class="Constant">&quot;literal&quot;</span><span class="Delimiter">));</span>
   <span class="Delimiter">}</span>
   if <span class="Delimiter">(</span>name == <span class="Constant">&quot;_&quot;</span> &amp;&amp; type == <span class="Constant">NULL</span><span class="Delimiter">)</span> <span class="Delimiter">{</span>
-    type = new type_tree<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">);</span>
     assert<span class="Delimiter">(</span>!properties<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">).</span>second<span class="Delimiter">);</span>
     properties<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">).</span>second = new string_tree<span class="Delimiter">(</span><span class="Constant">&quot;dummy&quot;</span><span class="Delimiter">);</span>
+    type = new type_tree<span class="Delimiter">(</span>get<span class="Delimiter">(</span>Type_ordinal<span class="Delimiter">,</span> <span class="Constant">&quot;literal&quot;</span><span class="Delimiter">));</span>
   <span class="Delimiter">}</span>
   <span class="Comment">// End Parsing reagent</span>
 <span class="Delimiter">}</span>
@@ -311,7 +311,7 @@ type_tree* new_type_tree<span class="Delimiter">(</span>const string_tree* prope
       result<span class="Delimiter">-&gt;</span>value = get<span class="Delimiter">(</span>Type_ordinal<span class="Delimiter">,</span> type_name<span class="Delimiter">);</span>
     else if <span class="Delimiter">(</span>is_integer<span class="Delimiter">(</span>type_name<span class="Delimiter">))</span>  <span class="Comment">// sometimes types will contain non-type tags, like numbers for the size of an array</span>
       result<span class="Delimiter">-&gt;</span>value = <span class="Constant">0</span><span class="Delimiter">;</span>
-    else
+    else if <span class="Delimiter">(</span>properties<span class="Delimiter">-&gt;</span>value != <span class="Constant">&quot;-&gt;&quot;</span><span class="Delimiter">)</span>  <span class="Comment">// used in recipe types</span>
       result<span class="Delimiter">-&gt;</span>value = -<span class="Constant">1</span><span class="Delimiter">;</span>  <span class="Comment">// should never happen; will trigger errors later</span>
   <span class="Delimiter">}</span>
   result<span class="Delimiter">-&gt;</span>left = new_type_tree<span class="Delimiter">(</span>properties<span class="Delimiter">-&gt;</span>left<span class="Delimiter">);</span>
@@ -321,7 +321,11 @@ type_tree* new_type_tree<span class="Delimiter">(</span>const string_tree* prope
 
 <span class="Comment">//: avoid memory leaks for the type tree</span>
 
-reagent::reagent<span class="Delimiter">(</span>const reagent&amp; old<span class="Delimiter">)</span> :original_string<span class="Delimiter">(</span>old<span class="Delimiter">.</span>original_string<span class="Delimiter">),</span> properties<span class="Delimiter">(</span>old<span class="Delimiter">.</span>properties<span class="Delimiter">),</span> name<span class="Delimiter">(</span>old<span class="Delimiter">.</span>name<span class="Delimiter">),</span> value<span class="Delimiter">(</span>old<span class="Delimiter">.</span>value<span class="Delimiter">),</span> initialized<span class="Delimiter">(</span>old<span class="Delimiter">.</span>initialized<span class="Delimiter">)</span> <span class="Delimiter">{</span>
+reagent::reagent<span class="Delimiter">(</span>const reagent&amp; old<span class="Delimiter">)</span> <span class="Delimiter">{</span>
+  original_string = old<span class="Delimiter">.</span>original_string<span class="Delimiter">;</span>
+  name = old<span class="Delimiter">.</span>name<span class="Delimiter">;</span>
+  value = old<span class="Delimiter">.</span>value<span class="Delimiter">;</span>
+  initialized = old<span class="Delimiter">.</span>initialized<span class="Delimiter">;</span>
   properties<span class="Delimiter">.</span>clear<span class="Delimiter">();</span>
   for <span class="Delimiter">(</span>long long int i = <span class="Constant">0</span><span class="Delimiter">;</span> i &lt; SIZE<span class="Delimiter">(</span>old<span class="Delimiter">.</span>properties<span class="Delimiter">);</span> ++i<span class="Delimiter">)</span> <span class="Delimiter">{</span>
     properties<span class="Delimiter">.</span>push_back<span class="Delimiter">(</span>pair&lt;string<span class="Delimiter">,</span> string_tree*&gt;<span class="Delimiter">(</span>old<span class="Delimiter">.</span>properties<span class="Delimiter">.</span>at<span class="Delimiter">(</span>i<span class="Delimiter">).</span>first<span class="Delimiter">,</span>
@@ -330,7 +334,8 @@ reagent::reagent<span class="Delimiter">(</span>const reagent&amp; old<span clas
   type = old<span class="Delimiter">.</span>type ? new type_tree<span class="Delimiter">(</span>*old<span class="Delimiter">.</span>type<span class="Delimiter">)</span> : <span class="Constant">NULL</span><span class="Delimiter">;</span>
 <span class="Delimiter">}</span>
 
-type_tree::type_tree<span class="Delimiter">(</span>const type_tree&amp; old<span class="Delimiter">)</span> :value<span class="Delimiter">(</span>old<span class="Delimiter">.</span>value<span class="Delimiter">)</span> <span class="Delimiter">{</span>
+type_tree::type_tree<span class="Delimiter">(</span>const type_tree&amp; old<span class="Delimiter">)</span> <span class="Delimiter">{</span>
+  value = old<span class="Delimiter">.</span>value<span class="Delimiter">;</span>
   left = old<span class="Delimiter">.</span>left ? new type_tree<span class="Delimiter">(</span>*old<span class="Delimiter">.</span>left<span class="Delimiter">)</span> : <span class="Constant">NULL</span><span class="Delimiter">;</span>
   right = old<span class="Delimiter">.</span>right ? new type_tree<span class="Delimiter">(</span>*old<span class="Delimiter">.</span>right<span class="Delimiter">)</span> : <span class="Constant">NULL</span><span class="Delimiter">;</span>
 <span class="Delimiter">}</span>
diff --git a/html/011load.cc.html b/html/011load.cc.html
index e3be7973..1bb04a8c 100644
--- a/html/011load.cc.html
+++ b/html/011load.cc.html
@@ -13,10 +13,9 @@
 pre { white-space: pre-wrap; font-family: monospace; color: #eeeeee; background-color: #080808; }
 body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 * { font-size: 1.05em; }
-.traceContains { color: #008000; }
 .traceAbsent { color: #c00000; }
+.traceContains { color: #008000; }
 .cSpecial { color: #008000; }
-.CommentedCode { color: #6c6c6c; }
 .Comment { color: #9090ff; }
 .Delimiter { color: #a04060; }
 .Special { color: #ff6060; }
@@ -94,9 +93,8 @@ long long int slurp_recipe<span class="Delimiter">(</span>istream&amp; in<span c
   <span class="Delimiter">}</span>
   slurp_body<span class="Delimiter">(</span>in<span class="Delimiter">,</span> result<span class="Delimiter">);</span>
   <span class="Comment">// End recipe Body(result)</span>
-  get_or_insert<span class="Delimiter">(</span>Recipe<span class="Delimiter">,</span> get<span class="Delimiter">(</span>Recipe_ordinal<span class="Delimiter">,</span> result<span class="Delimiter">.</span>name<span class="Delimiter">))</span> = result<span class="Delimiter">;</span>
+  put<span class="Delimiter">(</span>Recipe<span class="Delimiter">,</span> get<span class="Delimiter">(</span>Recipe_ordinal<span class="Delimiter">,</span> result<span class="Delimiter">.</span>name<span class="Delimiter">),</span> result<span class="Delimiter">);</span>
   <span class="Comment">// track added recipes because we may need to undo them in tests; see below</span>
-<span class="CommentedCode">//?   LOG &lt;&lt; &quot;recently added recipe: &quot; &lt;&lt; result.name &lt;&lt; ' ' &lt;&lt; get(Recipe_ordinal, result.name) &lt;&lt; '\n';</span>
   Recently_added_recipes<span class="Delimiter">.</span>push_back<span class="Delimiter">(</span>get<span class="Delimiter">(</span>Recipe_ordinal<span class="Delimiter">,</span> result<span class="Delimiter">.</span>name<span class="Delimiter">));</span>
   <span class="Identifier">return</span> get<span class="Delimiter">(</span>Recipe_ordinal<span class="Delimiter">,</span> result<span class="Delimiter">.</span>name<span class="Delimiter">);</span>
 <span class="Delimiter">}</span>
@@ -280,7 +278,6 @@ void clear_recently_added_recipes<span class="Delimiter">()</span> <span class="
     if <span class="Delimiter">(</span>Recently_added_recipes<span class="Delimiter">.</span>at<span class="Delimiter">(</span>i<span class="Delimiter">)</span> &gt;= Reserved_for_tests  <span class="Comment">// don't renumber existing recipes, like 'interactive'</span>
         &amp;&amp; contains_key<span class="Delimiter">(</span>Recipe<span class="Delimiter">,</span> Recently_added_recipes<span class="Delimiter">.</span>at<span class="Delimiter">(</span>i<span class="Delimiter">)))</span>  <span class="Comment">// in case previous test had duplicate definitions</span>
       Recipe_ordinal<span class="Delimiter">.</span>erase<span class="Delimiter">(</span>get<span class="Delimiter">(</span>Recipe<span class="Delimiter">,</span> Recently_added_recipes<span class="Delimiter">.</span>at<span class="Delimiter">(</span>i<span class="Delimiter">)).</span>name<span class="Delimiter">);</span>
-<span class="CommentedCode">//?   LOG &lt;&lt; &quot;erase recipe &quot; &lt;&lt; Recently_added_recipes.at(i) &lt;&lt; ' ' &lt;&lt; get(Recipe, Recently_added_recipes.at(i)).name &lt;&lt; '\n';</span>
     Recipe<span class="Delimiter">.</span>erase<span class="Delimiter">(</span>Recently_added_recipes<span class="Delimiter">.</span>at<span class="Delimiter">(</span>i<span class="Delimiter">));</span>
   <span class="Delimiter">}</span>
   <span class="Comment">// Clear Other State For Recently_added_recipes</span>
diff --git a/html/020run.cc.html b/html/020run.cc.html
index d0213a69..4194981e 100644
--- a/html/020run.cc.html
+++ b/html/020run.cc.html
@@ -17,8 +17,8 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 .CommentedCode { color: #6c6c6c; }
 .PreProc { color: #c000c0; }
 .Delimiter { color: #a04060; }
-.traceContains { color: #008000; }
 .traceAbsent { color: #c00000; }
+.traceContains { color: #008000; }
 .cSpecial { color: #008000; }
 .Comment { color: #9090ff; }
 .Constant { color: #00a0a0; }
@@ -176,6 +176,7 @@ transform_all<span class="Delimiter">();</span>
 
 <span class="Comment">//: Step 2: load any .mu files provided at the commandline</span>
 <span class="Delimiter">:(before &quot;End Commandline Parsing&quot;)</span>
+<span class="Comment">// Check For .mu Files</span>
 if <span class="Delimiter">(</span>argc &gt; <span class="Constant">1</span><span class="Delimiter">)</span> <span class="Delimiter">{</span>
   <span class="Comment">// skip argv[0]</span>
   argv++<span class="Delimiter">;</span>
@@ -309,12 +310,14 @@ void write_memory<span class="Delimiter">(</span>reagent x<span class="Delimiter
   if <span class="Delimiter">(</span>is_dummy<span class="Delimiter">(</span>x<span class="Delimiter">))</span> <span class="Identifier">return</span><span class="Delimiter">;</span>
   if <span class="Delimiter">(</span>is_literal<span class="Delimiter">(</span>x<span class="Delimiter">))</span> <span class="Identifier">return</span><span class="Delimiter">;</span>
   long long int base = x<span class="Delimiter">.</span>value<span class="Delimiter">;</span>
+  if <span class="Delimiter">(</span>base == <span class="Constant">0</span><span class="Delimiter">)</span> <span class="Identifier">return</span><span class="Delimiter">;</span>
   if <span class="Delimiter">(</span>size_mismatch<span class="Delimiter">(</span>x<span class="Delimiter">,</span> data<span class="Delimiter">))</span> <span class="Delimiter">{</span>
     raise_error &lt;&lt; maybe<span class="Delimiter">(</span>current_recipe_name<span class="Delimiter">())</span> &lt;&lt; <span class="Constant">&quot;size mismatch in storing to &quot;</span> &lt;&lt; x<span class="Delimiter">.</span>original_string &lt;&lt; <span class="Constant">&quot; (&quot;</span> &lt;&lt; size_of<span class="Delimiter">(</span>x<span class="Delimiter">.</span>type<span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot; vs &quot;</span> &lt;&lt; SIZE<span class="Delimiter">(</span>data<span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;) at '&quot;</span> &lt;&lt; current_instruction<span class="Delimiter">().</span>to_string<span class="Delimiter">()</span> &lt;&lt; <span class="Constant">&quot;'</span><span class="cSpecial">\n</span><span class="Constant">&quot;</span> &lt;&lt; end<span class="Delimiter">();</span>
     <span class="Identifier">return</span><span class="Delimiter">;</span>
   <span class="Delimiter">}</span>
+  <span class="Comment">// End write_memory(reagent x, long long int base) Special-cases</span>
   for <span class="Delimiter">(</span>long long int offset = <span class="Constant">0</span><span class="Delimiter">;</span> offset &lt; SIZE<span class="Delimiter">(</span>data<span class="Delimiter">);</span> ++offset<span class="Delimiter">)</span> <span class="Delimiter">{</span>
-    if <span class="Delimiter">(</span>base+offset == <span class="Constant">0</span><span class="Delimiter">)</span> <span class="Identifier">continue</span><span class="Delimiter">;</span>
+    assert<span class="Delimiter">(</span>base+offset &gt; <span class="Constant">0</span><span class="Delimiter">);</span>
     trace<span class="Delimiter">(</span><span class="Constant">9999</span><span class="Delimiter">,</span> <span class="Constant">&quot;mem&quot;</span><span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;storing &quot;</span> &lt;&lt; no_scientific<span class="Delimiter">(</span>data<span class="Delimiter">.</span>at<span class="Delimiter">(</span>offset<span class="Delimiter">))</span> &lt;&lt; <span class="Constant">&quot; in location &quot;</span> &lt;&lt; base+offset &lt;&lt; end<span class="Delimiter">();</span>
     put<span class="Delimiter">(</span>Memory<span class="Delimiter">,</span> base+offset<span class="Delimiter">,</span> data<span class="Delimiter">.</span>at<span class="Delimiter">(</span>offset<span class="Delimiter">));</span>
   <span class="Delimiter">}</span>
@@ -362,6 +365,7 @@ void run<span class="Delimiter">(</span>string form<span class="Delimiter">)</sp
   vector&lt;recipe_ordinal&gt; tmp = load<span class="Delimiter">(</span>form<span class="Delimiter">);</span>
   transform_all<span class="Delimiter">();</span>
   if <span class="Delimiter">(</span>tmp<span class="Delimiter">.</span>empty<span class="Delimiter">())</span> <span class="Identifier">return</span><span class="Delimiter">;</span>
+  if <span class="Delimiter">(</span>trace_count<span class="Delimiter">(</span><span class="Constant">&quot;error&quot;</span><span class="Delimiter">)</span> &gt; <span class="Constant">0</span><span class="Delimiter">)</span> <span class="Identifier">return</span><span class="Delimiter">;</span>
   run<span class="Delimiter">(</span>tmp<span class="Delimiter">.</span>front<span class="Delimiter">());</span>
 <span class="Delimiter">}</span>
 
diff --git a/html/021check_instruction.cc.html b/html/021check_instruction.cc.html
index 585c2c3a..c0229312 100644
--- a/html/021check_instruction.cc.html
+++ b/html/021check_instruction.cc.html
@@ -170,10 +170,6 @@ bool types_strictly_match<span class="Delimiter">(</span>type_tree* lhs<span cla
   <span class="Identifier">return</span> types_strictly_match<span class="Delimiter">(</span>lhs<span class="Delimiter">-&gt;</span>left<span class="Delimiter">,</span> rhs<span class="Delimiter">-&gt;</span>left<span class="Delimiter">)</span> &amp;&amp; types_strictly_match<span class="Delimiter">(</span>lhs<span class="Delimiter">-&gt;</span>right<span class="Delimiter">,</span> rhs<span class="Delimiter">-&gt;</span>right<span class="Delimiter">);</span>
 <span class="Delimiter">}</span>
 
-bool is_raw<span class="Delimiter">(</span>const reagent&amp; r<span class="Delimiter">)</span> <span class="Delimiter">{</span>
-  <span class="Identifier">return</span> has_property<span class="Delimiter">(</span>r<span class="Delimiter">,</span> <span class="Constant">&quot;raw&quot;</span><span class="Delimiter">);</span>
-<span class="Delimiter">}</span>
-
 bool is_unsafe<span class="Delimiter">(</span>const reagent&amp; r<span class="Delimiter">)</span> <span class="Delimiter">{</span>
   <span class="Identifier">return</span> has_property<span class="Delimiter">(</span>r<span class="Delimiter">,</span> <span class="Constant">&quot;unsafe&quot;</span><span class="Delimiter">);</span>
 <span class="Delimiter">}</span>
@@ -192,9 +188,11 @@ bool is_mu_address<span class="Delimiter">(</span>reagent r<span class="Delimite
 
 bool is_mu_number<span class="Delimiter">(</span>reagent r<span class="Delimiter">)</span> <span class="Delimiter">{</span>
   if <span class="Delimiter">(</span>!r<span class="Delimiter">.</span>type<span class="Delimiter">)</span> <span class="Identifier">return</span> <span class="Constant">false</span><span class="Delimiter">;</span>
-  if <span class="Delimiter">(</span>is_literal<span class="Delimiter">(</span>r<span class="Delimiter">))</span>
+  if <span class="Delimiter">(</span>is_literal<span class="Delimiter">(</span>r<span class="Delimiter">))</span> <span class="Delimiter">{</span>
+    if <span class="Delimiter">(</span>!r<span class="Delimiter">.</span>properties<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">).</span>second<span class="Delimiter">)</span> <span class="Identifier">return</span> <span class="Constant">false</span><span class="Delimiter">;</span>
     <span class="Identifier">return</span> r<span class="Delimiter">.</span>properties<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">).</span>second<span class="Delimiter">-&gt;</span>value == <span class="Constant">&quot;literal-number&quot;</span>
         || r<span class="Delimiter">.</span>properties<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">).</span>second<span class="Delimiter">-&gt;</span>value == <span class="Constant">&quot;literal&quot;</span><span class="Delimiter">;</span>
+  <span class="Delimiter">}</span>
   if <span class="Delimiter">(</span>r<span class="Delimiter">.</span>type<span class="Delimiter">-&gt;</span>value == get<span class="Delimiter">(</span>Type_ordinal<span class="Delimiter">,</span> <span class="Constant">&quot;character&quot;</span><span class="Delimiter">))</span> <span class="Identifier">return</span> <span class="Constant">true</span><span class="Delimiter">;</span>  <span class="Comment">// permit arithmetic on unicode code points</span>
   <span class="Identifier">return</span> r<span class="Delimiter">.</span>type<span class="Delimiter">-&gt;</span>value == get<span class="Delimiter">(</span>Type_ordinal<span class="Delimiter">,</span> <span class="Constant">&quot;number&quot;</span><span class="Delimiter">);</span>
 <span class="Delimiter">}</span>
diff --git a/html/022arithmetic.cc.html b/html/022arithmetic.cc.html
index 0a353d6d..f7e89060 100644
--- a/html/022arithmetic.cc.html
+++ b/html/022arithmetic.cc.html
@@ -137,6 +137,10 @@ case SUBTRACT: <span class="Delimiter">{</span>
   products<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">).</span>push_back<span class="Delimiter">(</span>result<span class="Delimiter">);</span>
   <span class="Identifier">break</span><span class="Delimiter">;</span>
 <span class="Delimiter">}</span>
+<span class="Delimiter">:(code)</span>
+bool is_raw<span class="Delimiter">(</span>const reagent&amp; r<span class="Delimiter">)</span> <span class="Delimiter">{</span>
+  <span class="Identifier">return</span> has_property<span class="Delimiter">(</span>r<span class="Delimiter">,</span> <span class="Constant">&quot;raw&quot;</span><span class="Delimiter">);</span>
+<span class="Delimiter">}</span>
 
 <span class="Delimiter">:(scenario subtract_literal)</span>
 recipe main [
@@ -302,6 +306,9 @@ case DIVIDE_WITH_REMAINDER: <span class="Delimiter">{</span>
   long long int b = static_cast&lt;long long int&gt;<span class="Delimiter">(</span>ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">1</span><span class="Delimiter">).</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">));</span>
   if <span class="Delimiter">(</span>b == <span class="Constant">0</span><span class="Delimiter">)</span> <span class="Delimiter">{</span>
     raise_error &lt;&lt; maybe<span class="Delimiter">(</span>current_recipe_name<span class="Delimiter">())</span> &lt;&lt; <span class="Constant">&quot;divide by zero in '&quot;</span> &lt;&lt; current_instruction<span class="Delimiter">().</span>to_string<span class="Delimiter">()</span> &lt;&lt; <span class="Constant">&quot;'</span><span class="cSpecial">\n</span><span class="Constant">&quot;</span> &lt;&lt; end<span class="Delimiter">();</span>
+    products<span class="Delimiter">.</span>resize<span class="Delimiter">(</span><span class="Constant">2</span><span class="Delimiter">);</span>
+    products<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">).</span>push_back<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">);</span>
+    products<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">1</span><span class="Delimiter">).</span>push_back<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">);</span>
     <span class="Identifier">break</span><span class="Delimiter">;</span>
   <span class="Delimiter">}</span>
   long long int quotient = a / b<span class="Delimiter">;</span>
diff --git a/html/029tools.cc.html b/html/029tools.cc.html
index 5355d922..69b67fb9 100644
--- a/html/029tools.cc.html
+++ b/html/029tools.cc.html
@@ -13,8 +13,8 @@
 pre { white-space: pre-wrap; font-family: monospace; color: #eeeeee; background-color: #080808; }
 body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 * { font-size: 1.05em; }
-.traceContains { color: #008000; }
 .SalientComment { color: #00ffff; }
+.traceContains { color: #008000; }
 .cSpecial { color: #008000; }
 .CommentedCode { color: #6c6c6c; }
 .Comment { color: #9090ff; }
diff --git a/html/030container.cc.html b/html/030container.cc.html
index 77c582c7..00935788 100644
--- a/html/030container.cc.html
+++ b/html/030container.cc.html
@@ -13,8 +13,8 @@
 pre { white-space: pre-wrap; font-family: monospace; color: #eeeeee; background-color: #080808; }
 body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 * { font-size: 1.05em; }
-.traceContains { color: #008000; }
 .SalientComment { color: #00ffff; }
+.traceContains { color: #008000; }
 .cSpecial { color: #008000; }
 .Comment { color: #9090ff; }
 .Delimiter { color: #a04060; }
@@ -55,7 +55,7 @@ get<span class="Delimiter">(</span>Type<span class="Delimiter">,</span> point<sp
 recipe main [
   <span class="Constant">1</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">34</span>
   <span class="Constant">2</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">35</span>
-  <span class="Constant">3</span>:point<span class="Special"> &lt;- </span>copy <span class="Constant">1</span>:point/<span class="Special">raw</span>  <span class="Comment"># unsafe</span>
+  <span class="Constant">3</span>:point<span class="Special"> &lt;- </span>copy <span class="Constant">1</span>:point/unsafe
 ]
 <span class="traceContains">+mem: storing 34 in location 3</span>
 <span class="traceContains">+mem: storing 35 in location 4</span>
@@ -85,7 +85,7 @@ recipe main [
   <span class="Constant">12</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">34</span>
   <span class="Constant">13</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">35</span>
   <span class="Constant">14</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">36</span>
-  <span class="Constant">15</span>:point-number<span class="Special"> &lt;- </span>copy <span class="Constant">12</span>:point-number/<span class="Special">raw</span>  <span class="Comment"># unsafe</span>
+  <span class="Constant">15</span>:point-number<span class="Special"> &lt;- </span>copy <span class="Constant">12</span>:point-number/unsafe
 ]
 <span class="traceContains">+mem: storing 36 in location 17</span>
 
@@ -100,7 +100,7 @@ recipe main [
   <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">34</span>  <span class="Comment"># second</span>
   <span class="Constant">5</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">35</span>
   <span class="Constant">6</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">36</span>
-  <span class="Constant">7</span>:boolean<span class="Special"> &lt;- </span>equal <span class="Constant">1</span>:point-number/<span class="Special">raw</span><span class="Delimiter">,</span> <span class="Constant">4</span>:point-number/<span class="Special">raw</span>  <span class="Comment"># unsafe</span>
+  <span class="Constant">7</span>:boolean<span class="Special"> &lt;- </span>equal <span class="Constant">1</span>:point-number/<span class="Special">raw</span><span class="Delimiter">,</span> <span class="Constant">4</span>:point-number/unsafe
 ]
 <span class="traceContains">+mem: storing 1 in location 7</span>
 
@@ -112,7 +112,7 @@ recipe main [
   <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">34</span>  <span class="Comment"># second</span>
   <span class="Constant">5</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">35</span>
   <span class="Constant">6</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">37</span>  <span class="Comment"># different</span>
-  <span class="Constant">7</span>:boolean<span class="Special"> &lt;- </span>equal <span class="Constant">1</span>:point-number/<span class="Special">raw</span><span class="Delimiter">,</span> <span class="Constant">4</span>:point-number/<span class="Special">raw</span>  <span class="Comment"># unsafe</span>
+  <span class="Constant">7</span>:boolean<span class="Special"> &lt;- </span>equal <span class="Constant">1</span>:point-number/<span class="Special">raw</span><span class="Delimiter">,</span> <span class="Constant">4</span>:point-number/unsafe
 ]
 <span class="traceContains">+mem: storing 0 in location 7</span>
 
@@ -587,10 +587,7 @@ void check_or_set_invalid_types<span class="Delimiter">(</span>type_tree* type<s
   <span class="Comment">// can't assert that type_name is non-null, even at the top of a recursive call tree</span>
   if <span class="Delimiter">(</span>!type<span class="Delimiter">)</span> <span class="Identifier">return</span><span class="Delimiter">;</span>  <span class="Comment">// will throw a more precise error elsewhere</span>
   <span class="Comment">// End Container Type Checks</span>
-  if <span class="Delimiter">(</span>type<span class="Delimiter">-&gt;</span>value == <span class="Constant">0</span><span class="Delimiter">)</span> <span class="Delimiter">{</span>
-    assert<span class="Delimiter">(</span>!type<span class="Delimiter">-&gt;</span>left &amp;&amp; !type<span class="Delimiter">-&gt;</span>right<span class="Delimiter">);</span>
-    <span class="Identifier">return</span><span class="Delimiter">;</span>
-  <span class="Delimiter">}</span>
+  if <span class="Delimiter">(</span>type<span class="Delimiter">-&gt;</span>value == <span class="Constant">0</span><span class="Delimiter">)</span> <span class="Identifier">return</span><span class="Delimiter">;</span>
   if <span class="Delimiter">(</span>!contains_key<span class="Delimiter">(</span>Type<span class="Delimiter">,</span> type<span class="Delimiter">-&gt;</span>value<span class="Delimiter">))</span> <span class="Delimiter">{</span>
     if <span class="Delimiter">(</span>type_name &amp;&amp; contains_key<span class="Delimiter">(</span>Type_ordinal<span class="Delimiter">,</span> type_name<span class="Delimiter">-&gt;</span>value<span class="Delimiter">))</span>
       type<span class="Delimiter">-&gt;</span>value = get<span class="Delimiter">(</span>Type_ordinal<span class="Delimiter">,</span> type_name<span class="Delimiter">-&gt;</span>value<span class="Delimiter">);</span>
diff --git a/html/031address.cc.html b/html/031address.cc.html
index cabdc541..e039b331 100644
--- a/html/031address.cc.html
+++ b/html/031address.cc.html
@@ -13,8 +13,8 @@
 pre { white-space: pre-wrap; font-family: monospace; color: #eeeeee; background-color: #080808; }
 body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 * { font-size: 1.05em; }
-.traceContains { color: #008000; }
 .traceAbsent { color: #c00000; }
+.traceContains { color: #008000; }
 .cSpecial { color: #008000; }
 .SalientComment { color: #00ffff; }
 .Comment { color: #9090ff; }
@@ -85,14 +85,17 @@ void canonize<span class="Delimiter">(</span>reagent&amp; x<span class="Delimite
 void lookup_memory<span class="Delimiter">(</span>reagent&amp; x<span class="Delimiter">)</span> <span class="Delimiter">{</span>
   if <span class="Delimiter">(</span>!x<span class="Delimiter">.</span>type || x<span class="Delimiter">.</span>type<span class="Delimiter">-&gt;</span>value != get<span class="Delimiter">(</span>Type_ordinal<span class="Delimiter">,</span> <span class="Constant">&quot;address&quot;</span><span class="Delimiter">))</span> <span class="Delimiter">{</span>
     raise_error &lt;&lt; maybe<span class="Delimiter">(</span>current_recipe_name<span class="Delimiter">())</span> &lt;&lt; <span class="Constant">&quot;tried to /lookup &quot;</span> &lt;&lt; x<span class="Delimiter">.</span>original_string &lt;&lt; <span class="Constant">&quot; but it isn't an address</span><span class="cSpecial">\n</span><span class="Constant">&quot;</span> &lt;&lt; end<span class="Delimiter">();</span>
+    <span class="Identifier">return</span><span class="Delimiter">;</span>
   <span class="Delimiter">}</span>
   <span class="Comment">// compute value</span>
   if <span class="Delimiter">(</span>x<span class="Delimiter">.</span>value == <span class="Constant">0</span><span class="Delimiter">)</span> <span class="Delimiter">{</span>
     raise_error &lt;&lt; maybe<span class="Delimiter">(</span>current_recipe_name<span class="Delimiter">())</span> &lt;&lt; <span class="Constant">&quot;tried to /lookup 0</span><span class="cSpecial">\n</span><span class="Constant">&quot;</span> &lt;&lt; end<span class="Delimiter">();</span>
+    <span class="Identifier">return</span><span class="Delimiter">;</span>
   <span class="Delimiter">}</span>
   trace<span class="Delimiter">(</span><span class="Constant">9999</span><span class="Delimiter">,</span> <span class="Constant">&quot;mem&quot;</span><span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;location &quot;</span> &lt;&lt; x<span class="Delimiter">.</span>value &lt;&lt; <span class="Constant">&quot; is &quot;</span> &lt;&lt; no_scientific<span class="Delimiter">(</span>get_or_insert<span class="Delimiter">(</span>Memory<span class="Delimiter">,</span> x<span class="Delimiter">.</span>value<span class="Delimiter">))</span> &lt;&lt; end<span class="Delimiter">();</span>
   x<span class="Delimiter">.</span>set_value<span class="Delimiter">(</span>get_or_insert<span class="Delimiter">(</span>Memory<span class="Delimiter">,</span> x<span class="Delimiter">.</span>value<span class="Delimiter">));</span>
-  drop_address_from_type<span class="Delimiter">(</span>x<span class="Delimiter">);</span>
+  drop_from_type<span class="Delimiter">(</span>x<span class="Delimiter">,</span> <span class="Constant">&quot;address&quot;</span><span class="Delimiter">);</span>
+  <span class="Comment">// End Drop Address In lookup_memory(x)</span>
   drop_one_lookup<span class="Delimiter">(</span>x<span class="Delimiter">);</span>
 <span class="Delimiter">}</span>
 
@@ -123,15 +126,20 @@ bool canonize_type<span class="Delimiter">(</span>reagent&amp; r<span class="Del
       raise_error &lt;&lt; <span class="Constant">&quot;can't lookup non-address: &quot;</span> &lt;&lt; r<span class="Delimiter">.</span>to_string<span class="Delimiter">()</span> &lt;&lt; <span class="Constant">&quot;: &quot;</span> &lt;&lt; debug_string<span class="Delimiter">(</span>r<span class="Delimiter">.</span>type<span class="Delimiter">)</span> &lt;&lt; <span class="cSpecial">'\n'</span> &lt;&lt; end<span class="Delimiter">();</span>
       <span class="Identifier">return</span> <span class="Constant">false</span><span class="Delimiter">;</span>
     <span class="Delimiter">}</span>
-    drop_address_from_type<span class="Delimiter">(</span>r<span class="Delimiter">);</span>
+    drop_from_type<span class="Delimiter">(</span>r<span class="Delimiter">,</span> <span class="Constant">&quot;address&quot;</span><span class="Delimiter">);</span>
+    <span class="Comment">// End Drop Address In canonize_type(r)</span>
     drop_one_lookup<span class="Delimiter">(</span>r<span class="Delimiter">);</span>
   <span class="Delimiter">}</span>
   <span class="Identifier">return</span> <span class="Constant">true</span><span class="Delimiter">;</span>
 <span class="Delimiter">}</span>
 
-void drop_address_from_type<span class="Delimiter">(</span>reagent&amp; r<span class="Delimiter">)</span> <span class="Delimiter">{</span>
+void drop_from_type<span class="Delimiter">(</span>reagent&amp; r<span class="Delimiter">,</span> string expected_type<span class="Delimiter">)</span> <span class="Delimiter">{</span>
   if <span class="Delimiter">(</span>!r<span class="Delimiter">.</span>type<span class="Delimiter">)</span> <span class="Delimiter">{</span>
-    raise_error &lt;&lt; <span class="Constant">&quot;can't drop address from &quot;</span> &lt;&lt; debug_string<span class="Delimiter">(</span>r<span class="Delimiter">)</span> &lt;&lt; <span class="cSpecial">'\n'</span> &lt;&lt; end<span class="Delimiter">();</span>
+    raise_error &lt;&lt; <span class="Constant">&quot;can't drop &quot;</span> &lt;&lt; expected_type &lt;&lt; <span class="Constant">&quot; from &quot;</span> &lt;&lt; debug_string<span class="Delimiter">(</span>r<span class="Delimiter">)</span> &lt;&lt; <span class="cSpecial">'\n'</span> &lt;&lt; end<span class="Delimiter">();</span>
+    <span class="Identifier">return</span><span class="Delimiter">;</span>
+  <span class="Delimiter">}</span>
+  if <span class="Delimiter">(</span>r<span class="Delimiter">.</span>properties<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">).</span>second<span class="Delimiter">-&gt;</span>value != expected_type<span class="Delimiter">)</span> <span class="Delimiter">{</span>
+    raise_error &lt;&lt; <span class="Constant">&quot;can't drop &quot;</span> &lt;&lt; expected_type &lt;&lt; <span class="Constant">&quot; from &quot;</span> &lt;&lt; debug_string<span class="Delimiter">(</span>r<span class="Delimiter">)</span> &lt;&lt; <span class="cSpecial">'\n'</span> &lt;&lt; end<span class="Delimiter">();</span>
     <span class="Identifier">return</span><span class="Delimiter">;</span>
   <span class="Delimiter">}</span>
   type_tree* tmp = r<span class="Delimiter">.</span>type<span class="Delimiter">;</span>
diff --git a/html/032array.cc.html b/html/032array.cc.html
index d2689076..2dde32d7 100644
--- a/html/032array.cc.html
+++ b/html/032array.cc.html
@@ -13,9 +13,10 @@
 pre { white-space: pre-wrap; font-family: monospace; color: #eeeeee; background-color: #080808; }
 body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 * { font-size: 1.05em; }
-.traceContains { color: #008000; }
 .SalientComment { color: #00ffff; }
+.traceContains { color: #008000; }
 .cSpecial { color: #008000; }
+.CommentedCode { color: #6c6c6c; }
 .Comment { color: #9090ff; }
 .Delimiter { color: #a04060; }
 .Special { color: #ff6060; }
@@ -146,7 +147,7 @@ if <span class="Delimiter">(</span>r<span class="Delimiter">.</span>type &amp;&a
     raise_error &lt;&lt; maybe<span class="Delimiter">(</span>current_recipe_name<span class="Delimiter">())</span> &lt;&lt; <span class="Constant">&quot;'&quot;</span> &lt;&lt; r<span class="Delimiter">.</span>original_string &lt;&lt; <span class="Constant">&quot;' is an array of what?</span><span class="cSpecial">\n</span><span class="Constant">&quot;</span> &lt;&lt; end<span class="Delimiter">();</span>
     <span class="Identifier">return</span> <span class="Constant">1</span><span class="Delimiter">;</span>
   <span class="Delimiter">}</span>
-  <span class="Comment">// skip the 'array' type to get at the element type</span>
+<span class="CommentedCode">//?   trace(9999, &quot;mem&quot;) &lt;&lt; &quot;computing size of array starting at &quot; &lt;&lt; r.value &lt;&lt; end();</span>
   <span class="Identifier">return</span> <span class="Constant">1</span> + get_or_insert<span class="Delimiter">(</span>Memory<span class="Delimiter">,</span> r<span class="Delimiter">.</span>value<span class="Delimiter">)</span>*size_of<span class="Delimiter">(</span>array_element<span class="Delimiter">(</span>r<span class="Delimiter">.</span>type<span class="Delimiter">));</span>
 <span class="Delimiter">}</span>
 
@@ -205,6 +206,7 @@ case INDEX: <span class="Delimiter">{</span>
   reagent base = current_instruction<span class="Delimiter">().</span>ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">);</span>
   canonize<span class="Delimiter">(</span>base<span class="Delimiter">);</span>
   long long int base_address = base<span class="Delimiter">.</span>value<span class="Delimiter">;</span>
+  trace<span class="Delimiter">(</span><span class="Constant">9998</span><span class="Delimiter">,</span> <span class="Constant">&quot;run&quot;</span><span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;base address is &quot;</span> &lt;&lt; base_address &lt;&lt; end<span class="Delimiter">();</span>
   if <span class="Delimiter">(</span>base_address == <span class="Constant">0</span><span class="Delimiter">)</span> <span class="Delimiter">{</span>
     raise_error &lt;&lt; maybe<span class="Delimiter">(</span>current_recipe_name<span class="Delimiter">())</span> &lt;&lt; <span class="Constant">&quot;tried to access location 0 in '&quot;</span> &lt;&lt; current_instruction<span class="Delimiter">().</span>to_string<span class="Delimiter">()</span> &lt;&lt; <span class="Constant">&quot;'</span><span class="cSpecial">\n</span><span class="Constant">&quot;</span> &lt;&lt; end<span class="Delimiter">();</span>
     <span class="Identifier">break</span><span class="Delimiter">;</span>
@@ -253,7 +255,7 @@ recipe main [
   <span class="Constant">5</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">14</span>
   <span class="Constant">6</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">15</span>
   <span class="Constant">7</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">16</span>
-  <span class="Constant">8</span>:address:array:point<span class="Special"> &lt;- </span>copy <span class="Constant">1</span>
+  <span class="Constant">8</span>:address:array:point<span class="Special"> &lt;- </span>copy <span class="Constant">1</span>/unsafe
   index *<span class="Constant">8</span>:address:array:point<span class="Delimiter">,</span> <span class="Constant">4</span>  <span class="Comment"># less than size of array in locations, but larger than its length in elements</span>
 ]
 <span class="traceContains">+error: main: invalid index 4</span>
@@ -373,7 +375,7 @@ recipe main [
   <span class="Constant">5</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">14</span>
   <span class="Constant">6</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">15</span>
   <span class="Constant">7</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">16</span>
-  <span class="Constant">8</span>:address:array:point<span class="Special"> &lt;- </span>copy <span class="Constant">1</span>  <span class="Comment"># unsafe</span>
+  <span class="Constant">8</span>:address:array:point<span class="Special"> &lt;- </span>copy <span class="Constant">1</span>/unsafe
   index-address *<span class="Constant">8</span>:address:array:point<span class="Delimiter">,</span> <span class="Constant">4</span>  <span class="Comment"># less than size of array in locations, but larger than its length in elements</span>
 ]
 <span class="traceContains">+error: main: invalid index 4</span>
@@ -464,10 +466,12 @@ bool is_mu_string<span class="Delimiter">(</span>const reagent&amp; x<span class
   <span class="Identifier">return</span> x<span class="Delimiter">.</span>type
     &amp;&amp; x<span class="Delimiter">.</span>type<span class="Delimiter">-&gt;</span>value == get<span class="Delimiter">(</span>Type_ordinal<span class="Delimiter">,</span> <span class="Constant">&quot;address&quot;</span><span class="Delimiter">)</span>
     &amp;&amp; x<span class="Delimiter">.</span>type<span class="Delimiter">-&gt;</span>right
-    &amp;&amp; x<span class="Delimiter">.</span>type<span class="Delimiter">-&gt;</span>right<span class="Delimiter">-&gt;</span>value == get<span class="Delimiter">(</span>Type_ordinal<span class="Delimiter">,</span> <span class="Constant">&quot;array&quot;</span><span class="Delimiter">)</span>
+    &amp;&amp; x<span class="Delimiter">.</span>type<span class="Delimiter">-&gt;</span>right<span class="Delimiter">-&gt;</span>value == get<span class="Delimiter">(</span>Type_ordinal<span class="Delimiter">,</span> <span class="Constant">&quot;shared&quot;</span><span class="Delimiter">)</span>
     &amp;&amp; x<span class="Delimiter">.</span>type<span class="Delimiter">-&gt;</span>right<span class="Delimiter">-&gt;</span>right
-    &amp;&amp; x<span class="Delimiter">.</span>type<span class="Delimiter">-&gt;</span>right<span class="Delimiter">-&gt;</span>right<span class="Delimiter">-&gt;</span>value == get<span class="Delimiter">(</span>Type_ordinal<span class="Delimiter">,</span> <span class="Constant">&quot;character&quot;</span><span class="Delimiter">)</span>
-    &amp;&amp; x<span class="Delimiter">.</span>type<span class="Delimiter">-&gt;</span>right<span class="Delimiter">-&gt;</span>right<span class="Delimiter">-&gt;</span>right == <span class="Constant">NULL</span><span class="Delimiter">;</span>
+    &amp;&amp; x<span class="Delimiter">.</span>type<span class="Delimiter">-&gt;</span>right<span class="Delimiter">-&gt;</span>right<span class="Delimiter">-&gt;</span>value == get<span class="Delimiter">(</span>Type_ordinal<span class="Delimiter">,</span> <span class="Constant">&quot;array&quot;</span><span class="Delimiter">)</span>
+    &amp;&amp; x<span class="Delimiter">.</span>type<span class="Delimiter">-&gt;</span>right<span class="Delimiter">-&gt;</span>right<span class="Delimiter">-&gt;</span>right
+    &amp;&amp; x<span class="Delimiter">.</span>type<span class="Delimiter">-&gt;</span>right<span class="Delimiter">-&gt;</span>right<span class="Delimiter">-&gt;</span>right<span class="Delimiter">-&gt;</span>value == get<span class="Delimiter">(</span>Type_ordinal<span class="Delimiter">,</span> <span class="Constant">&quot;character&quot;</span><span class="Delimiter">)</span>
+    &amp;&amp; x<span class="Delimiter">.</span>type<span class="Delimiter">-&gt;</span>right<span class="Delimiter">-&gt;</span>right<span class="Delimiter">-&gt;</span>right<span class="Delimiter">-&gt;</span>right == <span class="Constant">NULL</span><span class="Delimiter">;</span>
 <span class="Delimiter">}</span>
 </pre>
 </body>
diff --git a/html/033exclusive_container.cc.html b/html/033exclusive_container.cc.html
index a4fc191a..f3e258c8 100644
--- a/html/033exclusive_container.cc.html
+++ b/html/033exclusive_container.cc.html
@@ -60,7 +60,7 @@ recipe main [
   <span class="Constant">1</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">1</span>  <span class="Comment"># 'point' variant</span>
   <span class="Constant">2</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">34</span>
   <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">35</span>
-  <span class="Constant">4</span>:number-or-point<span class="Special"> &lt;- </span>copy <span class="Constant">1</span>:number-or-point/<span class="Special">raw</span>  <span class="Comment"># unsafe</span>
+  <span class="Constant">4</span>:number-or-point<span class="Special"> &lt;- </span>copy <span class="Constant">1</span>:number-or-point/unsafe
 ]
 <span class="traceContains">+mem: storing 1 in location 4</span>
 <span class="traceContains">+mem: storing 34 in location 5</span>
@@ -94,7 +94,7 @@ recipe main [
   <span class="Constant">12</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">1</span>
   <span class="Constant">13</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">35</span>
   <span class="Constant">14</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">36</span>
-  <span class="Constant">20</span>:address:point<span class="Special"> &lt;- </span>maybe-convert <span class="Constant">12</span>:number-or-point/<span class="Special">raw</span><span class="Delimiter">,</span> <span class="Constant">1</span>:variant  <span class="Comment"># unsafe</span>
+  <span class="Constant">20</span>:address:point<span class="Special"> &lt;- </span>maybe-convert <span class="Constant">12</span>:number-or-point/unsafe<span class="Delimiter">,</span> <span class="Constant">1</span>:variant
 ]
 <span class="traceContains">+mem: storing 13 in location 20</span>
 
@@ -103,7 +103,7 @@ recipe main [
   <span class="Constant">12</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">1</span>
   <span class="Constant">13</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">35</span>
   <span class="Constant">14</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">36</span>
-  <span class="Constant">20</span>:address:point<span class="Special"> &lt;- </span>maybe-convert <span class="Constant">12</span>:number-or-point/<span class="Special">raw</span><span class="Delimiter">,</span> <span class="Constant">0</span>:variant  <span class="Comment"># unsafe</span>
+  <span class="Constant">20</span>:address:number<span class="Special"> &lt;- </span>maybe-convert <span class="Constant">12</span>:number-or-point/unsafe<span class="Delimiter">,</span> <span class="Constant">0</span>:variant
 ]
 <span class="traceContains">+mem: storing 0 in location 20</span>
 
@@ -113,18 +113,36 @@ MAYBE_CONVERT<span class="Delimiter">,</span>
 put<span class="Delimiter">(</span>Recipe_ordinal<span class="Delimiter">,</span> <span class="Constant">&quot;maybe-convert&quot;</span><span class="Delimiter">,</span> MAYBE_CONVERT<span class="Delimiter">);</span>
 <span class="Delimiter">:(before &quot;End Primitive Recipe Checks&quot;)</span>
 case MAYBE_CONVERT: <span class="Delimiter">{</span>
+  const recipe&amp; caller = get<span class="Delimiter">(</span>Recipe<span class="Delimiter">,</span> r<span class="Delimiter">);</span>
   if <span class="Delimiter">(</span>SIZE<span class="Delimiter">(</span>inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">)</span> != <span class="Constant">2</span><span class="Delimiter">)</span> <span class="Delimiter">{</span>
-    raise_error &lt;&lt; maybe<span class="Delimiter">(</span>get<span class="Delimiter">(</span>Recipe<span class="Delimiter">,</span> r<span class="Delimiter">).</span>name<span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;'maybe-convert' expects exactly 2 ingredients in '&quot;</span> &lt;&lt; inst<span class="Delimiter">.</span>to_string<span class="Delimiter">()</span> &lt;&lt; <span class="Constant">&quot;'</span><span class="cSpecial">\n</span><span class="Constant">&quot;</span> &lt;&lt; end<span class="Delimiter">();</span>
+    raise_error &lt;&lt; maybe<span class="Delimiter">(</span>caller<span class="Delimiter">.</span>name<span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;'maybe-convert' expects exactly 2 ingredients in '&quot;</span> &lt;&lt; inst<span class="Delimiter">.</span>to_string<span class="Delimiter">()</span> &lt;&lt; <span class="Constant">&quot;'</span><span class="cSpecial">\n</span><span class="Constant">&quot;</span> &lt;&lt; end<span class="Delimiter">();</span>
     <span class="Identifier">break</span><span class="Delimiter">;</span>
   <span class="Delimiter">}</span>
   reagent base = inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">);</span>
   canonize_type<span class="Delimiter">(</span>base<span class="Delimiter">);</span>
   if <span class="Delimiter">(</span>!base<span class="Delimiter">.</span>type || !base<span class="Delimiter">.</span>type<span class="Delimiter">-&gt;</span>value || get<span class="Delimiter">(</span>Type<span class="Delimiter">,</span> base<span class="Delimiter">.</span>type<span class="Delimiter">-&gt;</span>value<span class="Delimiter">).</span>kind != EXCLUSIVE_CONTAINER<span class="Delimiter">)</span> <span class="Delimiter">{</span>
-    raise_error &lt;&lt; maybe<span class="Delimiter">(</span>get<span class="Delimiter">(</span>Recipe<span class="Delimiter">,</span> r<span class="Delimiter">).</span>name<span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;first ingredient of 'maybe-convert' should be an exclusive-container, but got &quot;</span> &lt;&lt; base<span class="Delimiter">.</span>original_string &lt;&lt; <span class="cSpecial">'\n'</span> &lt;&lt; end<span class="Delimiter">();</span>
+    raise_error &lt;&lt; maybe<span class="Delimiter">(</span>caller<span class="Delimiter">.</span>name<span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;first ingredient of 'maybe-convert' should be an exclusive-container, but got &quot;</span> &lt;&lt; base<span class="Delimiter">.</span>original_string &lt;&lt; <span class="cSpecial">'\n'</span> &lt;&lt; end<span class="Delimiter">();</span>
     <span class="Identifier">break</span><span class="Delimiter">;</span>
   <span class="Delimiter">}</span>
   if <span class="Delimiter">(</span>!is_literal<span class="Delimiter">(</span>inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">1</span><span class="Delimiter">)))</span> <span class="Delimiter">{</span>
-    raise_error &lt;&lt; maybe<span class="Delimiter">(</span>get<span class="Delimiter">(</span>Recipe<span class="Delimiter">,</span> r<span class="Delimiter">).</span>name<span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;second ingredient of 'maybe-convert' should have type 'variant', but got &quot;</span> &lt;&lt; inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">1</span><span class="Delimiter">).</span>original_string &lt;&lt; <span class="cSpecial">'\n'</span> &lt;&lt; end<span class="Delimiter">();</span>
+    raise_error &lt;&lt; maybe<span class="Delimiter">(</span>caller<span class="Delimiter">.</span>name<span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;second ingredient of 'maybe-convert' should have type 'variant', but got &quot;</span> &lt;&lt; inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">1</span><span class="Delimiter">).</span>original_string &lt;&lt; <span class="cSpecial">'\n'</span> &lt;&lt; end<span class="Delimiter">();</span>
+    <span class="Identifier">break</span><span class="Delimiter">;</span>
+  <span class="Delimiter">}</span>
+  if <span class="Delimiter">(</span>inst<span class="Delimiter">.</span>products<span class="Delimiter">.</span>empty<span class="Delimiter">())</span> <span class="Identifier">break</span><span class="Delimiter">;</span>
+  reagent product = inst<span class="Delimiter">.</span>products<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">);</span>
+  if <span class="Delimiter">(</span>!canonize_type<span class="Delimiter">(</span>product<span class="Delimiter">))</span> <span class="Identifier">break</span><span class="Delimiter">;</span>
+  const reagent&amp; offset = inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">1</span><span class="Delimiter">);</span>
+  long long int tag = <span class="Constant">0</span><span class="Delimiter">;</span>
+  if <span class="Delimiter">(</span>is_integer<span class="Delimiter">(</span>offset<span class="Delimiter">.</span>name<span class="Delimiter">))</span> <span class="Delimiter">{</span>
+    tag = to_integer<span class="Delimiter">(</span>offset<span class="Delimiter">.</span>name<span class="Delimiter">);</span>
+  <span class="Delimiter">}</span>
+  else <span class="Delimiter">{</span>
+    tag = offset<span class="Delimiter">.</span>value<span class="Delimiter">;</span>
+  <span class="Delimiter">}</span>
+  reagent variant = variant_type<span class="Delimiter">(</span>base<span class="Delimiter">,</span> tag<span class="Delimiter">);</span>
+  variant<span class="Delimiter">.</span>type = new type_tree<span class="Delimiter">(</span>get<span class="Delimiter">(</span>Type_ordinal<span class="Delimiter">,</span> <span class="Constant">&quot;address&quot;</span><span class="Delimiter">),</span> variant<span class="Delimiter">.</span>type<span class="Delimiter">);</span>
+  if <span class="Delimiter">(</span>!types_coercible<span class="Delimiter">(</span>product<span class="Delimiter">,</span> variant<span class="Delimiter">))</span> <span class="Delimiter">{</span>
+    raise_error &lt;&lt; maybe<span class="Delimiter">(</span>caller<span class="Delimiter">.</span>name<span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;'maybe-convert &quot;</span> &lt;&lt; base<span class="Delimiter">.</span>original_string &lt;&lt; <span class="Constant">&quot;, &quot;</span> &lt;&lt; inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">1</span><span class="Delimiter">).</span>original_string &lt;&lt; <span class="Constant">&quot;' should write to &quot;</span> &lt;&lt; debug_string<span class="Delimiter">(</span>variant<span class="Delimiter">.</span>type<span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot; but &quot;</span> &lt;&lt; product<span class="Delimiter">.</span>name &lt;&lt; <span class="Constant">&quot; has type &quot;</span> &lt;&lt; debug_string<span class="Delimiter">(</span>product<span class="Delimiter">.</span>type<span class="Delimiter">)</span> &lt;&lt; <span class="cSpecial">'\n'</span> &lt;&lt; end<span class="Delimiter">();</span>
     <span class="Identifier">break</span><span class="Delimiter">;</span>
   <span class="Delimiter">}</span>
   <span class="Identifier">break</span><span class="Delimiter">;</span>
@@ -151,6 +169,30 @@ case MAYBE_CONVERT: <span class="Delimiter">{</span>
   <span class="Identifier">break</span><span class="Delimiter">;</span>
 <span class="Delimiter">}</span>
 
+<span class="Delimiter">:(code)</span>
+const reagent variant_type<span class="Delimiter">(</span>const reagent&amp; canonized_base<span class="Delimiter">,</span> long long int tag<span class="Delimiter">)</span> <span class="Delimiter">{</span>
+  assert<span class="Delimiter">(</span>tag &gt;= <span class="Constant">0</span><span class="Delimiter">);</span>
+  assert<span class="Delimiter">(</span>contains_key<span class="Delimiter">(</span>Type<span class="Delimiter">,</span> canonized_base<span class="Delimiter">.</span>type<span class="Delimiter">-&gt;</span>value<span class="Delimiter">));</span>
+  assert<span class="Delimiter">(</span>!get<span class="Delimiter">(</span>Type<span class="Delimiter">,</span> canonized_base<span class="Delimiter">.</span>type<span class="Delimiter">-&gt;</span>value<span class="Delimiter">).</span>name<span class="Delimiter">.</span>empty<span class="Delimiter">());</span>
+  const type_info&amp; info = get<span class="Delimiter">(</span>Type<span class="Delimiter">,</span> canonized_base<span class="Delimiter">.</span>type<span class="Delimiter">-&gt;</span>value<span class="Delimiter">);</span>
+  assert<span class="Delimiter">(</span>info<span class="Delimiter">.</span>kind == EXCLUSIVE_CONTAINER<span class="Delimiter">);</span>
+  reagent element<span class="Delimiter">;</span>
+  element<span class="Delimiter">.</span>type = new type_tree<span class="Delimiter">(</span>*info<span class="Delimiter">.</span>elements<span class="Delimiter">.</span>at<span class="Delimiter">(</span>tag<span class="Delimiter">));</span>
+  <span class="Comment">// End variant_type Special-cases</span>
+  <span class="Identifier">return</span> element<span class="Delimiter">;</span>
+<span class="Delimiter">}</span>
+
+<span class="Delimiter">:(scenario maybe_convert_product_type_mismatch)</span>
+<span class="Special">% Hide_errors = true;</span>
+recipe main [
+  <span class="Constant">12</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">1</span>
+  <span class="Constant">13</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">35</span>
+  <span class="Constant">14</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">36</span>
+  <span class="Constant">20</span>:address:number<span class="Special"> &lt;- </span>maybe-convert <span class="Constant">12</span>:number-or-point/unsafe<span class="Delimiter">,</span> <span class="Constant">1</span>:variant
+]
+<span class="traceContains">+error: main: 'maybe-convert 12:number-or-point/unsafe, 1:variant' should write to &lt;address : &lt;point : &lt;&gt;&gt;&gt; but 20 has type &lt;address : &lt;number : &lt;&gt;&gt;&gt;</span>
+
+
 <span class="SalientComment">//:: Allow exclusive containers to be defined in mu code.</span>
 
 <span class="Delimiter">:(scenario exclusive_container)</span>
diff --git a/html/034call.cc.html b/html/034call.cc.html
index 10ad7632..d2664036 100644
--- a/html/034call.cc.html
+++ b/html/034call.cc.html
@@ -150,8 +150,12 @@ default: <span class="Delimiter">{</span>
     assert<span class="Delimiter">(</span>Trace_stream<span class="Delimiter">-&gt;</span>callstack_depth &lt; <span class="Constant">9000</span><span class="Delimiter">);</span>  <span class="Comment">// 9998-101 plus cushion</span>
   <span class="Delimiter">}</span>
   Current_routine<span class="Delimiter">-&gt;</span>calls<span class="Delimiter">.</span>push_front<span class="Delimiter">(</span>call<span class="Delimiter">(</span>current_instruction<span class="Delimiter">().</span>operation<span class="Delimiter">));</span>
+  finish_call_housekeeping<span class="Delimiter">(</span>call_instruction<span class="Delimiter">,</span> ingredients<span class="Delimiter">);</span>
+  <span class="Identifier">continue</span><span class="Delimiter">;</span>  <span class="Comment">// not done with caller; don't increment step_index of caller</span>
+<span class="Delimiter">}</span>
+<span class="Delimiter">:(code)</span>
+void finish_call_housekeeping<span class="Delimiter">(</span>const instruction&amp; call_instruction<span class="Delimiter">,</span> const vector&lt;vector&lt;double&gt; &gt;&amp; ingredients<span class="Delimiter">)</span> <span class="Delimiter">{</span>
   <span class="Comment">// End Call Housekeeping</span>
-  <span class="Identifier">continue</span><span class="Delimiter">;</span>  <span class="Comment">// not done with caller; don't increment current_step_index()</span>
 <span class="Delimiter">}</span>
 
 <span class="Delimiter">:(scenario calling_undefined_recipe_fails)</span>
diff --git a/html/035call_ingredient.cc.html b/html/035call_ingredient.cc.html
index 34c4c270..640dc430 100644
--- a/html/035call_ingredient.cc.html
+++ b/html/035call_ingredient.cc.html
@@ -110,9 +110,8 @@ case NEXT_INGREDIENT: <span class="Delimiter">{</span>
     products<span class="Delimiter">.</span>resize<span class="Delimiter">(</span><span class="Constant">2</span><span class="Delimiter">);</span>
     <span class="Comment">// pad the first product with sufficient zeros to match its type</span>
     long long int size = size_of<span class="Delimiter">(</span>current_instruction<span class="Delimiter">().</span>products<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">));</span>
-    for <span class="Delimiter">(</span>long long int i = <span class="Constant">0</span><span class="Delimiter">;</span> i &lt; size<span class="Delimiter">;</span> ++i<span class="Delimiter">)</span> <span class="Delimiter">{</span>
+    for <span class="Delimiter">(</span>long long int i = <span class="Constant">0</span><span class="Delimiter">;</span> i &lt; size<span class="Delimiter">;</span> ++i<span class="Delimiter">)</span>
       products<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">).</span>push_back<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">);</span>
-    <span class="Delimiter">}</span>
     products<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">1</span><span class="Delimiter">).</span>push_back<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">);</span>
   <span class="Delimiter">}</span>
   <span class="Identifier">break</span><span class="Delimiter">;</span>
diff --git a/html/036call_reply.cc.html b/html/036call_reply.cc.html
index dac5314a..89005838 100644
--- a/html/036call_reply.cc.html
+++ b/html/036call_reply.cc.html
@@ -134,8 +134,10 @@ void check_types_of_reply_instructions<span class="Delimiter">(</span>recipe_ord
             <span class="Identifier">goto</span> finish_reply_check<span class="Delimiter">;</span>
           <span class="Delimiter">}</span>
           long long int ingredient_index = to_integer<span class="Delimiter">(</span>tmp<span class="Delimiter">-&gt;</span>value<span class="Delimiter">);</span>
-          if <span class="Delimiter">(</span>ingredient_index &gt;= SIZE<span class="Delimiter">(</span>caller_instruction<span class="Delimiter">.</span>ingredients<span class="Delimiter">))</span>
-            raise_error &lt;&lt; maybe<span class="Delimiter">(</span>caller<span class="Delimiter">.</span>name<span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;'same-as-ingredient' metadata overflows ingredients in: &quot;</span> &lt;&lt; caller_instruction<span class="Delimiter">.</span>to_string<span class="Delimiter">()</span> &lt;&lt; <span class="cSpecial">'\n'</span> &lt;&lt; end<span class="Delimiter">();</span>
+          if <span class="Delimiter">(</span>ingredient_index &gt;= SIZE<span class="Delimiter">(</span>caller_instruction<span class="Delimiter">.</span>ingredients<span class="Delimiter">))</span> <span class="Delimiter">{</span>
+            raise_error &lt;&lt; maybe<span class="Delimiter">(</span>caller<span class="Delimiter">.</span>name<span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;too few ingredients in '&quot;</span> &lt;&lt; caller_instruction<span class="Delimiter">.</span>to_string<span class="Delimiter">()</span> &lt;&lt; <span class="Constant">&quot;'</span><span class="cSpecial">\n</span><span class="Constant">&quot;</span> &lt;&lt; end<span class="Delimiter">();</span>
+            <span class="Identifier">goto</span> finish_reply_check<span class="Delimiter">;</span>
+          <span class="Delimiter">}</span>
           if <span class="Delimiter">(</span>!is_dummy<span class="Delimiter">(</span>caller_instruction<span class="Delimiter">.</span>products<span class="Delimiter">.</span>at<span class="Delimiter">(</span>i<span class="Delimiter">))</span> &amp;&amp; caller_instruction<span class="Delimiter">.</span>products<span class="Delimiter">.</span>at<span class="Delimiter">(</span>i<span class="Delimiter">).</span>name != caller_instruction<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span>ingredient_index<span class="Delimiter">).</span>name<span class="Delimiter">)</span>
             raise_error &lt;&lt; maybe<span class="Delimiter">(</span>caller<span class="Delimiter">.</span>name<span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;'&quot;</span> &lt;&lt; caller_instruction<span class="Delimiter">.</span>to_string<span class="Delimiter">()</span> &lt;&lt; <span class="Constant">&quot;' should write to &quot;</span> &lt;&lt; caller_instruction<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span>ingredient_index<span class="Delimiter">).</span>original_string &lt;&lt; <span class="Constant">&quot; rather than &quot;</span> &lt;&lt; caller_instruction<span class="Delimiter">.</span>products<span class="Delimiter">.</span>at<span class="Delimiter">(</span>i<span class="Delimiter">).</span>original_string &lt;&lt; <span class="cSpecial">'\n'</span> &lt;&lt; end<span class="Delimiter">();</span>
         <span class="Delimiter">}</span>
diff --git a/html/037recipe.cc.html b/html/037recipe.cc.html
deleted file mode 100644
index 44573495..00000000
--- a/html/037recipe.cc.html
+++ /dev/null
@@ -1,59 +0,0 @@
-<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
-<html>
-<head>
-<meta http-equiv="content-type" content="text/html; charset=UTF-8">
-<title>Mu - 037recipe.cc</title>
-<meta name="Generator" content="Vim/7.4">
-<meta name="plugin-version" content="vim7.4_v1">
-<meta name="syntax" content="cpp">
-<meta name="settings" content="use_css,pre_wrap,no_foldcolumn,expand_tabs,prevent_copy=">
-<meta name="colorscheme" content="minimal">
-<style type="text/css">
-<!--
-pre { white-space: pre-wrap; font-family: monospace; color: #eeeeee; background-color: #080808; }
-body { font-family: monospace; color: #eeeeee; background-color: #080808; }
-* { font-size: 1.05em; }
-.Comment { color: #9090ff; }
-.Delimiter { color: #a04060; }
-.Identifier { color: #804000; }
-.Constant { color: #00a0a0; }
--->
-</style>
-
-<script type='text/javascript'>
-<!--
-
--->
-</script>
-</head>
-<body>
-<pre id='vimCodeElement'>
-<span class="Comment">//: So far we've been calling a fixed recipe in each instruction, but we'd</span>
-<span class="Comment">//: also like to make the recipe a variable, pass recipes to &quot;higher-order&quot;</span>
-<span class="Comment">//: recipes, return recipes from recipes and so on.</span>
-
-<span class="Delimiter">:(before &quot;End Mu Types Initialization&quot;)</span>
-<span class="Comment">// 'recipe' is a literal</span>
-put<span class="Delimiter">(</span>Type_ordinal<span class="Delimiter">,</span> <span class="Constant">&quot;recipe&quot;</span><span class="Delimiter">,</span> <span class="Constant">0</span><span class="Delimiter">);</span>
-<span class="Comment">// 'recipe-ordinal' is the literal that can store recipe literals</span>
-type_ordinal recipe_ordinal = put<span class="Delimiter">(</span>Type_ordinal<span class="Delimiter">,</span> <span class="Constant">&quot;recipe-ordinal&quot;</span><span class="Delimiter">,</span> Next_type_ordinal++<span class="Delimiter">);</span>
-get_or_insert<span class="Delimiter">(</span>Type<span class="Delimiter">,</span> recipe_ordinal<span class="Delimiter">).</span>name = <span class="Constant">&quot;recipe-ordinal&quot;</span><span class="Delimiter">;</span>
-
-<span class="Delimiter">:(before &quot;End Reagent-parsing Exceptions&quot;)</span>
-if <span class="Delimiter">(</span>r<span class="Delimiter">.</span>properties<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">).</span>second &amp;&amp; r<span class="Delimiter">.</span>properties<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">).</span>second<span class="Delimiter">-&gt;</span>value == <span class="Constant">&quot;recipe&quot;</span><span class="Delimiter">)</span> <span class="Delimiter">{</span>
-  r<span class="Delimiter">.</span>set_value<span class="Delimiter">(</span>get<span class="Delimiter">(</span>Recipe_ordinal<span class="Delimiter">,</span> r<span class="Delimiter">.</span>name<span class="Delimiter">));</span>
-  <span class="Identifier">return</span><span class="Delimiter">;</span>
-<span class="Delimiter">}</span>
-
-<span class="Delimiter">:(code)</span>
-bool is_mu_recipe<span class="Delimiter">(</span>reagent r<span class="Delimiter">)</span> <span class="Delimiter">{</span>
-  if <span class="Delimiter">(</span>!r<span class="Delimiter">.</span>type<span class="Delimiter">)</span> <span class="Identifier">return</span> <span class="Constant">false</span><span class="Delimiter">;</span>
-  if <span class="Delimiter">(</span>r<span class="Delimiter">.</span>type<span class="Delimiter">-&gt;</span>value == get<span class="Delimiter">(</span>Type_ordinal<span class="Delimiter">,</span> <span class="Constant">&quot;recipe&quot;</span><span class="Delimiter">))</span> <span class="Identifier">return</span> <span class="Constant">true</span><span class="Delimiter">;</span>
-  if <span class="Delimiter">(</span>r<span class="Delimiter">.</span>type<span class="Delimiter">-&gt;</span>value == get<span class="Delimiter">(</span>Type_ordinal<span class="Delimiter">,</span> <span class="Constant">&quot;recipe-ordinal&quot;</span><span class="Delimiter">))</span> <span class="Identifier">return</span> <span class="Constant">true</span><span class="Delimiter">;</span>
-  <span class="Comment">// End is_mu_recipe Cases</span>
-  <span class="Identifier">return</span> <span class="Constant">false</span><span class="Delimiter">;</span>
-<span class="Delimiter">}</span>
-</pre>
-</body>
-</html>
-<!-- vim: set foldmethod=manual : -->
diff --git a/html/043new.cc.html b/html/038new.cc.html
index 81a1c1c7..1ba4365a 100644
--- a/html/043new.cc.html
+++ b/html/038new.cc.html
@@ -2,7 +2,7 @@
 <html>
 <head>
 <meta http-equiv="content-type" content="text/html; charset=UTF-8">
-<title>Mu - 043new.cc</title>
+<title>Mu - 038new.cc</title>
 <meta name="Generator" content="Vim/7.4">
 <meta name="plugin-version" content="vim7.4_v1">
 <meta name="syntax" content="cpp">
@@ -22,6 +22,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 .Special { color: #ff6060; }
 .Identifier { color: #804000; }
 .Constant { color: #00a0a0; }
+.Todo { color: #000000; background-color: #ffff00; padding-bottom: 1px; }
 -->
 </style>
 
@@ -33,15 +34,59 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 </head>
 <body>
 <pre id='vimCodeElement'>
-<span class="Comment">//: A simple memory allocator to create space for new variables at runtime.</span>
+<span class="Comment">//: Creating space for new variables at runtime.</span>
+
+<span class="Comment">//: Mu has two primitives for managing allocations:</span>
+<span class="Comment">//: - 'allocate' reserves a specified amount of space</span>
+<span class="Comment">//: - 'abandon' returns allocated space to be reused by future calls to 'allocate'</span>
+<span class="Comment">//:</span>
+<span class="Comment">//: In practice it's useful to let programs copy addresses anywhere they want,</span>
+<span class="Comment">//: but a prime source of (particularly security) bugs is accessing memory</span>
+<span class="Comment">//: after it's been abandoned. To avoid this, mu programs use a safer</span>
+<span class="Comment">//: primitive called 'new', which adds two features:</span>
+<span class="Comment">//:</span>
+<span class="Comment">//: - it takes a type rather than a size, to save you the trouble of</span>
+<span class="Comment">//: calculating sizes of different variables.</span>
+<span class="Comment">//: - it allocates an extra location where it tracks so-called 'reference</span>
+<span class="Comment">//: counts' or refcounts: the number of address variables in your program that</span>
+<span class="Comment">//: point to this allocation. The initial refcount of an allocation starts out</span>
+<span class="Comment">//: at 1 (the product of the 'new' instruction). When other variables are</span>
+<span class="Comment">//: copied from it the refcount is incremented. When a variable stops pointing</span>
+<span class="Comment">//: at it the refcount is decremented. When the refcount goes to 0 the</span>
+<span class="Comment">//: allocation is automatically abandoned.</span>
+<span class="Comment">//:</span>
+<span class="Comment">//: Mu programs guarantee you'll have no memory corruption bugs as long as you</span>
+<span class="Comment">//: use 'new' and never use 'allocate' or 'abandon'. However, they don't help</span>
+<span class="Comment">//: you at all to remember to abandon memory after you're done with it. To</span>
+<span class="Comment">//: minimize memory use, be sure to reset allocated addresses to 0 when you're</span>
+<span class="Comment">//: done with them.</span>
+
+<span class="Comment">//: To help you distinguish addresses that point at allocations, 'new' returns</span>
+<span class="Comment">//: type address:shared:___. Think of 'shared' as a generic container that</span>
+<span class="Comment">//: contains one extra field: the refcount. However, lookup operations will</span>
+<span class="Comment">//: transparently drop the 'shared' and access to the refcount. Copying</span>
+<span class="Comment">//: between shared and non-shared addresses is forbidden.</span>
+<span class="Delimiter">:(before &quot;End Mu Types Initialization&quot;)</span>
+type_ordinal shared = put<span class="Delimiter">(</span>Type_ordinal<span class="Delimiter">,</span> <span class="Constant">&quot;shared&quot;</span><span class="Delimiter">,</span> Next_type_ordinal++<span class="Delimiter">);</span>
+get_or_insert<span class="Delimiter">(</span>Type<span class="Delimiter">,</span> shared<span class="Delimiter">).</span>name = <span class="Constant">&quot;shared&quot;</span><span class="Delimiter">;</span>
+<span class="Delimiter">:(before &quot;End Drop Address In lookup_memory(x)&quot;)</span>
+if <span class="Delimiter">(</span>x<span class="Delimiter">.</span>properties<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">).</span>second<span class="Delimiter">-&gt;</span>value == <span class="Constant">&quot;shared&quot;</span><span class="Delimiter">)</span> <span class="Delimiter">{</span>
+  trace<span class="Delimiter">(</span><span class="Constant">9999</span><span class="Delimiter">,</span> <span class="Constant">&quot;mem&quot;</span><span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;skipping refcount at &quot;</span> &lt;&lt; x<span class="Delimiter">.</span>value &lt;&lt; end<span class="Delimiter">();</span>
+  x<span class="Delimiter">.</span>set_value<span class="Delimiter">(</span>x<span class="Delimiter">.</span>value+<span class="Constant">1</span><span class="Delimiter">);</span>  <span class="Comment">// skip refcount</span>
+  drop_from_type<span class="Delimiter">(</span>x<span class="Delimiter">,</span> <span class="Constant">&quot;shared&quot;</span><span class="Delimiter">);</span>
+<span class="Delimiter">}</span>
+<span class="Delimiter">:(before &quot;End Drop Address In canonize_type(r)&quot;)</span>
+if <span class="Delimiter">(</span>r<span class="Delimiter">.</span>properties<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">).</span>second<span class="Delimiter">-&gt;</span>value == <span class="Constant">&quot;shared&quot;</span><span class="Delimiter">)</span> <span class="Delimiter">{</span>
+  drop_from_type<span class="Delimiter">(</span>r<span class="Delimiter">,</span> <span class="Constant">&quot;shared&quot;</span><span class="Delimiter">);</span>
+<span class="Delimiter">}</span>
 
 <span class="Delimiter">:(scenarios run)</span>
 <span class="Delimiter">:(scenario new)</span>
 <span class="Comment"># call new two times with identical arguments; you should get back different results</span>
 recipe main [
-  <span class="Constant">1</span>:address:number/<span class="Special">raw &lt;- </span>new number:type
-  <span class="Constant">2</span>:address:number/<span class="Special">raw &lt;- </span>new number:type
-  <span class="Constant">3</span>:boolean/<span class="Special">raw &lt;- </span>equal <span class="Constant">1</span>:address:number/<span class="Special">raw</span><span class="Delimiter">,</span> <span class="Constant">2</span>:address:number/<span class="Special">raw</span>
+  <span class="Constant">1</span>:address:shared:number/<span class="Special">raw &lt;- </span>new number:type
+  <span class="Constant">2</span>:address:shared:number/<span class="Special">raw &lt;- </span>new number:type
+  <span class="Constant">3</span>:boolean/<span class="Special">raw &lt;- </span>equal <span class="Constant">1</span>:address:shared:number/<span class="Special">raw</span><span class="Delimiter">,</span> <span class="Constant">2</span>:address:shared:number/<span class="Special">raw</span>
 ]
 <span class="traceContains">+mem: storing 0 in location 3</span>
 
@@ -70,14 +115,33 @@ NEW<span class="Delimiter">,</span>
 put<span class="Delimiter">(</span>Recipe_ordinal<span class="Delimiter">,</span> <span class="Constant">&quot;new&quot;</span><span class="Delimiter">,</span> NEW<span class="Delimiter">);</span>
 <span class="Delimiter">:(before &quot;End Primitive Recipe Checks&quot;)</span>
 case NEW: <span class="Delimiter">{</span>
+  const recipe&amp; caller = get<span class="Delimiter">(</span>Recipe<span class="Delimiter">,</span> r<span class="Delimiter">);</span>
   if <span class="Delimiter">(</span>inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>empty<span class="Delimiter">()</span> || SIZE<span class="Delimiter">(</span>inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">)</span> &gt; <span class="Constant">2</span><span class="Delimiter">)</span> <span class="Delimiter">{</span>
-    raise_error &lt;&lt; maybe<span class="Delimiter">(</span>get<span class="Delimiter">(</span>Recipe<span class="Delimiter">,</span> r<span class="Delimiter">).</span>name<span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;'new' requires one or two ingredients, but got &quot;</span> &lt;&lt; inst<span class="Delimiter">.</span>to_string<span class="Delimiter">()</span> &lt;&lt; <span class="cSpecial">'\n'</span> &lt;&lt; end<span class="Delimiter">();</span>
+    raise_error &lt;&lt; maybe<span class="Delimiter">(</span>caller<span class="Delimiter">.</span>name<span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;'new' requires one or two ingredients, but got &quot;</span> &lt;&lt; inst<span class="Delimiter">.</span>to_string<span class="Delimiter">()</span> &lt;&lt; <span class="cSpecial">'\n'</span> &lt;&lt; end<span class="Delimiter">();</span>
     <span class="Identifier">break</span><span class="Delimiter">;</span>
   <span class="Delimiter">}</span>
   <span class="Comment">// End NEW Check Special-cases</span>
   reagent type = inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">);</span>
   if <span class="Delimiter">(</span>!is_mu_type_literal<span class="Delimiter">(</span>type<span class="Delimiter">))</span> <span class="Delimiter">{</span>
-    raise_error &lt;&lt; maybe<span class="Delimiter">(</span>get<span class="Delimiter">(</span>Recipe<span class="Delimiter">,</span> r<span class="Delimiter">).</span>name<span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;first ingredient of 'new' should be a type, but got &quot;</span> &lt;&lt; type<span class="Delimiter">.</span>original_string &lt;&lt; <span class="cSpecial">'\n'</span> &lt;&lt; end<span class="Delimiter">();</span>
+    raise_error &lt;&lt; maybe<span class="Delimiter">(</span>caller<span class="Delimiter">.</span>name<span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;first ingredient of 'new' should be a type, but got &quot;</span> &lt;&lt; type<span class="Delimiter">.</span>original_string &lt;&lt; <span class="cSpecial">'\n'</span> &lt;&lt; end<span class="Delimiter">();</span>
+    <span class="Identifier">break</span><span class="Delimiter">;</span>
+  <span class="Delimiter">}</span>
+  if <span class="Delimiter">(</span>inst<span class="Delimiter">.</span>products<span class="Delimiter">.</span>empty<span class="Delimiter">())</span> <span class="Delimiter">{</span>
+    raise_error &lt;&lt; maybe<span class="Delimiter">(</span>caller<span class="Delimiter">.</span>name<span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;result of 'new' should never be ignored</span><span class="cSpecial">\n</span><span class="Constant">&quot;</span> &lt;&lt; end<span class="Delimiter">();</span>
+    <span class="Identifier">break</span><span class="Delimiter">;</span>
+  <span class="Delimiter">}</span>
+  reagent product<span class="Delimiter">(</span>inst<span class="Delimiter">.</span>products<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">));</span>
+  canonize_type<span class="Delimiter">(</span>product<span class="Delimiter">);</span>
+  drop_from_type<span class="Delimiter">(</span>product<span class="Delimiter">,</span> <span class="Constant">&quot;address&quot;</span><span class="Delimiter">);</span>
+  drop_from_type<span class="Delimiter">(</span>product<span class="Delimiter">,</span> <span class="Constant">&quot;shared&quot;</span><span class="Delimiter">);</span>
+  if <span class="Delimiter">(</span>SIZE<span class="Delimiter">(</span>inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">)</span> &gt; <span class="Constant">1</span><span class="Delimiter">)</span> <span class="Delimiter">{</span>
+    <span class="Comment">// array allocation</span>
+    drop_from_type<span class="Delimiter">(</span>product<span class="Delimiter">,</span> <span class="Constant">&quot;array&quot;</span><span class="Delimiter">);</span>
+  <span class="Delimiter">}</span>
+  reagent expected_product<span class="Delimiter">(</span><span class="Constant">&quot;x:&quot;</span>+type<span class="Delimiter">.</span>name<span class="Delimiter">);</span>
+  <span class="Comment">// End Post-processing(expected_product) When Checking 'new'</span>
+  if <span class="Delimiter">(</span>!types_strictly_match<span class="Delimiter">(</span>product<span class="Delimiter">,</span> expected_product<span class="Delimiter">))</span> <span class="Delimiter">{</span>
+    raise_error &lt;&lt; maybe<span class="Delimiter">(</span>caller<span class="Delimiter">.</span>name<span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;product of 'new' has incorrect type: &quot;</span> &lt;&lt; inst<span class="Delimiter">.</span>to_string<span class="Delimiter">()</span> &lt;&lt; <span class="cSpecial">'\n'</span> &lt;&lt; end<span class="Delimiter">();</span>
     <span class="Identifier">break</span><span class="Delimiter">;</span>
   <span class="Delimiter">}</span>
   <span class="Identifier">break</span><span class="Delimiter">;</span>
@@ -122,6 +186,9 @@ case ALLOCATE: <span class="Delimiter">{</span>
     trace<span class="Delimiter">(</span><span class="Constant">9999</span><span class="Delimiter">,</span> <span class="Constant">&quot;mem&quot;</span><span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;array size is &quot;</span> &lt;&lt; ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">1</span><span class="Delimiter">).</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">)</span> &lt;&lt; end<span class="Delimiter">();</span>
     size = <span class="Comment">/*</span><span class="Comment">space for length</span><span class="Comment">*/</span><span class="Constant">1</span> + size*ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">1</span><span class="Delimiter">).</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">);</span>
   <span class="Delimiter">}</span>
+  <span class="Comment">// include space for refcount</span>
+  size++<span class="Delimiter">;</span>
+  trace<span class="Delimiter">(</span><span class="Constant">9999</span><span class="Delimiter">,</span> <span class="Constant">&quot;mem&quot;</span><span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;allocating size &quot;</span> &lt;&lt; size &lt;&lt; end<span class="Delimiter">();</span>
 <span class="CommentedCode">//?   Total_alloc += size;</span>
 <span class="CommentedCode">//?   Num_alloc++;</span>
   <span class="Comment">// compute the region of memory to return</span>
@@ -136,8 +203,10 @@ case ALLOCATE: <span class="Delimiter">{</span>
   for <span class="Delimiter">(</span>long long int address = result<span class="Delimiter">;</span> address &lt; result+size<span class="Delimiter">;</span> ++address<span class="Delimiter">)</span>
     put<span class="Delimiter">(</span>Memory<span class="Delimiter">,</span> address<span class="Delimiter">,</span> <span class="Constant">0</span><span class="Delimiter">);</span>
   <span class="Comment">// initialize array length</span>
-  if <span class="Delimiter">(</span>SIZE<span class="Delimiter">(</span>current_instruction<span class="Delimiter">().</span>ingredients<span class="Delimiter">)</span> &gt; <span class="Constant">1</span><span class="Delimiter">)</span>
-    put<span class="Delimiter">(</span>Memory<span class="Delimiter">,</span> result<span class="Delimiter">,</span> ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">1</span><span class="Delimiter">).</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">));</span>
+  if <span class="Delimiter">(</span>SIZE<span class="Delimiter">(</span>current_instruction<span class="Delimiter">().</span>ingredients<span class="Delimiter">)</span> &gt; <span class="Constant">1</span><span class="Delimiter">)</span> <span class="Delimiter">{</span>
+    trace<span class="Delimiter">(</span><span class="Constant">9999</span><span class="Delimiter">,</span> <span class="Constant">&quot;mem&quot;</span><span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;storing &quot;</span> &lt;&lt; ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">1</span><span class="Delimiter">).</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot; in location &quot;</span> &lt;&lt; result+<span class="Comment">/*</span><span class="Comment">skip refcount</span><span class="Comment">*/</span><span class="Constant">1</span> &lt;&lt; end<span class="Delimiter">();</span>
+    put<span class="Delimiter">(</span>Memory<span class="Delimiter">,</span> result+<span class="Comment">/*</span><span class="Comment">skip refcount</span><span class="Comment">*/</span><span class="Constant">1</span><span class="Delimiter">,</span> ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">1</span><span class="Delimiter">).</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">));</span>
+  <span class="Delimiter">}</span>
   <span class="Comment">// bump</span>
   Current_routine<span class="Delimiter">-&gt;</span>alloc += size<span class="Delimiter">;</span>
   <span class="Comment">// no support for reclaiming memory</span>
@@ -175,7 +244,7 @@ case NEW: <span class="Delimiter">{</span>
 void ensure_space<span class="Delimiter">(</span>long long int size<span class="Delimiter">)</span> <span class="Delimiter">{</span>
   if <span class="Delimiter">(</span>size &gt; Initial_memory_per_routine<span class="Delimiter">)</span> <span class="Delimiter">{</span>
     tb_shutdown<span class="Delimiter">();</span>
-    cerr &lt;&lt; <span class="Constant">&quot;can't allocate &quot;</span> &lt;&lt; size &lt;&lt; <span class="Constant">&quot; locations, that's too much.</span><span class="cSpecial">\n</span><span class="Constant">&quot;</span><span class="Delimiter">;</span>
+    cerr &lt;&lt; <span class="Constant">&quot;can't allocate &quot;</span> &lt;&lt; size &lt;&lt; <span class="Constant">&quot; locations, that's too much compared to &quot;</span> &lt;&lt; Initial_memory_per_routine &lt;&lt; <span class="Constant">&quot;.</span><span class="cSpecial">\n</span><span class="Constant">&quot;</span><span class="Delimiter">;</span>
     exit<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">);</span>
   <span class="Delimiter">}</span>
   if <span class="Delimiter">(</span>Current_routine<span class="Delimiter">-&gt;</span>alloc + size &gt; Current_routine<span class="Delimiter">-&gt;</span>alloc_max<span class="Delimiter">)</span> <span class="Delimiter">{</span>
@@ -191,73 +260,56 @@ void ensure_space<span class="Delimiter">(</span>long long int size<span class="
 <span class="Special">% Memory_allocated_until = 10;</span>
 <span class="Special">% put(Memory, Memory_allocated_until, 1);</span>
 recipe main [
-  <span class="Constant">1</span>:address:number<span class="Special"> &lt;- </span>new number:type
-  <span class="Constant">2</span>:number<span class="Special"> &lt;- </span>copy *<span class="Constant">1</span>:address:number
+  <span class="Constant">1</span>:address:shared:number<span class="Special"> &lt;- </span>new number:type
+  <span class="Constant">2</span>:number<span class="Special"> &lt;- </span>copy *<span class="Constant">1</span>:address:shared:number
 ]
 <span class="traceContains">+mem: storing 0 in location 2</span>
 
 <span class="Delimiter">:(scenario new_array)</span>
 recipe main [
-  <span class="Constant">1</span>:address:array:number/<span class="Special">raw &lt;- </span>new number:type<span class="Delimiter">,</span> <span class="Constant">5</span>
-  <span class="Constant">2</span>:address:number/<span class="Special">raw &lt;- </span>new number:type
-  <span class="Constant">3</span>:number/<span class="Special">raw &lt;- </span>subtract <span class="Constant">2</span>:address:number/<span class="Special">raw</span><span class="Delimiter">,</span> <span class="Constant">1</span>:address:array:number/<span class="Special">raw</span>
+  <span class="Constant">1</span>:address:shared:array:number/<span class="Special">raw &lt;- </span>new number:type<span class="Delimiter">,</span> <span class="Constant">5</span>
+  <span class="Constant">2</span>:address:shared:number/<span class="Special">raw &lt;- </span>new number:type
+  <span class="Constant">3</span>:number/<span class="Special">raw &lt;- </span>subtract <span class="Constant">2</span>:address:shared:number/<span class="Special">raw</span><span class="Delimiter">,</span> <span class="Constant">1</span>:address:shared:array:number/<span class="Special">raw</span>
 ]
-<span class="traceContains">+run: 1:address:array:number/raw &lt;- new number:type, 5</span>
+<span class="traceContains">+run: 1:address:shared:array:number/raw &lt;- new number:type, 5</span>
 <span class="traceContains">+mem: array size is 5</span>
-<span class="Comment"># don't forget the extra location for array size</span>
-<span class="traceContains">+mem: storing 6 in location 3</span>
+<span class="Comment"># don't forget the extra location for array size, and the second extra location for the refcount</span>
+<span class="traceContains">+mem: storing 7 in location 3</span>
 
 <span class="Delimiter">:(scenario new_empty_array)</span>
 recipe main [
-  <span class="Constant">1</span>:address:array:number/<span class="Special">raw &lt;- </span>new number:type<span class="Delimiter">,</span> <span class="Constant">0</span>
-  <span class="Constant">2</span>:address:number/<span class="Special">raw &lt;- </span>new number:type
-  <span class="Constant">3</span>:number/<span class="Special">raw &lt;- </span>subtract <span class="Constant">2</span>:address:number/<span class="Special">raw</span><span class="Delimiter">,</span> <span class="Constant">1</span>:address:array:number/<span class="Special">raw</span>
+  <span class="Constant">1</span>:address:shared:array:number/<span class="Special">raw &lt;- </span>new number:type<span class="Delimiter">,</span> <span class="Constant">0</span>
+  <span class="Constant">2</span>:address:shared:number/<span class="Special">raw &lt;- </span>new number:type
+  <span class="Constant">3</span>:number/<span class="Special">raw &lt;- </span>subtract <span class="Constant">2</span>:address:shared:number/<span class="Special">raw</span><span class="Delimiter">,</span> <span class="Constant">1</span>:address:shared:array:number/<span class="Special">raw</span>
 ]
-<span class="traceContains">+run: 1:address:array:number/raw &lt;- new number:type, 0</span>
+<span class="traceContains">+run: 1:address:shared:array:number/raw &lt;- new number:type, 0</span>
 <span class="traceContains">+mem: array size is 0</span>
-<span class="traceContains">+mem: storing 1 in location 3</span>
-
-<span class="Comment">//: Make sure that each routine gets a different alloc to start.</span>
-<span class="Delimiter">:(scenario new_concurrent)</span>
-recipe f1 [
-  start-running f2:recipe
-  <span class="Constant">1</span>:address:number/<span class="Special">raw &lt;- </span>new number:type
-  <span class="Comment"># wait for f2 to complete</span>
-  <span class="Delimiter">{</span>
-    loop-unless <span class="Constant">4</span>:number/<span class="Special">raw</span>
-  <span class="Delimiter">}</span>
-]
-recipe f2 [
-  <span class="Constant">2</span>:address:number/<span class="Special">raw &lt;- </span>new number:type
-  <span class="Comment"># hack: assumes scheduler implementation</span>
-  <span class="Constant">3</span>:boolean/<span class="Special">raw &lt;- </span>equal <span class="Constant">1</span>:address:number/<span class="Special">raw</span><span class="Delimiter">,</span> <span class="Constant">2</span>:address:number/<span class="Special">raw</span>
-  <span class="Comment"># signal f2 complete</span>
-  <span class="Constant">4</span>:number/<span class="Special">raw &lt;- </span>copy <span class="Constant">1</span>
-]
-<span class="traceContains">+mem: storing 0 in location 3</span>
+<span class="Comment"># one location for array size, and one for the refcount</span>
+<span class="traceContains">+mem: storing 2 in location 3</span>
 
 <span class="Comment">//: If a routine runs out of its initial allocation, it should allocate more.</span>
 <span class="Delimiter">:(scenario new_overflow)</span>
-<span class="Special">% Initial_memory_per_routine = 2;</span>
+<span class="Special">% Initial_memory_per_routine = 3;  // barely enough room for point allocation below</span>
 recipe main [
-  <span class="Constant">1</span>:address:number/<span class="Special">raw &lt;- </span>new number:type
-  <span class="Constant">2</span>:address:point/<span class="Special">raw &lt;- </span>new point:type  <span class="Comment"># not enough room in initial page</span>
+  <span class="Constant">1</span>:address:shared:number/<span class="Special">raw &lt;- </span>new number:type
+  <span class="Constant">2</span>:address:shared:point/<span class="Special">raw &lt;- </span>new point:type  <span class="Comment"># not enough room in initial page</span>
 ]
-<span class="traceContains">+new: routine allocated memory from 1000 to 1002</span>
-<span class="traceContains">+new: routine allocated memory from 1002 to 1004</span>
+<span class="traceContains">+new: routine allocated memory from 1000 to 1003</span>
+<span class="traceContains">+new: routine allocated memory from 1003 to 1006</span>
 
-<span class="Comment">//: We also provide a way to return memory, and to reuse reclaimed memory.</span>
+<span class="SalientComment">//:: A way to return memory, and to reuse reclaimed memory.</span>
 <span class="Comment">//: todo: custodians, etc. Following malloc/free is a temporary hack.</span>
 
 <span class="Delimiter">:(scenario new_reclaim)</span>
 recipe main [
-  <span class="Constant">1</span>:address:number<span class="Special"> &lt;- </span>new number:type
-  abandon <span class="Constant">1</span>:address:number
-  <span class="Constant">2</span>:address:number<span class="Special"> &lt;- </span>new number:type  <span class="Comment"># must be same size as abandoned memory to reuse</span>
-  <span class="Constant">3</span>:boolean<span class="Special"> &lt;- </span>equal <span class="Constant">1</span>:address:number<span class="Delimiter">,</span> <span class="Constant">2</span>:address:number
+  <span class="Constant">1</span>:address:shared:number<span class="Special"> &lt;- </span>new number:type
+  <span class="Constant">2</span>:address:shared:number<span class="Special"> &lt;- </span>copy <span class="Constant">1</span>:address:shared:number  <span class="Comment"># because 1 will get reset during abandon below</span>
+  abandon <span class="Constant">1</span>:address:shared:number  <span class="Comment"># unsafe</span>
+  <span class="Constant">3</span>:address:shared:number<span class="Special"> &lt;- </span>new number:type  <span class="Comment"># must be same size as abandoned memory to reuse</span>
+  <span class="Constant">4</span>:boolean<span class="Special"> &lt;- </span>equal <span class="Constant">2</span>:address:shared:number<span class="Delimiter">,</span> <span class="Constant">3</span>:address:shared:number
 ]
 <span class="Comment"># both allocations should have returned the same address</span>
-<span class="traceContains">+mem: storing 1 in location 3</span>
+<span class="traceContains">+mem: storing 1 in location 4</span>
 
 <span class="Delimiter">:(before &quot;End Globals&quot;)</span>
 map&lt;long long int<span class="Delimiter">,</span> long long int&gt; Free_list<span class="Delimiter">;</span>
@@ -276,8 +328,8 @@ case ABANDON: <span class="Delimiter">{</span>
   <span class="Delimiter">}</span>
   reagent types = inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">);</span>
   canonize_type<span class="Delimiter">(</span>types<span class="Delimiter">);</span>
-  if <span class="Delimiter">(</span>!types<span class="Delimiter">.</span>type || types<span class="Delimiter">.</span>type<span class="Delimiter">-&gt;</span>value != get<span class="Delimiter">(</span>Type_ordinal<span class="Delimiter">,</span> <span class="Constant">&quot;address&quot;</span><span class="Delimiter">))</span> <span class="Delimiter">{</span>
-    raise_error &lt;&lt; maybe<span class="Delimiter">(</span>get<span class="Delimiter">(</span>Recipe<span class="Delimiter">,</span> r<span class="Delimiter">).</span>name<span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;first ingredient of 'abandon' should be an address, but got &quot;</span> &lt;&lt; inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">).</span>original_string &lt;&lt; <span class="cSpecial">'\n'</span> &lt;&lt; end<span class="Delimiter">();</span>
+  if <span class="Delimiter">(</span>!types<span class="Delimiter">.</span>type || types<span class="Delimiter">.</span>type<span class="Delimiter">-&gt;</span>value != get<span class="Delimiter">(</span>Type_ordinal<span class="Delimiter">,</span> <span class="Constant">&quot;address&quot;</span><span class="Delimiter">)</span> || types<span class="Delimiter">.</span>type<span class="Delimiter">-&gt;</span>right<span class="Delimiter">-&gt;</span>value != get<span class="Delimiter">(</span>Type_ordinal<span class="Delimiter">,</span> <span class="Constant">&quot;shared&quot;</span><span class="Delimiter">))</span> <span class="Delimiter">{</span>
+    raise_error &lt;&lt; maybe<span class="Delimiter">(</span>get<span class="Delimiter">(</span>Recipe<span class="Delimiter">,</span> r<span class="Delimiter">).</span>name<span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;first ingredient of 'abandon' should be an address:shared:___, but got &quot;</span> &lt;&lt; inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">).</span>original_string &lt;&lt; <span class="cSpecial">'\n'</span> &lt;&lt; end<span class="Delimiter">();</span>
     <span class="Identifier">break</span><span class="Delimiter">;</span>
   <span class="Delimiter">}</span>
   <span class="Identifier">break</span><span class="Delimiter">;</span>
@@ -285,18 +337,27 @@ case ABANDON: <span class="Delimiter">{</span>
 <span class="Delimiter">:(before &quot;End Primitive Recipe Implementations&quot;)</span>
 case ABANDON: <span class="Delimiter">{</span>
   long long int address = ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">).</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">);</span>
+  trace<span class="Delimiter">(</span><span class="Constant">9999</span><span class="Delimiter">,</span> <span class="Constant">&quot;abandon&quot;</span><span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;address to abandon is &quot;</span> &lt;&lt; address &lt;&lt; end<span class="Delimiter">();</span>
   reagent types = current_instruction<span class="Delimiter">().</span>ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">);</span>
+  trace<span class="Delimiter">(</span><span class="Constant">9999</span><span class="Delimiter">,</span> <span class="Constant">&quot;abandon&quot;</span><span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;value of ingredient is &quot;</span> &lt;&lt; types<span class="Delimiter">.</span>value &lt;&lt; end<span class="Delimiter">();</span>
   canonize<span class="Delimiter">(</span>types<span class="Delimiter">);</span>
   <span class="Comment">// lookup_memory without drop_one_lookup {</span>
-  types<span class="Delimiter">.</span>set_value<span class="Delimiter">(</span>get_or_insert<span class="Delimiter">(</span>Memory<span class="Delimiter">,</span> types<span class="Delimiter">.</span>value<span class="Delimiter">));</span>
-  drop_address_from_type<span class="Delimiter">(</span>types<span class="Delimiter">);</span>
+  trace<span class="Delimiter">(</span><span class="Constant">9999</span><span class="Delimiter">,</span> <span class="Constant">&quot;abandon&quot;</span><span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;value of ingredient after canonization is &quot;</span> &lt;&lt; types<span class="Delimiter">.</span>value &lt;&lt; end<span class="Delimiter">();</span>
+  long long int address_location = types<span class="Delimiter">.</span>value<span class="Delimiter">;</span>
+  types<span class="Delimiter">.</span>set_value<span class="Delimiter">(</span>get_or_insert<span class="Delimiter">(</span>Memory<span class="Delimiter">,</span> types<span class="Delimiter">.</span>value<span class="Delimiter">)</span>+<span class="Comment">/*</span><span class="Comment">skip refcount</span><span class="Comment">*/</span><span class="Constant">1</span><span class="Delimiter">);</span>
+  drop_from_type<span class="Delimiter">(</span>types<span class="Delimiter">,</span> <span class="Constant">&quot;address&quot;</span><span class="Delimiter">);</span>
+  drop_from_type<span class="Delimiter">(</span>types<span class="Delimiter">,</span> <span class="Constant">&quot;shared&quot;</span><span class="Delimiter">);</span>
   <span class="Comment">// }</span>
-  abandon<span class="Delimiter">(</span>address<span class="Delimiter">,</span> size_of<span class="Delimiter">(</span>types<span class="Delimiter">));</span>
+  abandon<span class="Delimiter">(</span>address<span class="Delimiter">,</span> size_of<span class="Delimiter">(</span>types<span class="Delimiter">)</span>+<span class="Comment">/*</span><span class="Comment">refcount</span><span class="Comment">*/</span><span class="Constant">1</span><span class="Delimiter">);</span>
+  <span class="Comment">// clear the address</span>
+  trace<span class="Delimiter">(</span><span class="Constant">9999</span><span class="Delimiter">,</span> <span class="Constant">&quot;mem&quot;</span><span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;resetting location &quot;</span> &lt;&lt; address_location &lt;&lt; end<span class="Delimiter">();</span>
+  Memory[address_location] = <span class="Constant">0</span><span class="Delimiter">;</span>
   <span class="Identifier">break</span><span class="Delimiter">;</span>
 <span class="Delimiter">}</span>
 
 <span class="Delimiter">:(code)</span>
 void abandon<span class="Delimiter">(</span>long long int address<span class="Delimiter">,</span> long long int size<span class="Delimiter">)</span> <span class="Delimiter">{</span>
+  trace<span class="Delimiter">(</span><span class="Constant">9999</span><span class="Delimiter">,</span> <span class="Constant">&quot;abandon&quot;</span><span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;saving in free-list of size &quot;</span> &lt;&lt; size &lt;&lt; end<span class="Delimiter">();</span>
 <span class="CommentedCode">//?   Total_free += size;</span>
 <span class="CommentedCode">//?   Num_free++;</span>
 <span class="CommentedCode">//?   cerr &lt;&lt; &quot;abandon: &quot; &lt;&lt; size &lt;&lt; '\n';</span>
@@ -310,6 +371,7 @@ void abandon<span class="Delimiter">(</span>long long int address<span class="De
 
 <span class="Delimiter">:(before &quot;ensure_space(size)&quot; following &quot;case ALLOCATE&quot;)</span>
 if <span class="Delimiter">(</span>Free_list[size]<span class="Delimiter">)</span> <span class="Delimiter">{</span>
+  trace<span class="Delimiter">(</span><span class="Constant">9999</span><span class="Delimiter">,</span> <span class="Constant">&quot;abandon&quot;</span><span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;picking up space from free-list of size &quot;</span> &lt;&lt; size &lt;&lt; end<span class="Delimiter">();</span>
   long long int result = Free_list[size]<span class="Delimiter">;</span>
   Free_list[size] = get_or_insert<span class="Delimiter">(</span>Memory<span class="Delimiter">,</span> result<span class="Delimiter">);</span>
   for <span class="Delimiter">(</span>long long int curr = result+<span class="Constant">1</span><span class="Delimiter">;</span> curr &lt; result+size<span class="Delimiter">;</span> ++curr<span class="Delimiter">)</span> <span class="Delimiter">{</span>
@@ -319,7 +381,7 @@ if <span class="Delimiter">(</span>Free_list[size]<span class="Delimiter">)</spa
     <span class="Delimiter">}</span>
   <span class="Delimiter">}</span>
   if <span class="Delimiter">(</span>SIZE<span class="Delimiter">(</span>current_instruction<span class="Delimiter">().</span>ingredients<span class="Delimiter">)</span> &gt; <span class="Constant">1</span><span class="Delimiter">)</span>
-    put<span class="Delimiter">(</span>Memory<span class="Delimiter">,</span> result<span class="Delimiter">,</span> ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">1</span><span class="Delimiter">).</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">));</span>
+    put<span class="Delimiter">(</span>Memory<span class="Delimiter">,</span> result+<span class="Comment">/*</span><span class="Comment">skip refcount</span><span class="Comment">*/</span><span class="Constant">1</span><span class="Delimiter">,</span> ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">1</span><span class="Delimiter">).</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">));</span>
   else
     put<span class="Delimiter">(</span>Memory<span class="Delimiter">,</span> result<span class="Delimiter">,</span> <span class="Constant">0</span><span class="Delimiter">);</span>
   products<span class="Delimiter">.</span>resize<span class="Delimiter">(</span><span class="Constant">1</span><span class="Delimiter">);</span>
@@ -329,39 +391,113 @@ if <span class="Delimiter">(</span>Free_list[size]<span class="Delimiter">)</spa
 
 <span class="Delimiter">:(scenario new_differing_size_no_reclaim)</span>
 recipe main [
-  <span class="Constant">1</span>:address:number<span class="Special"> &lt;- </span>new number:type
-  abandon <span class="Constant">1</span>:address:number
-  <span class="Constant">2</span>:address:number<span class="Special"> &lt;- </span>new number:type<span class="Delimiter">,</span> <span class="Constant">2</span>  <span class="Comment"># different size</span>
-  <span class="Constant">3</span>:boolean<span class="Special"> &lt;- </span>equal <span class="Constant">1</span>:address:number<span class="Delimiter">,</span> <span class="Constant">2</span>:address:number
+  <span class="Constant">1</span>:address:shared:number<span class="Special"> &lt;- </span>new number:type
+  <span class="Constant">2</span>:address:shared:number<span class="Special"> &lt;- </span>copy <span class="Constant">1</span>:address:shared:number
+  abandon <span class="Constant">1</span>:address:shared:number
+  <span class="Constant">3</span>:address:shared:array:number<span class="Special"> &lt;- </span>new number:type<span class="Delimiter">,</span> <span class="Constant">2</span>  <span class="Comment"># different size</span>
+  <span class="Constant">4</span>:boolean<span class="Special"> &lt;- </span>equal <span class="Constant">2</span>:address:shared:number<span class="Delimiter">,</span> <span class="Constant">3</span>:address:shared:array:number
 ]
 <span class="Comment"># no reuse</span>
-<span class="traceContains">+mem: storing 0 in location 3</span>
+<span class="traceContains">+mem: storing 0 in location 4</span>
 
 <span class="Delimiter">:(scenario new_reclaim_array)</span>
 recipe main [
-  <span class="Constant">1</span>:address:array:number<span class="Special"> &lt;- </span>new number:type<span class="Delimiter">,</span> <span class="Constant">2</span>
-  abandon <span class="Constant">1</span>:address:array:number
-  <span class="Constant">2</span>:address:array:number<span class="Special"> &lt;- </span>new number:type<span class="Delimiter">,</span> <span class="Constant">2</span>
-  <span class="Constant">3</span>:boolean<span class="Special"> &lt;- </span>equal <span class="Constant">1</span>:address:array:number<span class="Delimiter">,</span> <span class="Constant">2</span>:address:array:number
+  <span class="Constant">1</span>:address:shared:array:number<span class="Special"> &lt;- </span>new number:type<span class="Delimiter">,</span> <span class="Constant">2</span>
+  <span class="Constant">2</span>:address:shared:array:number<span class="Special"> &lt;- </span>copy <span class="Constant">1</span>:address:shared:array:number
+  abandon <span class="Constant">1</span>:address:shared:array:number  <span class="Comment"># unsafe</span>
+  <span class="Constant">3</span>:address:shared:array:number<span class="Special"> &lt;- </span>new number:type<span class="Delimiter">,</span> <span class="Constant">2</span>
+  <span class="Constant">4</span>:boolean<span class="Special"> &lt;- </span>equal <span class="Constant">2</span>:address:shared:array:number<span class="Delimiter">,</span> <span class="Constant">3</span>:address:shared:array:number
 ]
 <span class="Comment"># reuse</span>
-<span class="traceContains">+mem: storing 1 in location 3</span>
+<span class="traceContains">+mem: storing 1 in location 4</span>
 
-<span class="SalientComment">//:: Next, extend 'new' to handle a unicode string literal argument.</span>
+<span class="Delimiter">:(scenario reset_on_abandon)</span>
+recipe main [
+  <span class="Constant">1</span>:address:shared:number<span class="Special"> &lt;- </span>new number:type
+  abandon <span class="Constant">1</span>:address:shared:number
+]
+<span class="Comment"># reuse</span>
+<span class="traceContains">+run: abandon 1:address:shared:number</span>
+<span class="traceContains">+mem: resetting location 1</span>
+
+<span class="SalientComment">//:: Manage refcounts when copying addresses.</span>
+
+<span class="Delimiter">:(scenario refcounts)</span>
+recipe main [
+  <span class="Constant">1</span>:address:shared:number<span class="Special"> &lt;- </span>copy <span class="Constant">1000</span>/unsafe
+  <span class="Constant">2</span>:address:shared:number<span class="Special"> &lt;- </span>copy <span class="Constant">1</span>:address:shared:number
+  <span class="Constant">1</span>:address:shared:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
+  <span class="Constant">2</span>:address:shared:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
+]
+<span class="traceContains">+run: 1:address:shared:number &lt;- copy 1000/unsafe</span>
+<span class="traceContains">+mem: incrementing refcount of 1000: 0 -&gt; 1</span>
+<span class="traceContains">+run: 2:address:shared:number &lt;- copy 1:address:shared:number</span>
+<span class="traceContains">+mem: incrementing refcount of 1000: 1 -&gt; 2</span>
+<span class="traceContains">+run: 1:address:shared:number &lt;- copy 0</span>
+<span class="traceContains">+mem: decrementing refcount of 1000: 2 -&gt; 1</span>
+<span class="traceContains">+run: 2:address:shared:number &lt;- copy 0</span>
+<span class="traceContains">+mem: decrementing refcount of 1000: 1 -&gt; 0</span>
+<span class="Comment"># the /unsafe corrupts memory but fortunately we won't be running any more 'new' in this scenario</span>
+<span class="traceContains">+mem: automatically abandoning 1000</span>
+
+<span class="Delimiter">:(before &quot;End write_memory(reagent x, long long int base) Special-cases&quot;)</span>
+if <span class="Delimiter">(</span>x<span class="Delimiter">.</span>type<span class="Delimiter">-&gt;</span>value == get<span class="Delimiter">(</span>Type_ordinal<span class="Delimiter">,</span> <span class="Constant">&quot;address&quot;</span><span class="Delimiter">)</span>
+    &amp;&amp; x<span class="Delimiter">.</span>type<span class="Delimiter">-&gt;</span>right
+    &amp;&amp; x<span class="Delimiter">.</span>type<span class="Delimiter">-&gt;</span>right<span class="Delimiter">-&gt;</span>value == get<span class="Delimiter">(</span>Type_ordinal<span class="Delimiter">,</span> <span class="Constant">&quot;shared&quot;</span><span class="Delimiter">))</span> <span class="Delimiter">{</span>
+  <span class="Comment">// compute old address of x, as well as new address we want to write in</span>
+  long long int old_address = get_or_insert<span class="Delimiter">(</span>Memory<span class="Delimiter">,</span> x<span class="Delimiter">.</span>value<span class="Delimiter">);</span>
+  assert<span class="Delimiter">(</span>scalar<span class="Delimiter">(</span>data<span class="Delimiter">));</span>
+  long long int new_address = data<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">);</span>
+  <span class="Comment">// decrement refcount of old address</span>
+  if <span class="Delimiter">(</span>old_address<span class="Delimiter">)</span> <span class="Delimiter">{</span>
+    long long int old_refcount = get_or_insert<span class="Delimiter">(</span>Memory<span class="Delimiter">,</span> old_address<span class="Delimiter">);</span>
+<span class="CommentedCode">//?     cerr &lt;&lt; old_refcount &lt;&lt; '\n';</span>
+<span class="CommentedCode">//?     assert(old_refcount &gt; 0);</span>
+    trace<span class="Delimiter">(</span><span class="Constant">9999</span><span class="Delimiter">,</span> <span class="Constant">&quot;mem&quot;</span><span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;decrementing refcount of &quot;</span> &lt;&lt; old_address &lt;&lt; <span class="Constant">&quot;: &quot;</span> &lt;&lt; old_refcount &lt;&lt; <span class="Constant">&quot; -&gt; &quot;</span> &lt;&lt; <span class="Delimiter">(</span>old_refcount-<span class="Constant">1</span><span class="Delimiter">)</span> &lt;&lt; end<span class="Delimiter">();</span>
+    put<span class="Delimiter">(</span>Memory<span class="Delimiter">,</span> old_address<span class="Delimiter">,</span> old_refcount-<span class="Constant">1</span><span class="Delimiter">);</span>
+  <span class="Delimiter">}</span>
+  <span class="Comment">// perform the write</span>
+  trace<span class="Delimiter">(</span><span class="Constant">9999</span><span class="Delimiter">,</span> <span class="Constant">&quot;mem&quot;</span><span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;storing &quot;</span> &lt;&lt; no_scientific<span class="Delimiter">(</span>data<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">))</span> &lt;&lt; <span class="Constant">&quot; in location &quot;</span> &lt;&lt; base &lt;&lt; end<span class="Delimiter">();</span>
+  put<span class="Delimiter">(</span>Memory<span class="Delimiter">,</span> base<span class="Delimiter">,</span> new_address<span class="Delimiter">);</span>
+  <span class="Comment">// increment refcount of new address</span>
+  if <span class="Delimiter">(</span>new_address<span class="Delimiter">)</span> <span class="Delimiter">{</span>
+    long long int new_refcount = get_or_insert<span class="Delimiter">(</span>Memory<span class="Delimiter">,</span> new_address<span class="Delimiter">);</span>
+<span class="CommentedCode">//?       assert(new_refcount &gt;= 0);  // == 0 only when new_address == old_address</span>
+    trace<span class="Delimiter">(</span><span class="Constant">9999</span><span class="Delimiter">,</span> <span class="Constant">&quot;mem&quot;</span><span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;incrementing refcount of &quot;</span> &lt;&lt; new_address &lt;&lt; <span class="Constant">&quot;: &quot;</span> &lt;&lt; new_refcount &lt;&lt; <span class="Constant">&quot; -&gt; &quot;</span> &lt;&lt; <span class="Delimiter">(</span>new_refcount+<span class="Constant">1</span><span class="Delimiter">)</span> &lt;&lt; end<span class="Delimiter">();</span>
+    put<span class="Delimiter">(</span>Memory<span class="Delimiter">,</span> new_address<span class="Delimiter">,</span> new_refcount+<span class="Constant">1</span><span class="Delimiter">);</span>
+  <span class="Delimiter">}</span>
+  <span class="Comment">// abandon old address if necessary</span>
+  <span class="Comment">// do this after all refcount updates are done just in case old and new are identical</span>
+  <span class="Comment">// </span><span class="Todo">TODO</span><span class="Comment">: doesn't work yet</span>
+  assert<span class="Delimiter">(</span>get_or_insert<span class="Delimiter">(</span>Memory<span class="Delimiter">,</span> old_address<span class="Delimiter">)</span> &gt;= <span class="Constant">0</span><span class="Delimiter">);</span>
+  if <span class="Delimiter">(</span>old_address &amp;&amp; get_or_insert<span class="Delimiter">(</span>Memory<span class="Delimiter">,</span> old_address<span class="Delimiter">)</span> == <span class="Constant">0</span><span class="Delimiter">)</span> <span class="Delimiter">{</span>
+    <span class="Comment">// lookup_memory without drop_one_lookup {</span>
+    trace<span class="Delimiter">(</span><span class="Constant">9999</span><span class="Delimiter">,</span> <span class="Constant">&quot;mem&quot;</span><span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;automatically abandoning &quot;</span> &lt;&lt; old_address &lt;&lt; end<span class="Delimiter">();</span>
+    trace<span class="Delimiter">(</span><span class="Constant">9999</span><span class="Delimiter">,</span> <span class="Constant">&quot;mem&quot;</span><span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;computing size to abandon at &quot;</span> &lt;&lt; x<span class="Delimiter">.</span>value &lt;&lt; end<span class="Delimiter">();</span>
+    x<span class="Delimiter">.</span>set_value<span class="Delimiter">(</span>get_or_insert<span class="Delimiter">(</span>Memory<span class="Delimiter">,</span> x<span class="Delimiter">.</span>value<span class="Delimiter">)</span>+<span class="Comment">/*</span><span class="Comment">skip refcount</span><span class="Comment">*/</span><span class="Constant">1</span><span class="Delimiter">);</span>
+    drop_from_type<span class="Delimiter">(</span>x<span class="Delimiter">,</span> <span class="Constant">&quot;address&quot;</span><span class="Delimiter">);</span>
+    drop_from_type<span class="Delimiter">(</span>x<span class="Delimiter">,</span> <span class="Constant">&quot;shared&quot;</span><span class="Delimiter">);</span>
+    <span class="Comment">// }</span>
+    abandon<span class="Delimiter">(</span>old_address<span class="Delimiter">,</span> size_of<span class="Delimiter">(</span>x<span class="Delimiter">)</span>+<span class="Comment">/*</span><span class="Comment">refcount</span><span class="Comment">*/</span><span class="Constant">1</span><span class="Delimiter">);</span>
+  <span class="Delimiter">}</span>
+  <span class="Identifier">return</span><span class="Delimiter">;</span>
+<span class="Delimiter">}</span>
+
+<span class="SalientComment">//:: Extend 'new' to handle a unicode string literal argument.</span>
 
 <span class="Delimiter">:(scenario new_string)</span>
 recipe main [
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new [abc def]
-  <span class="Constant">2</span>:character<span class="Special"> &lt;- </span>index *<span class="Constant">1</span>:address:array:character<span class="Delimiter">,</span> <span class="Constant">5</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new [abc def]
+  <span class="Constant">2</span>:character<span class="Special"> &lt;- </span>index *<span class="Constant">1</span>:address:shared:array:character<span class="Delimiter">,</span> <span class="Constant">5</span>
 ]
 <span class="Comment"># number code for 'e'</span>
 <span class="traceContains">+mem: storing 101 in location 2</span>
 
 <span class="Delimiter">:(scenario new_string_handles_unicode)</span>
 recipe main [
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new [a«c]
-  <span class="Constant">2</span>:number<span class="Special"> &lt;- </span>length *<span class="Constant">1</span>:address:array:character
-  <span class="Constant">3</span>:character<span class="Special"> &lt;- </span>index *<span class="Constant">1</span>:address:array:character<span class="Delimiter">,</span> <span class="Constant">1</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new [a«c]
+  <span class="Constant">2</span>:number<span class="Special"> &lt;- </span>length *<span class="Constant">1</span>:address:shared:array:character
+  <span class="Constant">3</span>:character<span class="Special"> &lt;- </span>index *<span class="Constant">1</span>:address:shared:array:character<span class="Delimiter">,</span> <span class="Constant">1</span>
 ]
 <span class="traceContains">+mem: storing 3 in location 2</span>
 <span class="Comment"># unicode for '«'</span>
@@ -387,6 +523,9 @@ long long int new_mu_string<span class="Delimiter">(</span>const string&amp; con
   ensure_space<span class="Delimiter">(</span>string_length+<span class="Constant">1</span><span class="Delimiter">);</span>  <span class="Comment">// don't forget the extra location for array size</span>
   <span class="Comment">// initialize string</span>
   long long int result = Current_routine<span class="Delimiter">-&gt;</span>alloc<span class="Delimiter">;</span>
+  <span class="Comment">// initialize refcount</span>
+  put<span class="Delimiter">(</span>Memory<span class="Delimiter">,</span> Current_routine<span class="Delimiter">-&gt;</span>alloc++<span class="Delimiter">,</span> <span class="Constant">0</span><span class="Delimiter">);</span>
+  <span class="Comment">// store length</span>
   put<span class="Delimiter">(</span>Memory<span class="Delimiter">,</span> Current_routine<span class="Delimiter">-&gt;</span>alloc++<span class="Delimiter">,</span> string_length<span class="Delimiter">);</span>
   long long int curr = <span class="Constant">0</span><span class="Delimiter">;</span>
   const char* raw_contents = contents<span class="Delimiter">.</span>c_str<span class="Delimiter">();</span>
@@ -402,45 +541,41 @@ long long int new_mu_string<span class="Delimiter">(</span>const string&amp; con
   <span class="Identifier">return</span> result<span class="Delimiter">;</span>
 <span class="Delimiter">}</span>
 
-<span class="Comment">//: pass in commandline args as ingredients to main</span>
-<span class="Comment">//: todo: test this</span>
-
-<span class="Delimiter">:(after &quot;Update main_routine&quot;)</span>
-Current_routine = main_routine<span class="Delimiter">;</span>
-for <span class="Delimiter">(</span>long long int i = <span class="Constant">1</span><span class="Delimiter">;</span> i &lt; argc<span class="Delimiter">;</span> ++i<span class="Delimiter">)</span> <span class="Delimiter">{</span>
-  vector&lt;double&gt; arg<span class="Delimiter">;</span>
-  arg<span class="Delimiter">.</span>push_back<span class="Delimiter">(</span>new_mu_string<span class="Delimiter">(</span>argv[i]<span class="Delimiter">));</span>
-  current_call<span class="Delimiter">().</span>ingredient_atoms<span class="Delimiter">.</span>push_back<span class="Delimiter">(</span>arg<span class="Delimiter">);</span>
-<span class="Delimiter">}</span>
-
 <span class="Comment">//: stash recognizes strings</span>
 
 <span class="Delimiter">:(scenario stash_string)</span>
 recipe main [
-  x:address:array:character<span class="Special"> &lt;- </span>new [abc]
-  stash [foo:]<span class="Delimiter">,</span> x:address:array:character
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new [abc]
+  stash [foo:]<span class="Delimiter">,</span> <span class="Constant">1</span>:address:shared:array:character
 ]
 <span class="traceContains">+app: foo: abc</span>
 
 <span class="Delimiter">:(before &quot;End print Special-cases(reagent r, data)&quot;)</span>
 if <span class="Delimiter">(</span>is_mu_string<span class="Delimiter">(</span>r<span class="Delimiter">))</span> <span class="Delimiter">{</span>
   assert<span class="Delimiter">(</span>scalar<span class="Delimiter">(</span>data<span class="Delimiter">));</span>
-  <span class="Identifier">return</span> read_mu_string<span class="Delimiter">(</span>data<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">));</span>
+  <span class="Identifier">return</span> read_mu_string<span class="Delimiter">(</span>data<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">))</span>+<span class="Constant">' '</span><span class="Delimiter">;</span>
 <span class="Delimiter">}</span>
 
 <span class="Delimiter">:(scenario unicode_string)</span>
 recipe main [
-  x:address:array:character<span class="Special"> &lt;- </span>new [♠]
-  stash [foo:]<span class="Delimiter">,</span> x:address:array:character
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new [♠]
+  stash [foo:]<span class="Delimiter">,</span> <span class="Constant">1</span>:address:shared:array:character
 ]
 <span class="traceContains">+app: foo: ♠</span>
 
+<span class="Delimiter">:(scenario stash_space_after_string)</span>
+recipe main [
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new [abc]
+  stash <span class="Constant">1</span>:address:shared:array:character<span class="Delimiter">,</span> [foo]
+]
+<span class="traceContains">+app: abc foo</span>
+
 <span class="Comment">//: Allocate more to routine when initializing a literal string</span>
 <span class="Delimiter">:(scenario new_string_overflow)</span>
 <span class="Special">% Initial_memory_per_routine = 2;</span>
 recipe main [
-  <span class="Constant">1</span>:address:number/<span class="Special">raw &lt;- </span>new number:type
-  <span class="Constant">2</span>:address:array:character/<span class="Special">raw &lt;- </span>new [a]  <span class="Comment"># not enough room in initial page, if you take the array size into account</span>
+  <span class="Constant">1</span>:address:shared:number/<span class="Special">raw &lt;- </span>new number:type
+  <span class="Constant">2</span>:address:shared:array:character/<span class="Special">raw &lt;- </span>new [a]  <span class="Comment"># not enough room in initial page, if you take the array size into account</span>
 ]
 <span class="traceContains">+new: routine allocated memory from 1000 to 1002</span>
 <span class="traceContains">+new: routine allocated memory from 1002 to 1004</span>
@@ -460,6 +595,8 @@ long long int unicode_length<span class="Delimiter">(</span>const string&amp; s<
 <span class="Delimiter">}</span>
 
 string read_mu_string<span class="Delimiter">(</span>long long int address<span class="Delimiter">)</span> <span class="Delimiter">{</span>
+  if <span class="Delimiter">(</span>address == <span class="Constant">0</span><span class="Delimiter">)</span> <span class="Identifier">return</span> <span class="Constant">&quot;&quot;</span><span class="Delimiter">;</span>
+  address++<span class="Delimiter">;</span>  <span class="Comment">// skip refcount</span>
   long long int size = get_or_insert<span class="Delimiter">(</span>Memory<span class="Delimiter">,</span> address<span class="Delimiter">);</span>
   if <span class="Delimiter">(</span>size == <span class="Constant">0</span><span class="Delimiter">)</span> <span class="Identifier">return</span> <span class="Constant">&quot;&quot;</span><span class="Delimiter">;</span>
   ostringstream tmp<span class="Delimiter">;</span>
diff --git a/html/042name.cc.html b/html/042name.cc.html
index 08b875ef..e6f0b296 100644
--- a/html/042name.cc.html
+++ b/html/042name.cc.html
@@ -13,8 +13,8 @@
 pre { white-space: pre-wrap; font-family: monospace; color: #eeeeee; background-color: #080808; }
 body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 * { font-size: 1.05em; }
-.traceContains { color: #008000; }
 .traceAbsent { color: #c00000; }
+.traceContains { color: #008000; }
 .Identifier { color: #804000; }
 .cSpecial { color: #008000; }
 .Constant { color: #00a0a0; }
@@ -54,7 +54,7 @@ recipe main [
 <span class="traceContains">+error: main: use before set: y</span>
 <span class="Comment"># todo: detect conditional defines</span>
 
-<span class="Delimiter">:(before &quot;End Instruction Modifying Transforms&quot;)</span>
+<span class="Delimiter">:(after &quot;End Type Modifying Transforms&quot;)</span>
 Transform<span class="Delimiter">.</span>push_back<span class="Delimiter">(</span>transform_names<span class="Delimiter">);</span>  <span class="Comment">// idempotent</span>
 
 <span class="Delimiter">:(before &quot;End Globals&quot;)</span>
@@ -80,18 +80,20 @@ void transform_names<span class="Delimiter">(</span>const recipe_ordinal r<span
     <span class="Comment">// End transform_names(inst) Special-cases</span>
     <span class="Comment">// map names to addresses</span>
     for <span class="Delimiter">(</span>long long int in = <span class="Constant">0</span><span class="Delimiter">;</span> in &lt; SIZE<span class="Delimiter">(</span>inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">);</span> ++in<span class="Delimiter">)</span> <span class="Delimiter">{</span>
+      if <span class="Delimiter">(</span>disqualified<span class="Delimiter">(</span>inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span>in<span class="Delimiter">),</span> inst<span class="Delimiter">,</span> caller<span class="Delimiter">.</span>name<span class="Delimiter">))</span> <span class="Identifier">continue</span><span class="Delimiter">;</span>
       if <span class="Delimiter">(</span>is_numeric_location<span class="Delimiter">(</span>inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span>in<span class="Delimiter">)))</span> numeric_locations_used = <span class="Constant">true</span><span class="Delimiter">;</span>
       if <span class="Delimiter">(</span>is_named_location<span class="Delimiter">(</span>inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span>in<span class="Delimiter">)))</span> names_used = <span class="Constant">true</span><span class="Delimiter">;</span>
-      if <span class="Delimiter">(</span>disqualified<span class="Delimiter">(</span>inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span>in<span class="Delimiter">),</span> inst<span class="Delimiter">,</span> caller<span class="Delimiter">.</span>name<span class="Delimiter">))</span> <span class="Identifier">continue</span><span class="Delimiter">;</span>
+      if <span class="Delimiter">(</span>is_integer<span class="Delimiter">(</span>inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span>in<span class="Delimiter">).</span>name<span class="Delimiter">))</span> <span class="Identifier">continue</span><span class="Delimiter">;</span>
       if <span class="Delimiter">(</span>!already_transformed<span class="Delimiter">(</span>inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span>in<span class="Delimiter">),</span> names<span class="Delimiter">))</span> <span class="Delimiter">{</span>
         raise_error &lt;&lt; maybe<span class="Delimiter">(</span>caller<span class="Delimiter">.</span>name<span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;use before set: &quot;</span> &lt;&lt; inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span>in<span class="Delimiter">).</span>name &lt;&lt; <span class="cSpecial">'\n'</span> &lt;&lt; end<span class="Delimiter">();</span>
       <span class="Delimiter">}</span>
       inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span>in<span class="Delimiter">).</span>set_value<span class="Delimiter">(</span>lookup_name<span class="Delimiter">(</span>inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span>in<span class="Delimiter">),</span> r<span class="Delimiter">));</span>
     <span class="Delimiter">}</span>
     for <span class="Delimiter">(</span>long long int out = <span class="Constant">0</span><span class="Delimiter">;</span> out &lt; SIZE<span class="Delimiter">(</span>inst<span class="Delimiter">.</span>products<span class="Delimiter">);</span> ++out<span class="Delimiter">)</span> <span class="Delimiter">{</span>
+      if <span class="Delimiter">(</span>disqualified<span class="Delimiter">(</span>inst<span class="Delimiter">.</span>products<span class="Delimiter">.</span>at<span class="Delimiter">(</span>out<span class="Delimiter">),</span> inst<span class="Delimiter">,</span> caller<span class="Delimiter">.</span>name<span class="Delimiter">))</span> <span class="Identifier">continue</span><span class="Delimiter">;</span>
       if <span class="Delimiter">(</span>is_numeric_location<span class="Delimiter">(</span>inst<span class="Delimiter">.</span>products<span class="Delimiter">.</span>at<span class="Delimiter">(</span>out<span class="Delimiter">)))</span> numeric_locations_used = <span class="Constant">true</span><span class="Delimiter">;</span>
       if <span class="Delimiter">(</span>is_named_location<span class="Delimiter">(</span>inst<span class="Delimiter">.</span>products<span class="Delimiter">.</span>at<span class="Delimiter">(</span>out<span class="Delimiter">)))</span> names_used = <span class="Constant">true</span><span class="Delimiter">;</span>
-      if <span class="Delimiter">(</span>disqualified<span class="Delimiter">(</span>inst<span class="Delimiter">.</span>products<span class="Delimiter">.</span>at<span class="Delimiter">(</span>out<span class="Delimiter">),</span> inst<span class="Delimiter">,</span> caller<span class="Delimiter">.</span>name<span class="Delimiter">))</span> <span class="Identifier">continue</span><span class="Delimiter">;</span>
+      if <span class="Delimiter">(</span>is_integer<span class="Delimiter">(</span>inst<span class="Delimiter">.</span>products<span class="Delimiter">.</span>at<span class="Delimiter">(</span>out<span class="Delimiter">).</span>name<span class="Delimiter">))</span> <span class="Identifier">continue</span><span class="Delimiter">;</span>
       if <span class="Delimiter">(</span>names<span class="Delimiter">.</span>find<span class="Delimiter">(</span>inst<span class="Delimiter">.</span>products<span class="Delimiter">.</span>at<span class="Delimiter">(</span>out<span class="Delimiter">).</span>name<span class="Delimiter">)</span> == names<span class="Delimiter">.</span>end<span class="Delimiter">())</span> <span class="Delimiter">{</span>
         trace<span class="Delimiter">(</span><span class="Constant">9993</span><span class="Delimiter">,</span> <span class="Constant">&quot;name&quot;</span><span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;assign &quot;</span> &lt;&lt; inst<span class="Delimiter">.</span>products<span class="Delimiter">.</span>at<span class="Delimiter">(</span>out<span class="Delimiter">).</span>name &lt;&lt; <span class="Constant">&quot; &quot;</span> &lt;&lt; curr_idx &lt;&lt; end<span class="Delimiter">();</span>
         names[inst<span class="Delimiter">.</span>products<span class="Delimiter">.</span>at<span class="Delimiter">(</span>out<span class="Delimiter">).</span>name] = curr_idx<span class="Delimiter">;</span>
@@ -106,12 +108,12 @@ void transform_names<span class="Delimiter">(</span>const recipe_ordinal r<span
 
 bool disqualified<span class="Delimiter">(</span><span class="Comment">/*</span><span class="Comment">mutable</span><span class="Comment">*/</span> reagent&amp; x<span class="Delimiter">,</span> const instruction&amp; inst<span class="Delimiter">,</span> const string&amp; recipe_name<span class="Delimiter">)</span> <span class="Delimiter">{</span>
   if <span class="Delimiter">(</span>!x<span class="Delimiter">.</span>type<span class="Delimiter">)</span> <span class="Delimiter">{</span>
+    <span class="Comment">// End transform_names Exceptions</span>
     raise_error &lt;&lt; maybe<span class="Delimiter">(</span>recipe_name<span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;missing type for &quot;</span> &lt;&lt; x<span class="Delimiter">.</span>original_string &lt;&lt; <span class="Constant">&quot; in '&quot;</span> &lt;&lt; inst<span class="Delimiter">.</span>to_string<span class="Delimiter">()</span> &lt;&lt; <span class="Constant">&quot;'</span><span class="cSpecial">\n</span><span class="Constant">&quot;</span> &lt;&lt; end<span class="Delimiter">();</span>
     <span class="Identifier">return</span> <span class="Constant">true</span><span class="Delimiter">;</span>
   <span class="Delimiter">}</span>
   if <span class="Delimiter">(</span>is_raw<span class="Delimiter">(</span>x<span class="Delimiter">))</span> <span class="Identifier">return</span> <span class="Constant">true</span><span class="Delimiter">;</span>
   if <span class="Delimiter">(</span>is_literal<span class="Delimiter">(</span>x<span class="Delimiter">))</span> <span class="Identifier">return</span> <span class="Constant">true</span><span class="Delimiter">;</span>
-  if <span class="Delimiter">(</span>is_integer<span class="Delimiter">(</span>x<span class="Delimiter">.</span>name<span class="Delimiter">))</span> <span class="Identifier">return</span> <span class="Constant">true</span><span class="Delimiter">;</span>
   <span class="Comment">// End Disqualified Reagents</span>
   if <span class="Delimiter">(</span>x<span class="Delimiter">.</span>initialized<span class="Delimiter">)</span> <span class="Identifier">return</span> <span class="Constant">true</span><span class="Delimiter">;</span>
   <span class="Identifier">return</span> <span class="Constant">false</span><span class="Delimiter">;</span>
@@ -126,8 +128,10 @@ long long int lookup_name<span class="Delimiter">(</span>const reagent&amp; r<sp
 <span class="Delimiter">}</span>
 
 type_ordinal skip_addresses<span class="Delimiter">(</span>type_tree* type<span class="Delimiter">,</span> const string&amp; recipe_name<span class="Delimiter">)</span> <span class="Delimiter">{</span>
+  type_ordinal address = get<span class="Delimiter">(</span>Type_ordinal<span class="Delimiter">,</span> <span class="Constant">&quot;address&quot;</span><span class="Delimiter">);</span>
+  type_ordinal shared = get<span class="Delimiter">(</span>Type_ordinal<span class="Delimiter">,</span> <span class="Constant">&quot;shared&quot;</span><span class="Delimiter">);</span>
   for <span class="Delimiter">(;</span> type<span class="Delimiter">;</span> type = type<span class="Delimiter">-&gt;</span>right<span class="Delimiter">)</span> <span class="Delimiter">{</span>
-    if <span class="Delimiter">(</span>type<span class="Delimiter">-&gt;</span>value != get<span class="Delimiter">(</span>Type_ordinal<span class="Delimiter">,</span> <span class="Constant">&quot;address&quot;</span><span class="Delimiter">))</span>
+    if <span class="Delimiter">(</span>type<span class="Delimiter">-&gt;</span>value != address &amp;&amp; type<span class="Delimiter">-&gt;</span>value != shared<span class="Delimiter">)</span>
       <span class="Identifier">return</span> type<span class="Delimiter">-&gt;</span>value<span class="Delimiter">;</span>
   <span class="Delimiter">}</span>
   raise_error &lt;&lt; maybe<span class="Delimiter">(</span>recipe_name<span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;expected a container&quot;</span> &lt;&lt; <span class="cSpecial">'\n'</span> &lt;&lt; end<span class="Delimiter">();</span>
@@ -222,7 +226,7 @@ get<span class="Delimiter">(</span>Type<span class="Delimiter">,</span> point<sp
 get<span class="Delimiter">(</span>Type<span class="Delimiter">,</span> point<span class="Delimiter">).</span>element_names<span class="Delimiter">.</span>push_back<span class="Delimiter">(</span><span class="Constant">&quot;y&quot;</span><span class="Delimiter">);</span>
 <span class="Delimiter">:(scenario transform_names_transforms_container_elements)</span>
 recipe main [
-  p:address:point<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>  <span class="Comment"># unsafe</span>
+  p:address:point<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
   a:number<span class="Special"> &lt;- </span>get *p:address:point<span class="Delimiter">,</span> y:offset
   b:number<span class="Special"> &lt;- </span>get *p:address:point<span class="Delimiter">,</span> x:offset
 ]
@@ -266,7 +270,7 @@ recipe main [
   <span class="Constant">12</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">1</span>
   <span class="Constant">13</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">35</span>
   <span class="Constant">14</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">36</span>
-  <span class="Constant">20</span>:address:point<span class="Special"> &lt;- </span>maybe-convert <span class="Constant">12</span>:number-or-point/<span class="Special">raw</span><span class="Delimiter">,</span> p:variant  <span class="Comment"># unsafe</span>
+  <span class="Constant">20</span>:address:point<span class="Special"> &lt;- </span>maybe-convert <span class="Constant">12</span>:number-or-point/unsafe<span class="Delimiter">,</span> p:variant
 ]
 <span class="traceContains">+name: variant p of type number-or-point has tag 1</span>
 <span class="traceContains">+mem: storing 13 in location 20</span>
diff --git a/html/044space.cc.html b/html/043space.cc.html
index 10e456cb..7f14f589 100644
--- a/html/044space.cc.html
+++ b/html/043space.cc.html
@@ -2,7 +2,7 @@
 <html>
 <head>
 <meta http-equiv="content-type" content="text/html; charset=UTF-8">
-<title>Mu - 044space.cc</title>
+<title>Mu - 043space.cc</title>
 <meta name="Generator" content="Vim/7.4">
 <meta name="plugin-version" content="vim7.4_v1">
 <meta name="syntax" content="cpp">
@@ -13,8 +13,8 @@
 pre { white-space: pre-wrap; font-family: monospace; color: #eeeeee; background-color: #080808; }
 body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 * { font-size: 1.05em; }
-.traceContains { color: #008000; }
 .traceAbsent { color: #c00000; }
+.traceContains { color: #008000; }
 .SalientComment { color: #00ffff; }
 .cSpecial { color: #008000; }
 .Comment { color: #9090ff; }
@@ -38,23 +38,26 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="Comment">//: (unless they have the /raw property)</span>
 
 <span class="Delimiter">:(scenario set_default_space)</span>
-<span class="Comment"># if default-space is 10, and if an array of 5 locals lies from location 11 to 15 (inclusive),</span>
-<span class="Comment"># then location 0 is really location 11, location 1 is really location 12, and so on.</span>
+<span class="Comment"># if default-space is 10, and if an array of 5 locals lies from location 12 to 16 (inclusive),</span>
+<span class="Comment"># then local 0 is really location 12, local 1 is really location 13, and so on.</span>
 recipe main [
-  <span class="Constant">10</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">5</span>  <span class="Comment"># pretend array; in practice we'll use new</span>
-  default-space:address:array:location<span class="Special"> &lt;- </span>copy <span class="Constant">10</span>/unsafe
+  <span class="Comment"># pretend shared:array:location; in practice we'll use new</span>
+  <span class="Constant">10</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>  <span class="Comment"># refcount</span>
+  <span class="Constant">11</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">5</span>  <span class="Comment"># length</span>
+  default-space:address:shared:array:location<span class="Special"> &lt;- </span>copy <span class="Constant">10</span>/unsafe
   <span class="Constant">1</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">23</span>
 ]
-<span class="traceContains">+mem: storing 23 in location 12</span>
+<span class="traceContains">+mem: storing 23 in location 13</span>
 
 <span class="Delimiter">:(scenario lookup_sidesteps_default_space)</span>
 recipe main [
   <span class="Comment"># pretend pointer from outside</span>
   <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">34</span>
-  <span class="Comment"># pretend array</span>
-  <span class="Constant">1000</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">5</span>
+  <span class="Comment"># pretend shared:array:location; in practice we'll use new</span>
+  <span class="Constant">1000</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>  <span class="Comment"># refcount</span>
+  <span class="Constant">1001</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">5</span>  <span class="Comment"># length</span>
   <span class="Comment"># actual start of this recipe</span>
-  default-space:address:array:location<span class="Special"> &lt;- </span>copy <span class="Constant">1000</span>/unsafe
+  default-space:address:shared:array:location<span class="Special"> &lt;- </span>copy <span class="Constant">1000</span>/unsafe
   <span class="Constant">1</span>:address:number<span class="Special"> &lt;- </span>copy <span class="Constant">3</span>/unsafe
   <span class="Constant">8</span>:number/<span class="Special">raw &lt;- </span>copy *<span class="Constant">1</span>:address:number
 ]
@@ -95,6 +98,56 @@ void absolutize<span class="Delimiter">(</span>reagent&amp; x<span class="Delimi
   assert<span class="Delimiter">(</span>is_raw<span class="Delimiter">(</span>x<span class="Delimiter">));</span>
 <span class="Delimiter">}</span>
 
+long long int space_base<span class="Delimiter">(</span>const reagent&amp; x<span class="Delimiter">)</span> <span class="Delimiter">{</span>
+  <span class="Comment">// temporary stub; will be replaced in a later layer</span>
+  <span class="Identifier">return</span> current_call<span class="Delimiter">().</span>default_space ? <span class="Delimiter">(</span>current_call<span class="Delimiter">().</span>default_space+<span class="Comment">/*</span><span class="Comment">skip refcount</span><span class="Comment">*/</span><span class="Constant">1</span><span class="Delimiter">)</span> : <span class="Constant">0</span><span class="Delimiter">;</span>
+<span class="Delimiter">}</span>
+
+long long int address<span class="Delimiter">(</span>long long int offset<span class="Delimiter">,</span> long long int base<span class="Delimiter">)</span> <span class="Delimiter">{</span>
+  if <span class="Delimiter">(</span>base == <span class="Constant">0</span><span class="Delimiter">)</span> <span class="Identifier">return</span> offset<span class="Delimiter">;</span>  <span class="Comment">// raw</span>
+  long long int size = get_or_insert<span class="Delimiter">(</span>Memory<span class="Delimiter">,</span> base<span class="Delimiter">);</span>
+  if <span class="Delimiter">(</span>offset &gt;= size<span class="Delimiter">)</span> <span class="Delimiter">{</span>
+    <span class="Comment">// todo: test</span>
+    raise_error &lt;&lt; <span class="Constant">&quot;location &quot;</span> &lt;&lt; offset &lt;&lt; <span class="Constant">&quot; is out of bounds &quot;</span> &lt;&lt; size &lt;&lt; <span class="Constant">&quot; at &quot;</span> &lt;&lt; base &lt;&lt; <span class="cSpecial">'\n'</span> &lt;&lt; end<span class="Delimiter">();</span>
+    <span class="Identifier">return</span> <span class="Constant">0</span><span class="Delimiter">;</span>
+  <span class="Delimiter">}</span>
+  <span class="Identifier">return</span> base + <span class="Comment">/*</span><span class="Comment">skip length</span><span class="Comment">*/</span><span class="Constant">1</span> + offset<span class="Delimiter">;</span>
+<span class="Delimiter">}</span>
+
+<span class="SalientComment">//:: reads and writes to the 'default-space' variable have special behavior</span>
+
+<span class="Delimiter">:(after &quot;void write_memory(reagent x, vector&lt;double&gt; data)&quot;)</span>
+  if <span class="Delimiter">(</span>x<span class="Delimiter">.</span>name == <span class="Constant">&quot;default-space&quot;</span><span class="Delimiter">)</span> <span class="Delimiter">{</span>
+    if <span class="Delimiter">(</span>!scalar<span class="Delimiter">(</span>data<span class="Delimiter">)</span>
+        || !x<span class="Delimiter">.</span>type
+        || x<span class="Delimiter">.</span>type<span class="Delimiter">-&gt;</span>value != get<span class="Delimiter">(</span>Type_ordinal<span class="Delimiter">,</span> <span class="Constant">&quot;address&quot;</span><span class="Delimiter">)</span>
+        || !x<span class="Delimiter">.</span>type<span class="Delimiter">-&gt;</span>right
+        || x<span class="Delimiter">.</span>type<span class="Delimiter">-&gt;</span>right<span class="Delimiter">-&gt;</span>value != get<span class="Delimiter">(</span>Type_ordinal<span class="Delimiter">,</span> <span class="Constant">&quot;shared&quot;</span><span class="Delimiter">)</span>
+        || !x<span class="Delimiter">.</span>type<span class="Delimiter">-&gt;</span>right<span class="Delimiter">-&gt;</span>right
+        || x<span class="Delimiter">.</span>type<span class="Delimiter">-&gt;</span>right<span class="Delimiter">-&gt;</span>right<span class="Delimiter">-&gt;</span>value != get<span class="Delimiter">(</span>Type_ordinal<span class="Delimiter">,</span> <span class="Constant">&quot;array&quot;</span><span class="Delimiter">)</span>
+        || !x<span class="Delimiter">.</span>type<span class="Delimiter">-&gt;</span>right<span class="Delimiter">-&gt;</span>right<span class="Delimiter">-&gt;</span>right
+        || x<span class="Delimiter">.</span>type<span class="Delimiter">-&gt;</span>right<span class="Delimiter">-&gt;</span>right<span class="Delimiter">-&gt;</span>right<span class="Delimiter">-&gt;</span>value != get<span class="Delimiter">(</span>Type_ordinal<span class="Delimiter">,</span> <span class="Constant">&quot;location&quot;</span><span class="Delimiter">)</span>
+        || x<span class="Delimiter">.</span>type<span class="Delimiter">-&gt;</span>right<span class="Delimiter">-&gt;</span>right<span class="Delimiter">-&gt;</span>right<span class="Delimiter">-&gt;</span>right<span class="Delimiter">)</span> <span class="Delimiter">{</span>
+      raise_error &lt;&lt; maybe<span class="Delimiter">(</span>current_recipe_name<span class="Delimiter">())</span> &lt;&lt; <span class="Constant">&quot;'default-space' should be of type address:shared:array:location, but tried to write &quot;</span> &lt;&lt; to_string<span class="Delimiter">(</span>data<span class="Delimiter">)</span> &lt;&lt; <span class="cSpecial">'\n'</span> &lt;&lt; end<span class="Delimiter">();</span>
+    <span class="Delimiter">}</span>
+    current_call<span class="Delimiter">().</span>default_space = data<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">);</span>
+    <span class="Identifier">return</span><span class="Delimiter">;</span>
+  <span class="Delimiter">}</span>
+
+<span class="Delimiter">:(scenario get_default_space)</span>
+recipe main [
+  default-space:address:shared:array:location<span class="Special"> &lt;- </span>copy <span class="Constant">10</span>/unsafe
+  <span class="Constant">1</span>:address:shared:array:location/<span class="Special">raw &lt;- </span>copy default-space:address:shared:array:location
+]
+<span class="traceContains">+mem: storing 10 in location 1</span>
+
+<span class="Delimiter">:(after &quot;vector&lt;double&gt; read_memory(reagent x)&quot;)</span>
+  if <span class="Delimiter">(</span>x<span class="Delimiter">.</span>name == <span class="Constant">&quot;default-space&quot;</span><span class="Delimiter">)</span> <span class="Delimiter">{</span>
+    vector&lt;double&gt; result<span class="Delimiter">;</span>
+    result<span class="Delimiter">.</span>push_back<span class="Delimiter">(</span>current_call<span class="Delimiter">().</span>default_space<span class="Delimiter">);</span>
+    <span class="Identifier">return</span> result<span class="Delimiter">;</span>
+  <span class="Delimiter">}</span>
+
 <span class="SalientComment">//:: fix 'get'</span>
 
 <span class="Delimiter">:(scenario lookup_sidesteps_default_space_in_get)</span>
@@ -102,10 +155,11 @@ recipe main [
   <span class="Comment"># pretend pointer to container from outside</span>
   <span class="Constant">12</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">34</span>
   <span class="Constant">13</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">35</span>
-  <span class="Comment"># pretend array</span>
-  <span class="Constant">1000</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">5</span>
+  <span class="Comment"># pretend shared:array:location; in practice we'll use new</span>
+  <span class="Constant">1000</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>  <span class="Comment"># refcount</span>
+  <span class="Constant">1001</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">5</span>  <span class="Comment"># length</span>
   <span class="Comment"># actual start of this recipe</span>
-  default-space:address:array:location<span class="Special"> &lt;- </span>copy <span class="Constant">1000</span>/unsafe
+  default-space:address:shared:array:location<span class="Special"> &lt;- </span>copy <span class="Constant">1000</span>/unsafe
   <span class="Constant">1</span>:address:point<span class="Special"> &lt;- </span>copy <span class="Constant">12</span>/unsafe
   <span class="Constant">9</span>:number/<span class="Special">raw &lt;- </span>get *<span class="Constant">1</span>:address:point<span class="Delimiter">,</span> <span class="Constant">1</span>:offset
 ]
@@ -122,10 +176,11 @@ recipe main [
   <span class="Constant">12</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">2</span>
   <span class="Constant">13</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">34</span>
   <span class="Constant">14</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">35</span>
-  <span class="Comment"># pretend array</span>
-  <span class="Constant">1000</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">5</span>
+  <span class="Comment"># pretend shared:array:location; in practice we'll use new</span>
+  <span class="Constant">1000</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>  <span class="Comment"># refcount</span>
+  <span class="Constant">1001</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">5</span>  <span class="Comment"># length</span>
   <span class="Comment"># actual start of this recipe</span>
-  default-space:address:array:location<span class="Special"> &lt;- </span>copy <span class="Constant">1000</span>/unsafe
+  default-space:address:shared:array:location<span class="Special"> &lt;- </span>copy <span class="Constant">1000</span>/unsafe
   <span class="Constant">1</span>:address:array:number<span class="Special"> &lt;- </span>copy <span class="Constant">12</span>/unsafe
   <span class="Constant">9</span>:number/<span class="Special">raw &lt;- </span>index *<span class="Constant">1</span>:address:array:number<span class="Delimiter">,</span> <span class="Constant">1</span>
 ]
@@ -154,7 +209,7 @@ if <span class="Delimiter">(</span>s == <span class="Constant">&quot;number-of-l
 
 <span class="Delimiter">:(before &quot;End Rewrite Instruction(curr, recipe result)&quot;)</span>
 <span class="Comment">// rewrite `new-default-space` to</span>
-<span class="Comment">//   `default-space:address:array:location &lt;- new location:type, number-of-locals:literal`</span>
+<span class="Comment">//   `default-space:address:shared:array:location &lt;- new location:type, number-of-locals:literal`</span>
 <span class="Comment">// where N is Name[recipe][&quot;&quot;]</span>
 if <span class="Delimiter">(</span>curr<span class="Delimiter">.</span>name == <span class="Constant">&quot;new-default-space&quot;</span><span class="Delimiter">)</span> <span class="Delimiter">{</span>
   rewrite_default_space_instruction<span class="Delimiter">(</span>curr<span class="Delimiter">);</span>
@@ -185,7 +240,7 @@ recipe main [
 recipe foo [
   local-scope
   x:number<span class="Special"> &lt;- </span>copy <span class="Constant">34</span>
-  reply default-space:address:array:location
+  reply default-space:address:shared:array:location
 ]
 <span class="Comment"># both calls to foo should have received the same default-space</span>
 <span class="traceContains">+mem: storing 1 in location 3</span>
@@ -210,7 +265,7 @@ void try_reclaim_locals<span class="Delimiter">()</span> <span class="Delimiter"
   const instruction&amp; inst = get<span class="Delimiter">(</span>Recipe<span class="Delimiter">,</span> r<span class="Delimiter">).</span>steps<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">);</span>
   if <span class="Delimiter">(</span>inst<span class="Delimiter">.</span>old_name != <span class="Constant">&quot;local-scope&quot;</span><span class="Delimiter">)</span> <span class="Identifier">return</span><span class="Delimiter">;</span>
   abandon<span class="Delimiter">(</span>current_call<span class="Delimiter">().</span>default_space<span class="Delimiter">,</span>
-          <span class="Comment">/*</span><span class="Comment">array length</span><span class="Comment">*/</span><span class="Constant">1</span>+<span class="Comment">/*</span><span class="Comment">number-of-locals</span><span class="Comment">*/</span>Name[r][<span class="Constant">&quot;&quot;</span>]<span class="Delimiter">);</span>
+          <span class="Comment">/*</span><span class="Comment">refcount</span><span class="Comment">*/</span><span class="Constant">1</span> + <span class="Comment">/*</span><span class="Comment">array length</span><span class="Comment">*/</span><span class="Constant">1</span> + <span class="Comment">/*</span><span class="Comment">number-of-locals</span><span class="Comment">*/</span>Name[r][<span class="Constant">&quot;&quot;</span>]<span class="Delimiter">);</span>
 <span class="Delimiter">}</span>
 
 void rewrite_default_space_instruction<span class="Delimiter">(</span>instruction&amp; curr<span class="Delimiter">)</span> <span class="Delimiter">{</span>
@@ -221,55 +276,8 @@ void rewrite_default_space_instruction<span class="Delimiter">(</span>instructio
   curr<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>push_back<span class="Delimiter">(</span>reagent<span class="Delimiter">(</span><span class="Constant">&quot;number-of-locals:literal&quot;</span><span class="Delimiter">));</span>
   if <span class="Delimiter">(</span>!curr<span class="Delimiter">.</span>products<span class="Delimiter">.</span>empty<span class="Delimiter">())</span>
     raise_error &lt;&lt; <span class="Constant">&quot;new-default-space can't take any results</span><span class="cSpecial">\n</span><span class="Constant">&quot;</span> &lt;&lt; end<span class="Delimiter">();</span>
-  curr<span class="Delimiter">.</span>products<span class="Delimiter">.</span>push_back<span class="Delimiter">(</span>reagent<span class="Delimiter">(</span><span class="Constant">&quot;default-space:address:array:location&quot;</span><span class="Delimiter">));</span>
+  curr<span class="Delimiter">.</span>products<span class="Delimiter">.</span>push_back<span class="Delimiter">(</span>reagent<span class="Delimiter">(</span><span class="Constant">&quot;default-space:address:shared:array:location&quot;</span><span class="Delimiter">));</span>
 <span class="Delimiter">}</span>
-
-<span class="SalientComment">//:: helpers</span>
-
-<span class="Delimiter">:(code)</span>
-long long int space_base<span class="Delimiter">(</span>const reagent&amp; x<span class="Delimiter">)</span> <span class="Delimiter">{</span>
-  <span class="Comment">// temporary stub; will be replaced in a later layer</span>
-  <span class="Identifier">return</span> current_call<span class="Delimiter">().</span>default_space<span class="Delimiter">;</span>
-<span class="Delimiter">}</span>
-
-long long int address<span class="Delimiter">(</span>long long int offset<span class="Delimiter">,</span> long long int base<span class="Delimiter">)</span> <span class="Delimiter">{</span>
-  if <span class="Delimiter">(</span>base == <span class="Constant">0</span><span class="Delimiter">)</span> <span class="Identifier">return</span> offset<span class="Delimiter">;</span>  <span class="Comment">// raw</span>
-  if <span class="Delimiter">(</span>offset &gt;= static_cast&lt;long long int&gt;<span class="Delimiter">(</span>get_or_insert<span class="Delimiter">(</span>Memory<span class="Delimiter">,</span> base<span class="Delimiter">)))</span> <span class="Delimiter">{</span>
-    <span class="Comment">// todo: test</span>
-    raise_error &lt;&lt; <span class="Constant">&quot;location &quot;</span> &lt;&lt; offset &lt;&lt; <span class="Constant">&quot; is out of bounds &quot;</span> &lt;&lt; no_scientific<span class="Delimiter">(</span>get_or_insert<span class="Delimiter">(</span>Memory<span class="Delimiter">,</span> base<span class="Delimiter">))</span> &lt;&lt; <span class="Constant">&quot; at &quot;</span> &lt;&lt; base &lt;&lt; <span class="cSpecial">'\n'</span> &lt;&lt; end<span class="Delimiter">();</span>
-  <span class="Delimiter">}</span>
-  <span class="Identifier">return</span> base+<span class="Constant">1</span> + offset<span class="Delimiter">;</span>
-<span class="Delimiter">}</span>
-
-<span class="Delimiter">:(after &quot;void write_memory(reagent x, vector&lt;double&gt; data)&quot;)</span>
-  if <span class="Delimiter">(</span>x<span class="Delimiter">.</span>name == <span class="Constant">&quot;default-space&quot;</span><span class="Delimiter">)</span> <span class="Delimiter">{</span>
-    if <span class="Delimiter">(</span>!scalar<span class="Delimiter">(</span>data<span class="Delimiter">)</span>
-        || !x<span class="Delimiter">.</span>type
-        || x<span class="Delimiter">.</span>type<span class="Delimiter">-&gt;</span>value != get<span class="Delimiter">(</span>Type_ordinal<span class="Delimiter">,</span> <span class="Constant">&quot;address&quot;</span><span class="Delimiter">)</span>
-        || !x<span class="Delimiter">.</span>type<span class="Delimiter">-&gt;</span>right
-        || x<span class="Delimiter">.</span>type<span class="Delimiter">-&gt;</span>right<span class="Delimiter">-&gt;</span>value != get<span class="Delimiter">(</span>Type_ordinal<span class="Delimiter">,</span> <span class="Constant">&quot;array&quot;</span><span class="Delimiter">)</span>
-        || !x<span class="Delimiter">.</span>type<span class="Delimiter">-&gt;</span>right<span class="Delimiter">-&gt;</span>right
-        || x<span class="Delimiter">.</span>type<span class="Delimiter">-&gt;</span>right<span class="Delimiter">-&gt;</span>right<span class="Delimiter">-&gt;</span>value != get<span class="Delimiter">(</span>Type_ordinal<span class="Delimiter">,</span> <span class="Constant">&quot;location&quot;</span><span class="Delimiter">)</span>
-        || x<span class="Delimiter">.</span>type<span class="Delimiter">-&gt;</span>right<span class="Delimiter">-&gt;</span>right<span class="Delimiter">-&gt;</span>right<span class="Delimiter">)</span> <span class="Delimiter">{</span>
-      raise_error &lt;&lt; maybe<span class="Delimiter">(</span>current_recipe_name<span class="Delimiter">())</span> &lt;&lt; <span class="Constant">&quot;'default-space' should be of type address:array:location, but tried to write &quot;</span> &lt;&lt; to_string<span class="Delimiter">(</span>data<span class="Delimiter">)</span> &lt;&lt; <span class="cSpecial">'\n'</span> &lt;&lt; end<span class="Delimiter">();</span>
-    <span class="Delimiter">}</span>
-    current_call<span class="Delimiter">().</span>default_space = data<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">);</span>
-    <span class="Identifier">return</span><span class="Delimiter">;</span>
-  <span class="Delimiter">}</span>
-
-<span class="Delimiter">:(scenario get_default_space)</span>
-recipe main [
-  default-space:address:array:location<span class="Special"> &lt;- </span>copy <span class="Constant">10</span>/unsafe
-  <span class="Constant">1</span>:address:array:location/<span class="Special">raw &lt;- </span>copy default-space:address:array:location
-]
-<span class="traceContains">+mem: storing 10 in location 1</span>
-
-<span class="Delimiter">:(after &quot;vector&lt;double&gt; read_memory(reagent x)&quot;)</span>
-  if <span class="Delimiter">(</span>x<span class="Delimiter">.</span>name == <span class="Constant">&quot;default-space&quot;</span><span class="Delimiter">)</span> <span class="Delimiter">{</span>
-    vector&lt;double&gt; result<span class="Delimiter">;</span>
-    result<span class="Delimiter">.</span>push_back<span class="Delimiter">(</span>current_call<span class="Delimiter">().</span>default_space<span class="Delimiter">);</span>
-    <span class="Identifier">return</span> result<span class="Delimiter">;</span>
-  <span class="Delimiter">}</span>
 </pre>
 </body>
 </html>
diff --git a/html/045space_surround.cc.html b/html/044space_surround.cc.html
index 29d58818..47e01b94 100644
--- a/html/045space_surround.cc.html
+++ b/html/044space_surround.cc.html
@@ -2,7 +2,7 @@
 <html>
 <head>
 <meta http-equiv="content-type" content="text/html; charset=UTF-8">
-<title>Mu - 045space_surround.cc</title>
+<title>Mu - 044space_surround.cc</title>
 <meta name="Generator" content="Vim/7.4">
 <meta name="plugin-version" content="vim7.4_v1">
 <meta name="syntax" content="cpp">
@@ -15,6 +15,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 * { font-size: 1.05em; }
 .traceContains { color: #008000; }
 .cSpecial { color: #008000; }
+.CommentedCode { color: #6c6c6c; }
 .Comment { color: #9090ff; }
 .Delimiter { color: #a04060; }
 .Special { color: #ff6060; }
@@ -40,21 +41,26 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="Delimiter">:(scenario surrounding_space)</span>
 <span class="Comment"># location 1 in space 1 refers to the space surrounding the default space, here 20.</span>
 recipe main [
-  <span class="Constant">10</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">5</span>  <span class="Comment"># pretend array</span>
-  <span class="Constant">20</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">5</span>  <span class="Comment"># pretend array</span>
-  default-space:address:array:location<span class="Special"> &lt;- </span>copy <span class="Constant">10</span>/unsafe
-  <span class="Constant">0</span>:address:array:location/names:dummy<span class="Special"> &lt;- </span>copy <span class="Constant">20</span>/unsafe  <span class="Comment"># later layers will explain the /names: property</span>
+  <span class="Comment"># pretend shared:array:location; in practice we'll use new</span>
+  <span class="Constant">10</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>  <span class="Comment"># refcount</span>
+  <span class="Constant">11</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">5</span>  <span class="Comment"># length</span>
+  <span class="Comment"># pretend shared:array:location; in practice we'll use new</span>
+  <span class="Constant">20</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>  <span class="Comment"># refcount</span>
+  <span class="Constant">21</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">5</span>  <span class="Comment"># length</span>
+  <span class="Comment"># actual start of this recipe</span>
+  default-space:address:shared:array:location<span class="Special"> &lt;- </span>copy <span class="Constant">10</span>/unsafe
+  <span class="Constant">0</span>:address:shared:array:location/names:dummy<span class="Special"> &lt;- </span>copy <span class="Constant">20</span>/unsafe  <span class="Comment"># later layers will explain the /names: property</span>
   <span class="Constant">1</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">32</span>
   <span class="Constant">1</span>:number/space:<span class="Constant">1</span><span class="Special"> &lt;- </span>copy <span class="Constant">33</span>
 ]
-recipe dummy [
+recipe dummy [  <span class="Comment"># just for the /names: property above</span>
 ]
-<span class="Comment"># chain space</span>
-<span class="traceContains">+mem: storing 20 in location 11</span>
-<span class="Comment"># store to default-space</span>
-<span class="traceContains">+mem: storing 32 in location 12</span>
-<span class="Comment"># store to chained space</span>
-<span class="traceContains">+mem: storing 33 in location 22</span>
+<span class="Comment"># chain space: 10 + /*skip refcount*/1 + /*skip length*/1</span>
+<span class="traceContains">+mem: storing 20 in location 12</span>
+<span class="Comment"># store to default space: 10 + /*skip refcount*/1 + /*skip length*/1 + /*index*/1</span>
+<span class="traceContains">+mem: storing 32 in location 13</span>
+<span class="Comment"># store to chained space: /*contents of location 12*/20 + /*skip refcount*/1 + /*skip length*/1 + /*index*/1</span>
+<span class="traceContains">+mem: storing 33 in location 23</span>
 
 <span class="Comment">//: If you think of a space as a collection of variables with a common</span>
 <span class="Comment">//: lifetime, surrounding allows managing shorter lifetimes inside a longer</span>
@@ -62,14 +68,17 @@ recipe dummy [
 
 <span class="Delimiter">:(replace{} &quot;long long int space_base(const reagent&amp; x)&quot;)</span>
 long long int space_base<span class="Delimiter">(</span>const reagent&amp; x<span class="Delimiter">)</span> <span class="Delimiter">{</span>
-  <span class="Identifier">return</span> space_base<span class="Delimiter">(</span>x<span class="Delimiter">,</span> space_index<span class="Delimiter">(</span>x<span class="Delimiter">),</span> current_call<span class="Delimiter">().</span>default_space<span class="Delimiter">);</span>
+  long long int base = current_call<span class="Delimiter">().</span>default_space ? <span class="Delimiter">(</span>current_call<span class="Delimiter">().</span>default_space+<span class="Comment">/*</span><span class="Comment">skip refcount</span><span class="Comment">*/</span><span class="Constant">1</span><span class="Delimiter">)</span> : <span class="Constant">0</span><span class="Delimiter">;</span>
+  <span class="Identifier">return</span> space_base<span class="Delimiter">(</span>x<span class="Delimiter">,</span> space_index<span class="Delimiter">(</span>x<span class="Delimiter">),</span> base<span class="Delimiter">);</span>
 <span class="Delimiter">}</span>
 
 long long int space_base<span class="Delimiter">(</span>const reagent&amp; x<span class="Delimiter">,</span> long long int space_index<span class="Delimiter">,</span> long long int base<span class="Delimiter">)</span> <span class="Delimiter">{</span>
+<span class="CommentedCode">//?   trace(9999, &quot;space&quot;) &lt;&lt; &quot;space-base: &quot; &lt;&lt; space_index &lt;&lt; &quot; &quot; &lt;&lt; base &lt;&lt; end();</span>
   if <span class="Delimiter">(</span>space_index == <span class="Constant">0</span><span class="Delimiter">)</span> <span class="Delimiter">{</span>
     <span class="Identifier">return</span> base<span class="Delimiter">;</span>
   <span class="Delimiter">}</span>
-  long long int result = space_base<span class="Delimiter">(</span>x<span class="Delimiter">,</span> space_index-<span class="Constant">1</span><span class="Delimiter">,</span> get_or_insert<span class="Delimiter">(</span>Memory<span class="Delimiter">,</span> base+<span class="Constant">1</span><span class="Delimiter">));</span>
+  long long int result = space_base<span class="Delimiter">(</span>x<span class="Delimiter">,</span> space_index-<span class="Constant">1</span><span class="Delimiter">,</span> get_or_insert<span class="Delimiter">(</span>Memory<span class="Delimiter">,</span> base+<span class="Comment">/*</span><span class="Comment">skip length</span><span class="Comment">*/</span><span class="Constant">1</span><span class="Delimiter">))</span>+<span class="Comment">/*</span><span class="Comment">skip refcount</span><span class="Comment">*/</span><span class="Constant">1</span><span class="Delimiter">;</span>
+<span class="CommentedCode">//?   trace(9999, &quot;space&quot;) &lt;&lt; &quot;space-base: &quot; &lt;&lt; space_index &lt;&lt; &quot; &quot; &lt;&lt; base &lt;&lt; &quot; =&gt; &quot; &lt;&lt; result &lt;&lt; end();</span>
   <span class="Identifier">return</span> result<span class="Delimiter">;</span>
 <span class="Delimiter">}</span>
 
diff --git a/html/046closure_name.cc.html b/html/045closure_name.cc.html
index 13c7ddd2..ae93ad02 100644
--- a/html/046closure_name.cc.html
+++ b/html/045closure_name.cc.html
@@ -2,7 +2,7 @@
 <html>
 <head>
 <meta http-equiv="content-type" content="text/html; charset=UTF-8">
-<title>Mu - 046closure_name.cc</title>
+<title>Mu - 045closure_name.cc</title>
 <meta name="Generator" content="Vim/7.4">
 <meta name="plugin-version" content="vim7.4_v1">
 <meta name="syntax" content="cpp">
@@ -39,22 +39,22 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="Delimiter">:(scenario closure)</span>
 recipe main [
-  default-space:address:array:location<span class="Special"> &lt;- </span>new location:type<span class="Delimiter">,</span> <span class="Constant">30</span>
-  <span class="Constant">1</span>:address:array:location/names:new-counter<span class="Special"> &lt;- </span>new-counter
-  <span class="Constant">2</span>:number/<span class="Special">raw &lt;- </span>increment-counter <span class="Constant">1</span>:address:array:location/names:new-counter
-  <span class="Constant">3</span>:number/<span class="Special">raw &lt;- </span>increment-counter <span class="Constant">1</span>:address:array:location/names:new-counter
+  default-space:address:shared:array:location<span class="Special"> &lt;- </span>new location:type<span class="Delimiter">,</span> <span class="Constant">30</span>
+  <span class="Constant">1</span>:address:shared:array:location/names:new-counter<span class="Special"> &lt;- </span>new-counter
+  <span class="Constant">2</span>:number/<span class="Special">raw &lt;- </span>increment-counter <span class="Constant">1</span>:address:shared:array:location/names:new-counter
+  <span class="Constant">3</span>:number/<span class="Special">raw &lt;- </span>increment-counter <span class="Constant">1</span>:address:shared:array:location/names:new-counter
 ]
 
 recipe new-counter [
-  default-space:address:array:location<span class="Special"> &lt;- </span>new location:type<span class="Delimiter">,</span> <span class="Constant">30</span>
+  default-space:address:shared:array:location<span class="Special"> &lt;- </span>new location:type<span class="Delimiter">,</span> <span class="Constant">30</span>
   x:number<span class="Special"> &lt;- </span>copy <span class="Constant">23</span>
   y:number<span class="Special"> &lt;- </span>copy <span class="Constant">3</span>  <span class="Comment"># variable that will be incremented</span>
-  reply default-space:address:array:location
+  reply default-space:address:shared:array:location
 ]
 
 recipe increment-counter [
-  default-space:address:array:location<span class="Special"> &lt;- </span>new location:type<span class="Delimiter">,</span> <span class="Constant">30</span>
-  <span class="Constant">0</span>:address:array:location/names:new-counter<span class="Special"> &lt;- </span>next-ingredient  <span class="Comment"># outer space must be created by 'new-counter' above</span>
+  default-space:address:shared:array:location<span class="Special"> &lt;- </span>new location:type<span class="Delimiter">,</span> <span class="Constant">30</span>
+  <span class="Constant">0</span>:address:shared:array:location/names:new-counter<span class="Special"> &lt;- </span>next-ingredient  <span class="Comment"># outer space must be created by 'new-counter' above</span>
   y:number/space:<span class="Constant">1</span><span class="Special"> &lt;- </span>add y:number/space:<span class="Constant">1</span><span class="Delimiter">,</span> <span class="Constant">1</span>  <span class="Comment"># increment</span>
   y:number<span class="Special"> &lt;- </span>copy <span class="Constant">234</span>  <span class="Comment"># dummy</span>
   reply y:number/space:<span class="Constant">1</span>
@@ -86,11 +86,13 @@ void collect_surrounding_spaces<span class="Delimiter">(</span>const recipe_ordi
       if <span class="Delimiter">(</span>!type
           || type<span class="Delimiter">-&gt;</span>value != get<span class="Delimiter">(</span>Type_ordinal<span class="Delimiter">,</span> <span class="Constant">&quot;address&quot;</span><span class="Delimiter">)</span>
           || !type<span class="Delimiter">-&gt;</span>right
-          || type<span class="Delimiter">-&gt;</span>right<span class="Delimiter">-&gt;</span>value != get<span class="Delimiter">(</span>Type_ordinal<span class="Delimiter">,</span> <span class="Constant">&quot;array&quot;</span><span class="Delimiter">)</span>
+          || type<span class="Delimiter">-&gt;</span>right<span class="Delimiter">-&gt;</span>value != get<span class="Delimiter">(</span>Type_ordinal<span class="Delimiter">,</span> <span class="Constant">&quot;shared&quot;</span><span class="Delimiter">)</span>
           || !type<span class="Delimiter">-&gt;</span>right<span class="Delimiter">-&gt;</span>right
-          || type<span class="Delimiter">-&gt;</span>right<span class="Delimiter">-&gt;</span>right<span class="Delimiter">-&gt;</span>value != get<span class="Delimiter">(</span>Type_ordinal<span class="Delimiter">,</span> <span class="Constant">&quot;location&quot;</span><span class="Delimiter">)</span>
-          || type<span class="Delimiter">-&gt;</span>right<span class="Delimiter">-&gt;</span>right<span class="Delimiter">-&gt;</span>right<span class="Delimiter">)</span> <span class="Delimiter">{</span>
-        raise_error &lt;&lt; <span class="Constant">&quot;slot 0 should always have type address:array:location, but is &quot;</span> &lt;&lt; inst<span class="Delimiter">.</span>products<span class="Delimiter">.</span>at<span class="Delimiter">(</span>j<span class="Delimiter">).</span>to_string<span class="Delimiter">()</span> &lt;&lt; <span class="cSpecial">'\n'</span> &lt;&lt; end<span class="Delimiter">();</span>
+          || type<span class="Delimiter">-&gt;</span>right<span class="Delimiter">-&gt;</span>right<span class="Delimiter">-&gt;</span>value != get<span class="Delimiter">(</span>Type_ordinal<span class="Delimiter">,</span> <span class="Constant">&quot;array&quot;</span><span class="Delimiter">)</span>
+          || !type<span class="Delimiter">-&gt;</span>right<span class="Delimiter">-&gt;</span>right<span class="Delimiter">-&gt;</span>right
+          || type<span class="Delimiter">-&gt;</span>right<span class="Delimiter">-&gt;</span>right<span class="Delimiter">-&gt;</span>right<span class="Delimiter">-&gt;</span>value != get<span class="Delimiter">(</span>Type_ordinal<span class="Delimiter">,</span> <span class="Constant">&quot;location&quot;</span><span class="Delimiter">)</span>
+          || type<span class="Delimiter">-&gt;</span>right<span class="Delimiter">-&gt;</span>right<span class="Delimiter">-&gt;</span>right<span class="Delimiter">-&gt;</span>right<span class="Delimiter">)</span> <span class="Delimiter">{</span>
+        raise_error &lt;&lt; <span class="Constant">&quot;slot 0 should always have type address:shared:array:location, but is &quot;</span> &lt;&lt; inst<span class="Delimiter">.</span>products<span class="Delimiter">.</span>at<span class="Delimiter">(</span>j<span class="Delimiter">).</span>to_string<span class="Delimiter">()</span> &lt;&lt; <span class="cSpecial">'\n'</span> &lt;&lt; end<span class="Delimiter">();</span>
         <span class="Identifier">continue</span><span class="Delimiter">;</span>
       <span class="Delimiter">}</span>
       string_tree* s = property<span class="Delimiter">(</span>inst<span class="Delimiter">.</span>products<span class="Delimiter">.</span>at<span class="Delimiter">(</span>j<span class="Delimiter">),</span> <span class="Constant">&quot;names&quot;</span><span class="Delimiter">);</span>
diff --git a/html/047global.cc.html b/html/046global.cc.html
index b2017a82..d5a1331c 100644
--- a/html/047global.cc.html
+++ b/html/046global.cc.html
@@ -2,7 +2,7 @@
 <html>
 <head>
 <meta http-equiv="content-type" content="text/html; charset=UTF-8">
-<title>Mu - 047global.cc</title>
+<title>Mu - 046global.cc</title>
 <meta name="Generator" content="Vim/7.4">
 <meta name="plugin-version" content="vim7.4_v1">
 <meta name="syntax" content="cpp">
@@ -38,17 +38,22 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="Delimiter">:(scenario global_space)</span>
 recipe main [
-  <span class="Comment"># pretend arrays; in practice we'll use new</span>
-  <span class="Constant">10</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">5</span>
-  <span class="Constant">20</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">5</span>
+  <span class="Comment"># pretend shared:array:location; in practice we'll use new</span>
+  <span class="Constant">10</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>  <span class="Comment"># refcount</span>
+  <span class="Constant">11</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">5</span>  <span class="Comment"># length</span>
+  <span class="Comment"># pretend shared:array:location; in practice we'll use new</span>
+  <span class="Constant">20</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>  <span class="Comment"># refcount</span>
+  <span class="Constant">21</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">5</span>  <span class="Comment"># length</span>
   <span class="Comment"># actual start of this recipe</span>
-  global-space:address:array:location<span class="Special"> &lt;- </span>copy <span class="Constant">20</span>/unsafe
-  default-space:address:array:location<span class="Special"> &lt;- </span>copy <span class="Constant">10</span>/unsafe
+  global-space:address:shared:array:location<span class="Special"> &lt;- </span>copy <span class="Constant">20</span>/unsafe
+  default-space:address:shared:array:location<span class="Special"> &lt;- </span>copy <span class="Constant">10</span>/unsafe
   <span class="Constant">1</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">23</span>
   <span class="Constant">1</span>:number/space:global<span class="Special"> &lt;- </span>copy <span class="Constant">24</span>
 ]
-<span class="traceContains">+mem: storing 23 in location 12</span>
-<span class="traceContains">+mem: storing 24 in location 22</span>
+<span class="Comment"># store to default space: 10 + /*skip refcount*/1 + /*skip length*/1 + /*index*/1</span>
+<span class="traceContains">+mem: storing 23 in location 13</span>
+<span class="Comment"># store to chained space: /*contents of location 12*/20 + /*skip refcount*/1 + /*skip length*/1 + /*index*/1</span>
+<span class="traceContains">+mem: storing 24 in location 23</span>
 
 <span class="Comment">//: to support it, create another special variable called global space</span>
 <span class="Delimiter">:(before &quot;End Disqualified Reagents&quot;)</span>
@@ -68,11 +73,13 @@ global_space = <span class="Constant">0</span><span class="Delimiter">;</span>
         || !x<span class="Delimiter">.</span>type
         || x<span class="Delimiter">.</span>type<span class="Delimiter">-&gt;</span>value != get<span class="Delimiter">(</span>Type_ordinal<span class="Delimiter">,</span> <span class="Constant">&quot;address&quot;</span><span class="Delimiter">)</span>
         || !x<span class="Delimiter">.</span>type<span class="Delimiter">-&gt;</span>right
-        || x<span class="Delimiter">.</span>type<span class="Delimiter">-&gt;</span>right<span class="Delimiter">-&gt;</span>value != get<span class="Delimiter">(</span>Type_ordinal<span class="Delimiter">,</span> <span class="Constant">&quot;array&quot;</span><span class="Delimiter">)</span>
+        || x<span class="Delimiter">.</span>type<span class="Delimiter">-&gt;</span>right<span class="Delimiter">-&gt;</span>value != get<span class="Delimiter">(</span>Type_ordinal<span class="Delimiter">,</span> <span class="Constant">&quot;shared&quot;</span><span class="Delimiter">)</span>
         || !x<span class="Delimiter">.</span>type<span class="Delimiter">-&gt;</span>right<span class="Delimiter">-&gt;</span>right
-        || x<span class="Delimiter">.</span>type<span class="Delimiter">-&gt;</span>right<span class="Delimiter">-&gt;</span>right<span class="Delimiter">-&gt;</span>value != get<span class="Delimiter">(</span>Type_ordinal<span class="Delimiter">,</span> <span class="Constant">&quot;location&quot;</span><span class="Delimiter">)</span>
-        || x<span class="Delimiter">.</span>type<span class="Delimiter">-&gt;</span>right<span class="Delimiter">-&gt;</span>right<span class="Delimiter">-&gt;</span>right<span class="Delimiter">)</span> <span class="Delimiter">{</span>
-      raise_error &lt;&lt; maybe<span class="Delimiter">(</span>current_recipe_name<span class="Delimiter">())</span> &lt;&lt; <span class="Constant">&quot;'global-space' should be of type address:array:location, but tried to write &quot;</span> &lt;&lt; to_string<span class="Delimiter">(</span>data<span class="Delimiter">)</span> &lt;&lt; <span class="cSpecial">'\n'</span> &lt;&lt; end<span class="Delimiter">();</span>
+        || x<span class="Delimiter">.</span>type<span class="Delimiter">-&gt;</span>right<span class="Delimiter">-&gt;</span>right<span class="Delimiter">-&gt;</span>value != get<span class="Delimiter">(</span>Type_ordinal<span class="Delimiter">,</span> <span class="Constant">&quot;array&quot;</span><span class="Delimiter">)</span>
+        || !x<span class="Delimiter">.</span>type<span class="Delimiter">-&gt;</span>right<span class="Delimiter">-&gt;</span>right<span class="Delimiter">-&gt;</span>right
+        || x<span class="Delimiter">.</span>type<span class="Delimiter">-&gt;</span>right<span class="Delimiter">-&gt;</span>right<span class="Delimiter">-&gt;</span>right<span class="Delimiter">-&gt;</span>value != get<span class="Delimiter">(</span>Type_ordinal<span class="Delimiter">,</span> <span class="Constant">&quot;location&quot;</span><span class="Delimiter">)</span>
+        || x<span class="Delimiter">.</span>type<span class="Delimiter">-&gt;</span>right<span class="Delimiter">-&gt;</span>right<span class="Delimiter">-&gt;</span>right<span class="Delimiter">-&gt;</span>right<span class="Delimiter">)</span> <span class="Delimiter">{</span>
+      raise_error &lt;&lt; maybe<span class="Delimiter">(</span>current_recipe_name<span class="Delimiter">())</span> &lt;&lt; <span class="Constant">&quot;'global-space' should be of type address:shared:array:location, but tried to write &quot;</span> &lt;&lt; to_string<span class="Delimiter">(</span>data<span class="Delimiter">)</span> &lt;&lt; <span class="cSpecial">'\n'</span> &lt;&lt; end<span class="Delimiter">();</span>
     <span class="Delimiter">}</span>
     if <span class="Delimiter">(</span>Current_routine<span class="Delimiter">-&gt;</span>global_space<span class="Delimiter">)</span>
       raise_error &lt;&lt; <span class="Constant">&quot;routine already has a global-space; you can't over-write your globals&quot;</span> &lt;&lt; end<span class="Delimiter">();</span>
@@ -85,7 +92,7 @@ global_space = <span class="Constant">0</span><span class="Delimiter">;</span>
   if <span class="Delimiter">(</span>is_global<span class="Delimiter">(</span>x<span class="Delimiter">))</span> <span class="Delimiter">{</span>
     if <span class="Delimiter">(</span>!Current_routine<span class="Delimiter">-&gt;</span>global_space<span class="Delimiter">)</span>
       raise_error &lt;&lt; <span class="Constant">&quot;routine has no global space</span><span class="cSpecial">\n</span><span class="Constant">&quot;</span> &lt;&lt; end<span class="Delimiter">();</span>
-    <span class="Identifier">return</span> Current_routine<span class="Delimiter">-&gt;</span>global_space<span class="Delimiter">;</span>
+    <span class="Identifier">return</span> Current_routine<span class="Delimiter">-&gt;</span>global_space + <span class="Comment">/*</span><span class="Comment">skip refcount</span><span class="Comment">*/</span><span class="Constant">1</span><span class="Delimiter">;</span>
   <span class="Delimiter">}</span>
 
 <span class="Comment">//: for now let's not bother giving global variables names.</span>
@@ -94,7 +101,7 @@ global_space = <span class="Constant">0</span><span class="Delimiter">;</span>
 <span class="Delimiter">:(scenario global_space_with_names)</span>
 <span class="Special">% Hide_errors = true;</span>
 recipe main [
-  global-space:address:array:location<span class="Special"> &lt;- </span>new location:type<span class="Delimiter">,</span> <span class="Constant">10</span>
+  global-space:address:shared:array:location<span class="Special"> &lt;- </span>new location:type<span class="Delimiter">,</span> <span class="Constant">10</span>
   x:number<span class="Special"> &lt;- </span>copy <span class="Constant">23</span>
   <span class="Constant">1</span>:number/space:global<span class="Special"> &lt;- </span>copy <span class="Constant">24</span>
 ]
diff --git a/html/048check_type_by_name.cc.html b/html/047check_type_by_name.cc.html
index 13703a0e..0bc520b9 100644
--- a/html/048check_type_by_name.cc.html
+++ b/html/047check_type_by_name.cc.html
@@ -2,7 +2,7 @@
 <html>
 <head>
 <meta http-equiv="content-type" content="text/html; charset=UTF-8">
-<title>Mu - 048check_type_by_name.cc</title>
+<title>Mu - 047check_type_by_name.cc</title>
 <meta name="Generator" content="Vim/7.4">
 <meta name="plugin-version" content="vim7.4_v1">
 <meta name="syntax" content="cpp">
@@ -81,16 +81,14 @@ void deduce_missing_type<span class="Delimiter">(</span>map&lt;string<span class
 
 void check_type<span class="Delimiter">(</span>map&lt;string<span class="Delimiter">,</span> type_tree*&gt;&amp; type<span class="Delimiter">,</span> map&lt;string<span class="Delimiter">,</span> string_tree*&gt;&amp; type_name<span class="Delimiter">,</span> const reagent&amp; x<span class="Delimiter">,</span> const recipe_ordinal r<span class="Delimiter">)</span> <span class="Delimiter">{</span>
   if <span class="Delimiter">(</span>is_literal<span class="Delimiter">(</span>x<span class="Delimiter">))</span> <span class="Identifier">return</span><span class="Delimiter">;</span>
-  <span class="Comment">// if you use raw locations you're probably doing something unsafe</span>
-  if <span class="Delimiter">(</span>is_integer<span class="Delimiter">(</span>x<span class="Delimiter">.</span>name<span class="Delimiter">))</span> <span class="Identifier">return</span><span class="Delimiter">;</span>
-  if <span class="Delimiter">(</span>!x<span class="Delimiter">.</span>type<span class="Delimiter">)</span> <span class="Identifier">return</span><span class="Delimiter">;</span>  <span class="Comment">// will throw a more precise error elsewhere</span>
+  if <span class="Delimiter">(</span>is_integer<span class="Delimiter">(</span>x<span class="Delimiter">.</span>name<span class="Delimiter">))</span> <span class="Identifier">return</span><span class="Delimiter">;</span>  <span class="Comment">// if you use raw locations you're probably doing something unsafe</span>
+  if <span class="Delimiter">(</span>!x<span class="Delimiter">.</span>type<span class="Delimiter">)</span> <span class="Identifier">return</span><span class="Delimiter">;</span>  <span class="Comment">// might get filled in by other logic later</span>
   if <span class="Delimiter">(</span>!contains_key<span class="Delimiter">(</span>type<span class="Delimiter">,</span> x<span class="Delimiter">.</span>name<span class="Delimiter">))</span> <span class="Delimiter">{</span>
     trace<span class="Delimiter">(</span><span class="Constant">9992</span><span class="Delimiter">,</span> <span class="Constant">&quot;transform&quot;</span><span class="Delimiter">)</span> &lt;&lt; x<span class="Delimiter">.</span>name &lt;&lt; <span class="Constant">&quot; =&gt; &quot;</span> &lt;&lt; debug_string<span class="Delimiter">(</span>x<span class="Delimiter">.</span>type<span class="Delimiter">)</span> &lt;&lt; end<span class="Delimiter">();</span>
     type[x<span class="Delimiter">.</span>name] = x<span class="Delimiter">.</span>type<span class="Delimiter">;</span>
   <span class="Delimiter">}</span>
-  if <span class="Delimiter">(</span>!contains_key<span class="Delimiter">(</span>type_name<span class="Delimiter">,</span> x<span class="Delimiter">.</span>name<span class="Delimiter">))</span> <span class="Delimiter">{</span>
+  if <span class="Delimiter">(</span>!contains_key<span class="Delimiter">(</span>type_name<span class="Delimiter">,</span> x<span class="Delimiter">.</span>name<span class="Delimiter">))</span>
     type_name[x<span class="Delimiter">.</span>name] = x<span class="Delimiter">.</span>properties<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">).</span>second<span class="Delimiter">;</span>
-  <span class="Delimiter">}</span>
   if <span class="Delimiter">(</span>!types_strictly_match<span class="Delimiter">(</span>type[x<span class="Delimiter">.</span>name]<span class="Delimiter">,</span> x<span class="Delimiter">.</span>type<span class="Delimiter">))</span>
     raise_error &lt;&lt; maybe<span class="Delimiter">(</span>get<span class="Delimiter">(</span>Recipe<span class="Delimiter">,</span> r<span class="Delimiter">).</span>name<span class="Delimiter">)</span> &lt;&lt; x<span class="Delimiter">.</span>name &lt;&lt; <span class="Constant">&quot; used with multiple types</span><span class="cSpecial">\n</span><span class="Constant">&quot;</span> &lt;&lt; end<span class="Delimiter">();</span>
 <span class="Delimiter">}</span>
@@ -125,10 +123,10 @@ recipe main [
 <span class="Delimiter">:(scenario typo_in_address_type_fails)</span>
 <span class="Special">% Hide_errors = true;</span>
 recipe main [
-  y:address:charcter<span class="Special"> &lt;- </span>new character:type
+  y:address:shared:charcter<span class="Special"> &lt;- </span>new character:type
   *y<span class="Special"> &lt;- </span>copy <span class="Constant">67</span>
 ]
-<span class="traceContains">+error: main: unknown type charcter in 'y:address:charcter &lt;- new character:type'</span>
+<span class="traceContains">+error: main: unknown type charcter in 'y:address:shared:charcter &lt;- new character:type'</span>
 </pre>
 </body>
 </html>
diff --git a/html/050scenario.cc.html b/html/050scenario.cc.html
index 523ea59f..a44b76d0 100644
--- a/html/050scenario.cc.html
+++ b/html/050scenario.cc.html
@@ -13,16 +13,16 @@
 pre { white-space: pre-wrap; font-family: monospace; color: #eeeeee; background-color: #080808; }
 body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 * { font-size: 1.05em; }
+.traceAbsent { color: #c00000; }
 .traceContains { color: #008000; }
-.CommentedCode { color: #6c6c6c; }
 .SalientComment { color: #00ffff; }
 .cSpecial { color: #008000; }
-.traceAbsent { color: #c00000; }
 .Comment { color: #9090ff; }
 .Delimiter { color: #a04060; }
 .Special { color: #ff6060; }
 .Identifier { color: #804000; }
 .Constant { color: #00a0a0; }
+.CommentedCode { color: #6c6c6c; }
 -->
 </style>
 
@@ -135,18 +135,26 @@ scenario foo [
 
 <span class="Delimiter">:(scenario read_scenario_with_bracket_in_comment_in_nested_string)</span>
 scenario foo [
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new [<span class="Comment"># not a comment]</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new [<span class="Comment"># not a comment]</span>
 ]
-<span class="traceContains">+run: 1:address:array:character &lt;- new [# not a comment]</span>
+<span class="traceContains">+run: 1:address:shared:array:character &lt;- new [# not a comment]</span>
 
 <span class="SalientComment">//:: Run scenarios when we run 'mu test'.</span>
 <span class="Comment">//: Treat the text of the scenario as a regular series of instructions.</span>
 
+<span class="Delimiter">:(before &quot;End Globals&quot;)</span>
+long long int Num_core_mu_tests = <span class="Constant">0</span><span class="Delimiter">;</span>
+<span class="Delimiter">:(after &quot;Check For .mu Files&quot;)</span>
+Num_core_mu_tests = SIZE<span class="Delimiter">(</span>Scenarios<span class="Delimiter">);</span>
 <span class="Delimiter">:(before &quot;End Tests&quot;)</span>
 time_t mu_time<span class="Delimiter">;</span> time<span class="Delimiter">(</span>&amp;mu_time<span class="Delimiter">);</span>
 cerr &lt;&lt; <span class="Constant">&quot;</span><span class="cSpecial">\n</span><span class="Constant">Mu tests: &quot;</span> &lt;&lt; ctime<span class="Delimiter">(</span>&amp;mu_time<span class="Delimiter">);</span>
 for <span class="Delimiter">(</span>long long int i = <span class="Constant">0</span><span class="Delimiter">;</span> i &lt; SIZE<span class="Delimiter">(</span>Scenarios<span class="Delimiter">);</span> ++i<span class="Delimiter">)</span> <span class="Delimiter">{</span>
 <span class="CommentedCode">//?   cerr &lt;&lt; i &lt;&lt; &quot;: &quot; &lt;&lt; Scenarios.at(i).name &lt;&lt; '\n';</span>
+  if <span class="Delimiter">(</span>i == Num_core_mu_tests<span class="Delimiter">)</span> <span class="Delimiter">{</span>
+    time<span class="Delimiter">(</span>&amp;t<span class="Delimiter">);</span>
+    cerr &lt;&lt; <span class="Constant">&quot;</span><span class="cSpecial">\n</span><span class="Constant">App tests: &quot;</span> &lt;&lt; ctime<span class="Delimiter">(</span>&amp;t<span class="Delimiter">);</span>
+  <span class="Delimiter">}</span>
   run_mu_scenario<span class="Delimiter">(</span>Scenarios<span class="Delimiter">.</span>at<span class="Delimiter">(</span>i<span class="Delimiter">));</span>
   if <span class="Delimiter">(</span>Passed<span class="Delimiter">)</span> cerr &lt;&lt; <span class="Constant">&quot;.&quot;</span><span class="Delimiter">;</span>
 <span class="Delimiter">}</span>
@@ -173,7 +181,6 @@ void run_mu_scenario<span class="Delimiter">(</span>const scenario&amp; s<span c
     Trace_stream = new trace_stream<span class="Delimiter">;</span>
     setup<span class="Delimiter">();</span>
   <span class="Delimiter">}</span>
-  assert<span class="Delimiter">(</span>Routines<span class="Delimiter">.</span>empty<span class="Delimiter">());</span>
   vector&lt;recipe_ordinal&gt; tmp = load<span class="Delimiter">(</span><span class="Constant">&quot;recipe scenario-&quot;</span>+s<span class="Delimiter">.</span>name+<span class="Constant">&quot; [ &quot;</span>+s<span class="Delimiter">.</span>to_run+<span class="Constant">&quot; ]&quot;</span><span class="Delimiter">);</span>
   bind_special_scenario_names<span class="Delimiter">(</span>tmp<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">));</span>
   transform_all<span class="Delimiter">();</span>
diff --git a/html/052tangle.cc.html b/html/052tangle.cc.html
index 131de37a..42f5b7ca 100644
--- a/html/052tangle.cc.html
+++ b/html/052tangle.cc.html
@@ -13,8 +13,8 @@
 pre { white-space: pre-wrap; font-family: monospace; color: #eeeeee; background-color: #080808; }
 body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 * { font-size: 1.05em; }
-.traceContains { color: #008000; }
 .traceAbsent { color: #c00000; }
+.traceContains { color: #008000; }
 .cSpecial { color: #008000; }
 .Comment { color: #9090ff; }
 .Delimiter { color: #a04060; }
@@ -216,12 +216,6 @@ before +label1 [
   <span class="Constant">2</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
 ]
 <span class="traceContains">+error: can't tangle before label +label1</span>
-<span class="traceContains">+mem: storing 0 in location 1</span>
-<span class="traceContains">+mem: storing 0 in location 4</span>
-<span class="Comment"># label1</span>
-<span class="traceAbsent">-mem: storing 0 in location 2</span>
-<span class="Comment"># nothing else</span>
-$mem: <span class="Constant">2</span>
 
 <span class="Delimiter">:(scenario tangle_keeps_labels_separate)</span>
 recipe main [
diff --git a/html/053rewrite_stash.cc.html b/html/053rewrite_stash.cc.html
index ba867faf..6bef7eed 100644
--- a/html/053rewrite_stash.cc.html
+++ b/html/053rewrite_stash.cc.html
@@ -68,7 +68,7 @@ void rewrite_stashes_to_text_named<span class="Delimiter">(</span>recipe&amp; ca
         def<span class="Delimiter">.</span>name = <span class="Constant">&quot;to-text-line&quot;</span><span class="Delimiter">;</span>
         def<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>push_back<span class="Delimiter">(</span>inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span>j<span class="Delimiter">));</span>
         ostringstream ingredient_name<span class="Delimiter">;</span>
-        ingredient_name &lt;&lt; <span class="Constant">&quot;stash_&quot;</span> &lt;&lt; stash_instruction_idx &lt;&lt; <span class="Constant">'_'</span> &lt;&lt; j &lt;&lt; <span class="Constant">&quot;:address:array:character&quot;</span><span class="Delimiter">;</span>
+        ingredient_name &lt;&lt; <span class="Constant">&quot;stash_&quot;</span> &lt;&lt; stash_instruction_idx &lt;&lt; <span class="Constant">'_'</span> &lt;&lt; j &lt;&lt; <span class="Constant">&quot;:address:shared:array:character&quot;</span><span class="Delimiter">;</span>
         def<span class="Delimiter">.</span>products<span class="Delimiter">.</span>push_back<span class="Delimiter">(</span>reagent<span class="Delimiter">(</span>ingredient_name<span class="Delimiter">.</span>str<span class="Delimiter">()));</span>
         new_instructions<span class="Delimiter">.</span>push_back<span class="Delimiter">(</span>def<span class="Delimiter">);</span>
         inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span>j<span class="Delimiter">).</span>clear<span class="Delimiter">();</span>  <span class="Comment">// reclaim old memory</span>
diff --git a/html/054dilated_reagent.cc.html b/html/054dilated_reagent.cc.html
index 1d908069..55526228 100644
--- a/html/054dilated_reagent.cc.html
+++ b/html/054dilated_reagent.cc.html
@@ -51,6 +51,22 @@ recipe main [
 ]
 <span class="Comment"># successfully parsed</span>
 
+<span class="Delimiter">:(scenarios run)</span>
+<span class="Delimiter">:(scenario dilated_reagent_with_comment)</span>
+<span class="Special">% Hide_errors = true;</span>
+recipe main [
+  <span class="Delimiter">{</span><span class="Constant">1</span>: number<span class="Delimiter">,</span> foo: bar<span class="Delimiter">}</span><span class="Special"> &lt;- </span>copy <span class="Constant">34</span>  <span class="Comment"># test comment</span>
+]
+<span class="traceContains">+parse:   product: {&quot;1&quot;: &quot;number&quot;, &quot;foo&quot;: &quot;bar&quot;}</span>
+$error: <span class="Constant">0</span>
+
+<span class="Delimiter">:(scenario dilated_reagent_with_comment_immediately_following)</span>
+<span class="Special">% Hide_errors = true;</span>
+recipe main [
+  <span class="Constant">1</span>:number<span class="Special"> &lt;- </span>copy <span class="Delimiter">{</span><span class="Constant">34</span>: literal<span class="Delimiter">}</span>  <span class="Comment"># test comment</span>
+]
+$error: <span class="Constant">0</span>
+
 <span class="Comment">//: First augment next_word to group balanced brackets together.</span>
 
 <span class="Delimiter">:(before &quot;End next_word Special-cases&quot;)</span>
@@ -106,6 +122,7 @@ string slurp_balanced_bracket<span class="Delimiter">(</span>istream&amp; in<spa
     result &lt;&lt; c<span class="Delimiter">;</span>
     if <span class="Delimiter">(</span>open_brackets<span class="Delimiter">.</span>empty<span class="Delimiter">())</span> <span class="Identifier">break</span><span class="Delimiter">;</span>
   <span class="Delimiter">}</span>
+  skip_whitespace_and_comments_but_not_newline<span class="Delimiter">(</span>in<span class="Delimiter">);</span>
   <span class="Identifier">return</span> result<span class="Delimiter">.</span>str<span class="Delimiter">();</span>
 <span class="Delimiter">}</span>
 
@@ -130,7 +147,7 @@ if <span class="Delimiter">(</span>s<span class="Delimiter">.</span>at<span clas
       <span class="Comment">// this type can't be an integer literal</span>
     put<span class="Delimiter">(</span>Type_ordinal<span class="Delimiter">,</span> type_name<span class="Delimiter">,</span> Next_type_ordinal++<span class="Delimiter">);</span>
   <span class="Delimiter">}</span>
-  type = new type_tree<span class="Delimiter">(</span>get<span class="Delimiter">(</span>Type_ordinal<span class="Delimiter">,</span> type_name<span class="Delimiter">));</span>
+  type = new_type_tree<span class="Delimiter">(</span>properties<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">).</span>second<span class="Delimiter">);</span>
   <span class="Identifier">return</span><span class="Delimiter">;</span>
 <span class="Delimiter">}</span>
 
diff --git a/html/055parse_tree.cc.html b/html/055parse_tree.cc.html
index 1d97dee4..ec8d3f77 100644
--- a/html/055parse_tree.cc.html
+++ b/html/055parse_tree.cc.html
@@ -103,11 +103,14 @@ container bar [
 
 <span class="Delimiter">:(scenario dilated_reagent_with_new)</span>
 recipe main [
-  x:address:number<span class="Special"> &lt;- </span>new <span class="Delimiter">{(</span>foo bar<span class="Delimiter">)</span>: type<span class="Delimiter">}</span>
+  x:address:shared:address:number<span class="Special"> &lt;- </span>new <span class="Delimiter">{(</span>address number<span class="Delimiter">)</span>: type<span class="Delimiter">}</span>
 ]
-<span class="Comment"># type isn't defined so size is meaningless, but at least we parse the type correctly</span>
-<span class="traceContains">+new: size of &lt;&quot;foo&quot; : &lt;&quot;bar&quot; : &lt;&gt;&gt;&gt; is 1</span>
+<span class="traceContains">+new: size of &lt;&quot;address&quot; : &lt;&quot;number&quot; : &lt;&gt;&gt;&gt; is 1</span>
 
+<span class="Delimiter">:(before &quot;End Post-processing(expected_product) When Checking 'new'&quot;)</span>
+expected_product<span class="Delimiter">.</span>properties<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">).</span>second = parse_string_tree<span class="Delimiter">(</span>expected_product<span class="Delimiter">.</span>properties<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">).</span>second<span class="Delimiter">);</span>
+delete expected_product<span class="Delimiter">.</span>type<span class="Delimiter">;</span>
+expected_product<span class="Delimiter">.</span>type = new_type_tree<span class="Delimiter">(</span>expected_product<span class="Delimiter">.</span>properties<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">).</span>second<span class="Delimiter">);</span>
 <span class="Delimiter">:(before &quot;End Post-processing(type_name) When Converting 'new'&quot;)</span>
 type_name = parse_string_tree<span class="Delimiter">(</span>type_name<span class="Delimiter">);</span>
 </pre>
diff --git a/html/056recipe_header.cc.html b/html/056recipe_header.cc.html
index 08cc8fdd..48da455e 100644
--- a/html/056recipe_header.cc.html
+++ b/html/056recipe_header.cc.html
@@ -175,15 +175,133 @@ if <span class="Delimiter">(</span>result<span class="Delimiter">.</span>has_hea
 <span class="Delimiter">:(before &quot;End Rewrite Instruction(curr, recipe result)&quot;)</span>
 if <span class="Delimiter">(</span>curr<span class="Delimiter">.</span>name == <span class="Constant">&quot;load-ingredients&quot;</span><span class="Delimiter">)</span> <span class="Delimiter">{</span>
   curr<span class="Delimiter">.</span>clear<span class="Delimiter">();</span>
+  recipe_ordinal op = get<span class="Delimiter">(</span>Recipe_ordinal<span class="Delimiter">,</span> <span class="Constant">&quot;next-ingredient-without-typechecking&quot;</span><span class="Delimiter">);</span>
   for <span class="Delimiter">(</span>long long int i = <span class="Constant">0</span><span class="Delimiter">;</span> i &lt; SIZE<span class="Delimiter">(</span>result<span class="Delimiter">.</span>ingredients<span class="Delimiter">);</span> ++i<span class="Delimiter">)</span> <span class="Delimiter">{</span>
-    curr<span class="Delimiter">.</span>operation = get<span class="Delimiter">(</span>Recipe_ordinal<span class="Delimiter">,</span> <span class="Constant">&quot;next-ingredient&quot;</span><span class="Delimiter">);</span>
-    curr<span class="Delimiter">.</span>name = <span class="Constant">&quot;next-ingredient&quot;</span><span class="Delimiter">;</span>
+    curr<span class="Delimiter">.</span>operation = op<span class="Delimiter">;</span>
+    curr<span class="Delimiter">.</span>name = <span class="Constant">&quot;next-ingredient-without-typechecking&quot;</span><span class="Delimiter">;</span>
     curr<span class="Delimiter">.</span>products<span class="Delimiter">.</span>push_back<span class="Delimiter">(</span>result<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span>i<span class="Delimiter">));</span>
     result<span class="Delimiter">.</span>steps<span class="Delimiter">.</span>push_back<span class="Delimiter">(</span>curr<span class="Delimiter">);</span>
     curr<span class="Delimiter">.</span>clear<span class="Delimiter">();</span>
   <span class="Delimiter">}</span>
 <span class="Delimiter">}</span>
 
+<span class="Comment">//: internal version of next-ingredient; don't call this directly</span>
+<span class="Delimiter">:(before &quot;End Primitive Recipe Declarations&quot;)</span>
+NEXT_INGREDIENT_WITHOUT_TYPECHECKING<span class="Delimiter">,</span>
+<span class="Delimiter">:(before &quot;End Primitive Recipe Numbers&quot;)</span>
+put<span class="Delimiter">(</span>Recipe_ordinal<span class="Delimiter">,</span> <span class="Constant">&quot;next-ingredient-without-typechecking&quot;</span><span class="Delimiter">,</span> NEXT_INGREDIENT_WITHOUT_TYPECHECKING<span class="Delimiter">);</span>
+<span class="Delimiter">:(before &quot;End Primitive Recipe Checks&quot;)</span>
+case NEXT_INGREDIENT_WITHOUT_TYPECHECKING: <span class="Delimiter">{</span>
+  <span class="Identifier">break</span><span class="Delimiter">;</span>
+<span class="Delimiter">}</span>
+<span class="Delimiter">:(before &quot;End Primitive Recipe Implementations&quot;)</span>
+case NEXT_INGREDIENT_WITHOUT_TYPECHECKING: <span class="Delimiter">{</span>
+  assert<span class="Delimiter">(</span>!Current_routine<span class="Delimiter">-&gt;</span>calls<span class="Delimiter">.</span>empty<span class="Delimiter">());</span>
+  if <span class="Delimiter">(</span>current_call<span class="Delimiter">().</span>next_ingredient_to_process &lt; SIZE<span class="Delimiter">(</span>current_call<span class="Delimiter">().</span>ingredient_atoms<span class="Delimiter">))</span> <span class="Delimiter">{</span>
+    products<span class="Delimiter">.</span>push_back<span class="Delimiter">(</span>
+        current_call<span class="Delimiter">().</span>ingredient_atoms<span class="Delimiter">.</span>at<span class="Delimiter">(</span>current_call<span class="Delimiter">().</span>next_ingredient_to_process<span class="Delimiter">));</span>
+    assert<span class="Delimiter">(</span>SIZE<span class="Delimiter">(</span>products<span class="Delimiter">)</span> == <span class="Constant">1</span><span class="Delimiter">);</span>  products<span class="Delimiter">.</span>resize<span class="Delimiter">(</span><span class="Constant">2</span><span class="Delimiter">);</span>  <span class="Comment">// push a new vector</span>
+    products<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">1</span><span class="Delimiter">).</span>push_back<span class="Delimiter">(</span><span class="Constant">1</span><span class="Delimiter">);</span>
+    ++current_call<span class="Delimiter">().</span>next_ingredient_to_process<span class="Delimiter">;</span>
+  <span class="Delimiter">}</span>
+  else <span class="Delimiter">{</span>
+    products<span class="Delimiter">.</span>resize<span class="Delimiter">(</span><span class="Constant">2</span><span class="Delimiter">);</span>
+    <span class="Comment">// pad the first product with sufficient zeros to match its type</span>
+    long long int size = size_of<span class="Delimiter">(</span>current_instruction<span class="Delimiter">().</span>products<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">));</span>
+    for <span class="Delimiter">(</span>long long int i = <span class="Constant">0</span><span class="Delimiter">;</span> i &lt; size<span class="Delimiter">;</span> ++i<span class="Delimiter">)</span>
+      products<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">).</span>push_back<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">);</span>
+    products<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">1</span><span class="Delimiter">).</span>push_back<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">);</span>
+  <span class="Delimiter">}</span>
+  <span class="Identifier">break</span><span class="Delimiter">;</span>
+<span class="Delimiter">}</span>
+
+<span class="SalientComment">//:: Check all calls against headers.</span>
+
+<span class="Delimiter">:(scenario show_clear_error_on_bad_call)</span>
+<span class="Special">% Hide_errors = true;</span>
+recipe main [
+  <span class="Constant">1</span>:number<span class="Special"> &lt;- </span>foo <span class="Constant">34</span>
+]
+recipe foo x:boolean <span class="Delimiter">-&gt;</span> y:number [
+  local-scope
+  load-ingredients
+  reply <span class="Constant">35</span>
+]
+<span class="traceContains">+error: main: ingredient 0 has the wrong type at '1:number &lt;- foo 34'</span>
+
+<span class="Delimiter">:(scenario show_clear_error_on_bad_call_2)</span>
+<span class="Special">% Hide_errors = true;</span>
+recipe main [
+  <span class="Constant">1</span>:boolean<span class="Special"> &lt;- </span>foo <span class="Constant">34</span>
+]
+recipe foo x:number <span class="Delimiter">-&gt;</span> y:number [
+  local-scope
+  load-ingredients
+  reply x
+]
+<span class="traceContains">+error: main: product 0 has the wrong type at '1:boolean &lt;- foo 34'</span>
+
+<span class="Delimiter">:(after &quot;Transform.push_back(check_instruction)&quot;)</span>
+Transform<span class="Delimiter">.</span>push_back<span class="Delimiter">(</span>check_calls_against_header<span class="Delimiter">);</span>  <span class="Comment">// idempotent</span>
+<span class="Delimiter">:(code)</span>
+void check_calls_against_header<span class="Delimiter">(</span>const recipe_ordinal r<span class="Delimiter">)</span> <span class="Delimiter">{</span>
+  trace<span class="Delimiter">(</span><span class="Constant">9991</span><span class="Delimiter">,</span> <span class="Constant">&quot;transform&quot;</span><span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;--- type-check calls inside recipe &quot;</span> &lt;&lt; get<span class="Delimiter">(</span>Recipe<span class="Delimiter">,</span> r<span class="Delimiter">).</span>name &lt;&lt; end<span class="Delimiter">();</span>
+  const recipe&amp; caller = get<span class="Delimiter">(</span>Recipe<span class="Delimiter">,</span> r<span class="Delimiter">);</span>
+  for <span class="Delimiter">(</span>long long int i = <span class="Constant">0</span><span class="Delimiter">;</span> i &lt; SIZE<span class="Delimiter">(</span>caller<span class="Delimiter">.</span>steps<span class="Delimiter">);</span> ++i<span class="Delimiter">)</span> <span class="Delimiter">{</span>
+    const instruction&amp; inst = caller<span class="Delimiter">.</span>steps<span class="Delimiter">.</span>at<span class="Delimiter">(</span>i<span class="Delimiter">);</span>
+    if <span class="Delimiter">(</span>inst<span class="Delimiter">.</span>operation &lt; MAX_PRIMITIVE_RECIPES<span class="Delimiter">)</span> <span class="Identifier">continue</span><span class="Delimiter">;</span>
+    const recipe&amp; callee = get<span class="Delimiter">(</span>Recipe<span class="Delimiter">,</span> inst<span class="Delimiter">.</span>operation<span class="Delimiter">);</span>
+    if <span class="Delimiter">(</span>!callee<span class="Delimiter">.</span>has_header<span class="Delimiter">)</span> <span class="Identifier">continue</span><span class="Delimiter">;</span>
+    for <span class="Delimiter">(</span>long int i = <span class="Constant">0</span><span class="Delimiter">;</span> i &lt; min<span class="Delimiter">(</span>SIZE<span class="Delimiter">(</span>inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">),</span> SIZE<span class="Delimiter">(</span>callee<span class="Delimiter">.</span>ingredients<span class="Delimiter">));</span> ++i<span class="Delimiter">)</span> <span class="Delimiter">{</span>
+      if <span class="Delimiter">(</span>!types_coercible<span class="Delimiter">(</span>callee<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span>i<span class="Delimiter">),</span> inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span>i<span class="Delimiter">)))</span>
+        raise_error &lt;&lt; maybe<span class="Delimiter">(</span>caller<span class="Delimiter">.</span>name<span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;ingredient &quot;</span> &lt;&lt; i &lt;&lt; <span class="Constant">&quot; has the wrong type at '&quot;</span> &lt;&lt; inst<span class="Delimiter">.</span>to_string<span class="Delimiter">()</span> &lt;&lt; <span class="Constant">&quot;'</span><span class="cSpecial">\n</span><span class="Constant">&quot;</span> &lt;&lt; end<span class="Delimiter">();</span>
+      if <span class="Delimiter">(</span>is_unique_address<span class="Delimiter">(</span>inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span>i<span class="Delimiter">)))</span>
+        raise &lt;&lt; maybe<span class="Delimiter">(</span>caller<span class="Delimiter">.</span>name<span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;try to avoid passing non-shared addresses into calls, like ingredient &quot;</span> &lt;&lt; i &lt;&lt; <span class="Constant">&quot; at '&quot;</span> &lt;&lt; inst<span class="Delimiter">.</span>to_string<span class="Delimiter">()</span> &lt;&lt; <span class="Constant">&quot;'</span><span class="cSpecial">\n</span><span class="Constant">&quot;</span> &lt;&lt; end<span class="Delimiter">();</span>
+    <span class="Delimiter">}</span>
+    for <span class="Delimiter">(</span>long int i = <span class="Constant">0</span><span class="Delimiter">;</span> i &lt; min<span class="Delimiter">(</span>SIZE<span class="Delimiter">(</span>inst<span class="Delimiter">.</span>products<span class="Delimiter">),</span> SIZE<span class="Delimiter">(</span>callee<span class="Delimiter">.</span>products<span class="Delimiter">));</span> ++i<span class="Delimiter">)</span> <span class="Delimiter">{</span>
+      if <span class="Delimiter">(</span>is_dummy<span class="Delimiter">(</span>inst<span class="Delimiter">.</span>products<span class="Delimiter">.</span>at<span class="Delimiter">(</span>i<span class="Delimiter">)))</span> <span class="Identifier">continue</span><span class="Delimiter">;</span>
+      if <span class="Delimiter">(</span>!types_coercible<span class="Delimiter">(</span>callee<span class="Delimiter">.</span>products<span class="Delimiter">.</span>at<span class="Delimiter">(</span>i<span class="Delimiter">),</span> inst<span class="Delimiter">.</span>products<span class="Delimiter">.</span>at<span class="Delimiter">(</span>i<span class="Delimiter">)))</span>
+        raise_error &lt;&lt; maybe<span class="Delimiter">(</span>caller<span class="Delimiter">.</span>name<span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;product &quot;</span> &lt;&lt; i &lt;&lt; <span class="Constant">&quot; has the wrong type at '&quot;</span> &lt;&lt; inst<span class="Delimiter">.</span>to_string<span class="Delimiter">()</span> &lt;&lt; <span class="Constant">&quot;'</span><span class="cSpecial">\n</span><span class="Constant">&quot;</span> &lt;&lt; end<span class="Delimiter">();</span>
+      if <span class="Delimiter">(</span>is_unique_address<span class="Delimiter">(</span>inst<span class="Delimiter">.</span>products<span class="Delimiter">.</span>at<span class="Delimiter">(</span>i<span class="Delimiter">)))</span>
+        raise &lt;&lt; maybe<span class="Delimiter">(</span>caller<span class="Delimiter">.</span>name<span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;try to avoid getting non-shared addresses out of calls, like product &quot;</span> &lt;&lt; i &lt;&lt; <span class="Constant">&quot; at '&quot;</span> &lt;&lt; inst<span class="Delimiter">.</span>to_string<span class="Delimiter">()</span> &lt;&lt; <span class="Constant">&quot;'</span><span class="cSpecial">\n</span><span class="Constant">&quot;</span> &lt;&lt; end<span class="Delimiter">();</span>
+    <span class="Delimiter">}</span>
+  <span class="Delimiter">}</span>
+<span class="Delimiter">}</span>
+
+bool is_unique_address<span class="Delimiter">(</span>reagent x<span class="Delimiter">)</span> <span class="Delimiter">{</span>
+  if <span class="Delimiter">(</span>!canonize_type<span class="Delimiter">(</span>x<span class="Delimiter">))</span> <span class="Identifier">return</span> <span class="Constant">false</span><span class="Delimiter">;</span>
+  if <span class="Delimiter">(</span>!x<span class="Delimiter">.</span>type<span class="Delimiter">)</span> <span class="Identifier">return</span> <span class="Constant">false</span><span class="Delimiter">;</span>
+  if <span class="Delimiter">(</span>x<span class="Delimiter">.</span>type<span class="Delimiter">-&gt;</span>value != get<span class="Delimiter">(</span>Type_ordinal<span class="Delimiter">,</span> <span class="Constant">&quot;address&quot;</span><span class="Delimiter">))</span> <span class="Identifier">return</span> <span class="Constant">false</span><span class="Delimiter">;</span>
+  if <span class="Delimiter">(</span>!x<span class="Delimiter">.</span>type<span class="Delimiter">-&gt;</span>right<span class="Delimiter">)</span> <span class="Identifier">return</span> <span class="Constant">true</span><span class="Delimiter">;</span>
+  <span class="Identifier">return</span> x<span class="Delimiter">.</span>type<span class="Delimiter">-&gt;</span>right<span class="Delimiter">-&gt;</span>value != get<span class="Delimiter">(</span>Type_ordinal<span class="Delimiter">,</span> <span class="Constant">&quot;shared&quot;</span><span class="Delimiter">);</span>
+<span class="Delimiter">}</span>
+
+<span class="Comment">//: additionally, warn on calls receiving non-shared addresses</span>
+
+<span class="Delimiter">:(scenario warn_on_calls_with_addresses)</span>
+<span class="Special">% Hide_warnings= true;</span>
+recipe main [
+  <span class="Constant">1</span>:address:number<span class="Special"> &lt;- </span>copy <span class="Constant">3</span>/unsafe
+  foo <span class="Constant">1</span>:address:number
+]
+recipe foo x:address:number [
+  local-scope
+  load-ingredients
+]
+<span class="traceContains">+warn: main: try to avoid passing non-shared addresses into calls, like ingredient 0 at 'foo 1:address:number'</span>
+
+<span class="Delimiter">:(scenario warn_on_calls_with_addresses_2)</span>
+<span class="Special">% Hide_warnings= true;</span>
+recipe main [
+  <span class="Constant">1</span>:address:number<span class="Special"> &lt;- </span>foo
+]
+recipe foo <span class="Delimiter">-&gt;</span> x:address:number [
+  local-scope
+  load-ingredients
+  x<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
+]
+<span class="traceContains">+warn: main: try to avoid getting non-shared addresses out of calls, like product 0 at '1:address:number &lt;- foo '</span>
+
 <span class="SalientComment">//:: Check types going in and out of all recipes with headers.</span>
 
 <span class="Delimiter">:(scenarios transform)</span>
@@ -235,6 +353,7 @@ Transform<span class="Delimiter">.</span>push_back<span class="Delimiter">(</spa
 void check_header_ingredients<span class="Delimiter">(</span>const recipe_ordinal r<span class="Delimiter">)</span> <span class="Delimiter">{</span>
   recipe&amp; caller_recipe = get<span class="Delimiter">(</span>Recipe<span class="Delimiter">,</span> r<span class="Delimiter">);</span>
   if <span class="Delimiter">(</span>caller_recipe<span class="Delimiter">.</span>products<span class="Delimiter">.</span>empty<span class="Delimiter">())</span> <span class="Identifier">return</span><span class="Delimiter">;</span>
+  caller_recipe<span class="Delimiter">.</span>ingredient_index<span class="Delimiter">.</span>clear<span class="Delimiter">();</span>
   trace<span class="Delimiter">(</span><span class="Constant">9991</span><span class="Delimiter">,</span> <span class="Constant">&quot;transform&quot;</span><span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;--- checking reply instructions against header for &quot;</span> &lt;&lt; caller_recipe<span class="Delimiter">.</span>name &lt;&lt; end<span class="Delimiter">();</span>
   for <span class="Delimiter">(</span>long long int i = <span class="Constant">0</span><span class="Delimiter">;</span> i &lt; SIZE<span class="Delimiter">(</span>caller_recipe<span class="Delimiter">.</span>ingredients<span class="Delimiter">);</span> ++i<span class="Delimiter">)</span> <span class="Delimiter">{</span>
     if <span class="Delimiter">(</span>contains_key<span class="Delimiter">(</span>caller_recipe<span class="Delimiter">.</span>ingredient_index<span class="Delimiter">,</span> caller_recipe<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span>i<span class="Delimiter">).</span>name<span class="Delimiter">))</span>
@@ -284,10 +403,8 @@ void deduce_types_from_header<span class="Delimiter">(</span>const recipe_ordina
     trace<span class="Delimiter">(</span><span class="Constant">9992</span><span class="Delimiter">,</span> <span class="Constant">&quot;transform&quot;</span><span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;instruction: &quot;</span> &lt;&lt; inst<span class="Delimiter">.</span>to_string<span class="Delimiter">()</span> &lt;&lt; end<span class="Delimiter">();</span>
     for <span class="Delimiter">(</span>long long int i = <span class="Constant">0</span><span class="Delimiter">;</span> i &lt; SIZE<span class="Delimiter">(</span>inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">);</span> ++i<span class="Delimiter">)</span> <span class="Delimiter">{</span>
       if <span class="Delimiter">(</span>inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span>i<span class="Delimiter">).</span>type<span class="Delimiter">)</span> <span class="Identifier">continue</span><span class="Delimiter">;</span>
-      if <span class="Delimiter">(</span>header_type<span class="Delimiter">.</span>find<span class="Delimiter">(</span>inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span>i<span class="Delimiter">).</span>name<span class="Delimiter">)</span> == header_type<span class="Delimiter">.</span>end<span class="Delimiter">())</span> <span class="Delimiter">{</span>
-        raise &lt;&lt; maybe<span class="Delimiter">(</span>caller_recipe<span class="Delimiter">.</span>name<span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;unknown variable &quot;</span> &lt;&lt; inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span>i<span class="Delimiter">).</span>name &lt;&lt; <span class="Constant">&quot; in '&quot;</span> &lt;&lt; inst<span class="Delimiter">.</span>to_string<span class="Delimiter">()</span> &lt;&lt; <span class="Constant">&quot;'</span><span class="cSpecial">\n</span><span class="Constant">&quot;</span> &lt;&lt; end<span class="Delimiter">();</span>
+      if <span class="Delimiter">(</span>header_type<span class="Delimiter">.</span>find<span class="Delimiter">(</span>inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span>i<span class="Delimiter">).</span>name<span class="Delimiter">)</span> == header_type<span class="Delimiter">.</span>end<span class="Delimiter">())</span>
         <span class="Identifier">continue</span><span class="Delimiter">;</span>
-      <span class="Delimiter">}</span>
       if <span class="Delimiter">(</span>!inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span>i<span class="Delimiter">).</span>type<span class="Delimiter">)</span>
         inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span>i<span class="Delimiter">).</span>type = new type_tree<span class="Delimiter">(</span>*get<span class="Delimiter">(</span>header_type<span class="Delimiter">,</span> inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span>i<span class="Delimiter">).</span>name<span class="Delimiter">));</span>
       if <span class="Delimiter">(</span>!inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span>i<span class="Delimiter">).</span>properties<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">).</span>second<span class="Delimiter">)</span>
@@ -297,10 +414,8 @@ void deduce_types_from_header<span class="Delimiter">(</span>const recipe_ordina
     for <span class="Delimiter">(</span>long long int i = <span class="Constant">0</span><span class="Delimiter">;</span> i &lt; SIZE<span class="Delimiter">(</span>inst<span class="Delimiter">.</span>products<span class="Delimiter">);</span> ++i<span class="Delimiter">)</span> <span class="Delimiter">{</span>
       trace<span class="Delimiter">(</span><span class="Constant">9993</span><span class="Delimiter">,</span> <span class="Constant">&quot;transform&quot;</span><span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;  product: &quot;</span> &lt;&lt; debug_string<span class="Delimiter">(</span>inst<span class="Delimiter">.</span>products<span class="Delimiter">.</span>at<span class="Delimiter">(</span>i<span class="Delimiter">))</span> &lt;&lt; end<span class="Delimiter">();</span>
       if <span class="Delimiter">(</span>inst<span class="Delimiter">.</span>products<span class="Delimiter">.</span>at<span class="Delimiter">(</span>i<span class="Delimiter">).</span>type<span class="Delimiter">)</span> <span class="Identifier">continue</span><span class="Delimiter">;</span>
-      if <span class="Delimiter">(</span>header_type<span class="Delimiter">.</span>find<span class="Delimiter">(</span>inst<span class="Delimiter">.</span>products<span class="Delimiter">.</span>at<span class="Delimiter">(</span>i<span class="Delimiter">).</span>name<span class="Delimiter">)</span> == header_type<span class="Delimiter">.</span>end<span class="Delimiter">())</span> <span class="Delimiter">{</span>
-        raise &lt;&lt; maybe<span class="Delimiter">(</span>caller_recipe<span class="Delimiter">.</span>name<span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;unknown variable &quot;</span> &lt;&lt; inst<span class="Delimiter">.</span>products<span class="Delimiter">.</span>at<span class="Delimiter">(</span>i<span class="Delimiter">).</span>name &lt;&lt; <span class="Constant">&quot; in '&quot;</span> &lt;&lt; inst<span class="Delimiter">.</span>to_string<span class="Delimiter">()</span> &lt;&lt; <span class="Constant">&quot;'</span><span class="cSpecial">\n</span><span class="Constant">&quot;</span> &lt;&lt; end<span class="Delimiter">();</span>
+      if <span class="Delimiter">(</span>header_type<span class="Delimiter">.</span>find<span class="Delimiter">(</span>inst<span class="Delimiter">.</span>products<span class="Delimiter">.</span>at<span class="Delimiter">(</span>i<span class="Delimiter">).</span>name<span class="Delimiter">)</span> == header_type<span class="Delimiter">.</span>end<span class="Delimiter">())</span>
         <span class="Identifier">continue</span><span class="Delimiter">;</span>
-      <span class="Delimiter">}</span>
       if <span class="Delimiter">(</span>!inst<span class="Delimiter">.</span>products<span class="Delimiter">.</span>at<span class="Delimiter">(</span>i<span class="Delimiter">).</span>type<span class="Delimiter">)</span>
         inst<span class="Delimiter">.</span>products<span class="Delimiter">.</span>at<span class="Delimiter">(</span>i<span class="Delimiter">).</span>type = new type_tree<span class="Delimiter">(</span>*get<span class="Delimiter">(</span>header_type<span class="Delimiter">,</span> inst<span class="Delimiter">.</span>products<span class="Delimiter">.</span>at<span class="Delimiter">(</span>i<span class="Delimiter">).</span>name<span class="Delimiter">));</span>
       if <span class="Delimiter">(</span>!inst<span class="Delimiter">.</span>products<span class="Delimiter">.</span>at<span class="Delimiter">(</span>i<span class="Delimiter">).</span>properties<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">).</span>second<span class="Delimiter">)</span>
@@ -415,6 +530,10 @@ recipe add2 x:number<span class="Delimiter">,</span> y:number <span class="Delim
   load-ingredients
 ]
 <span class="traceContains">+error: main: '3:number &lt;- add2 1:number, 2:number' should write to 1:number rather than 3:number</span>
+
+<span class="Delimiter">:(before &quot;End Includes&quot;)</span>
+using std::min<span class="Delimiter">;</span>
+using std::max<span class="Delimiter">;</span>
 </pre>
 </body>
 </html>
diff --git a/html/057static_dispatch.cc.html b/html/057static_dispatch.cc.html
index 04d02ab2..319c72e9 100644
--- a/html/057static_dispatch.cc.html
+++ b/html/057static_dispatch.cc.html
@@ -13,8 +13,8 @@
 pre { white-space: pre-wrap; font-family: monospace; color: #eeeeee; background-color: #080808; }
 body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 * { font-size: 1.05em; }
-.traceContains { color: #008000; }
 .traceAbsent { color: #c00000; }
+.traceContains { color: #008000; }
 .Identifier { color: #804000; }
 .cSpecial { color: #008000; }
 .Comment { color: #9090ff; }
@@ -65,16 +65,14 @@ for <span class="Delimiter">(</span>map&lt;string<span class="Delimiter">,</span
 <span class="Delimiter">}</span>
 
 <span class="Delimiter">:(before &quot;End Load Recipe Header(result)&quot;)</span>
-if <span class="Delimiter">(</span>contains_key<span class="Delimiter">(</span>Recipe_ordinal<span class="Delimiter">,</span> result<span class="Delimiter">.</span>name<span class="Delimiter">))</span> <span class="Delimiter">{</span>
+if <span class="Delimiter">(</span>result<span class="Delimiter">.</span>name != <span class="Constant">&quot;main&quot;</span> &amp;&amp; contains_key<span class="Delimiter">(</span>Recipe_ordinal<span class="Delimiter">,</span> result<span class="Delimiter">.</span>name<span class="Delimiter">))</span> <span class="Delimiter">{</span>
   const recipe_ordinal r = get<span class="Delimiter">(</span>Recipe_ordinal<span class="Delimiter">,</span> result<span class="Delimiter">.</span>name<span class="Delimiter">);</span>
-<span class="CommentedCode">//?   LOG &lt;&lt; &quot;checking &quot; &lt;&lt; r &lt;&lt; &quot; &quot; &lt;&lt; result.name &lt;&lt; '\n';</span>
 <span class="CommentedCode">//?   cerr &lt;&lt; result.name &lt;&lt; &quot;: &quot; &lt;&lt; contains_key(Recipe, r) &lt;&lt; (contains_key(Recipe, r) ? get(Recipe, r).has_header : 0) &lt;&lt; matching_variant_name(result) &lt;&lt; '\n';</span>
   if <span class="Delimiter">(</span>!contains_key<span class="Delimiter">(</span>Recipe<span class="Delimiter">,</span> r<span class="Delimiter">)</span> || get<span class="Delimiter">(</span>Recipe<span class="Delimiter">,</span> r<span class="Delimiter">).</span>has_header<span class="Delimiter">)</span> <span class="Delimiter">{</span>
     string new_name = matching_variant_name<span class="Delimiter">(</span>result<span class="Delimiter">);</span>
     if <span class="Delimiter">(</span>new_name<span class="Delimiter">.</span>empty<span class="Delimiter">())</span> <span class="Delimiter">{</span>
       <span class="Comment">// variant doesn't already exist</span>
       new_name = next_unused_recipe_name<span class="Delimiter">(</span>result<span class="Delimiter">.</span>name<span class="Delimiter">);</span>
-<span class="CommentedCode">//?       LOG &lt;&lt; &quot;adding a variant of &quot; &lt;&lt; result.name &lt;&lt; &quot;: &quot; &lt;&lt; new_name &lt;&lt; &quot; is now &quot; &lt;&lt; Next_recipe_ordinal &lt;&lt; '\n';</span>
       put<span class="Delimiter">(</span>Recipe_ordinal<span class="Delimiter">,</span> new_name<span class="Delimiter">,</span> Next_recipe_ordinal++<span class="Delimiter">);</span>
       get_or_insert<span class="Delimiter">(</span>Recipe_variants<span class="Delimiter">,</span> result<span class="Delimiter">.</span>name<span class="Delimiter">).</span>push_back<span class="Delimiter">(</span>get<span class="Delimiter">(</span>Recipe_ordinal<span class="Delimiter">,</span> new_name<span class="Delimiter">));</span>
     <span class="Delimiter">}</span>
@@ -84,7 +82,6 @@ if <span class="Delimiter">(</span>contains_key<span class="Delimiter">(</span>R
 <span class="Delimiter">}</span>
 else <span class="Delimiter">{</span>
   <span class="Comment">// save first variant</span>
-<span class="CommentedCode">//?   LOG &lt;&lt; &quot;saving first variant of &quot; &lt;&lt; result.name &lt;&lt; &quot;: &quot; &lt;&lt; Next_recipe_ordinal &lt;&lt; '\n';</span>
   put<span class="Delimiter">(</span>Recipe_ordinal<span class="Delimiter">,</span> result<span class="Delimiter">.</span>name<span class="Delimiter">,</span> Next_recipe_ordinal++<span class="Delimiter">);</span>
   get_or_insert<span class="Delimiter">(</span>Recipe_variants<span class="Delimiter">,</span> result<span class="Delimiter">.</span>name<span class="Delimiter">).</span>push_back<span class="Delimiter">(</span>get<span class="Delimiter">(</span>Recipe_ordinal<span class="Delimiter">,</span> result<span class="Delimiter">.</span>name<span class="Delimiter">));</span>
 <span class="Delimiter">}</span>
@@ -93,14 +90,11 @@ else <span class="Delimiter">{</span>
 string matching_variant_name<span class="Delimiter">(</span>const recipe&amp; rr<span class="Delimiter">)</span> <span class="Delimiter">{</span>
   const vector&lt;recipe_ordinal&gt;&amp; variants = get_or_insert<span class="Delimiter">(</span>Recipe_variants<span class="Delimiter">,</span> rr<span class="Delimiter">.</span>name<span class="Delimiter">);</span>
   for <span class="Delimiter">(</span>long long int i = <span class="Constant">0</span><span class="Delimiter">;</span> i &lt; SIZE<span class="Delimiter">(</span>variants<span class="Delimiter">);</span> ++i<span class="Delimiter">)</span> <span class="Delimiter">{</span>
-<span class="CommentedCode">//?     LOG &lt;&lt; &quot;checking variant &quot; &lt;&lt; variants.at(i) &lt;&lt; &quot; of &quot; &lt;&lt; rr.name &lt;&lt; '\n';</span>
     if <span class="Delimiter">(</span>!contains_key<span class="Delimiter">(</span>Recipe<span class="Delimiter">,</span> variants<span class="Delimiter">.</span>at<span class="Delimiter">(</span>i<span class="Delimiter">)))</span> <span class="Identifier">continue</span><span class="Delimiter">;</span>
     const recipe&amp; candidate = get<span class="Delimiter">(</span>Recipe<span class="Delimiter">,</span> variants<span class="Delimiter">.</span>at<span class="Delimiter">(</span>i<span class="Delimiter">));</span>
     if <span class="Delimiter">(</span>!all_reagents_match<span class="Delimiter">(</span>rr<span class="Delimiter">,</span> candidate<span class="Delimiter">))</span> <span class="Identifier">continue</span><span class="Delimiter">;</span>
-<span class="CommentedCode">//?     LOG &lt;&lt; &quot;  exists\n&quot;;</span>
     <span class="Identifier">return</span> candidate<span class="Delimiter">.</span>name<span class="Delimiter">;</span>
   <span class="Delimiter">}</span>
-<span class="CommentedCode">//?   LOG &lt;&lt; &quot;  does not exist\n&quot;;</span>
   <span class="Identifier">return</span> <span class="Constant">&quot;&quot;</span><span class="Delimiter">;</span>
 <span class="Delimiter">}</span>
 
@@ -178,7 +172,7 @@ for <span class="Delimiter">(</span>long long int i = <span class="Constant">0</
 <span class="Delimiter">}</span>
 
 <span class="Comment">//: after filling in all missing types (because we'll be introducing 'blank' types in this transform in a later layer, for shape-shifting recipes)</span>
-<span class="Delimiter">:(after &quot;End Type Modifying Transforms&quot;)</span>
+<span class="Delimiter">:(after &quot;Transform.push_back(transform_names)&quot;)</span>
 Transform<span class="Delimiter">.</span>push_back<span class="Delimiter">(</span>resolve_ambiguous_calls<span class="Delimiter">);</span>  <span class="Comment">// idempotent</span>
 
 <span class="Delimiter">:(code)</span>
@@ -224,13 +218,8 @@ long long int variant_score<span class="Delimiter">(</span>const instruction&amp
     <span class="Identifier">return</span> -<span class="Constant">1</span><span class="Delimiter">;</span>
   <span class="Delimiter">}</span>
   const vector&lt;reagent&gt;&amp; header_ingredients = get<span class="Delimiter">(</span>Recipe<span class="Delimiter">,</span> variant<span class="Delimiter">).</span>ingredients<span class="Delimiter">;</span>
-  if <span class="Delimiter">(</span>SIZE<span class="Delimiter">(</span>inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">)</span> &lt; SIZE<span class="Delimiter">(</span>header_ingredients<span class="Delimiter">))</span> <span class="Delimiter">{</span>
-    trace<span class="Delimiter">(</span><span class="Constant">9993</span><span class="Delimiter">,</span> <span class="Constant">&quot;transform&quot;</span><span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;too few ingredients&quot;</span> &lt;&lt; end<span class="Delimiter">();</span>
-<span class="CommentedCode">//?     cerr &lt;&lt; &quot;too few ingredients\n&quot;;</span>
-    <span class="Identifier">return</span> -<span class="Constant">1</span><span class="Delimiter">;</span>
-  <span class="Delimiter">}</span>
 <span class="CommentedCode">//?   cerr &lt;&lt; &quot;=== checking ingredients\n&quot;;</span>
-  for <span class="Delimiter">(</span>long long int i = <span class="Constant">0</span><span class="Delimiter">;</span> i &lt; SIZE<span class="Delimiter">(</span>header_ingredients<span class="Delimiter">);</span> ++i<span class="Delimiter">)</span> <span class="Delimiter">{</span>
+  for <span class="Delimiter">(</span>long long int i = <span class="Constant">0</span><span class="Delimiter">;</span> i &lt; min<span class="Delimiter">(</span>SIZE<span class="Delimiter">(</span>inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">),</span> SIZE<span class="Delimiter">(</span>header_ingredients<span class="Delimiter">));</span> ++i<span class="Delimiter">)</span> <span class="Delimiter">{</span>
     if <span class="Delimiter">(</span>!types_match<span class="Delimiter">(</span>header_ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span>i<span class="Delimiter">),</span> inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span>i<span class="Delimiter">)))</span> <span class="Delimiter">{</span>
       trace<span class="Delimiter">(</span><span class="Constant">9993</span><span class="Delimiter">,</span> <span class="Constant">&quot;transform&quot;</span><span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;mismatch: ingredient &quot;</span> &lt;&lt; i &lt;&lt; end<span class="Delimiter">();</span>
 <span class="CommentedCode">//?       cerr &lt;&lt; &quot;mismatch: ingredient &quot; &lt;&lt; i &lt;&lt; '\n';</span>
@@ -253,13 +242,8 @@ long long int variant_score<span class="Delimiter">(</span>const instruction&amp
     <span class="Delimiter">}</span>
   <span class="Delimiter">}</span>
 <span class="CommentedCode">//?   cerr &lt;&lt; &quot;=== done checking ingredients\n&quot;;</span>
-  if <span class="Delimiter">(</span>SIZE<span class="Delimiter">(</span>inst<span class="Delimiter">.</span>products<span class="Delimiter">)</span> &gt; SIZE<span class="Delimiter">(</span>get<span class="Delimiter">(</span>Recipe<span class="Delimiter">,</span> variant<span class="Delimiter">).</span>products<span class="Delimiter">))</span> <span class="Delimiter">{</span>
-    trace<span class="Delimiter">(</span><span class="Constant">9993</span><span class="Delimiter">,</span> <span class="Constant">&quot;transform&quot;</span><span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;too few products&quot;</span> &lt;&lt; end<span class="Delimiter">();</span>
-<span class="CommentedCode">//?     cerr &lt;&lt; &quot;too few products\n&quot;;</span>
-    <span class="Identifier">return</span> -<span class="Constant">1</span><span class="Delimiter">;</span>
-  <span class="Delimiter">}</span>
   const vector&lt;reagent&gt;&amp; header_products = get<span class="Delimiter">(</span>Recipe<span class="Delimiter">,</span> variant<span class="Delimiter">).</span>products<span class="Delimiter">;</span>
-  for <span class="Delimiter">(</span>long long int i = <span class="Constant">0</span><span class="Delimiter">;</span> i &lt; SIZE<span class="Delimiter">(</span>inst<span class="Delimiter">.</span>products<span class="Delimiter">);</span> ++i<span class="Delimiter">)</span> <span class="Delimiter">{</span>
+  for <span class="Delimiter">(</span>long long int i = <span class="Constant">0</span><span class="Delimiter">;</span> i &lt; min<span class="Delimiter">(</span>SIZE<span class="Delimiter">(</span>header_products<span class="Delimiter">),</span> SIZE<span class="Delimiter">(</span>inst<span class="Delimiter">.</span>products<span class="Delimiter">));</span> ++i<span class="Delimiter">)</span> <span class="Delimiter">{</span>
     if <span class="Delimiter">(</span>is_dummy<span class="Delimiter">(</span>inst<span class="Delimiter">.</span>products<span class="Delimiter">.</span>at<span class="Delimiter">(</span>i<span class="Delimiter">)))</span> <span class="Identifier">continue</span><span class="Delimiter">;</span>
     if <span class="Delimiter">(</span>!types_match<span class="Delimiter">(</span>header_products<span class="Delimiter">.</span>at<span class="Delimiter">(</span>i<span class="Delimiter">),</span> inst<span class="Delimiter">.</span>products<span class="Delimiter">.</span>at<span class="Delimiter">(</span>i<span class="Delimiter">)))</span> <span class="Delimiter">{</span>
       trace<span class="Delimiter">(</span><span class="Constant">9993</span><span class="Delimiter">,</span> <span class="Constant">&quot;transform&quot;</span><span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;mismatch: product &quot;</span> &lt;&lt; i &lt;&lt; end<span class="Delimiter">();</span>
@@ -283,8 +267,8 @@ long long int variant_score<span class="Delimiter">(</span>const instruction&amp
     <span class="Delimiter">}</span>
   <span class="Delimiter">}</span>
   <span class="Comment">// the greater the number of unused ingredients/products, the lower the score</span>
-  <span class="Identifier">return</span> result - <span class="Delimiter">(</span>SIZE<span class="Delimiter">(</span>get<span class="Delimiter">(</span>Recipe<span class="Delimiter">,</span> variant<span class="Delimiter">).</span>products<span class="Delimiter">)</span>-SIZE<span class="Delimiter">(</span>inst<span class="Delimiter">.</span>products<span class="Delimiter">))</span>
-                - <span class="Delimiter">(</span>SIZE<span class="Delimiter">(</span>inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">)</span>-SIZE<span class="Delimiter">(</span>get<span class="Delimiter">(</span>Recipe<span class="Delimiter">,</span> variant<span class="Delimiter">).</span>ingredients<span class="Delimiter">));</span>  <span class="Comment">// ok to go negative</span>
+  <span class="Identifier">return</span> result - abs<span class="Delimiter">(</span>SIZE<span class="Delimiter">(</span>get<span class="Delimiter">(</span>Recipe<span class="Delimiter">,</span> variant<span class="Delimiter">).</span>products<span class="Delimiter">)</span>-SIZE<span class="Delimiter">(</span>inst<span class="Delimiter">.</span>products<span class="Delimiter">))</span>
+                - abs<span class="Delimiter">(</span>SIZE<span class="Delimiter">(</span>inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">)</span>-SIZE<span class="Delimiter">(</span>get<span class="Delimiter">(</span>Recipe<span class="Delimiter">,</span> variant<span class="Delimiter">).</span>ingredients<span class="Delimiter">));</span>
 <span class="Delimiter">}</span>
 
 <span class="Delimiter">:(scenario static_dispatch_disabled_on_headerless_definition)</span>
@@ -348,13 +332,13 @@ $error: <span class="Constant">0</span>
 <span class="Delimiter">:(scenario static_dispatch_works_with_compound_type_containing_container_defined_after_first_use)</span>
 <span class="Special">% Hide_errors = true;</span>
 recipe main [
-  x:address:foo<span class="Special"> &lt;- </span>new foo:type
+  x:address:shared:foo<span class="Special"> &lt;- </span>new foo:type
   test x
 ]
 container foo [
   x:number
 ]
-recipe test a:address:foo <span class="Delimiter">-&gt;</span> z:number [
+recipe test a:address:shared:foo <span class="Delimiter">-&gt;</span> z:number [
   local-scope
   load-ingredients
   z:number<span class="Special"> &lt;- </span>get *a<span class="Delimiter">,</span> x:offset
@@ -364,10 +348,10 @@ $error: <span class="Constant">0</span>
 <span class="Delimiter">:(scenario static_dispatch_works_with_compound_type_containing_container_defined_after_second_use)</span>
 <span class="Special">% Hide_errors = true;</span>
 recipe main [
-  x:address:foo<span class="Special"> &lt;- </span>new foo:type
+  x:address:shared:foo<span class="Special"> &lt;- </span>new foo:type
   test x
 ]
-recipe test a:address:foo <span class="Delimiter">-&gt;</span> z:number [
+recipe test a:address:shared:foo <span class="Delimiter">-&gt;</span> z:number [
   local-scope
   load-ingredients
   z:number<span class="Special"> &lt;- </span>get *a<span class="Delimiter">,</span> x:offset
@@ -400,7 +384,7 @@ recipe foo x:number <span class="Delimiter">-&gt;</span> y:number [
   load-ingredients
   reply <span class="Constant">34</span>
 ]
-<span class="traceContains">+error: foo: wrong type for ingredient x:number</span>
+<span class="traceContains">+error: main: ingredient 0 has the wrong type at '1:number/raw &lt;- foo x'</span>
 <span class="traceAbsent">-mem: storing 34 in location 1</span>
 
 <span class="Delimiter">:(scenario static_dispatch_dispatches_literal_to_boolean_before_character)</span>
@@ -454,43 +438,6 @@ recipe foo x:number <span class="Delimiter">-&gt;</span> y:number [
 <span class="Comment"># number variant is preferred</span>
 <span class="traceContains">+mem: storing 35 in location 1</span>
 
-<span class="Comment">//: after we make all attempts to dispatch, any unhandled cases will end up at</span>
-<span class="Comment">//: some wrong variant and trigger an error while trying to load-ingredients</span>
-
-<span class="Delimiter">:(scenario static_dispatch_shows_clear_error_on_missing_variant)</span>
-<span class="Special">% Hide_errors = true;</span>
-recipe main [
-  <span class="Constant">1</span>:number<span class="Special"> &lt;- </span>foo <span class="Constant">34</span>
-]
-recipe foo x:boolean <span class="Delimiter">-&gt;</span> y:number [
-  local-scope
-  load-ingredients
-  reply <span class="Constant">35</span>
-]
-<span class="traceContains">+error: foo: wrong type for ingredient x:boolean</span>
-<span class="traceContains">+error:   (we're inside recipe foo x:boolean -&gt; y:number)</span>
-<span class="traceContains">+error:   (we're trying to call '1:number &lt;- foo 34' inside recipe main)</span>
-
-<span class="Delimiter">:(before &quot;End next-ingredient Type Mismatch Error&quot;)</span>
-raise_error &lt;&lt; <span class="Constant">&quot;   (we're inside &quot;</span> &lt;&lt; header_label<span class="Delimiter">(</span>current_call<span class="Delimiter">().</span>running_recipe<span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;)</span><span class="cSpecial">\n</span><span class="Constant">&quot;</span> &lt;&lt; end<span class="Delimiter">();</span>
-raise_error &lt;&lt; <span class="Constant">&quot;   (we're trying to call '&quot;</span> &lt;&lt; to_instruction<span class="Delimiter">(</span>*++Current_routine<span class="Delimiter">-&gt;</span>calls<span class="Delimiter">.</span>begin<span class="Delimiter">()).</span>to_string<span class="Delimiter">()</span> &lt;&lt; <span class="Constant">&quot;' inside &quot;</span> &lt;&lt; header_label<span class="Delimiter">((</span>++Current_routine<span class="Delimiter">-&gt;</span>calls<span class="Delimiter">.</span>begin<span class="Delimiter">())-&gt;</span>running_recipe<span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;)</span><span class="cSpecial">\n</span><span class="Constant">&quot;</span> &lt;&lt; end<span class="Delimiter">();</span>
-
-<span class="Delimiter">:(scenario static_dispatch_shows_clear_error_on_missing_variant_2)</span>
-<span class="Special">% Hide_errors = true;</span>
-recipe main [
-  <span class="Constant">1</span>:boolean<span class="Special"> &lt;- </span>foo <span class="Constant">34</span>
-]
-recipe foo x:number <span class="Delimiter">-&gt;</span> y:number [
-  local-scope
-  load-ingredients
-  reply x
-]
-<span class="traceContains">+error: foo: reply ingredient x can't be saved in 1:boolean</span>
-<span class="traceContains">+error:   (we just returned from recipe foo x:number -&gt; y:number)</span>
-
-<span class="Delimiter">:(before &quot;End reply Type Mismatch Error&quot;)</span>
-raise_error &lt;&lt; <span class="Constant">&quot;   (we just returned from &quot;</span> &lt;&lt; header_label<span class="Delimiter">(</span>caller_instruction<span class="Delimiter">.</span>operation<span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;)</span><span class="cSpecial">\n</span><span class="Constant">&quot;</span> &lt;&lt; end<span class="Delimiter">();</span>
-
 <span class="Delimiter">:(code)</span>
 string header_label<span class="Delimiter">(</span>recipe_ordinal r<span class="Delimiter">)</span> <span class="Delimiter">{</span>
   const recipe&amp; caller = get<span class="Delimiter">(</span>Recipe<span class="Delimiter">,</span> r<span class="Delimiter">);</span>
@@ -527,6 +474,27 @@ recipe! foo x:address:number <span class="Delimiter">-&gt;</span> y:number [
 <span class="traceContains">+mem: storing 34 in location 2</span>
 $error: <span class="Constant">0</span>
 $warn: <span class="Constant">0</span>
+
+<span class="Delimiter">:(scenario dispatch_errors_come_after_unknown_name_errors)</span>
+<span class="Special">% Hide_errors = true;</span>
+recipe main [
+  y:number<span class="Special"> &lt;- </span>foo x
+]
+recipe foo a:number <span class="Delimiter">-&gt;</span> b:number [
+  local-scope
+  load-ingredients
+  reply <span class="Constant">34</span>
+]
+recipe foo a:boolean <span class="Delimiter">-&gt;</span> b:number [
+  local-scope
+  load-ingredients
+  reply <span class="Constant">35</span>
+]
+<span class="traceContains">+error: main: missing type for x in 'y:number &lt;- foo x'</span>
+<span class="traceContains">+error: main: failed to find a matching call for 'y:number &lt;- foo x'</span>
+
+<span class="Delimiter">:(before &quot;End Includes&quot;)</span>
+using std::abs<span class="Delimiter">;</span>
 </pre>
 </body>
 </html>
diff --git a/html/059shape_shifting_recipe.cc.html b/html/059shape_shifting_recipe.cc.html
index 4b895042..dcbcd680 100644
--- a/html/059shape_shifting_recipe.cc.html
+++ b/html/059shape_shifting_recipe.cc.html
@@ -109,32 +109,28 @@ if <span class="Delimiter">(</span>best_score == -<span class="Constant">1</span
   if <span class="Delimiter">(</span>exemplar<span class="Delimiter">)</span> <span class="Delimiter">{</span>
 <span class="CommentedCode">//?     cerr &lt;&lt; &quot;specializing &quot; &lt;&lt; inst.name &lt;&lt; '\n';</span>
     trace<span class="Delimiter">(</span><span class="Constant">9992</span><span class="Delimiter">,</span> <span class="Constant">&quot;transform&quot;</span><span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;found variant to specialize: &quot;</span> &lt;&lt; exemplar &lt;&lt; <span class="Constant">' '</span> &lt;&lt; get<span class="Delimiter">(</span>Recipe<span class="Delimiter">,</span> exemplar<span class="Delimiter">).</span>name &lt;&lt; end<span class="Delimiter">();</span>
-    LOG &lt;&lt; <span class="Constant">&quot;found variant to specialize: &quot;</span> &lt;&lt; exemplar &lt;&lt; <span class="Constant">' '</span> &lt;&lt; header<span class="Delimiter">(</span>get<span class="Delimiter">(</span>Recipe<span class="Delimiter">,</span> exemplar<span class="Delimiter">))</span> &lt;&lt; <span class="cSpecial">'\n'</span><span class="Delimiter">;</span>
     recipe_ordinal new_recipe_ordinal = new_variant<span class="Delimiter">(</span>exemplar<span class="Delimiter">,</span> inst<span class="Delimiter">,</span> caller_recipe<span class="Delimiter">);</span>
+    if <span class="Delimiter">(</span>new_recipe_ordinal == <span class="Constant">0</span><span class="Delimiter">)</span> <span class="Identifier">goto</span> done_constructing_variant<span class="Delimiter">;</span>
     variants<span class="Delimiter">.</span>push_back<span class="Delimiter">(</span>new_recipe_ordinal<span class="Delimiter">);</span>
     <span class="Comment">// perform all transforms on the new specialization</span>
     const string&amp; new_name = get<span class="Delimiter">(</span>Recipe<span class="Delimiter">,</span> variants<span class="Delimiter">.</span>back<span class="Delimiter">()).</span>name<span class="Delimiter">;</span>
     trace<span class="Delimiter">(</span><span class="Constant">9992</span><span class="Delimiter">,</span> <span class="Constant">&quot;transform&quot;</span><span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;transforming new specialization: &quot;</span> &lt;&lt; new_name &lt;&lt; end<span class="Delimiter">();</span>
-    LOG &lt;&lt; <span class="Constant">&quot;transforming new specialization: &quot;</span> &lt;&lt; header<span class="Delimiter">(</span>get<span class="Delimiter">(</span>Recipe<span class="Delimiter">,</span> variants<span class="Delimiter">.</span>back<span class="Delimiter">()))</span> &lt;&lt; <span class="cSpecial">'\n'</span><span class="Delimiter">;</span>
     for <span class="Delimiter">(</span>long long int t = <span class="Constant">0</span><span class="Delimiter">;</span> t &lt; SIZE<span class="Delimiter">(</span>Transform<span class="Delimiter">);</span> ++t<span class="Delimiter">)</span> <span class="Delimiter">{</span>
       <span class="Delimiter">(</span>*Transform<span class="Delimiter">.</span>at<span class="Delimiter">(</span>t<span class="Delimiter">))(</span>new_recipe_ordinal<span class="Delimiter">);</span>
     <span class="Delimiter">}</span>
     get<span class="Delimiter">(</span>Recipe<span class="Delimiter">,</span> new_recipe_ordinal<span class="Delimiter">).</span>transformed_until = SIZE<span class="Delimiter">(</span>Transform<span class="Delimiter">)</span>-<span class="Constant">1</span><span class="Delimiter">;</span>
-    LOG &lt;&lt; <span class="Constant">&quot;replacing &quot;</span> &lt;&lt; inst<span class="Delimiter">.</span>name &lt;&lt; <span class="Constant">&quot; with &quot;</span> &lt;&lt; get<span class="Delimiter">(</span>Recipe<span class="Delimiter">,</span> variants<span class="Delimiter">.</span>back<span class="Delimiter">()).</span>name &lt;&lt; <span class="cSpecial">'\n'</span><span class="Delimiter">;</span>
     inst<span class="Delimiter">.</span>name = get<span class="Delimiter">(</span>Recipe<span class="Delimiter">,</span> variants<span class="Delimiter">.</span>back<span class="Delimiter">()).</span>name<span class="Delimiter">;</span>
     trace<span class="Delimiter">(</span><span class="Constant">9992</span><span class="Delimiter">,</span> <span class="Constant">&quot;transform&quot;</span><span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;new specialization: &quot;</span> &lt;&lt; inst<span class="Delimiter">.</span>name &lt;&lt; end<span class="Delimiter">();</span>
-    LOG &lt;&lt; <span class="Constant">&quot;new specialization: &quot;</span> &lt;&lt; inst<span class="Delimiter">.</span>name &lt;&lt; <span class="cSpecial">'\n'</span><span class="Delimiter">;</span>
   <span class="Delimiter">}</span>
+  done_constructing_variant:<span class="Delimiter">;</span>
 <span class="Delimiter">}</span>
 
 <span class="Comment">//: make sure we have no unspecialized shape-shifting recipes being called</span>
 <span class="Comment">//: before running mu programs</span>
 
 <span class="Delimiter">:(before &quot;End Instruction Operation Checks&quot;)</span>
-<span class="CommentedCode">//? LOG &lt;&lt; inst.operation &lt;&lt; &quot; &quot; &lt;&lt; contains_key(Recipe, inst.operation) &lt;&lt; '\n';</span>
 if <span class="Delimiter">(</span>contains_key<span class="Delimiter">(</span>Recipe<span class="Delimiter">,</span> inst<span class="Delimiter">.</span>operation<span class="Delimiter">)</span> &amp;&amp; inst<span class="Delimiter">.</span>operation &gt;= MAX_PRIMITIVE_RECIPES
     &amp;&amp; any_type_ingredient_in_header<span class="Delimiter">(</span>inst<span class="Delimiter">.</span>operation<span class="Delimiter">))</span> <span class="Delimiter">{</span>
-<span class="CommentedCode">//?   LOG &lt;&lt; header(caller) &lt;&lt; &quot;instruction &quot; &lt;&lt; inst.name &lt;&lt; &quot; has no valid specialization\n&quot;;</span>
   raise_error &lt;&lt; maybe<span class="Delimiter">(</span>caller<span class="Delimiter">.</span>name<span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;instruction &quot;</span> &lt;&lt; inst<span class="Delimiter">.</span>name &lt;&lt; <span class="Constant">&quot; has no valid specialization</span><span class="cSpecial">\n</span><span class="Constant">&quot;</span> &lt;&lt; end<span class="Delimiter">();</span>
   <span class="Identifier">return</span><span class="Delimiter">;</span>
 <span class="Delimiter">}</span>
@@ -319,7 +315,7 @@ recipe_ordinal new_variant<span class="Delimiter">(</span>recipe_ordinal exempla
     if <span class="Delimiter">(</span>!error<span class="Delimiter">)</span> replace_type_ingredients<span class="Delimiter">(</span>new_recipe<span class="Delimiter">,</span> mappings<span class="Delimiter">);</span>
     for <span class="Delimiter">(</span>map&lt;string<span class="Delimiter">,</span> const string_tree*&gt;::iterator p = mappings<span class="Delimiter">.</span>begin<span class="Delimiter">();</span> p != mappings<span class="Delimiter">.</span>end<span class="Delimiter">();</span> ++p<span class="Delimiter">)</span>
       delete p<span class="Delimiter">-&gt;</span>second<span class="Delimiter">;</span>
-    if <span class="Delimiter">(</span>error<span class="Delimiter">)</span> <span class="Identifier">return</span> exemplar<span class="Delimiter">;</span>
+    if <span class="Delimiter">(</span>error<span class="Delimiter">)</span> <span class="Identifier">return</span> <span class="Constant">0</span><span class="Delimiter">;</span>  <span class="Comment">// todo: delete new_recipe_ordinal from Recipes and other global state</span>
   <span class="Delimiter">}</span>
   ensure_all_concrete_types<span class="Delimiter">(</span>new_recipe<span class="Delimiter">,</span> get<span class="Delimiter">(</span>Recipe<span class="Delimiter">,</span> exemplar<span class="Delimiter">));</span>
   <span class="Identifier">return</span> new_recipe_ordinal<span class="Delimiter">;</span>
@@ -574,14 +570,14 @@ container foo:_t [
 
 <span class="Delimiter">:(scenario shape_shifting_recipe_handles_shape_shifting_new_ingredient)</span>
 recipe main [
-  <span class="Constant">1</span>:address:foo:point<span class="Special"> &lt;- </span>bar <span class="Constant">3</span>
-  <span class="Constant">11</span>:foo:point<span class="Special"> &lt;- </span>copy *<span class="Constant">1</span>:address:foo:point
+  <span class="Constant">1</span>:address:shared:foo:point<span class="Special"> &lt;- </span>bar <span class="Constant">3</span>
+  <span class="Constant">11</span>:foo:point<span class="Special"> &lt;- </span>copy *<span class="Constant">1</span>:address:shared:foo:point
 ]
 container foo:_t [
   x:_t
   y:number
 ]
-recipe bar x:number <span class="Delimiter">-&gt;</span> result:address:foo:_t [
+recipe bar x:number <span class="Delimiter">-&gt;</span> result:address:shared:foo:_t [
   local-scope
   load-ingredients
   <span class="Comment"># new refers to _t in its ingredient *value*</span>
@@ -593,10 +589,10 @@ recipe bar x:number <span class="Delimiter">-&gt;</span> result:address:foo:_t [
 
 <span class="Delimiter">:(scenario shape_shifting_recipe_handles_shape_shifting_new_ingredient_2)</span>
 recipe main [
-  <span class="Constant">1</span>:address:foo:point<span class="Special"> &lt;- </span>bar <span class="Constant">3</span>
-  <span class="Constant">11</span>:foo:point<span class="Special"> &lt;- </span>copy *<span class="Constant">1</span>:address:foo:point
+  <span class="Constant">1</span>:address:shared:foo:point<span class="Special"> &lt;- </span>bar <span class="Constant">3</span>
+  <span class="Constant">11</span>:foo:point<span class="Special"> &lt;- </span>copy *<span class="Constant">1</span>:address:shared:foo:point
 ]
-recipe bar x:number <span class="Delimiter">-&gt;</span> result:address:foo:_t [
+recipe bar x:number <span class="Delimiter">-&gt;</span> result:address:shared:foo:_t [
   local-scope
   load-ingredients
   <span class="Comment"># new refers to _t in its ingredient *value*</span>
@@ -613,11 +609,11 @@ container foo:_t [
 
 <span class="Delimiter">:(scenario shape_shifting_recipe_supports_compound_types)</span>
 recipe main [
-  <span class="Constant">1</span>:address:point<span class="Special"> &lt;- </span>new point:type
-  <span class="Constant">2</span>:address:number<span class="Special"> &lt;- </span>get-address *<span class="Constant">1</span>:address:point<span class="Delimiter">,</span> y:offset
+  <span class="Constant">1</span>:address:shared:point<span class="Special"> &lt;- </span>new point:type
+  <span class="Constant">2</span>:address:number<span class="Special"> &lt;- </span>get-address *<span class="Constant">1</span>:address:shared:point<span class="Delimiter">,</span> y:offset
   *<span class="Constant">2</span>:address:number<span class="Special"> &lt;- </span>copy <span class="Constant">34</span>
-  <span class="Constant">3</span>:address:point<span class="Special"> &lt;- </span>bar <span class="Constant">1</span>:address:point  <span class="Comment"># specialize _t to address:point</span>
-  <span class="Constant">4</span>:point<span class="Special"> &lt;- </span>copy *<span class="Constant">3</span>:address:point
+  <span class="Constant">3</span>:address:shared:point<span class="Special"> &lt;- </span>bar <span class="Constant">1</span>:address:shared:point  <span class="Comment"># specialize _t to address:shared:point</span>
+  <span class="Constant">4</span>:point<span class="Special"> &lt;- </span>copy *<span class="Constant">3</span>:address:shared:point
 ]
 recipe bar a:_t <span class="Delimiter">-&gt;</span> result:_t [
   local-scope
@@ -630,13 +626,13 @@ recipe bar a:_t <span class="Delimiter">-&gt;</span> result:_t [
 <span class="Special">% Hide_errors = true;</span>
 recipe main [
   a:number<span class="Special"> &lt;- </span>copy <span class="Constant">3</span>
-  b:address:number<span class="Special"> &lt;- </span>foo a
+  b:address:shared:number<span class="Special"> &lt;- </span>foo a
 ]
 recipe foo a:_t <span class="Delimiter">-&gt;</span> b:_t [
   load-ingredients
   b<span class="Special"> &lt;- </span>copy a
 ]
-<span class="traceContains">+error: main: no call found for 'b:address:number &lt;- foo a'</span>
+<span class="traceContains">+error: main: no call found for 'b:address:shared:number &lt;- foo a'</span>
 
 <span class="Delimiter">:(scenario specialize_inside_recipe_without_header)</span>
 recipe main [
@@ -685,7 +681,7 @@ recipe foo x:_elem <span class="Delimiter">-&gt;</span> y:_elem [
 recipe main [
   local-scope
   <span class="Comment"># permit '0' to map to address to shape-shifting type-ingredient</span>
-  <span class="Constant">1</span>:address:character/<span class="Special">raw &lt;- </span>foo <span class="Constant">0</span>
+  <span class="Constant">1</span>:address:shared:character/<span class="Special">raw &lt;- </span>foo <span class="Constant">0</span>
 ]
 recipe foo x:address:_elem <span class="Delimiter">-&gt;</span> y:address:_elem [
   local-scope
@@ -755,7 +751,7 @@ container d2:_elem [
 <span class="Comment"># static dispatch between shape-shifting variants, _including pointer lookups_</span>
 recipe main [
   e1:d1:number<span class="Special"> &lt;- </span>merge <span class="Constant">3</span>
-  e2:address:d2:number<span class="Special"> &lt;- </span>new <span class="Delimiter">{(</span>d2 number<span class="Delimiter">)</span>: type<span class="Delimiter">}</span>
+  e2:address:shared:d2:number<span class="Special"> &lt;- </span>new <span class="Delimiter">{(</span>d2 number<span class="Delimiter">)</span>: type<span class="Delimiter">}</span>
   <span class="Constant">1</span>:number/<span class="Special">raw &lt;- </span>foo e1
   <span class="Constant">2</span>:number/<span class="Special">raw &lt;- </span>foo *e2  <span class="Comment"># different from previous scenario</span>
 ]
@@ -838,15 +834,15 @@ recipe foo x:_elem <span class="Delimiter">-&gt;</span> y:number [
 <span class="Delimiter">:(scenarios run)</span>
 <span class="Delimiter">:(scenario specialize_most_similar_variant)</span>
 recipe main [
-  <span class="Constant">1</span>:address:number<span class="Special"> &lt;- </span>new number:type
-  <span class="Constant">2</span>:number<span class="Special"> &lt;- </span>foo <span class="Constant">1</span>:address:number
+  <span class="Constant">1</span>:address:shared:number<span class="Special"> &lt;- </span>new number:type
+  <span class="Constant">2</span>:number<span class="Special"> &lt;- </span>foo <span class="Constant">1</span>:address:shared:number
 ]
 recipe foo x:_elem <span class="Delimiter">-&gt;</span> y:number [
   local-scope
   load-ingredients
   reply <span class="Constant">34</span>
 ]
-recipe foo x:address:_elem <span class="Delimiter">-&gt;</span> y:number [
+recipe foo x:address:shared:_elem <span class="Delimiter">-&gt;</span> y:number [
   local-scope
   load-ingredients
   reply <span class="Constant">35</span>
diff --git a/html/060immutable.cc.html b/html/060immutable.cc.html
index 8d8c7633..777149a7 100644
--- a/html/060immutable.cc.html
+++ b/html/060immutable.cc.html
@@ -39,7 +39,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="Special">% Hide_warnings = true;</span>
 recipe main [
   local-scope
-  p:address:point<span class="Special"> &lt;- </span>new point:type
+  p:address:shared:point<span class="Special"> &lt;- </span>new point:type
   foo *p
 ]
 recipe foo p:point [
@@ -54,10 +54,10 @@ $warn: <span class="Constant">0</span>
 <span class="Special">% Hide_warnings = true;</span>
 recipe main [
   local-scope
-  p:address:point<span class="Special"> &lt;- </span>new point:type
+  p:address:shared:point<span class="Special"> &lt;- </span>new point:type
   p<span class="Special"> &lt;- </span>foo p
 ]
-recipe foo p:address:point <span class="Delimiter">-&gt;</span> p:address:point [
+recipe foo p:address:shared:point <span class="Delimiter">-&gt;</span> p:address:shared:point [
   local-scope
   load-ingredients
   x:address:number<span class="Special"> &lt;- </span>get-address *p<span class="Delimiter">,</span> x:offset
@@ -69,13 +69,13 @@ $warn: <span class="Constant">0</span>
 <span class="Special">% Hide_warnings = true;</span>
 recipe main [
   local-scope
-  p:address:d1<span class="Special"> &lt;- </span>new d1:type
+  p:address:shared:d1<span class="Special"> &lt;- </span>new d1:type
   q:number<span class="Special"> &lt;- </span>foo p
 ]
-recipe foo p:address:d1 <span class="Delimiter">-&gt;</span> q:number [
+recipe foo p:address:shared:d1 <span class="Delimiter">-&gt;</span> q:number [
   local-scope
   load-ingredients
-  x:address:d1<span class="Special"> &lt;- </span>new d1:type
+  x:address:shared:d1<span class="Special"> &lt;- </span>new d1:type
   y:address:number<span class="Special"> &lt;- </span>get-address *x<span class="Delimiter">,</span> p:offset  <span class="Comment"># ignore this 'p'</span>
   q<span class="Special"> &lt;- </span>copy <span class="Constant">34</span>
 ]
@@ -89,10 +89,10 @@ $warn: <span class="Constant">0</span>
 <span class="Special">% Hide_warnings = true;</span>
 recipe main [
   local-scope
-  p:address:point<span class="Special"> &lt;- </span>new point:type
+  p:address:shared:point<span class="Special"> &lt;- </span>new point:type
   foo p
 ]
-recipe foo p:address:point [
+recipe foo p:address:shared:point [
   local-scope
   load-ingredients
   x:address:number<span class="Special"> &lt;- </span>get-address *p<span class="Delimiter">,</span> x:offset
@@ -104,15 +104,15 @@ recipe foo p:address:point [
 <span class="Special">% Hide_warnings = true;</span>
 recipe main [
   local-scope
-  p:address:point<span class="Special"> &lt;- </span>new point:type
+  p:address:shared:point<span class="Special"> &lt;- </span>new point:type
   foo p
 ]
-recipe foo p:address:point [
+recipe foo p:address:shared:point [
   local-scope
   load-ingredients
   bar p
 ]
-recipe bar p:address:point <span class="Delimiter">-&gt;</span> p:address:point [
+recipe bar p:address:shared:point <span class="Delimiter">-&gt;</span> p:address:shared:point [
   local-scope
   load-ingredients
   x:address:number<span class="Special"> &lt;- </span>get-address *p<span class="Delimiter">,</span> x:offset
@@ -124,13 +124,13 @@ recipe bar p:address:point <span class="Delimiter">-&gt;</span> p:address:point
 <span class="Special">% Hide_warnings = true;</span>
 recipe main [
   local-scope
-  p:address:point<span class="Special"> &lt;- </span>new point:type
+  p:address:shared:point<span class="Special"> &lt;- </span>new point:type
   foo p
 ]
-recipe foo p:address:point [
+recipe foo p:address:shared:point [
   local-scope
   load-ingredients
-  q:address:point<span class="Special"> &lt;- </span>copy p
+  q:address:shared:point<span class="Special"> &lt;- </span>copy p
   x:address:number<span class="Special"> &lt;- </span>get-address *q<span class="Delimiter">,</span> x:offset
 ]
 <span class="traceContains">+warn: foo: cannot modify q after instruction 'x:address:number &lt;- get-address *q, x:offset' because that would modify ingredient p which is not also a product of foo</span>
@@ -138,19 +138,19 @@ recipe foo p:address:point [
 <span class="Delimiter">:(scenario can_traverse_immutable_ingredients)</span>
 <span class="Special">% Hide_warnings = true;</span>
 container test-list [
-  next:address:test-list
+  next:address:shared:test-list
 ]
 recipe main [
   local-scope
-  p:address:test-list<span class="Special"> &lt;- </span>new test-list:type
+  p:address:shared:test-list<span class="Special"> &lt;- </span>new test-list:type
   foo p
 ]
-recipe foo p:address:test-list [
+recipe foo p:address:shared:test-list [
   local-scope
   load-ingredients
-  p2:address:test-list<span class="Special"> &lt;- </span>bar p
+  p2:address:shared:test-list<span class="Special"> &lt;- </span>bar p
 ]
-recipe bar x:address:test-list <span class="Delimiter">-&gt;</span> y:address:test-list [
+recipe bar x:address:shared:test-list <span class="Delimiter">-&gt;</span> y:address:shared:test-list [
   local-scope
   load-ingredients
   y<span class="Special"> &lt;- </span>get *x<span class="Delimiter">,</span> next:offset
@@ -160,11 +160,11 @@ $warn: <span class="Constant">0</span>
 <span class="Delimiter">:(scenario handle_optional_ingredients_in_immutability_checks)</span>
 <span class="Special">% Hide_warnings = true;</span>
 recipe main [
-  k:address:number<span class="Special"> &lt;- </span>new number:type
+  k:address:shared:number<span class="Special"> &lt;- </span>new number:type
   test k
 ]
 <span class="Comment"># recipe taking an immutable address ingredient</span>
-recipe test k:address:number [
+recipe test k:address:shared:number [
   local-scope
   load-ingredients
   foo k
@@ -173,7 +173,7 @@ recipe test k:address:number [
 recipe foo <span class="Delimiter">-&gt;</span> [
   local-scope
   load-ingredients
-  k:address:number<span class="Delimiter">,</span> found?:boolean<span class="Special"> &lt;- </span>next-ingredient
+  k:address:shared:number<span class="Delimiter">,</span> found?:boolean<span class="Special"> &lt;- </span>next-ingredient
 ]
 $warn: <span class="Constant">0</span>
 
@@ -246,25 +246,25 @@ set&lt;long long int&gt; scan_contained_in_product_indices<span class="Delimiter
 <span class="Delimiter">:(scenario immutability_infects_contained_in_variables)</span>
 <span class="Special">% Hide_warnings = true;</span>
 container test-list [
-  next:address:test-list
+  next:address:shared:test-list
 ]
 recipe main [
   local-scope
-  p:address:test-list<span class="Special"> &lt;- </span>new test-list:type
+  p:address:shared:test-list<span class="Special"> &lt;- </span>new test-list:type
   foo p
 ]
-recipe foo p:address:test-list [  <span class="Comment"># p is immutable</span>
+recipe foo p:address:shared:test-list [  <span class="Comment"># p is immutable</span>
   local-scope
   load-ingredients
-  p2:address:test-list<span class="Special"> &lt;- </span>test-next p  <span class="Comment"># p2 is immutable</span>
-  p3:address:address:test-list<span class="Special"> &lt;- </span>get-address *p2<span class="Delimiter">,</span> next:offset  <span class="Comment"># signal modification of p2</span>
+  p2:address:shared:test-list<span class="Special"> &lt;- </span>test-next p  <span class="Comment"># p2 is immutable</span>
+  p3:address:address:shared:test-list<span class="Special"> &lt;- </span>get-address *p2<span class="Delimiter">,</span> next:offset  <span class="Comment"># signal modification of p2</span>
 ]
-recipe test-next x:address:test-list <span class="Delimiter">-&gt;</span> y:address:test-list/contained-in:x [
+recipe test-next x:address:shared:test-list <span class="Delimiter">-&gt;</span> y:address:shared:test-list/contained-in:x [
   local-scope
   load-ingredients
   y<span class="Special"> &lt;- </span>get *x<span class="Delimiter">,</span> next:offset
 ]
-<span class="traceContains">+warn: foo: cannot modify p2 after instruction 'p3:address:address:test-list &lt;- get-address *p2, next:offset' because that would modify ingredient p which is not also a product of foo</span>
+<span class="traceContains">+warn: foo: cannot modify p2 after instruction 'p3:address:address:shared:test-list &lt;- get-address *p2, next:offset' because that would modify ingredient p which is not also a product of foo</span>
 
 <span class="Delimiter">:(code)</span>
 void check_immutable_ingredient_in_instruction<span class="Delimiter">(</span>const instruction&amp; inst<span class="Delimiter">,</span> const set&lt;string&gt;&amp; current_ingredient_and_aliases<span class="Delimiter">,</span> const string&amp; original_ingredient_name<span class="Delimiter">,</span> const recipe&amp; caller<span class="Delimiter">)</span> <span class="Delimiter">{</span>
@@ -349,28 +349,28 @@ set&lt;long long int&gt; ingredient_indices<span class="Delimiter">(</span>const
 <span class="Delimiter">:(scenario can_modify_contained_in_addresses)</span>
 <span class="Special">% Hide_warnings = true;</span>
 container test-list [
-  next:address:test-list
+  next:address:shared:test-list
 ]
 recipe main [
   local-scope
-  p:address:test-list<span class="Special"> &lt;- </span>new test-list:type
+  p:address:shared:test-list<span class="Special"> &lt;- </span>new test-list:type
   foo p
 ]
-recipe foo p:address:test-list <span class="Delimiter">-&gt;</span> p:address:test-list [
+recipe foo p:address:shared:test-list <span class="Delimiter">-&gt;</span> p:address:shared:test-list [
   local-scope
   load-ingredients
-  p2:address:test-list<span class="Special"> &lt;- </span>test-next p
+  p2:address:shared:test-list<span class="Special"> &lt;- </span>test-next p
   p<span class="Special"> &lt;- </span>test-remove p2<span class="Delimiter">,</span> p
 ]
-recipe test-next x:address:test-list <span class="Delimiter">-&gt;</span> y:address:test-list [
+recipe test-next x:address:shared:test-list <span class="Delimiter">-&gt;</span> y:address:shared:test-list [
   local-scope
   load-ingredients
   y<span class="Special"> &lt;- </span>get *x<span class="Delimiter">,</span> next:offset
 ]
-recipe test-remove x:address:test-list/contained-in:from<span class="Delimiter">,</span> from:address:test-list <span class="Delimiter">-&gt;</span> from:address:test-list [
+recipe test-remove x:address:shared:test-list/contained-in:from<span class="Delimiter">,</span> from:address:shared:test-list <span class="Delimiter">-&gt;</span> from:address:shared:test-list [
   local-scope
   load-ingredients
-  x2:address:address:test-list<span class="Special"> &lt;- </span>get-address *x<span class="Delimiter">,</span> next:offset  <span class="Comment"># pretend modification</span>
+  x2:address:address:shared:test-list<span class="Special"> &lt;- </span>get-address *x<span class="Delimiter">,</span> next:offset  <span class="Comment"># pretend modification</span>
 ]
 $warn: <span class="Constant">0</span>
 
diff --git a/html/061abandon_checks.cc.html b/html/061abandon_checks.cc.html
deleted file mode 100644
index 9f91f90e..00000000
--- a/html/061abandon_checks.cc.html
+++ /dev/null
@@ -1,159 +0,0 @@
-<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
-<html>
-<head>
-<meta http-equiv="content-type" content="text/html; charset=UTF-8">
-<title>Mu - 061abandon_checks.cc</title>
-<meta name="Generator" content="Vim/7.4">
-<meta name="plugin-version" content="vim7.4_v1">
-<meta name="syntax" content="cpp">
-<meta name="settings" content="use_css,pre_wrap,no_foldcolumn,expand_tabs,prevent_copy=">
-<meta name="colorscheme" content="minimal">
-<style type="text/css">
-<!--
-pre { white-space: pre-wrap; font-family: monospace; color: #eeeeee; background-color: #080808; }
-body { font-family: monospace; color: #eeeeee; background-color: #080808; }
-* { font-size: 1.05em; }
-.Comment { color: #9090ff; }
-.Delimiter { color: #a04060; }
-.Special { color: #ff6060; }
--->
-</style>
-
-<script type='text/javascript'>
-<!--
-
--->
-</script>
-</head>
-<body>
-<pre id='vimCodeElement'>
-<span class="Delimiter">:(scenarios transform)</span>  <span class="Comment">// many of the tests below are *extremely* unsafe</span>
-<span class="Delimiter">:(scenario abandon_in_same_recipe_as_new)</span>
-recipe test [
-  x:address:number<span class="Special"> &lt;- </span>new number:type
-  abandon x
-]
-<span class="Comment"># no warnings</span>
-
-<span class="Delimiter">:(scenario abandon_in_separate_recipe_from_new)</span>
-recipe test [
-  x:address:number<span class="Special"> &lt;- </span>test-new
-  test-abandon x
-]
-recipe test-new <span class="Delimiter">-&gt;</span> result:address:number [
-  result<span class="Special"> &lt;- </span>new number:type
-]
-recipe test-abandon x:address:number [
-  load-ingredients
-  abandon x
-]
-<span class="Comment"># no warnings</span>
-
-<span class="Delimiter">:(scenario define_after_abandon_in_same_recipe_as_new)</span>
-recipe test [
-  x:address:number<span class="Special"> &lt;- </span>new number:type
-  abandon x
-  x<span class="Special"> &lt;- </span>new number:type
-  reply x
-]
-<span class="Comment"># no warnings</span>
-
-<span class="Delimiter">:(scenario define_after_abandon_in_separate_recipe_from_new)</span>
-recipe test [
-  x:address:number<span class="Special"> &lt;- </span>test-new
-  test-abandon x
-  x<span class="Special"> &lt;- </span>test-new
-  reply x
-]
-recipe test-new <span class="Delimiter">-&gt;</span> result:address:number [
-  result<span class="Special"> &lt;- </span>new number:type
-]
-recipe test-abandon x:address:number [
-  load-ingredients
-  abandon x
-]
-<span class="Comment"># no warnings</span>
-
-<span class="Delimiter">:(scenario abandon_inside_loop_initializing_variable)</span>
-recipe test [
-  <span class="Delimiter">{</span>
-    x:address:number<span class="Special"> &lt;- </span>new number:type
-    abandon x
-    loop
-  <span class="Delimiter">}</span>
-]
-<span class="Comment"># no warnings</span>
-
-<span class="Delimiter">:(scenario abandon_inside_loop_initializing_variable_2)</span>
-recipe test [
-  <span class="Delimiter">{</span>
-    x:address:number<span class="Special"> &lt;- </span>test-new
-    test-abandon x
-    loop
-  <span class="Delimiter">}</span>
-]
-recipe test-new <span class="Delimiter">-&gt;</span> result:address:number [
-  result<span class="Special"> &lt;- </span>new number:type
-]
-recipe test-abandon x:address:number [
-  load-ingredients
-  abandon x
-]
-<span class="Comment"># no warnings</span>
-
-<span class="Delimiter">:(scenario abandon_inside_loop_initializing_variable_3)</span>
-recipe test [
-  <span class="Delimiter">{</span>
-    x:address:number<span class="Special"> &lt;- </span>test-new
-    test-abandon x
-    x:address:number<span class="Special"> &lt;- </span>test-new  <span class="Comment"># modify x to a new value</span>
-    y:address:number<span class="Special"> &lt;- </span>copy x  <span class="Comment"># use x after reinitialization</span>
-    loop
-  <span class="Delimiter">}</span>
-]
-recipe test-new <span class="Delimiter">-&gt;</span> result:address:number [
-  result<span class="Special"> &lt;- </span>new number:type
-]
-recipe test-abandon x:address:number [
-  load-ingredients
-  abandon x
-]
-<span class="Comment"># no warnings</span>
-
-<span class="Delimiter">:(scenario abandon_inside_loop_initializing_variable_4)</span>
-container test-list [
-  value:number
-  next:address:test-list
-]
-recipe test-cleanup x:address:test-list [
-  load-ingredients
-  <span class="Delimiter">{</span>
-    next:address:test-list<span class="Special"> &lt;- </span>test-next x
-    test-abandon x
-    x<span class="Special"> &lt;- </span>copy next
-    loop
-  <span class="Delimiter">}</span>
-]
-recipe test-next x:address:test-list <span class="Delimiter">-&gt;</span> result:address:test-list/contained-in:x [
-  load-ingredients
-  result<span class="Special"> &lt;- </span>get *x<span class="Delimiter">,</span> next:offset
-]
-recipe test-abandon x:address:test-list [
-  load-ingredients
-  abandon x
-]
-<span class="Comment"># no warnings</span>
-
-<span class="Delimiter">:(scenario abandon_non_unique_address_after_define)</span>
-recipe test [
-  x:address:number<span class="Special"> &lt;- </span>new number:type
-  y:address:number<span class="Special"> &lt;- </span>copy x
-  abandon x
-  y:address:number<span class="Special"> &lt;- </span>new number:type  <span class="Comment"># overwrite alias</span>
-  z:address:number<span class="Special"> &lt;- </span>copy y
-]
-<span class="Comment"># no warnings</span>
-</pre>
-</body>
-</html>
-<!-- vim: set foldmethod=manual : -->
diff --git a/html/061recipe.cc.html b/html/061recipe.cc.html
new file mode 100644
index 00000000..163347ff
--- /dev/null
+++ b/html/061recipe.cc.html
@@ -0,0 +1,235 @@
+<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
+<html>
+<head>
+<meta http-equiv="content-type" content="text/html; charset=UTF-8">
+<title>Mu - 061recipe.cc</title>
+<meta name="Generator" content="Vim/7.4">
+<meta name="plugin-version" content="vim7.4_v1">
+<meta name="syntax" content="cpp">
+<meta name="settings" content="use_css,pre_wrap,no_foldcolumn,expand_tabs,prevent_copy=">
+<meta name="colorscheme" content="minimal">
+<style type="text/css">
+<!--
+pre { white-space: pre-wrap; font-family: monospace; color: #eeeeee; background-color: #080808; }
+body { font-family: monospace; color: #eeeeee; background-color: #080808; }
+* { font-size: 1.05em; }
+.SalientComment { color: #00ffff; }
+.traceContains { color: #008000; }
+.cSpecial { color: #008000; }
+.Comment { color: #9090ff; }
+.Delimiter { color: #a04060; }
+.Special { color: #ff6060; }
+.Identifier { color: #804000; }
+.Constant { color: #00a0a0; }
+-->
+</style>
+
+<script type='text/javascript'>
+<!--
+
+-->
+</script>
+</head>
+<body>
+<pre id='vimCodeElement'>
+<span class="Comment">//: So far we've been calling a fixed recipe in each instruction, but we'd</span>
+<span class="Comment">//: also like to make the recipe a variable, pass recipes to &quot;higher-order&quot;</span>
+<span class="Comment">//: recipes, return recipes from recipes and so on.</span>
+
+<span class="Delimiter">:(scenario call_literal_recipe)</span>
+recipe main [
+  <span class="Constant">1</span>:number<span class="Special"> &lt;- </span>call f<span class="Delimiter">,</span> <span class="Constant">34</span>
+]
+recipe f x:number <span class="Delimiter">-&gt;</span> y:number [
+  local-scope
+  load-ingredients
+  y<span class="Special"> &lt;- </span>copy x
+]
+<span class="traceContains">+mem: storing 34 in location 1</span>
+
+<span class="Delimiter">:(scenario call_variable)</span>
+recipe main [
+  <span class="Delimiter">{</span><span class="Constant">1</span>: <span class="Delimiter">(</span>recipe number <span class="Delimiter">-&gt;</span> number<span class="Delimiter">)}</span><span class="Special"> &lt;- </span>copy f
+  <span class="Constant">2</span>:number<span class="Special"> &lt;- </span>call <span class="Delimiter">{</span><span class="Constant">1</span>: <span class="Delimiter">(</span>recipe number <span class="Delimiter">-&gt;</span> number<span class="Delimiter">)},</span> <span class="Constant">34</span>
+]
+recipe f x:number <span class="Delimiter">-&gt;</span> y:number [
+  local-scope
+  load-ingredients
+  y<span class="Special"> &lt;- </span>copy x
+]
+<span class="traceContains">+mem: storing 34 in location 2</span>
+
+<span class="Delimiter">:(before &quot;End Mu Types Initialization&quot;)</span>
+put<span class="Delimiter">(</span>Type_ordinal<span class="Delimiter">,</span> <span class="Constant">&quot;recipe-literal&quot;</span><span class="Delimiter">,</span> <span class="Constant">0</span><span class="Delimiter">);</span>
+<span class="Comment">// 'recipe' variables can store recipe-literal</span>
+type_ordinal recipe = put<span class="Delimiter">(</span>Type_ordinal<span class="Delimiter">,</span> <span class="Constant">&quot;recipe&quot;</span><span class="Delimiter">,</span> Next_type_ordinal++<span class="Delimiter">);</span>
+get_or_insert<span class="Delimiter">(</span>Type<span class="Delimiter">,</span> recipe<span class="Delimiter">).</span>name = <span class="Constant">&quot;recipe&quot;</span><span class="Delimiter">;</span>
+
+<span class="Delimiter">:(before &quot;End transform_names Exceptions&quot;)</span>
+if <span class="Delimiter">(</span>!x<span class="Delimiter">.</span>properties<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">).</span>second &amp;&amp; contains_key<span class="Delimiter">(</span>Recipe_ordinal<span class="Delimiter">,</span> x<span class="Delimiter">.</span>name<span class="Delimiter">))</span> <span class="Delimiter">{</span>
+  x<span class="Delimiter">.</span>properties<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">).</span>second = new string_tree<span class="Delimiter">(</span><span class="Constant">&quot;recipe-literal&quot;</span><span class="Delimiter">);</span>
+  x<span class="Delimiter">.</span>type = new type_tree<span class="Delimiter">(</span>get<span class="Delimiter">(</span>Type_ordinal<span class="Delimiter">,</span> <span class="Constant">&quot;recipe-literal&quot;</span><span class="Delimiter">));</span>
+  x<span class="Delimiter">.</span>set_value<span class="Delimiter">(</span>get<span class="Delimiter">(</span>Recipe_ordinal<span class="Delimiter">,</span> x<span class="Delimiter">.</span>name<span class="Delimiter">));</span>
+  <span class="Identifier">return</span> <span class="Constant">true</span><span class="Delimiter">;</span>
+<span class="Delimiter">}</span>
+
+<span class="Delimiter">:(before &quot;End Primitive Recipe Declarations&quot;)</span>
+CALL<span class="Delimiter">,</span>
+<span class="Delimiter">:(before &quot;End Primitive Recipe Numbers&quot;)</span>
+put<span class="Delimiter">(</span>Recipe_ordinal<span class="Delimiter">,</span> <span class="Constant">&quot;call&quot;</span><span class="Delimiter">,</span> CALL<span class="Delimiter">);</span>
+<span class="Delimiter">:(before &quot;End Primitive Recipe Checks&quot;)</span>
+case CALL: <span class="Delimiter">{</span>
+  if <span class="Delimiter">(</span>inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>empty<span class="Delimiter">())</span> <span class="Delimiter">{</span>
+    raise_error &lt;&lt; maybe<span class="Delimiter">(</span>get<span class="Delimiter">(</span>Recipe<span class="Delimiter">,</span> r<span class="Delimiter">).</span>name<span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;'call' requires at least one ingredient (the recipe to call)</span><span class="cSpecial">\n</span><span class="Constant">&quot;</span> &lt;&lt; end<span class="Delimiter">();</span>
+    <span class="Identifier">break</span><span class="Delimiter">;</span>
+  <span class="Delimiter">}</span>
+  if <span class="Delimiter">(</span>!is_mu_recipe<span class="Delimiter">(</span>inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">)))</span> <span class="Delimiter">{</span>
+    raise_error &lt;&lt; maybe<span class="Delimiter">(</span>get<span class="Delimiter">(</span>Recipe<span class="Delimiter">,</span> r<span class="Delimiter">).</span>name<span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;first ingredient of 'call' should be a recipe, but got &quot;</span> &lt;&lt; inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">).</span>original_string &lt;&lt; <span class="cSpecial">'\n'</span> &lt;&lt; end<span class="Delimiter">();</span>
+    <span class="Identifier">break</span><span class="Delimiter">;</span>
+  <span class="Delimiter">}</span>
+  <span class="Identifier">break</span><span class="Delimiter">;</span>
+<span class="Delimiter">}</span>
+<span class="Delimiter">:(before &quot;End Primitive Recipe Implementations&quot;)</span>
+case CALL: <span class="Delimiter">{</span>
+  <span class="Comment">// Begin Call</span>
+  if <span class="Delimiter">(</span>Trace_stream<span class="Delimiter">)</span> <span class="Delimiter">{</span>
+    ++Trace_stream<span class="Delimiter">-&gt;</span>callstack_depth<span class="Delimiter">;</span>
+    trace<span class="Delimiter">(</span><span class="Constant">&quot;trace&quot;</span><span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;indirect 'call': incrementing callstack depth to &quot;</span> &lt;&lt; Trace_stream<span class="Delimiter">-&gt;</span>callstack_depth &lt;&lt; end<span class="Delimiter">();</span>
+    assert<span class="Delimiter">(</span>Trace_stream<span class="Delimiter">-&gt;</span>callstack_depth &lt; <span class="Constant">9000</span><span class="Delimiter">);</span>  <span class="Comment">// 9998-101 plus cushion</span>
+  <span class="Delimiter">}</span>
+  const instruction&amp; caller_instruction = current_instruction<span class="Delimiter">();</span>
+  Current_routine<span class="Delimiter">-&gt;</span>calls<span class="Delimiter">.</span>push_front<span class="Delimiter">(</span>call<span class="Delimiter">(</span>ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">).</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">)));</span>
+  ingredients<span class="Delimiter">.</span>erase<span class="Delimiter">(</span>ingredients<span class="Delimiter">.</span>begin<span class="Delimiter">());</span>  <span class="Comment">// drop the callee</span>
+  finish_call_housekeeping<span class="Delimiter">(</span>caller_instruction<span class="Delimiter">,</span> ingredients<span class="Delimiter">);</span>
+  <span class="Identifier">continue</span><span class="Delimiter">;</span>
+<span class="Delimiter">}</span>
+
+<span class="SalientComment">//:: check types for 'call' instructions</span>
+
+<span class="Delimiter">:(scenario call_check_literal_recipe)</span>
+<span class="Special">% Hide_errors = true;</span>
+recipe main [
+  <span class="Constant">1</span>:number<span class="Special"> &lt;- </span>call f<span class="Delimiter">,</span> <span class="Constant">34</span>
+]
+recipe f x:boolean <span class="Delimiter">-&gt;</span> y:boolean [
+  local-scope
+  load-ingredients
+  y<span class="Special"> &lt;- </span>copy x
+]
+<span class="traceContains">+error: main: ingredient 0 has the wrong type at '1:number &lt;- call f, 34'</span>
+<span class="traceContains">+error: main: product 0 has the wrong type at '1:number &lt;- call f, 34'</span>
+
+<span class="Delimiter">:(scenario call_check_variable_recipe)</span>
+<span class="Special">% Hide_errors = true;</span>
+recipe main [
+  <span class="Delimiter">{</span><span class="Constant">1</span>: <span class="Delimiter">(</span>recipe boolean <span class="Delimiter">-&gt;</span> boolean<span class="Delimiter">)}</span><span class="Special"> &lt;- </span>copy f
+  <span class="Constant">2</span>:number<span class="Special"> &lt;- </span>call <span class="Delimiter">{</span><span class="Constant">1</span>: <span class="Delimiter">(</span>recipe boolean <span class="Delimiter">-&gt;</span> boolean<span class="Delimiter">)},</span> <span class="Constant">34</span>
+]
+recipe f x:boolean <span class="Delimiter">-&gt;</span> y:boolean [
+  local-scope
+  load-ingredients
+  y<span class="Special"> &lt;- </span>copy x
+]
+<span class="traceContains">+error: main: ingredient 0 has the wrong type at '2:number &lt;- call {1: (recipe boolean -&gt; boolean)}, 34'</span>
+<span class="traceContains">+error: main: product 0 has the wrong type at '2:number &lt;- call {1: (recipe boolean -&gt; boolean)}, 34'</span>
+
+<span class="Delimiter">:(after &quot;Transform.push_back(check_instruction)&quot;)</span>
+Transform<span class="Delimiter">.</span>push_back<span class="Delimiter">(</span>check_indirect_calls_against_header<span class="Delimiter">);</span>  <span class="Comment">// idempotent</span>
+<span class="Delimiter">:(code)</span>
+void check_indirect_calls_against_header<span class="Delimiter">(</span>const recipe_ordinal r<span class="Delimiter">)</span> <span class="Delimiter">{</span>
+  trace<span class="Delimiter">(</span><span class="Constant">9991</span><span class="Delimiter">,</span> <span class="Constant">&quot;transform&quot;</span><span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;--- type-check 'call' instructions inside recipe &quot;</span> &lt;&lt; get<span class="Delimiter">(</span>Recipe<span class="Delimiter">,</span> r<span class="Delimiter">).</span>name &lt;&lt; end<span class="Delimiter">();</span>
+  const recipe&amp; caller = get<span class="Delimiter">(</span>Recipe<span class="Delimiter">,</span> r<span class="Delimiter">);</span>
+  for <span class="Delimiter">(</span>long long int i = <span class="Constant">0</span><span class="Delimiter">;</span> i &lt; SIZE<span class="Delimiter">(</span>caller<span class="Delimiter">.</span>steps<span class="Delimiter">);</span> ++i<span class="Delimiter">)</span> <span class="Delimiter">{</span>
+    const instruction&amp; inst = caller<span class="Delimiter">.</span>steps<span class="Delimiter">.</span>at<span class="Delimiter">(</span>i<span class="Delimiter">);</span>
+    if <span class="Delimiter">(</span>inst<span class="Delimiter">.</span>operation != CALL<span class="Delimiter">)</span> <span class="Identifier">continue</span><span class="Delimiter">;</span>
+    if <span class="Delimiter">(</span>inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>empty<span class="Delimiter">())</span> <span class="Identifier">continue</span><span class="Delimiter">;</span>  <span class="Comment">// error raised above</span>
+    const reagent&amp; callee = inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">);</span>
+    if <span class="Delimiter">(</span>!is_mu_recipe<span class="Delimiter">(</span>callee<span class="Delimiter">))</span> <span class="Identifier">continue</span><span class="Delimiter">;</span>  <span class="Comment">// error raised above</span>
+    const recipe callee_header = is_literal<span class="Delimiter">(</span>callee<span class="Delimiter">)</span> ? get<span class="Delimiter">(</span>Recipe<span class="Delimiter">,</span> callee<span class="Delimiter">.</span>value<span class="Delimiter">)</span> : from_reagent<span class="Delimiter">(</span>inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">));</span>
+    if <span class="Delimiter">(</span>!callee_header<span class="Delimiter">.</span>has_header<span class="Delimiter">)</span> <span class="Identifier">continue</span><span class="Delimiter">;</span>
+    for <span class="Delimiter">(</span>long int i = <span class="Comment">/*</span><span class="Comment">skip callee</span><span class="Comment">*/</span><span class="Constant">1</span><span class="Delimiter">;</span> i &lt; min<span class="Delimiter">(</span>SIZE<span class="Delimiter">(</span>inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">),</span> SIZE<span class="Delimiter">(</span>callee_header<span class="Delimiter">.</span>ingredients<span class="Delimiter">)</span>+<span class="Comment">/*</span><span class="Comment">skip callee</span><span class="Comment">*/</span><span class="Constant">1</span><span class="Delimiter">);</span> ++i<span class="Delimiter">)</span> <span class="Delimiter">{</span>
+      if <span class="Delimiter">(</span>!types_coercible<span class="Delimiter">(</span>callee_header<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span>i-<span class="Comment">/*</span><span class="Comment">skip callee</span><span class="Comment">*/</span><span class="Constant">1</span><span class="Delimiter">),</span> inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span>i<span class="Delimiter">)))</span>
+        raise_error &lt;&lt; maybe<span class="Delimiter">(</span>caller<span class="Delimiter">.</span>name<span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;ingredient &quot;</span> &lt;&lt; i-<span class="Comment">/*</span><span class="Comment">skip callee</span><span class="Comment">*/</span><span class="Constant">1</span> &lt;&lt; <span class="Constant">&quot; has the wrong type at '&quot;</span> &lt;&lt; inst<span class="Delimiter">.</span>to_string<span class="Delimiter">()</span> &lt;&lt; <span class="Constant">&quot;'</span><span class="cSpecial">\n</span><span class="Constant">&quot;</span> &lt;&lt; end<span class="Delimiter">();</span>
+    <span class="Delimiter">}</span>
+    for <span class="Delimiter">(</span>long int i = <span class="Constant">0</span><span class="Delimiter">;</span> i &lt; min<span class="Delimiter">(</span>SIZE<span class="Delimiter">(</span>inst<span class="Delimiter">.</span>products<span class="Delimiter">),</span> SIZE<span class="Delimiter">(</span>callee_header<span class="Delimiter">.</span>products<span class="Delimiter">));</span> ++i<span class="Delimiter">)</span> <span class="Delimiter">{</span>
+      if <span class="Delimiter">(</span>is_dummy<span class="Delimiter">(</span>inst<span class="Delimiter">.</span>products<span class="Delimiter">.</span>at<span class="Delimiter">(</span>i<span class="Delimiter">)))</span> <span class="Identifier">continue</span><span class="Delimiter">;</span>
+      if <span class="Delimiter">(</span>!types_coercible<span class="Delimiter">(</span>callee_header<span class="Delimiter">.</span>products<span class="Delimiter">.</span>at<span class="Delimiter">(</span>i<span class="Delimiter">),</span> inst<span class="Delimiter">.</span>products<span class="Delimiter">.</span>at<span class="Delimiter">(</span>i<span class="Delimiter">)))</span>
+        raise_error &lt;&lt; maybe<span class="Delimiter">(</span>caller<span class="Delimiter">.</span>name<span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;product &quot;</span> &lt;&lt; i &lt;&lt; <span class="Constant">&quot; has the wrong type at '&quot;</span> &lt;&lt; inst<span class="Delimiter">.</span>to_string<span class="Delimiter">()</span> &lt;&lt; <span class="Constant">&quot;'</span><span class="cSpecial">\n</span><span class="Constant">&quot;</span> &lt;&lt; end<span class="Delimiter">();</span>
+    <span class="Delimiter">}</span>
+  <span class="Delimiter">}</span>
+<span class="Delimiter">}</span>
+
+recipe from_reagent<span class="Delimiter">(</span>const reagent&amp; r<span class="Delimiter">)</span> <span class="Delimiter">{</span>
+  assert<span class="Delimiter">(</span>r<span class="Delimiter">.</span>properties<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">).</span>second<span class="Delimiter">-&gt;</span>value == <span class="Constant">&quot;recipe&quot;</span><span class="Delimiter">);</span>
+  recipe result_header<span class="Delimiter">;</span>  <span class="Comment">// will contain only ingredients and products, nothing else</span>
+  result_header<span class="Delimiter">.</span>has_header = <span class="Constant">true</span><span class="Delimiter">;</span>
+  const string_tree* curr = r<span class="Delimiter">.</span>properties<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">).</span>second<span class="Delimiter">-&gt;</span>right<span class="Delimiter">;</span>
+  for <span class="Delimiter">(;</span> curr<span class="Delimiter">;</span> curr=curr<span class="Delimiter">-&gt;</span>right<span class="Delimiter">)</span> <span class="Delimiter">{</span>
+    if <span class="Delimiter">(</span>curr<span class="Delimiter">-&gt;</span>value == <span class="Constant">&quot;-&gt;&quot;</span><span class="Delimiter">)</span> <span class="Delimiter">{</span>
+      curr = curr<span class="Delimiter">-&gt;</span>right<span class="Delimiter">;</span>  <span class="Comment">// skip delimiter</span>
+      <span class="Identifier">break</span><span class="Delimiter">;</span>
+    <span class="Delimiter">}</span>
+    result_header<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>push_back<span class="Delimiter">(</span><span class="Constant">&quot;recipe:&quot;</span>+curr<span class="Delimiter">-&gt;</span>value<span class="Delimiter">);</span>
+  <span class="Delimiter">}</span>
+  for <span class="Delimiter">(;</span> curr<span class="Delimiter">;</span> curr=curr<span class="Delimiter">-&gt;</span>right<span class="Delimiter">)</span> <span class="Delimiter">{</span>
+    result_header<span class="Delimiter">.</span>products<span class="Delimiter">.</span>push_back<span class="Delimiter">(</span><span class="Constant">&quot;recipe:&quot;</span>+curr<span class="Delimiter">-&gt;</span>value<span class="Delimiter">);</span>
+  <span class="Delimiter">}</span>
+  <span class="Identifier">return</span> result_header<span class="Delimiter">;</span>
+<span class="Delimiter">}</span>
+
+bool is_mu_recipe<span class="Delimiter">(</span>reagent r<span class="Delimiter">)</span> <span class="Delimiter">{</span>
+  if <span class="Delimiter">(</span>!r<span class="Delimiter">.</span>type<span class="Delimiter">)</span> <span class="Identifier">return</span> <span class="Constant">false</span><span class="Delimiter">;</span>
+  if <span class="Delimiter">(</span>r<span class="Delimiter">.</span>properties<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">).</span>second<span class="Delimiter">-&gt;</span>value == <span class="Constant">&quot;recipe&quot;</span><span class="Delimiter">)</span> <span class="Identifier">return</span> <span class="Constant">true</span><span class="Delimiter">;</span>
+  if <span class="Delimiter">(</span>r<span class="Delimiter">.</span>properties<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">).</span>second<span class="Delimiter">-&gt;</span>value == <span class="Constant">&quot;recipe-literal&quot;</span><span class="Delimiter">)</span> <span class="Identifier">return</span> <span class="Constant">true</span><span class="Delimiter">;</span>
+  <span class="Comment">// End is_mu_recipe Cases</span>
+  <span class="Identifier">return</span> <span class="Constant">false</span><span class="Delimiter">;</span>
+<span class="Delimiter">}</span>
+
+<span class="Delimiter">:(scenario copy_typecheck_recipe_variable)</span>
+<span class="Special">% Hide_errors = true;</span>
+recipe main [
+  <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">34</span>  <span class="Comment"># abc def</span>
+  <span class="Delimiter">{</span><span class="Constant">1</span>: <span class="Delimiter">(</span>recipe number <span class="Delimiter">-&gt;</span> number<span class="Delimiter">)}</span><span class="Special"> &lt;- </span>copy f  <span class="Comment"># store literal in a matching variable</span>
+  <span class="Delimiter">{</span><span class="Constant">2</span>: <span class="Delimiter">(</span>recipe boolean <span class="Delimiter">-&gt;</span> boolean<span class="Delimiter">)}</span><span class="Special"> &lt;- </span>copy <span class="Delimiter">{</span><span class="Constant">1</span>: <span class="Delimiter">(</span>recipe number <span class="Delimiter">-&gt;</span> number<span class="Delimiter">)}</span>  <span class="Comment"># mismatch between recipe variables</span>
+]
+recipe f x:number <span class="Delimiter">-&gt;</span> y:number [
+  local-scope
+  load-ingredients
+  y<span class="Special"> &lt;- </span>copy x
+]
+<span class="traceContains">+error: main: can't copy {1: (recipe number -&gt; number)} to {2: (recipe boolean -&gt; boolean)}; types don't match</span>
+
+<span class="Delimiter">:(scenario copy_typecheck_recipe_variable_2)</span>
+<span class="Special">% Hide_errors = true;</span>
+recipe main [
+  <span class="Delimiter">{</span><span class="Constant">1</span>: <span class="Delimiter">(</span>recipe number <span class="Delimiter">-&gt;</span> number<span class="Delimiter">)}</span><span class="Special"> &lt;- </span>copy f  <span class="Comment"># mismatch with a recipe literal</span>
+]
+recipe f x:boolean <span class="Delimiter">-&gt;</span> y:boolean [
+  local-scope
+  load-ingredients
+  y<span class="Special"> &lt;- </span>copy x
+]
+<span class="traceContains">+error: main: can't copy f to {1: (recipe number -&gt; number)}; types don't match</span>
+
+<span class="Delimiter">:(before &quot;End Matching Types For Literal(lhs)&quot;)</span>
+if <span class="Delimiter">(</span>is_mu_recipe<span class="Delimiter">(</span>lhs<span class="Delimiter">))</span> <span class="Delimiter">{</span>
+  if <span class="Delimiter">(</span>!contains_key<span class="Delimiter">(</span>Recipe<span class="Delimiter">,</span> rhs<span class="Delimiter">.</span>value<span class="Delimiter">))</span> <span class="Delimiter">{</span>
+    raise_error &lt;&lt; <span class="Constant">&quot;trying to store recipe &quot;</span> &lt;&lt; rhs<span class="Delimiter">.</span>name &lt;&lt; <span class="Constant">&quot; into &quot;</span> &lt;&lt; debug_string<span class="Delimiter">(</span>lhs<span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot; but there's no such recipe</span><span class="cSpecial">\n</span><span class="Constant">&quot;</span> &lt;&lt; end<span class="Delimiter">();</span>
+    <span class="Identifier">return</span> <span class="Constant">false</span><span class="Delimiter">;</span>
+  <span class="Delimiter">}</span>
+  const recipe&amp; rrhs = get<span class="Delimiter">(</span>Recipe<span class="Delimiter">,</span> rhs<span class="Delimiter">.</span>value<span class="Delimiter">);</span>
+  const recipe&amp; rlhs = from_reagent<span class="Delimiter">(</span>lhs<span class="Delimiter">);</span>
+  for <span class="Delimiter">(</span>long int i = <span class="Constant">0</span><span class="Delimiter">;</span> i &lt; min<span class="Delimiter">(</span>SIZE<span class="Delimiter">(</span>rlhs<span class="Delimiter">.</span>ingredients<span class="Delimiter">),</span> SIZE<span class="Delimiter">(</span>rrhs<span class="Delimiter">.</span>ingredients<span class="Delimiter">));</span> ++i<span class="Delimiter">)</span> <span class="Delimiter">{</span>
+    if <span class="Delimiter">(</span>!types_match<span class="Delimiter">(</span>rlhs<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span>i<span class="Delimiter">),</span> rrhs<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span>i<span class="Delimiter">)))</span>
+      <span class="Identifier">return</span> <span class="Constant">false</span><span class="Delimiter">;</span>
+  <span class="Delimiter">}</span>
+  for <span class="Delimiter">(</span>long int i = <span class="Constant">0</span><span class="Delimiter">;</span> i &lt; min<span class="Delimiter">(</span>SIZE<span class="Delimiter">(</span>rlhs<span class="Delimiter">.</span>products<span class="Delimiter">),</span> SIZE<span class="Delimiter">(</span>rrhs<span class="Delimiter">.</span>products<span class="Delimiter">));</span> ++i<span class="Delimiter">)</span> <span class="Delimiter">{</span>
+    if <span class="Delimiter">(</span>!types_match<span class="Delimiter">(</span>rlhs<span class="Delimiter">.</span>products<span class="Delimiter">.</span>at<span class="Delimiter">(</span>i<span class="Delimiter">),</span> rrhs<span class="Delimiter">.</span>products<span class="Delimiter">.</span>at<span class="Delimiter">(</span>i<span class="Delimiter">)))</span>
+      <span class="Identifier">return</span> <span class="Constant">false</span><span class="Delimiter">;</span>
+  <span class="Delimiter">}</span>
+  <span class="Identifier">return</span> <span class="Constant">true</span><span class="Delimiter">;</span>
+<span class="Delimiter">}</span>
+</pre>
+</body>
+</html>
+<!-- vim: set foldmethod=manual : -->
diff --git a/html/038scheduler.cc.html b/html/062scheduler.cc.html
index 56396b68..d772144e 100644
--- a/html/038scheduler.cc.html
+++ b/html/062scheduler.cc.html
@@ -2,7 +2,7 @@
 <html>
 <head>
 <meta http-equiv="content-type" content="text/html; charset=UTF-8">
-<title>Mu - 038scheduler.cc</title>
+<title>Mu - 062scheduler.cc</title>
 <meta name="Generator" content="Vim/7.4">
 <meta name="plugin-version" content="vim7.4_v1">
 <meta name="syntax" content="cpp">
@@ -13,8 +13,8 @@
 pre { white-space: pre-wrap; font-family: monospace; color: #eeeeee; background-color: #080808; }
 body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 * { font-size: 1.05em; }
-.traceContains { color: #008000; }
 .traceAbsent { color: #c00000; }
+.traceContains { color: #008000; }
 .SalientComment { color: #00ffff; }
 .cSpecial { color: #008000; }
 .Comment { color: #9090ff; }
@@ -38,7 +38,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="Delimiter">:(scenario scheduler)</span>
 recipe f1 [
-  start-running f2:recipe
+  start-running f2
   <span class="Comment"># wait for f2 to run</span>
   <span class="Delimiter">{</span>
     jump-unless <span class="Constant">1</span>:number<span class="Delimiter">,</span> -<span class="Constant">1</span>
@@ -147,11 +147,17 @@ Current_routine = <span class="Constant">NULL</span><span class="Delimiter">;</s
 <span class="Delimiter">:(replace{} &quot;void run_main(int argc, char* argv[])&quot;)</span>
 void run_main<span class="Delimiter">(</span>int argc<span class="Delimiter">,</span> char* argv[]<span class="Delimiter">)</span> <span class="Delimiter">{</span>
   recipe_ordinal r = get<span class="Delimiter">(</span>Recipe_ordinal<span class="Delimiter">,</span> <span class="Constant">&quot;main&quot;</span><span class="Delimiter">);</span>
-  if <span class="Delimiter">(</span>r<span class="Delimiter">)</span> <span class="Delimiter">{</span>
-    routine* main_routine = new routine<span class="Delimiter">(</span>r<span class="Delimiter">);</span>
-    <span class="Comment">// Update main_routine</span>
-    run<span class="Delimiter">(</span>main_routine<span class="Delimiter">);</span>
+  assert<span class="Delimiter">(</span>r<span class="Delimiter">);</span>
+  routine* main_routine = new routine<span class="Delimiter">(</span>r<span class="Delimiter">);</span>
+  <span class="Comment">// pass in commandline args as ingredients to main</span>
+  <span class="Comment">// todo: test this</span>
+  Current_routine = main_routine<span class="Delimiter">;</span>
+  for <span class="Delimiter">(</span>long long int i = <span class="Constant">1</span><span class="Delimiter">;</span> i &lt; argc<span class="Delimiter">;</span> ++i<span class="Delimiter">)</span> <span class="Delimiter">{</span>
+    vector&lt;double&gt; arg<span class="Delimiter">;</span>
+    arg<span class="Delimiter">.</span>push_back<span class="Delimiter">(</span>new_mu_string<span class="Delimiter">(</span>argv[i]<span class="Delimiter">));</span>
+    current_call<span class="Delimiter">().</span>ingredient_atoms<span class="Delimiter">.</span>push_back<span class="Delimiter">(</span>arg<span class="Delimiter">);</span>
   <span class="Delimiter">}</span>
+  run<span class="Delimiter">(</span>main_routine<span class="Delimiter">);</span>
 <span class="Delimiter">}</span>
 
 <span class="SalientComment">//:: To schedule new routines to run, call 'start-running'.</span>
@@ -186,7 +192,7 @@ case START_RUNNING: <span class="Delimiter">{</span>
     <span class="Identifier">break</span><span class="Delimiter">;</span>
   <span class="Delimiter">}</span>
   if <span class="Delimiter">(</span>!is_mu_recipe<span class="Delimiter">(</span>inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">)))</span> <span class="Delimiter">{</span>
-    raise_error &lt;&lt; maybe<span class="Delimiter">(</span>get<span class="Delimiter">(</span>Recipe<span class="Delimiter">,</span> r<span class="Delimiter">).</span>name<span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;first ingredient of 'start-running' should be a recipe, but got &quot;</span> &lt;&lt; inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">).</span>original_string &lt;&lt; <span class="cSpecial">'\n'</span> &lt;&lt; end<span class="Delimiter">();</span>
+    raise_error &lt;&lt; maybe<span class="Delimiter">(</span>get<span class="Delimiter">(</span>Recipe<span class="Delimiter">,</span> r<span class="Delimiter">).</span>name<span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;first ingredient of 'start-running' should be a recipe, but got &quot;</span> &lt;&lt; debug_string<span class="Delimiter">(</span>inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">))</span> &lt;&lt; <span class="cSpecial">'\n'</span> &lt;&lt; end<span class="Delimiter">();</span>
     <span class="Identifier">break</span><span class="Delimiter">;</span>
   <span class="Delimiter">}</span>
   <span class="Identifier">break</span><span class="Delimiter">;</span>
@@ -222,7 +228,7 @@ recipe f1 [
 <span class="Delimiter">:(scenario scheduler_interleaves_routines)</span>
 <span class="Special">% Scheduling_interval = 1;</span>
 recipe f1 [
-  start-running f2:recipe
+  start-running f2
   <span class="Constant">1</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
   <span class="Constant">2</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
 ]
@@ -231,7 +237,7 @@ recipe f2 [
   <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
 ]
 <span class="traceContains">+schedule: f1</span>
-<span class="traceContains">+run: start-running f2:recipe</span>
+<span class="traceContains">+run: start-running f2</span>
 <span class="traceContains">+schedule: f2</span>
 <span class="traceContains">+run: 3:number &lt;- copy 0</span>
 <span class="traceContains">+schedule: f1</span>
@@ -243,7 +249,7 @@ recipe f2 [
 
 <span class="Delimiter">:(scenario start_running_takes_ingredients)</span>
 recipe f1 [
-  start-running f2:recipe<span class="Delimiter">,</span> <span class="Constant">3</span>
+  start-running f2<span class="Delimiter">,</span> <span class="Constant">3</span>
   <span class="Comment"># wait for f2 to run</span>
   <span class="Delimiter">{</span>
     jump-unless <span class="Constant">1</span>:number<span class="Delimiter">,</span> -<span class="Constant">1</span>
@@ -257,7 +263,7 @@ recipe f2 [
 
 <span class="Delimiter">:(scenario start_running_returns_routine_id)</span>
 recipe f1 [
-  <span class="Constant">1</span>:number<span class="Special"> &lt;- </span>start-running f2:recipe
+  <span class="Constant">1</span>:number<span class="Special"> &lt;- </span>start-running f2
 ]
 recipe f2 [
   <span class="Constant">12</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">44</span>
@@ -300,7 +306,7 @@ recipe f1 [
 <span class="Special">% Hide_errors = true;</span>
 <span class="Special">% Scheduling_interval = 2;</span>
 recipe f1 [
-  start-running f2:recipe
+  start-running f2
   <span class="Constant">1</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
   <span class="Constant">2</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
 ]
@@ -322,7 +328,7 @@ recipe f2 [
 
 <span class="Delimiter">:(scenario scheduler_kills_orphans)</span>
 recipe main [
-  start-running f1:recipe
+  start-running f1
   <span class="Comment"># f1 never actually runs because its parent completes without waiting for it</span>
 ]
 recipe f1 [
@@ -353,7 +359,7 @@ bool has_completed_parent<span class="Delimiter">(</span>long long int routine_i
 <span class="Delimiter">:(scenario routine_state_test)</span>
 <span class="Special">% Scheduling_interval = 2;</span>
 recipe f1 [
-  <span class="Constant">1</span>:number/child-id<span class="Special"> &lt;- </span>start-running f2:recipe
+  <span class="Constant">1</span>:number/child-id<span class="Special"> &lt;- </span>start-running f2
   <span class="Constant">12</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>  <span class="Comment"># race condition since we don't care about location 12</span>
   <span class="Comment"># thanks to Scheduling_interval, f2's one instruction runs in between here and completes</span>
   <span class="Constant">2</span>:number/state<span class="Special"> &lt;- </span>routine-state <span class="Constant">1</span>:number/child-id
@@ -475,7 +481,7 @@ case _DUMP_ROUTINES: <span class="Delimiter">{</span>
 <span class="Delimiter">:(scenario routine_discontinues_past_limit)</span>
 <span class="Special">% Scheduling_interval = 2;</span>
 recipe f1 [
-  <span class="Constant">1</span>:number/child-id<span class="Special"> &lt;- </span>start-running f2:recipe
+  <span class="Constant">1</span>:number/child-id<span class="Special"> &lt;- </span>start-running f2
   limit-time <span class="Constant">1</span>:number/child-id<span class="Delimiter">,</span> <span class="Constant">10</span>
   <span class="Comment"># padding loop just to make sure f2 has time to completed</span>
   <span class="Constant">2</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">20</span>
@@ -539,6 +545,26 @@ case LIMIT_TIME: <span class="Delimiter">{</span>
   <span class="Delimiter">}</span>
   <span class="Identifier">break</span><span class="Delimiter">;</span>
 <span class="Delimiter">}</span>
+
+<span class="SalientComment">//:: make sure that each routine gets a different alloc to start</span>
+
+<span class="Delimiter">:(scenario new_concurrent)</span>
+recipe f1 [
+  start-running f2
+  <span class="Constant">1</span>:address:shared:number/<span class="Special">raw &lt;- </span>new number:type
+  <span class="Comment"># wait for f2 to complete</span>
+  <span class="Delimiter">{</span>
+    loop-unless <span class="Constant">4</span>:number/<span class="Special">raw</span>
+  <span class="Delimiter">}</span>
+]
+recipe f2 [
+  <span class="Constant">2</span>:address:shared:number/<span class="Special">raw &lt;- </span>new number:type
+  <span class="Comment"># hack: assumes scheduler implementation</span>
+  <span class="Constant">3</span>:boolean/<span class="Special">raw &lt;- </span>equal <span class="Constant">1</span>:address:shared:number/<span class="Special">raw</span><span class="Delimiter">,</span> <span class="Constant">2</span>:address:shared:number/<span class="Special">raw</span>
+  <span class="Comment"># signal f2 complete</span>
+  <span class="Constant">4</span>:number/<span class="Special">raw &lt;- </span>copy <span class="Constant">1</span>
+]
+<span class="traceContains">+mem: storing 0 in location 3</span>
 </pre>
 </body>
 </html>
diff --git a/html/039wait.cc.html b/html/063wait.cc.html
index 057c54b6..08d4b049 100644
--- a/html/039wait.cc.html
+++ b/html/063wait.cc.html
@@ -2,7 +2,7 @@
 <html>
 <head>
 <meta http-equiv="content-type" content="text/html; charset=UTF-8">
-<title>Mu - 039wait.cc</title>
+<title>Mu - 063wait.cc</title>
 <meta name="Generator" content="Vim/7.4">
 <meta name="plugin-version" content="vim7.4_v1">
 <meta name="syntax" content="cpp">
@@ -39,7 +39,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="Delimiter">:(scenario wait_for_location)</span>
 recipe f1 [
   <span class="Constant">1</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
-  start-running f2:recipe
+  start-running f2
   wait-for-location <span class="Constant">1</span>:number
   <span class="Comment"># now wait for f2 to run and modify location 1 before using its value</span>
   <span class="Constant">2</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">1</span>:number
@@ -100,7 +100,7 @@ for <span class="Delimiter">(</span>long long int i = <span class="Constant">0</
 <span class="Delimiter">:(scenario wait_for_routine)</span>
 recipe f1 [
   <span class="Constant">1</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
-  <span class="Constant">12</span>:number/routine<span class="Special"> &lt;- </span>start-running f2:recipe
+  <span class="Constant">12</span>:number/routine<span class="Special"> &lt;- </span>start-running f2
   wait-for-routine <span class="Constant">12</span>:number/routine
   <span class="Comment"># now wait for f2 to run and modify location 1 before using its value</span>
   <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">1</span>:number
diff --git a/html/070text.mu.html b/html/070text.mu.html
index 38851b6c..fc695ef5 100644
--- a/html/070text.mu.html
+++ b/html/070text.mu.html
@@ -37,21 +37,21 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="Comment"># to-text-line gets called implicitly in various places</span>
 <span class="Comment"># define it to be identical to 'to-text' by default</span>
-<span class="muRecipe">recipe</span> to-text-line x:_elem<span class="muRecipe"> -&gt; </span>y:address:array:character [
+<span class="muRecipe">recipe</span> to-text-line x:_elem<span class="muRecipe"> -&gt; </span>y:address:shared:array:character [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   y<span class="Special"> &lt;- </span>to-text x
 ]
 
 <span class="Comment"># to-text on text is just the identity function</span>
-<span class="muRecipe">recipe</span> to-text x:address:array:character<span class="muRecipe"> -&gt; </span>y:address:array:character [
+<span class="muRecipe">recipe</span> to-text x:address:shared:array:character<span class="muRecipe"> -&gt; </span>y:address:shared:array:character [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
 <span class="CommentedCode">#?   $print [to-text text], 10/newline</span>
   <span class="muControl">reply</span> x
 ]
 
-<span class="muRecipe">recipe</span> equal a:address:array:character, b:address:array:character<span class="muRecipe"> -&gt; </span>result:boolean [
+<span class="muRecipe">recipe</span> equal a:address:shared:array:character, b:address:shared:array:character<span class="muRecipe"> -&gt; </span>result:boolean [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   a-len:number<span class="Special"> &lt;- </span>length *a
@@ -84,8 +84,8 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> text-equal-reflexive [
   run [
-    <span class="Constant">default-space</span>:address:array:location<span class="Special"> &lt;- </span>new <span class="Constant">location:type</span>, <span class="Constant">30</span>
-    x:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
+    <span class="Constant">default-space</span>:address:shared:array:location<span class="Special"> &lt;- </span>new <span class="Constant">location:type</span>, <span class="Constant">30</span>
+    x:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
     <span class="Constant">3</span>:boolean/<span class="Special">raw &lt;- </span>equal x, x
   ]
   memory-should-contain [
@@ -95,9 +95,9 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> text-equal-identical [
   run [
-    <span class="Constant">default-space</span>:address:array:location<span class="Special"> &lt;- </span>new <span class="Constant">location:type</span>, <span class="Constant">30</span>
-    x:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
-    y:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
+    <span class="Constant">default-space</span>:address:shared:array:location<span class="Special"> &lt;- </span>new <span class="Constant">location:type</span>, <span class="Constant">30</span>
+    x:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
+    y:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
     <span class="Constant">3</span>:boolean/<span class="Special">raw &lt;- </span>equal x, y
   ]
   memory-should-contain [
@@ -107,9 +107,9 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> text-equal-distinct-lengths [
   run [
-    <span class="Constant">default-space</span>:address:array:location<span class="Special"> &lt;- </span>new <span class="Constant">location:type</span>, <span class="Constant">30</span>
-    x:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
-    y:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abcd]</span>
+    <span class="Constant">default-space</span>:address:shared:array:location<span class="Special"> &lt;- </span>new <span class="Constant">location:type</span>, <span class="Constant">30</span>
+    x:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
+    y:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abcd]</span>
     <span class="Constant">3</span>:boolean/<span class="Special">raw &lt;- </span>equal x, y
   ]
   memory-should-contain [
@@ -125,9 +125,9 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> text-equal-with-empty [
   run [
-    <span class="Constant">default-space</span>:address:array:location<span class="Special"> &lt;- </span>new <span class="Constant">location:type</span>, <span class="Constant">30</span>
-    x:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
-    y:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abcd]</span>
+    <span class="Constant">default-space</span>:address:shared:array:location<span class="Special"> &lt;- </span>new <span class="Constant">location:type</span>, <span class="Constant">30</span>
+    x:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
+    y:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abcd]</span>
     <span class="Constant">3</span>:boolean/<span class="Special">raw &lt;- </span>equal x, y
   ]
   memory-should-contain [
@@ -137,9 +137,9 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> text-equal-common-lengths-but-distinct [
   run [
-    <span class="Constant">default-space</span>:address:array:location<span class="Special"> &lt;- </span>new <span class="Constant">location:type</span>, <span class="Constant">30</span>
-    x:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
-    y:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abd]</span>
+    <span class="Constant">default-space</span>:address:shared:array:location<span class="Special"> &lt;- </span>new <span class="Constant">location:type</span>, <span class="Constant">30</span>
+    x:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
+    y:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abd]</span>
     <span class="Constant">3</span>:boolean/<span class="Special">raw &lt;- </span>equal x, y
   ]
   memory-should-contain [
@@ -150,28 +150,28 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="Comment"># A new type to help incrementally construct texts.</span>
 <span class="muData">container</span> buffer [
   length:number
-  data:address:array:character
+  data:address:shared:array:character
 ]
 
-<span class="muRecipe">recipe</span> new-buffer capacity:number<span class="muRecipe"> -&gt; </span>result:address:buffer [
+<span class="muRecipe">recipe</span> new-buffer capacity:number<span class="muRecipe"> -&gt; </span>result:address:shared:buffer [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   result<span class="Special"> &lt;- </span>new <span class="Constant">buffer:type</span>
   len:address:number<span class="Special"> &lt;- </span>get-address *result, <span class="Constant">length:offset</span>
   *len:address:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
-  s:address:address:array:character<span class="Special"> &lt;- </span>get-address *result, <span class="Constant">data:offset</span>
+  s:address:address:shared:array:character<span class="Special"> &lt;- </span>get-address *result, <span class="Constant">data:offset</span>
   *s<span class="Special"> &lt;- </span>new <span class="Constant">character:type</span>, capacity
   <span class="muControl">reply</span> result
 ]
 
-<span class="muRecipe">recipe</span> grow-buffer in:address:buffer<span class="muRecipe"> -&gt; </span>in:address:buffer [
+<span class="muRecipe">recipe</span> grow-buffer in:address:shared:buffer<span class="muRecipe"> -&gt; </span>in:address:shared:buffer [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   <span class="Comment"># double buffer size</span>
-  x:address:address:array:character<span class="Special"> &lt;- </span>get-address *in, <span class="Constant">data:offset</span>
+  x:address:address:shared:array:character<span class="Special"> &lt;- </span>get-address *in, <span class="Constant">data:offset</span>
   oldlen:number<span class="Special"> &lt;- </span>length **x
   newlen:number<span class="Special"> &lt;- </span>multiply oldlen, <span class="Constant">2</span>
-  olddata:address:array:character<span class="Special"> &lt;- </span>copy *x
+  olddata:address:shared:array:character<span class="Special"> &lt;- </span>copy *x
   *x<span class="Special"> &lt;- </span>new <span class="Constant">character:type</span>, newlen
   <span class="Comment"># copy old contents</span>
   i:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
@@ -186,21 +186,21 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   <span class="Delimiter">}</span>
 ]
 
-<span class="muRecipe">recipe</span> buffer-full? in:address:buffer<span class="muRecipe"> -&gt; </span>result:boolean [
+<span class="muRecipe">recipe</span> buffer-full? in:address:shared:buffer<span class="muRecipe"> -&gt; </span>result:boolean [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   len:number<span class="Special"> &lt;- </span>get *in, <span class="Constant">length:offset</span>
-  s:address:array:character<span class="Special"> &lt;- </span>get *in, <span class="Constant">data:offset</span>
+  s:address:shared:array:character<span class="Special"> &lt;- </span>get *in, <span class="Constant">data:offset</span>
   capacity:number<span class="Special"> &lt;- </span>length *s
   result<span class="Special"> &lt;- </span>greater-or-equal len, capacity
 ]
 
 <span class="Comment"># most broadly applicable definition of append to a buffer: just call to-text</span>
-<span class="muRecipe">recipe</span> append buf:address:buffer, x:_elem<span class="muRecipe"> -&gt; </span>buf:address:buffer [
+<span class="muRecipe">recipe</span> append buf:address:shared:buffer, x:_elem<span class="muRecipe"> -&gt; </span>buf:address:shared:buffer [
   <span class="Constant">local-scope</span>
 <span class="CommentedCode">#?   $print [append _elem to buffer], 10/newline</span>
   <span class="Constant">load-ingredients</span>
-  text:address:array:character<span class="Special"> &lt;- </span>to-text x
+  text:address:shared:array:character<span class="Special"> &lt;- </span>to-text x
   len:number<span class="Special"> &lt;- </span>length *text
   i:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
   <span class="Delimiter">{</span>
@@ -213,7 +213,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   <span class="Delimiter">}</span>
 ]
 
-<span class="muRecipe">recipe</span> append in:address:buffer, c:character<span class="muRecipe"> -&gt; </span>in:address:buffer [
+<span class="muRecipe">recipe</span> append in:address:shared:buffer, c:character<span class="muRecipe"> -&gt; </span>in:address:shared:buffer [
   <span class="Constant">local-scope</span>
 <span class="CommentedCode">#?   $print [append character to buffer], 10/newline</span>
   <span class="Constant">load-ingredients</span>
@@ -233,7 +233,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     <span class="muControl">break-unless</span> full?
     in<span class="Special"> &lt;- </span>grow-buffer in
   <span class="Delimiter">}</span>
-  s:address:array:character<span class="Special"> &lt;- </span>get *in, <span class="Constant">data:offset</span>
+  s:address:shared:array:character<span class="Special"> &lt;- </span>get *in, <span class="Constant">data:offset</span>
   dest:address:character<span class="Special"> &lt;- </span>index-address *s, *len
   *dest<span class="Special"> &lt;- </span>copy c
   *len<span class="Special"> &lt;- </span>add *len, <span class="Constant">1</span>
@@ -242,20 +242,20 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="muScenario">scenario</span> buffer-append-works [
   run [
     <span class="Constant">local-scope</span>
-    x:address:buffer<span class="Special"> &lt;- </span>new-buffer <span class="Constant">3</span>
-    s1:address:array:character<span class="Special"> &lt;- </span>get *x:address:buffer, <span class="Constant">data:offset</span>
-    x:address:buffer<span class="Special"> &lt;- </span>append x:address:buffer, <span class="Constant">97</span>  <span class="Comment"># 'a'</span>
-    x:address:buffer<span class="Special"> &lt;- </span>append x:address:buffer, <span class="Constant">98</span>  <span class="Comment"># 'b'</span>
-    x:address:buffer<span class="Special"> &lt;- </span>append x:address:buffer, <span class="Constant">99</span>  <span class="Comment"># 'c'</span>
-    s2:address:array:character<span class="Special"> &lt;- </span>get *x:address:buffer, <span class="Constant">data:offset</span>
-    <span class="Constant">1</span>:boolean/<span class="Special">raw &lt;- </span>equal s1:address:array:character, s2:address:array:character
-    <span class="Constant">2</span>:array:character/<span class="Special">raw &lt;- </span>copy *s2:address:array:character
+    x:address:shared:buffer<span class="Special"> &lt;- </span>new-buffer <span class="Constant">3</span>
+    s1:address:shared:array:character<span class="Special"> &lt;- </span>get *x, <span class="Constant">data:offset</span>
+    x<span class="Special"> &lt;- </span>append x, <span class="Constant">97</span>  <span class="Comment"># 'a'</span>
+    x<span class="Special"> &lt;- </span>append x, <span class="Constant">98</span>  <span class="Comment"># 'b'</span>
+    x<span class="Special"> &lt;- </span>append x, <span class="Constant">99</span>  <span class="Comment"># 'c'</span>
+    s2:address:shared:array:character<span class="Special"> &lt;- </span>get *x, <span class="Constant">data:offset</span>
+    <span class="Constant">1</span>:boolean/<span class="Special">raw &lt;- </span>equal s1, s2
+    <span class="Constant">2</span>:array:character/<span class="Special">raw &lt;- </span>copy *s2
 <span class="Constant">    +buffer-filled</span>
-    x:address:buffer<span class="Special"> &lt;- </span>append x:address:buffer, <span class="Constant">100</span>  <span class="Comment"># 'd'</span>
-    s3:address:array:character<span class="Special"> &lt;- </span>get *x:address:buffer, <span class="Constant">data:offset</span>
-    <span class="Constant">10</span>:boolean/<span class="Special">raw &lt;- </span>equal s1:address:array:character, s3:address:array:character
-    <span class="Constant">11</span>:number/<span class="Special">raw &lt;- </span>get *x:address:buffer, <span class="Constant">length:offset</span>
-    <span class="Constant">12</span>:array:character/<span class="Special">raw &lt;- </span>copy *s3:address:array:character
+    x<span class="Special"> &lt;- </span>append x, <span class="Constant">100</span>  <span class="Comment"># 'd'</span>
+    s3:address:shared:array:character<span class="Special"> &lt;- </span>get *x, <span class="Constant">data:offset</span>
+    <span class="Constant">10</span>:boolean/<span class="Special">raw &lt;- </span>equal s1, s3
+    <span class="Constant">11</span>:number/<span class="Special">raw &lt;- </span>get *x, <span class="Constant">length:offset</span>
+    <span class="Constant">12</span>:array:character/<span class="Special">raw &lt;- </span>copy *s3
   ]
   memory-should-contain [
     <span class="Comment"># before +buffer-filled</span>
@@ -280,11 +280,11 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="muScenario">scenario</span> buffer-append-handles-backspace [
   run [
     <span class="Constant">local-scope</span>
-    x:address:buffer<span class="Special"> &lt;- </span>new-buffer <span class="Constant">3</span>
+    x:address:shared:buffer<span class="Special"> &lt;- </span>new-buffer <span class="Constant">3</span>
     x<span class="Special"> &lt;- </span>append x, <span class="Constant">97</span>  <span class="Comment"># 'a'</span>
     x<span class="Special"> &lt;- </span>append x, <span class="Constant">98</span>  <span class="Comment"># 'b'</span>
     x<span class="Special"> &lt;- </span>append x, <span class="Constant">8/backspace</span>
-    s:address:array:character<span class="Special"> &lt;- </span>buffer-to-array x
+    s:address:shared:array:character<span class="Special"> &lt;- </span>buffer-to-array x
     <span class="Constant">1</span>:array:character/<span class="Special">raw &lt;- </span>copy *s
   ]
   memory-should-contain [
@@ -294,7 +294,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   ]
 ]
 
-<span class="muRecipe">recipe</span> to-text n:number<span class="muRecipe"> -&gt; </span>result:address:array:character [
+<span class="muRecipe">recipe</span> to-text n:number<span class="muRecipe"> -&gt; </span>result:address:shared:array:character [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   <span class="Comment"># is n zero?</span>
@@ -312,14 +312,14 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     n<span class="Special"> &lt;- </span>multiply n, <span class="Constant">-1</span>
   <span class="Delimiter">}</span>
   <span class="Comment"># add digits from right to left into intermediate buffer</span>
-  tmp:address:buffer<span class="Special"> &lt;- </span>new-buffer <span class="Constant">30</span>
+  tmp:address:shared:buffer<span class="Special"> &lt;- </span>new-buffer <span class="Constant">30</span>
   digit-base:number<span class="Special"> &lt;- </span>copy <span class="Constant">48</span>  <span class="Comment"># '0'</span>
   <span class="Delimiter">{</span>
     done?:boolean<span class="Special"> &lt;- </span>equal n, <span class="Constant">0</span>
     <span class="muControl">break-if</span> done?
     n, digit:number<span class="Special"> &lt;- </span>divide-with-remainder n, <span class="Constant">10</span>
     c:character<span class="Special"> &lt;- </span>add digit-base, digit
-    tmp:address:buffer<span class="Special"> &lt;- </span>append tmp, c
+    tmp:address:shared:buffer<span class="Special"> &lt;- </span>append tmp, c
     <span class="muControl">loop</span>
   <span class="Delimiter">}</span>
   <span class="Comment"># add sign</span>
@@ -329,7 +329,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   <span class="Delimiter">}</span>
   <span class="Comment"># reverse buffer into text result</span>
   len:number<span class="Special"> &lt;- </span>get *tmp, <span class="Constant">length:offset</span>
-  buf:address:array:character<span class="Special"> &lt;- </span>get *tmp, <span class="Constant">data:offset</span>
+  buf:address:shared:array:character<span class="Special"> &lt;- </span>get *tmp, <span class="Constant">data:offset</span>
   result<span class="Special"> &lt;- </span>new <span class="Constant">character:type</span>, len
   i:number<span class="Special"> &lt;- </span>subtract len, <span class="Constant">1</span>  <span class="Comment"># source index, decreasing</span>
   j:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>  <span class="Comment"># destination index, increasing</span>
@@ -347,7 +347,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   <span class="Delimiter">}</span>
 ]
 
-<span class="muRecipe">recipe</span> buffer-to-array in:address:buffer<span class="muRecipe"> -&gt; </span>result:address:array:character [
+<span class="muRecipe">recipe</span> buffer-to-array in:address:shared:buffer<span class="muRecipe"> -&gt; </span>result:address:shared:array:character [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   <span class="Delimiter">{</span>
@@ -356,7 +356,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     <span class="muControl">reply</span> <span class="Constant">0</span>
   <span class="Delimiter">}</span>
   len:number<span class="Special"> &lt;- </span>get *in, <span class="Constant">length:offset</span>
-  s:address:array:character<span class="Special"> &lt;- </span>get *in, <span class="Constant">data:offset</span>
+  s:address:shared:array:character<span class="Special"> &lt;- </span>get *in, <span class="Constant">data:offset</span>
   <span class="Comment"># we can't just return s because it is usually the wrong length</span>
   result<span class="Special"> &lt;- </span>new <span class="Constant">character:type</span>, len
   i:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
@@ -373,8 +373,8 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> integer-to-decimal-digit-zero [
   run [
-    <span class="Constant">1</span>:address:array:character/<span class="Special">raw &lt;- </span>to-text <span class="Constant">0</span>
-    <span class="Constant">2</span>:array:character/<span class="Special">raw &lt;- </span>copy *<span class="Constant">1</span>:address:array:character/<span class="Special">raw</span>
+    <span class="Constant">1</span>:address:shared:array:character/<span class="Special">raw &lt;- </span>to-text <span class="Constant">0</span>
+    <span class="Constant">2</span>:array:character/<span class="Special">raw &lt;- </span>copy *<span class="Constant">1</span>:address:shared:array:character/<span class="Special">raw</span>
   ]
   memory-should-contain [
     <span class="Constant">2</span>:array:character<span class="Special"> &lt;- </span><span class="Constant">[0]</span>
@@ -383,8 +383,8 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> integer-to-decimal-digit-positive [
   run [
-    <span class="Constant">1</span>:address:array:character/<span class="Special">raw &lt;- </span>to-text <span class="Constant">234</span>
-    <span class="Constant">2</span>:array:character/<span class="Special">raw &lt;- </span>copy *<span class="Constant">1</span>:address:array:character/<span class="Special">raw</span>
+    <span class="Constant">1</span>:address:shared:array:character/<span class="Special">raw &lt;- </span>to-text <span class="Constant">234</span>
+    <span class="Constant">2</span>:array:character/<span class="Special">raw &lt;- </span>copy *<span class="Constant">1</span>:address:shared:array:character/<span class="Special">raw</span>
   ]
   memory-should-contain [
     <span class="Constant">2</span>:array:character<span class="Special"> &lt;- </span><span class="Constant">[234]</span>
@@ -393,8 +393,8 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> integer-to-decimal-digit-negative [
   run [
-    <span class="Constant">1</span>:address:array:character/<span class="Special">raw &lt;- </span>to-text <span class="Constant">-1</span>
-    <span class="Constant">2</span>:array:character/<span class="Special">raw &lt;- </span>copy *<span class="Constant">1</span>:address:array:character/<span class="Special">raw</span>
+    <span class="Constant">1</span>:address:shared:array:character/<span class="Special">raw &lt;- </span>to-text <span class="Constant">-1</span>
+    <span class="Constant">2</span>:array:character/<span class="Special">raw &lt;- </span>copy *<span class="Constant">1</span>:address:shared:array:character/<span class="Special">raw</span>
   ]
   memory-should-contain [
     <span class="Constant">2</span><span class="Special"> &lt;- </span><span class="Constant">2</span>
@@ -403,7 +403,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   ]
 ]
 
-<span class="muRecipe">recipe</span> append a:address:array:character, b:address:array:character<span class="muRecipe"> -&gt; </span>result:address:array:character [
+<span class="muRecipe">recipe</span> append a:address:shared:array:character, b:address:shared:array:character<span class="muRecipe"> -&gt; </span>result:address:shared:array:character [
   <span class="Constant">local-scope</span>
 <span class="CommentedCode">#?   $print [append text to text], 10/newline</span>
   <span class="Constant">load-ingredients</span>
@@ -445,10 +445,10 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> text-append-1 [
   run [
-    <span class="Constant">1</span>:address:array:character/<span class="Special">raw &lt;- </span>new <span class="Constant">[hello,]</span>
-    <span class="Constant">2</span>:address:array:character/<span class="Special">raw &lt;- </span>new <span class="Constant">[ world!]</span>
-    <span class="Constant">3</span>:address:array:character/<span class="Special">raw &lt;- </span>append <span class="Constant">1</span>:address:array:character/<span class="Special">raw</span>, <span class="Constant">2</span>:address:array:character/<span class="Special">raw</span>
-    <span class="Constant">4</span>:array:character/<span class="Special">raw &lt;- </span>copy *<span class="Constant">3</span>:address:array:character/<span class="Special">raw</span>
+    <span class="Constant">1</span>:address:shared:array:character/<span class="Special">raw &lt;- </span>new <span class="Constant">[hello,]</span>
+    <span class="Constant">2</span>:address:shared:array:character/<span class="Special">raw &lt;- </span>new <span class="Constant">[ world!]</span>
+    <span class="Constant">3</span>:address:shared:array:character/<span class="Special">raw &lt;- </span>append <span class="Constant">1</span>:address:shared:array:character/<span class="Special">raw</span>, <span class="Constant">2</span>:address:shared:array:character/<span class="Special">raw</span>
+    <span class="Constant">4</span>:array:character/<span class="Special">raw &lt;- </span>copy *<span class="Constant">3</span>:address:shared:array:character/<span class="Special">raw</span>
   ]
   memory-should-contain [
     <span class="Constant">4</span>:array:character<span class="Special"> &lt;- </span><span class="Constant">[hello, world!]</span>
@@ -457,19 +457,18 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> replace-character-in-text [
   run [
-    <span class="Constant">1</span>:address:array:character/<span class="Special">raw &lt;- </span>new <span class="Constant">[abc]</span>
-    <span class="Constant">1</span>:address:array:character/<span class="Special">raw &lt;- </span>replace <span class="Constant">1</span>:address:array:character/<span class="Special">raw</span>, <span class="Constant">98/b</span>, <span class="Constant">122/z</span>
-    <span class="Constant">2</span>:array:character/<span class="Special">raw &lt;- </span>copy *<span class="Constant">1</span>:address:array:character/<span class="Special">raw</span>
+    <span class="Constant">1</span>:address:shared:array:character/<span class="Special">raw &lt;- </span>new <span class="Constant">[abc]</span>
+    <span class="Constant">1</span>:address:shared:array:character/<span class="Special">raw &lt;- </span>replace <span class="Constant">1</span>:address:shared:array:character/<span class="Special">raw</span>, <span class="Constant">98/b</span>, <span class="Constant">122/z</span>
+    <span class="Constant">2</span>:array:character/<span class="Special">raw &lt;- </span>copy *<span class="Constant">1</span>:address:shared:array:character/<span class="Special">raw</span>
   ]
   memory-should-contain [
     <span class="Constant">2</span>:array:character<span class="Special"> &lt;- </span><span class="Constant">[azc]</span>
   ]
 ]
 
-<span class="muRecipe">recipe</span> replace s:address:array:character, oldc:character, newc:character<span class="muRecipe"> -&gt; </span>s:address:array:character [
+<span class="muRecipe">recipe</span> replace s:address:shared:array:character, oldc:character, newc:character, from:number/optional<span class="muRecipe"> -&gt; </span>s:address:shared:array:character [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
-  from:number, _<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>  <span class="Comment"># default to 0</span>
   len:number<span class="Special"> &lt;- </span>length *s
   i:number<span class="Special"> &lt;- </span>find-next s, oldc, from
   done?:boolean<span class="Special"> &lt;- </span>greater-or-equal i, len
@@ -482,9 +481,9 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> replace-character-at-start [
   run [
-    <span class="Constant">1</span>:address:array:character/<span class="Special">raw &lt;- </span>new <span class="Constant">[abc]</span>
-    <span class="Constant">1</span>:address:array:character/<span class="Special">raw &lt;- </span>replace <span class="Constant">1</span>:address:array:character/<span class="Special">raw</span>, <span class="Constant">97/a</span>, <span class="Constant">122/z</span>
-    <span class="Constant">2</span>:array:character/<span class="Special">raw &lt;- </span>copy *<span class="Constant">1</span>:address:array:character/<span class="Special">raw</span>
+    <span class="Constant">1</span>:address:shared:array:character/<span class="Special">raw &lt;- </span>new <span class="Constant">[abc]</span>
+    <span class="Constant">1</span>:address:shared:array:character/<span class="Special">raw &lt;- </span>replace <span class="Constant">1</span>:address:shared:array:character/<span class="Special">raw</span>, <span class="Constant">97/a</span>, <span class="Constant">122/z</span>
+    <span class="Constant">2</span>:array:character/<span class="Special">raw &lt;- </span>copy *<span class="Constant">1</span>:address:shared:array:character/<span class="Special">raw</span>
   ]
   memory-should-contain [
     <span class="Constant">2</span>:array:character<span class="Special"> &lt;- </span><span class="Constant">[zbc]</span>
@@ -493,9 +492,9 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> replace-character-at-end [
   run [
-    <span class="Constant">1</span>:address:array:character/<span class="Special">raw &lt;- </span>new <span class="Constant">[abc]</span>
-    <span class="Constant">1</span>:address:array:character/<span class="Special">raw &lt;- </span>replace <span class="Constant">1</span>:address:array:character/<span class="Special">raw</span>, <span class="Constant">99/c</span>, <span class="Constant">122/z</span>
-    <span class="Constant">2</span>:array:character/<span class="Special">raw &lt;- </span>copy *<span class="Constant">1</span>:address:array:character/<span class="Special">raw</span>
+    <span class="Constant">1</span>:address:shared:array:character/<span class="Special">raw &lt;- </span>new <span class="Constant">[abc]</span>
+    <span class="Constant">1</span>:address:shared:array:character/<span class="Special">raw &lt;- </span>replace <span class="Constant">1</span>:address:shared:array:character/<span class="Special">raw</span>, <span class="Constant">99/c</span>, <span class="Constant">122/z</span>
+    <span class="Constant">2</span>:array:character/<span class="Special">raw &lt;- </span>copy *<span class="Constant">1</span>:address:shared:array:character/<span class="Special">raw</span>
   ]
   memory-should-contain [
     <span class="Constant">2</span>:array:character<span class="Special"> &lt;- </span><span class="Constant">[abz]</span>
@@ -504,9 +503,9 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> replace-character-missing [
   run [
-    <span class="Constant">1</span>:address:array:character/<span class="Special">raw &lt;- </span>new <span class="Constant">[abc]</span>
-    <span class="Constant">1</span>:address:array:character/<span class="Special">raw &lt;- </span>replace <span class="Constant">1</span>:address:array:character/<span class="Special">raw</span>, <span class="Constant">100/d</span>, <span class="Constant">122/z</span>
-    <span class="Constant">2</span>:array:character/<span class="Special">raw &lt;- </span>copy *<span class="Constant">1</span>:address:array:character/<span class="Special">raw</span>
+    <span class="Constant">1</span>:address:shared:array:character/<span class="Special">raw &lt;- </span>new <span class="Constant">[abc]</span>
+    <span class="Constant">1</span>:address:shared:array:character/<span class="Special">raw &lt;- </span>replace <span class="Constant">1</span>:address:shared:array:character/<span class="Special">raw</span>, <span class="Constant">100/d</span>, <span class="Constant">122/z</span>
+    <span class="Constant">2</span>:array:character/<span class="Special">raw &lt;- </span>copy *<span class="Constant">1</span>:address:shared:array:character/<span class="Special">raw</span>
   ]
   memory-should-contain [
     <span class="Constant">2</span>:array:character<span class="Special"> &lt;- </span><span class="Constant">[abc]</span>
@@ -515,9 +514,9 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> replace-all-characters [
   run [
-    <span class="Constant">1</span>:address:array:character/<span class="Special">raw &lt;- </span>new <span class="Constant">[banana]</span>
-    <span class="Constant">1</span>:address:array:character/<span class="Special">raw &lt;- </span>replace <span class="Constant">1</span>:address:array:character/<span class="Special">raw</span>, <span class="Constant">97/a</span>, <span class="Constant">122/z</span>
-    <span class="Constant">2</span>:array:character/<span class="Special">raw &lt;- </span>copy *<span class="Constant">1</span>:address:array:character/<span class="Special">raw</span>
+    <span class="Constant">1</span>:address:shared:array:character/<span class="Special">raw &lt;- </span>new <span class="Constant">[banana]</span>
+    <span class="Constant">1</span>:address:shared:array:character/<span class="Special">raw &lt;- </span>replace <span class="Constant">1</span>:address:shared:array:character/<span class="Special">raw</span>, <span class="Constant">97/a</span>, <span class="Constant">122/z</span>
+    <span class="Constant">2</span>:array:character/<span class="Special">raw &lt;- </span>copy *<span class="Constant">1</span>:address:shared:array:character/<span class="Special">raw</span>
   ]
   memory-should-contain [
     <span class="Constant">2</span>:array:character<span class="Special"> &lt;- </span><span class="Constant">[bznznz]</span>
@@ -525,7 +524,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 ]
 
 <span class="Comment"># replace underscores in first with remaining args</span>
-<span class="muRecipe">recipe</span> interpolate template:address:array:character<span class="muRecipe"> -&gt; </span>result:address:array:character [
+<span class="muRecipe">recipe</span> interpolate template:address:shared:array:character<span class="muRecipe"> -&gt; </span>result:address:shared:array:character [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>  <span class="Comment"># consume just the template</span>
   <span class="Comment"># compute result-len, space to allocate for result</span>
@@ -533,7 +532,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   result-len:number<span class="Special"> &lt;- </span>copy tem-len
   <span class="Delimiter">{</span>
     <span class="Comment"># while ingredients remain</span>
-    a:address:array:character, arg-received?:boolean<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
+    a:address:shared:array:character, arg-received?:boolean<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
     <span class="muControl">break-unless</span> arg-received?
     <span class="Comment"># result-len = result-len + arg.length - 1 (for the 'underscore' being replaced)</span>
     a-len:number<span class="Special"> &lt;- </span>length *a
@@ -543,13 +542,13 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   <span class="Delimiter">}</span>
   rewind-ingredients
   _<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>  <span class="Comment"># skip template</span>
-  result:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">character:type</span>, result-len
+  result<span class="Special"> &lt;- </span>new <span class="Constant">character:type</span>, result-len
   <span class="Comment"># repeatedly copy sections of template and 'holes' into result</span>
   result-idx:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
   i:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
   <span class="Delimiter">{</span>
     <span class="Comment"># while arg received</span>
-    a:address:array:character, arg-received?:boolean<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
+    a:address:shared:array:character, arg-received?:boolean<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
     <span class="muControl">break-unless</span> arg-received?
     <span class="Comment"># copy template into result until '_'</span>
     <span class="Delimiter">{</span>
@@ -603,10 +602,10 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> interpolate-works [
   run [
-    <span class="Constant">1</span>:address:array:character/<span class="Special">raw &lt;- </span>new <span class="Constant">[abc _]</span>
-    <span class="Constant">2</span>:address:array:character/<span class="Special">raw &lt;- </span>new <span class="Constant">[def]</span>
-    <span class="Constant">3</span>:address:array:character/<span class="Special">raw &lt;- </span>interpolate <span class="Constant">1</span>:address:array:character/<span class="Special">raw</span>, <span class="Constant">2</span>:address:array:character/<span class="Special">raw</span>
-    <span class="Constant">4</span>:array:character/<span class="Special">raw &lt;- </span>copy *<span class="Constant">3</span>:address:array:character/<span class="Special">raw</span>
+    <span class="Constant">1</span>:address:shared:array:character/<span class="Special">raw &lt;- </span>new <span class="Constant">[abc _]</span>
+    <span class="Constant">2</span>:address:shared:array:character/<span class="Special">raw &lt;- </span>new <span class="Constant">[def]</span>
+    <span class="Constant">3</span>:address:shared:array:character/<span class="Special">raw &lt;- </span>interpolate <span class="Constant">1</span>:address:shared:array:character/<span class="Special">raw</span>, <span class="Constant">2</span>:address:shared:array:character/<span class="Special">raw</span>
+    <span class="Constant">4</span>:array:character/<span class="Special">raw &lt;- </span>copy *<span class="Constant">3</span>:address:shared:array:character/<span class="Special">raw</span>
   ]
   memory-should-contain [
     <span class="Constant">4</span>:array:character<span class="Special"> &lt;- </span><span class="Constant">[abc def]</span>
@@ -615,10 +614,10 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> interpolate-at-start [
   run [
-    <span class="Constant">1</span>:address:array:character/<span class="Special">raw &lt;- </span>new <span class="Constant">[_, hello!]</span>
-    <span class="Constant">2</span>:address:array:character/<span class="Special">raw &lt;- </span>new <span class="Constant">[abc]</span>
-    <span class="Constant">3</span>:address:array:character/<span class="Special">raw &lt;- </span>interpolate <span class="Constant">1</span>:address:array:character/<span class="Special">raw</span>, <span class="Constant">2</span>:address:array:character/<span class="Special">raw</span>
-    <span class="Constant">4</span>:array:character/<span class="Special">raw &lt;- </span>copy *<span class="Constant">3</span>:address:array:character/<span class="Special">raw</span>
+    <span class="Constant">1</span>:address:shared:array:character/<span class="Special">raw &lt;- </span>new <span class="Constant">[_, hello!]</span>
+    <span class="Constant">2</span>:address:shared:array:character/<span class="Special">raw &lt;- </span>new <span class="Constant">[abc]</span>
+    <span class="Constant">3</span>:address:shared:array:character/<span class="Special">raw &lt;- </span>interpolate <span class="Constant">1</span>:address:shared:array:character/<span class="Special">raw</span>, <span class="Constant">2</span>:address:shared:array:character/<span class="Special">raw</span>
+    <span class="Constant">4</span>:array:character/<span class="Special">raw &lt;- </span>copy *<span class="Constant">3</span>:address:shared:array:character/<span class="Special">raw</span>
   ]
   memory-should-contain [
     <span class="Constant">4</span>:array:character<span class="Special"> &lt;- </span><span class="Constant">[abc, hello!]</span>
@@ -628,10 +627,10 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> interpolate-at-end [
   run [
-    <span class="Constant">1</span>:address:array:character/<span class="Special">raw &lt;- </span>new <span class="Constant">[hello, _]</span>
-    <span class="Constant">2</span>:address:array:character/<span class="Special">raw &lt;- </span>new <span class="Constant">[abc]</span>
-    <span class="Constant">3</span>:address:array:character/<span class="Special">raw &lt;- </span>interpolate <span class="Constant">1</span>:address:array:character/<span class="Special">raw</span>, <span class="Constant">2</span>:address:array:character/<span class="Special">raw</span>
-    <span class="Constant">4</span>:array:character/<span class="Special">raw &lt;- </span>copy *<span class="Constant">3</span>:address:array:character/<span class="Special">raw</span>
+    <span class="Constant">1</span>:address:shared:array:character/<span class="Special">raw &lt;- </span>new <span class="Constant">[hello, _]</span>
+    <span class="Constant">2</span>:address:shared:array:character/<span class="Special">raw &lt;- </span>new <span class="Constant">[abc]</span>
+    <span class="Constant">3</span>:address:shared:array:character/<span class="Special">raw &lt;- </span>interpolate <span class="Constant">1</span>:address:shared:array:character/<span class="Special">raw</span>, <span class="Constant">2</span>:address:shared:array:character/<span class="Special">raw</span>
+    <span class="Constant">4</span>:array:character/<span class="Special">raw &lt;- </span>copy *<span class="Constant">3</span>:address:shared:array:character/<span class="Special">raw</span>
   ]
   memory-should-contain [
     <span class="Constant">4</span>:array:character<span class="Special"> &lt;- </span><span class="Constant">[hello, abc]</span>
@@ -700,7 +699,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   result<span class="Special"> &lt;- </span>equal c, <span class="Constant">12288/ideographic-space</span>
 ]
 
-<span class="muRecipe">recipe</span> trim s:address:array:character<span class="muRecipe"> -&gt; </span>result:address:array:character [
+<span class="muRecipe">recipe</span> trim s:address:shared:array:character<span class="muRecipe"> -&gt; </span>result:address:shared:array:character [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   len:number<span class="Special"> &lt;- </span>length *s
@@ -732,7 +731,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   <span class="Delimiter">}</span>
   <span class="Comment"># result = new character[end+1 - start]</span>
   new-len:number<span class="Special"> &lt;- </span>subtract end, start, <span class="Constant">-1</span>
-  result:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">character:type</span>, new-len
+  result:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">character:type</span>, new-len
   <span class="Comment"># copy the untrimmed parts between start and end</span>
   i:number<span class="Special"> &lt;- </span>copy start
   j:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
@@ -752,9 +751,9 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> trim-unmodified [
   run [
-    <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
-    <span class="Constant">2</span>:address:array:character<span class="Special"> &lt;- </span>trim <span class="Constant">1</span>:address:array:character
-    <span class="Constant">3</span>:array:character<span class="Special"> &lt;- </span>copy *<span class="Constant">2</span>:address:array:character
+    <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
+    <span class="Constant">2</span>:address:shared:array:character<span class="Special"> &lt;- </span>trim <span class="Constant">1</span>:address:shared:array:character
+    <span class="Constant">3</span>:array:character<span class="Special"> &lt;- </span>copy *<span class="Constant">2</span>:address:shared:array:character
   ]
   memory-should-contain [
     <span class="Constant">3</span>:array:character<span class="Special"> &lt;- </span><span class="Constant">[abc]</span>
@@ -763,9 +762,9 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> trim-left [
   run [
-    <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[  abc]</span>
-    <span class="Constant">2</span>:address:array:character<span class="Special"> &lt;- </span>trim <span class="Constant">1</span>:address:array:character
-    <span class="Constant">3</span>:array:character<span class="Special"> &lt;- </span>copy *<span class="Constant">2</span>:address:array:character
+    <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[  abc]</span>
+    <span class="Constant">2</span>:address:shared:array:character<span class="Special"> &lt;- </span>trim <span class="Constant">1</span>:address:shared:array:character
+    <span class="Constant">3</span>:array:character<span class="Special"> &lt;- </span>copy *<span class="Constant">2</span>:address:shared:array:character
   ]
   memory-should-contain [
     <span class="Constant">3</span>:array:character<span class="Special"> &lt;- </span><span class="Constant">[abc]</span>
@@ -774,9 +773,9 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> trim-right [
   run [
-    <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc  ]</span>
-    <span class="Constant">2</span>:address:array:character<span class="Special"> &lt;- </span>trim <span class="Constant">1</span>:address:array:character
-    <span class="Constant">3</span>:array:character<span class="Special"> &lt;- </span>copy *<span class="Constant">2</span>:address:array:character
+    <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc  ]</span>
+    <span class="Constant">2</span>:address:shared:array:character<span class="Special"> &lt;- </span>trim <span class="Constant">1</span>:address:shared:array:character
+    <span class="Constant">3</span>:array:character<span class="Special"> &lt;- </span>copy *<span class="Constant">2</span>:address:shared:array:character
   ]
   memory-should-contain [
     <span class="Constant">3</span>:array:character<span class="Special"> &lt;- </span><span class="Constant">[abc]</span>
@@ -785,9 +784,9 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> trim-left-right [
   run [
-    <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[  abc   ]</span>
-    <span class="Constant">2</span>:address:array:character<span class="Special"> &lt;- </span>trim <span class="Constant">1</span>:address:array:character
-    <span class="Constant">3</span>:array:character<span class="Special"> &lt;- </span>copy *<span class="Constant">2</span>:address:array:character
+    <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[  abc   ]</span>
+    <span class="Constant">2</span>:address:shared:array:character<span class="Special"> &lt;- </span>trim <span class="Constant">1</span>:address:shared:array:character
+    <span class="Constant">3</span>:array:character<span class="Special"> &lt;- </span>copy *<span class="Constant">2</span>:address:shared:array:character
   ]
   memory-should-contain [
     <span class="Constant">3</span>:array:character<span class="Special"> &lt;- </span><span class="Constant">[abc]</span>
@@ -796,21 +795,19 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> trim-newline-tab [
   run [
-    <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[  abc</span>
+    <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[ abc</span>
 <span class="Constant">]</span>
-    <span class="Constant">2</span>:address:array:character<span class="Special"> &lt;- </span>trim <span class="Constant">1</span>:address:array:character
-    <span class="Constant">3</span>:array:character<span class="Special"> &lt;- </span>copy *<span class="Constant">2</span>:address:array:character
+    <span class="Constant">2</span>:address:shared:array:character<span class="Special"> &lt;- </span>trim <span class="Constant">1</span>:address:shared:array:character
+    <span class="Constant">3</span>:array:character<span class="Special"> &lt;- </span>copy *<span class="Constant">2</span>:address:shared:array:character
   ]
   memory-should-contain [
     <span class="Constant">3</span>:array:character<span class="Special"> &lt;- </span><span class="Constant">[abc]</span>
   ]
 ]
 
-<span class="muRecipe">recipe</span> find-next text:address:array:character, pattern:character, idx:number<span class="muRecipe"> -&gt; </span>next-index:number [
+<span class="muRecipe">recipe</span> find-next text:address:shared:array:character, pattern:character, idx:number<span class="muRecipe"> -&gt; </span>next-index:number [
   <span class="Constant">local-scope</span>
-  text:address:array:character<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
-  pattern:character<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
-  idx:number<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
+  <span class="Constant">load-ingredients</span>
   len:number<span class="Special"> &lt;- </span>length *text
   <span class="Delimiter">{</span>
     eof?:boolean<span class="Special"> &lt;- </span>greater-or-equal idx, len
@@ -826,8 +823,8 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> text-find-next [
   run [
-    <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[a/b]</span>
-    <span class="Constant">2</span>:number<span class="Special"> &lt;- </span>find-next <span class="Constant">1</span>:address:array:character, <span class="Constant">47/slash</span>, <span class="Constant">0/start-index</span>
+    <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[a/b]</span>
+    <span class="Constant">2</span>:number<span class="Special"> &lt;- </span>find-next <span class="Constant">1</span>:address:shared:array:character, <span class="Constant">47/slash</span>, <span class="Constant">0/start-index</span>
   ]
   memory-should-contain [
     <span class="Constant">2</span><span class="Special"> &lt;- </span><span class="Constant">1</span>
@@ -836,8 +833,8 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> text-find-next-empty [
   run [
-    <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
-    <span class="Constant">2</span>:number<span class="Special"> &lt;- </span>find-next <span class="Constant">1</span>:address:array:character, <span class="Constant">47/slash</span>, <span class="Constant">0/start-index</span>
+    <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
+    <span class="Constant">2</span>:number<span class="Special"> &lt;- </span>find-next <span class="Constant">1</span>:address:shared:array:character, <span class="Constant">47/slash</span>, <span class="Constant">0/start-index</span>
   ]
   memory-should-contain [
     <span class="Constant">2</span><span class="Special"> &lt;- </span><span class="Constant">0</span>
@@ -846,8 +843,8 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> text-find-next-initial [
   run [
-    <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[/abc]</span>
-    <span class="Constant">2</span>:number<span class="Special"> &lt;- </span>find-next <span class="Constant">1</span>:address:array:character, <span class="Constant">47/slash</span>, <span class="Constant">0/start-index</span>
+    <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[/abc]</span>
+    <span class="Constant">2</span>:number<span class="Special"> &lt;- </span>find-next <span class="Constant">1</span>:address:shared:array:character, <span class="Constant">47/slash</span>, <span class="Constant">0/start-index</span>
   ]
   memory-should-contain [
     <span class="Constant">2</span><span class="Special"> &lt;- </span><span class="Constant">0</span>  <span class="Comment"># prefix match</span>
@@ -856,8 +853,8 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> text-find-next-final [
   run [
-    <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc/]</span>
-    <span class="Constant">2</span>:number<span class="Special"> &lt;- </span>find-next <span class="Constant">1</span>:address:array:character, <span class="Constant">47/slash</span>, <span class="Constant">0/start-index</span>
+    <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc/]</span>
+    <span class="Constant">2</span>:number<span class="Special"> &lt;- </span>find-next <span class="Constant">1</span>:address:shared:array:character, <span class="Constant">47/slash</span>, <span class="Constant">0/start-index</span>
   ]
   memory-should-contain [
     <span class="Constant">2</span><span class="Special"> &lt;- </span><span class="Constant">3</span>  <span class="Comment"># suffix match</span>
@@ -866,8 +863,8 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> text-find-next-missing [
   run [
-    <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
-    <span class="Constant">2</span>:number<span class="Special"> &lt;- </span>find-next <span class="Constant">1</span>:address:array:character, <span class="Constant">47/slash</span>, <span class="Constant">0/start-index</span>
+    <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
+    <span class="Constant">2</span>:number<span class="Special"> &lt;- </span>find-next <span class="Constant">1</span>:address:shared:array:character, <span class="Constant">47/slash</span>, <span class="Constant">0/start-index</span>
   ]
   memory-should-contain [
     <span class="Constant">2</span><span class="Special"> &lt;- </span><span class="Constant">3</span>  <span class="Comment"># no match</span>
@@ -876,8 +873,8 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> text-find-next-invalid-index [
   run [
-    <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
-    <span class="Constant">2</span>:number<span class="Special"> &lt;- </span>find-next <span class="Constant">1</span>:address:array:character, <span class="Constant">47/slash</span>, <span class="Constant">4/start-index</span>
+    <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
+    <span class="Constant">2</span>:number<span class="Special"> &lt;- </span>find-next <span class="Constant">1</span>:address:shared:array:character, <span class="Constant">47/slash</span>, <span class="Constant">4/start-index</span>
   ]
   memory-should-contain [
     <span class="Constant">2</span><span class="Special"> &lt;- </span><span class="Constant">4</span>  <span class="Comment"># no change</span>
@@ -886,8 +883,8 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> text-find-next-first [
   run [
-    <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[ab/c/]</span>
-    <span class="Constant">2</span>:number<span class="Special"> &lt;- </span>find-next <span class="Constant">1</span>:address:array:character, <span class="Constant">47/slash</span>, <span class="Constant">0/start-index</span>
+    <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[ab/c/]</span>
+    <span class="Constant">2</span>:number<span class="Special"> &lt;- </span>find-next <span class="Constant">1</span>:address:shared:array:character, <span class="Constant">47/slash</span>, <span class="Constant">0/start-index</span>
   ]
   memory-should-contain [
     <span class="Constant">2</span><span class="Special"> &lt;- </span><span class="Constant">2</span>  <span class="Comment"># first '/' of multiple</span>
@@ -896,8 +893,8 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> text-find-next-second [
   run [
-    <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[ab/c/]</span>
-    <span class="Constant">2</span>:number<span class="Special"> &lt;- </span>find-next <span class="Constant">1</span>:address:array:character, <span class="Constant">47/slash</span>, <span class="Constant">3/start-index</span>
+    <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[ab/c/]</span>
+    <span class="Constant">2</span>:number<span class="Special"> &lt;- </span>find-next <span class="Constant">1</span>:address:shared:array:character, <span class="Constant">47/slash</span>, <span class="Constant">3/start-index</span>
   ]
   memory-should-contain [
     <span class="Constant">2</span><span class="Special"> &lt;- </span><span class="Constant">4</span>  <span class="Comment"># second '/' of multiple</span>
@@ -906,7 +903,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="Comment"># search for a pattern of multiple characters</span>
 <span class="Comment"># fairly dumb algorithm</span>
-<span class="muRecipe">recipe</span> find-next text:address:array:character, pattern:address:array:character, idx:number<span class="muRecipe"> -&gt; </span>next-index:number [
+<span class="muRecipe">recipe</span> find-next text:address:shared:array:character, pattern:address:shared:array:character, idx:number<span class="muRecipe"> -&gt; </span>next-index:number [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   first:character<span class="Special"> &lt;- </span>index *pattern, <span class="Constant">0</span>
@@ -928,9 +925,9 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> find-next-text-1 [
   run [
-    <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
-    <span class="Constant">2</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[bc]</span>
-    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>find-next <span class="Constant">1</span>:address:array:character, <span class="Constant">2</span>:address:array:character, <span class="Constant">0</span>
+    <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
+    <span class="Constant">2</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[bc]</span>
+    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>find-next <span class="Constant">1</span>:address:shared:array:character, <span class="Constant">2</span>:address:shared:array:character, <span class="Constant">0</span>
   ]
   memory-should-contain [
     <span class="Constant">3</span><span class="Special"> &lt;- </span><span class="Constant">1</span>
@@ -939,9 +936,9 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> find-next-text-2 [
   run [
-    <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abcd]</span>
-    <span class="Constant">2</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[bc]</span>
-    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>find-next <span class="Constant">1</span>:address:array:character, <span class="Constant">2</span>:address:array:character, <span class="Constant">1</span>
+    <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abcd]</span>
+    <span class="Constant">2</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[bc]</span>
+    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>find-next <span class="Constant">1</span>:address:shared:array:character, <span class="Constant">2</span>:address:shared:array:character, <span class="Constant">1</span>
   ]
   memory-should-contain [
     <span class="Constant">3</span><span class="Special"> &lt;- </span><span class="Constant">1</span>
@@ -950,9 +947,9 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> find-next-no-match [
   run [
-    <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
-    <span class="Constant">2</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[bd]</span>
-    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>find-next <span class="Constant">1</span>:address:array:character, <span class="Constant">2</span>:address:array:character, <span class="Constant">0</span>
+    <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
+    <span class="Constant">2</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[bd]</span>
+    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>find-next <span class="Constant">1</span>:address:shared:array:character, <span class="Constant">2</span>:address:shared:array:character, <span class="Constant">0</span>
   ]
   memory-should-contain [
     <span class="Constant">3</span><span class="Special"> &lt;- </span><span class="Constant">3</span>  <span class="Comment"># not found</span>
@@ -961,9 +958,9 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> find-next-suffix-match [
   run [
-    <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abcd]</span>
-    <span class="Constant">2</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[cd]</span>
-    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>find-next <span class="Constant">1</span>:address:array:character, <span class="Constant">2</span>:address:array:character, <span class="Constant">0</span>
+    <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abcd]</span>
+    <span class="Constant">2</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[cd]</span>
+    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>find-next <span class="Constant">1</span>:address:shared:array:character, <span class="Constant">2</span>:address:shared:array:character, <span class="Constant">0</span>
   ]
   memory-should-contain [
     <span class="Constant">3</span><span class="Special"> &lt;- </span><span class="Constant">2</span>
@@ -972,9 +969,9 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> find-next-suffix-match-2 [
   run [
-    <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abcd]</span>
-    <span class="Constant">2</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[cde]</span>
-    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>find-next <span class="Constant">1</span>:address:array:character, <span class="Constant">2</span>:address:array:character, <span class="Constant">0</span>
+    <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abcd]</span>
+    <span class="Constant">2</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[cde]</span>
+    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>find-next <span class="Constant">1</span>:address:shared:array:character, <span class="Constant">2</span>:address:shared:array:character, <span class="Constant">0</span>
   ]
   memory-should-contain [
     <span class="Constant">3</span><span class="Special"> &lt;- </span><span class="Constant">4</span>  <span class="Comment"># not found</span>
@@ -982,7 +979,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 ]
 
 <span class="Comment"># checks if pattern matches at index 'idx'</span>
-<span class="muRecipe">recipe</span> match-at text:address:array:character, pattern:address:array:character, idx:number<span class="muRecipe"> -&gt; </span>result:boolean [
+<span class="muRecipe">recipe</span> match-at text:address:shared:array:character, pattern:address:shared:array:character, idx:number<span class="muRecipe"> -&gt; </span>result:boolean [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   pattern-len:number<span class="Special"> &lt;- </span>length *pattern
@@ -1015,9 +1012,9 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> match-at-checks-pattern-at-index [
   run [
-    <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
-    <span class="Constant">2</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[ab]</span>
-    <span class="Constant">3</span>:boolean<span class="Special"> &lt;- </span>match-at <span class="Constant">1</span>:address:array:character, <span class="Constant">2</span>:address:array:character, <span class="Constant">0</span>
+    <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
+    <span class="Constant">2</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[ab]</span>
+    <span class="Constant">3</span>:boolean<span class="Special"> &lt;- </span>match-at <span class="Constant">1</span>:address:shared:array:character, <span class="Constant">2</span>:address:shared:array:character, <span class="Constant">0</span>
   ]
   memory-should-contain [
     <span class="Constant">3</span><span class="Special"> &lt;- </span><span class="Constant">1</span>  <span class="Comment"># match found</span>
@@ -1026,8 +1023,8 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> match-at-reflexive [
   run [
-    <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
-    <span class="Constant">3</span>:boolean<span class="Special"> &lt;- </span>match-at <span class="Constant">1</span>:address:array:character, <span class="Constant">1</span>:address:array:character, <span class="Constant">0</span>
+    <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
+    <span class="Constant">3</span>:boolean<span class="Special"> &lt;- </span>match-at <span class="Constant">1</span>:address:shared:array:character, <span class="Constant">1</span>:address:shared:array:character, <span class="Constant">0</span>
   ]
   memory-should-contain [
     <span class="Constant">3</span><span class="Special"> &lt;- </span><span class="Constant">1</span>  <span class="Comment"># match found</span>
@@ -1036,9 +1033,9 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> match-at-outside-bounds [
   run [
-    <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
-    <span class="Constant">2</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[a]</span>
-    <span class="Constant">3</span>:boolean<span class="Special"> &lt;- </span>match-at <span class="Constant">1</span>:address:array:character, <span class="Constant">2</span>:address:array:character, <span class="Constant">4</span>
+    <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
+    <span class="Constant">2</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[a]</span>
+    <span class="Constant">3</span>:boolean<span class="Special"> &lt;- </span>match-at <span class="Constant">1</span>:address:shared:array:character, <span class="Constant">2</span>:address:shared:array:character, <span class="Constant">4</span>
   ]
   memory-should-contain [
     <span class="Constant">3</span><span class="Special"> &lt;- </span><span class="Constant">0</span>  <span class="Comment"># never matches</span>
@@ -1047,9 +1044,9 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> match-at-empty-pattern [
   run [
-    <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
-    <span class="Constant">2</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
-    <span class="Constant">3</span>:boolean<span class="Special"> &lt;- </span>match-at <span class="Constant">1</span>:address:array:character, <span class="Constant">2</span>:address:array:character, <span class="Constant">0</span>
+    <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
+    <span class="Constant">2</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
+    <span class="Constant">3</span>:boolean<span class="Special"> &lt;- </span>match-at <span class="Constant">1</span>:address:shared:array:character, <span class="Constant">2</span>:address:shared:array:character, <span class="Constant">0</span>
   ]
   memory-should-contain [
     <span class="Constant">3</span><span class="Special"> &lt;- </span><span class="Constant">1</span>  <span class="Comment"># always matches empty pattern given a valid index</span>
@@ -1058,9 +1055,9 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> match-at-empty-pattern-outside-bound [
   run [
-    <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
-    <span class="Constant">2</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
-    <span class="Constant">3</span>:boolean<span class="Special"> &lt;- </span>match-at <span class="Constant">1</span>:address:array:character, <span class="Constant">2</span>:address:array:character, <span class="Constant">4</span>
+    <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
+    <span class="Constant">2</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
+    <span class="Constant">3</span>:boolean<span class="Special"> &lt;- </span>match-at <span class="Constant">1</span>:address:shared:array:character, <span class="Constant">2</span>:address:shared:array:character, <span class="Constant">4</span>
   ]
   memory-should-contain [
     <span class="Constant">3</span><span class="Special"> &lt;- </span><span class="Constant">0</span>  <span class="Comment"># no match</span>
@@ -1069,9 +1066,9 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> match-at-empty-text [
   run [
-    <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
-    <span class="Constant">2</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
-    <span class="Constant">3</span>:boolean<span class="Special"> &lt;- </span>match-at <span class="Constant">1</span>:address:array:character, <span class="Constant">2</span>:address:array:character, <span class="Constant">0</span>
+    <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
+    <span class="Constant">2</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
+    <span class="Constant">3</span>:boolean<span class="Special"> &lt;- </span>match-at <span class="Constant">1</span>:address:shared:array:character, <span class="Constant">2</span>:address:shared:array:character, <span class="Constant">0</span>
   ]
   memory-should-contain [
     <span class="Constant">3</span><span class="Special"> &lt;- </span><span class="Constant">0</span>  <span class="Comment"># no match</span>
@@ -1080,8 +1077,8 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> match-at-empty-against-empty [
   run [
-    <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
-    <span class="Constant">3</span>:boolean<span class="Special"> &lt;- </span>match-at <span class="Constant">1</span>:address:array:character, <span class="Constant">1</span>:address:array:character, <span class="Constant">0</span>
+    <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
+    <span class="Constant">3</span>:boolean<span class="Special"> &lt;- </span>match-at <span class="Constant">1</span>:address:shared:array:character, <span class="Constant">1</span>:address:shared:array:character, <span class="Constant">0</span>
   ]
   memory-should-contain [
     <span class="Constant">3</span><span class="Special"> &lt;- </span><span class="Constant">1</span>  <span class="Comment"># matches because pattern is also empty</span>
@@ -1090,9 +1087,9 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> match-at-inside-bounds [
   run [
-    <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
-    <span class="Constant">2</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[bc]</span>
-    <span class="Constant">3</span>:boolean<span class="Special"> &lt;- </span>match-at <span class="Constant">1</span>:address:array:character, <span class="Constant">2</span>:address:array:character, <span class="Constant">1</span>
+    <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
+    <span class="Constant">2</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[bc]</span>
+    <span class="Constant">3</span>:boolean<span class="Special"> &lt;- </span>match-at <span class="Constant">1</span>:address:shared:array:character, <span class="Constant">2</span>:address:shared:array:character, <span class="Constant">1</span>
   ]
   memory-should-contain [
     <span class="Constant">3</span><span class="Special"> &lt;- </span><span class="Constant">1</span>  <span class="Comment"># match</span>
@@ -1101,16 +1098,16 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> match-at-inside-bounds-2 [
   run [
-    <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
-    <span class="Constant">2</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[bc]</span>
-    <span class="Constant">3</span>:boolean<span class="Special"> &lt;- </span>match-at <span class="Constant">1</span>:address:array:character, <span class="Constant">2</span>:address:array:character, <span class="Constant">0</span>
+    <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
+    <span class="Constant">2</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[bc]</span>
+    <span class="Constant">3</span>:boolean<span class="Special"> &lt;- </span>match-at <span class="Constant">1</span>:address:shared:array:character, <span class="Constant">2</span>:address:shared:array:character, <span class="Constant">0</span>
   ]
   memory-should-contain [
     <span class="Constant">3</span><span class="Special"> &lt;- </span><span class="Constant">0</span>  <span class="Comment"># no match</span>
   ]
 ]
 
-<span class="muRecipe">recipe</span> split s:address:array:character, delim:character<span class="muRecipe"> -&gt; </span>result:address:array:address:array:character [
+<span class="muRecipe">recipe</span> split s:address:shared:array:character, delim:character<span class="muRecipe"> -&gt; </span>result:address:shared:array:address:shared:array:character [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   <span class="Comment"># empty text? return empty array</span>
@@ -1118,7 +1115,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   <span class="Delimiter">{</span>
     empty?:boolean<span class="Special"> &lt;- </span>equal len, <span class="Constant">0</span>
     <span class="muControl">break-unless</span> empty?
-    result<span class="Special"> &lt;- </span>new <span class="Constant">location:type</span>, <span class="Constant">0</span>
+    result<span class="Special"> &lt;- </span>new <span class="Delimiter">{</span>(address shared array character): type<span class="Delimiter">}</span>, <span class="Constant">0</span>
     <span class="muControl">reply</span>
   <span class="Delimiter">}</span>
   <span class="Comment"># count #pieces we need room for</span>
@@ -1133,7 +1130,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     <span class="muControl">loop</span>
   <span class="Delimiter">}</span>
   <span class="Comment"># allocate space</span>
-  result<span class="Special"> &lt;- </span>new <span class="Constant">location:type</span>, count
+  result<span class="Special"> &lt;- </span>new <span class="Delimiter">{</span>(address shared array character): type<span class="Delimiter">}</span>, count
   <span class="Comment"># repeatedly copy slices start..end until delimiter into result[curr-result]</span>
   curr-result:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
   start:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
@@ -1143,8 +1140,8 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     <span class="muControl">break-if</span> done?
     end:number<span class="Special"> &lt;- </span>find-next s, delim, start
     <span class="Comment"># copy start..end into result[curr-result]</span>
-    dest:address:address:array:character<span class="Special"> &lt;- </span>index-address *result, curr-result
-    *dest<span class="Special"> &lt;- </span>copy s, start, end
+    dest:address:address:shared:array:character<span class="Special"> &lt;- </span>index-address *result, curr-result
+    *dest<span class="Special"> &lt;- </span>copy-range s, start, end
     <span class="Comment"># slide over to next slice</span>
     start<span class="Special"> &lt;- </span>add end, <span class="Constant">1</span>
     curr-result<span class="Special"> &lt;- </span>add curr-result, <span class="Constant">1</span>
@@ -1154,13 +1151,13 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> text-split-1 [
   run [
-    <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[a/b]</span>
-    <span class="Constant">2</span>:address:array:address:array:character<span class="Special"> &lt;- </span>split <span class="Constant">1</span>:address:array:character, <span class="Constant">47/slash</span>
-    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>length *<span class="Constant">2</span>:address:array:address:array:character
-    <span class="Constant">4</span>:address:array:character<span class="Special"> &lt;- </span>index *<span class="Constant">2</span>:address:array:address:array:character, <span class="Constant">0</span>
-    <span class="Constant">5</span>:address:array:character<span class="Special"> &lt;- </span>index *<span class="Constant">2</span>:address:array:address:array:character, <span class="Constant">1</span>
-    <span class="Constant">10</span>:array:character<span class="Special"> &lt;- </span>copy *<span class="Constant">4</span>:address:array:character
-    <span class="Constant">20</span>:array:character<span class="Special"> &lt;- </span>copy *<span class="Constant">5</span>:address:array:character
+    <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[a/b]</span>
+    <span class="Constant">2</span>:address:shared:array:address:shared:array:character<span class="Special"> &lt;- </span>split <span class="Constant">1</span>:address:shared:array:character, <span class="Constant">47/slash</span>
+    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>length *<span class="Constant">2</span>:address:shared:array:address:shared:array:character
+    <span class="Constant">4</span>:address:shared:array:character<span class="Special"> &lt;- </span>index *<span class="Constant">2</span>:address:shared:array:address:shared:array:character, <span class="Constant">0</span>
+    <span class="Constant">5</span>:address:shared:array:character<span class="Special"> &lt;- </span>index *<span class="Constant">2</span>:address:shared:array:address:shared:array:character, <span class="Constant">1</span>
+    <span class="Constant">10</span>:array:character<span class="Special"> &lt;- </span>copy *<span class="Constant">4</span>:address:shared:array:character
+    <span class="Constant">20</span>:array:character<span class="Special"> &lt;- </span>copy *<span class="Constant">5</span>:address:shared:array:character
   ]
   memory-should-contain [
     <span class="Constant">3</span><span class="Special"> &lt;- </span><span class="Constant">2</span>  <span class="Comment"># length of result</span>
@@ -1171,15 +1168,15 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> text-split-2 [
   run [
-    <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[a/b/c]</span>
-    <span class="Constant">2</span>:address:array:address:array:character<span class="Special"> &lt;- </span>split <span class="Constant">1</span>:address:array:character, <span class="Constant">47/slash</span>
-    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>length *<span class="Constant">2</span>:address:array:address:array:character
-    <span class="Constant">4</span>:address:array:character<span class="Special"> &lt;- </span>index *<span class="Constant">2</span>:address:array:address:array:character, <span class="Constant">0</span>
-    <span class="Constant">5</span>:address:array:character<span class="Special"> &lt;- </span>index *<span class="Constant">2</span>:address:array:address:array:character, <span class="Constant">1</span>
-    <span class="Constant">6</span>:address:array:character<span class="Special"> &lt;- </span>index *<span class="Constant">2</span>:address:array:address:array:character, <span class="Constant">2</span>
-    <span class="Constant">10</span>:array:character<span class="Special"> &lt;- </span>copy *<span class="Constant">4</span>:address:array:character
-    <span class="Constant">20</span>:array:character<span class="Special"> &lt;- </span>copy *<span class="Constant">5</span>:address:array:character
-    <span class="Constant">30</span>:array:character<span class="Special"> &lt;- </span>copy *<span class="Constant">6</span>:address:array:character
+    <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[a/b/c]</span>
+    <span class="Constant">2</span>:address:shared:array:address:shared:array:character<span class="Special"> &lt;- </span>split <span class="Constant">1</span>:address:shared:array:character, <span class="Constant">47/slash</span>
+    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>length *<span class="Constant">2</span>:address:shared:array:address:shared:array:character
+    <span class="Constant">4</span>:address:shared:array:character<span class="Special"> &lt;- </span>index *<span class="Constant">2</span>:address:shared:array:address:shared:array:character, <span class="Constant">0</span>
+    <span class="Constant">5</span>:address:shared:array:character<span class="Special"> &lt;- </span>index *<span class="Constant">2</span>:address:shared:array:address:shared:array:character, <span class="Constant">1</span>
+    <span class="Constant">6</span>:address:shared:array:character<span class="Special"> &lt;- </span>index *<span class="Constant">2</span>:address:shared:array:address:shared:array:character, <span class="Constant">2</span>
+    <span class="Constant">10</span>:array:character<span class="Special"> &lt;- </span>copy *<span class="Constant">4</span>:address:shared:array:character
+    <span class="Constant">20</span>:array:character<span class="Special"> &lt;- </span>copy *<span class="Constant">5</span>:address:shared:array:character
+    <span class="Constant">30</span>:array:character<span class="Special"> &lt;- </span>copy *<span class="Constant">6</span>:address:shared:array:character
   ]
   memory-should-contain [
     <span class="Constant">3</span><span class="Special"> &lt;- </span><span class="Constant">3</span>  <span class="Comment"># length of result</span>
@@ -1191,11 +1188,11 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> text-split-missing [
   run [
-    <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
-    <span class="Constant">2</span>:address:array:address:array:character<span class="Special"> &lt;- </span>split <span class="Constant">1</span>:address:array:character, <span class="Constant">47/slash</span>
-    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>length *<span class="Constant">2</span>:address:array:address:array:character
-    <span class="Constant">4</span>:address:array:character<span class="Special"> &lt;- </span>index *<span class="Constant">2</span>:address:array:address:array:character, <span class="Constant">0</span>
-    <span class="Constant">10</span>:array:character<span class="Special"> &lt;- </span>copy *<span class="Constant">4</span>:address:array:character
+    <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
+    <span class="Constant">2</span>:address:shared:array:address:shared:array:character<span class="Special"> &lt;- </span>split <span class="Constant">1</span>:address:shared:array:character, <span class="Constant">47/slash</span>
+    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>length *<span class="Constant">2</span>:address:shared:array:address:shared:array:character
+    <span class="Constant">4</span>:address:shared:array:character<span class="Special"> &lt;- </span>index *<span class="Constant">2</span>:address:shared:array:address:shared:array:character, <span class="Constant">0</span>
+    <span class="Constant">10</span>:array:character<span class="Special"> &lt;- </span>copy *<span class="Constant">4</span>:address:shared:array:character
   ]
   memory-should-contain [
     <span class="Constant">3</span><span class="Special"> &lt;- </span><span class="Constant">1</span>  <span class="Comment"># length of result</span>
@@ -1205,9 +1202,9 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> text-split-empty [
   run [
-    <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
-    <span class="Constant">2</span>:address:array:address:array:character<span class="Special"> &lt;- </span>split <span class="Constant">1</span>:address:array:character, <span class="Constant">47/slash</span>
-    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>length *<span class="Constant">2</span>:address:array:address:array:character
+    <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
+    <span class="Constant">2</span>:address:shared:array:address:shared:array:character<span class="Special"> &lt;- </span>split <span class="Constant">1</span>:address:shared:array:character, <span class="Constant">47/slash</span>
+    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>length *<span class="Constant">2</span>:address:shared:array:address:shared:array:character
   ]
   memory-should-contain [
     <span class="Constant">3</span><span class="Special"> &lt;- </span><span class="Constant">0</span>  <span class="Comment"># empty result</span>
@@ -1216,17 +1213,17 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> text-split-empty-piece [
   run [
-    <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[a/b//c]</span>
-    <span class="Constant">2</span>:address:array:address:array:character<span class="Special"> &lt;- </span>split <span class="Constant">1</span>:address:array:character, <span class="Constant">47/slash</span>
-    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>length *<span class="Constant">2</span>:address:array:address:array:character
-    <span class="Constant">4</span>:address:array:character<span class="Special"> &lt;- </span>index *<span class="Constant">2</span>:address:array:address:array:character, <span class="Constant">0</span>
-    <span class="Constant">5</span>:address:array:character<span class="Special"> &lt;- </span>index *<span class="Constant">2</span>:address:array:address:array:character, <span class="Constant">1</span>
-    <span class="Constant">6</span>:address:array:character<span class="Special"> &lt;- </span>index *<span class="Constant">2</span>:address:array:address:array:character, <span class="Constant">2</span>
-    <span class="Constant">7</span>:address:array:character<span class="Special"> &lt;- </span>index *<span class="Constant">2</span>:address:array:address:array:character, <span class="Constant">3</span>
-    <span class="Constant">10</span>:array:character<span class="Special"> &lt;- </span>copy *<span class="Constant">4</span>:address:array:character
-    <span class="Constant">20</span>:array:character<span class="Special"> &lt;- </span>copy *<span class="Constant">5</span>:address:array:character
-    <span class="Constant">30</span>:array:character<span class="Special"> &lt;- </span>copy *<span class="Constant">6</span>:address:array:character
-    <span class="Constant">40</span>:array:character<span class="Special"> &lt;- </span>copy *<span class="Constant">7</span>:address:array:character
+    <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[a/b//c]</span>
+    <span class="Constant">2</span>:address:shared:array:address:shared:array:character<span class="Special"> &lt;- </span>split <span class="Constant">1</span>:address:shared:array:character, <span class="Constant">47/slash</span>
+    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>length *<span class="Constant">2</span>:address:shared:array:address:shared:array:character
+    <span class="Constant">4</span>:address:shared:array:character<span class="Special"> &lt;- </span>index *<span class="Constant">2</span>:address:shared:array:address:shared:array:character, <span class="Constant">0</span>
+    <span class="Constant">5</span>:address:shared:array:character<span class="Special"> &lt;- </span>index *<span class="Constant">2</span>:address:shared:array:address:shared:array:character, <span class="Constant">1</span>
+    <span class="Constant">6</span>:address:shared:array:character<span class="Special"> &lt;- </span>index *<span class="Constant">2</span>:address:shared:array:address:shared:array:character, <span class="Constant">2</span>
+    <span class="Constant">7</span>:address:shared:array:character<span class="Special"> &lt;- </span>index *<span class="Constant">2</span>:address:shared:array:address:shared:array:character, <span class="Constant">3</span>
+    <span class="Constant">10</span>:array:character<span class="Special"> &lt;- </span>copy *<span class="Constant">4</span>:address:shared:array:character
+    <span class="Constant">20</span>:array:character<span class="Special"> &lt;- </span>copy *<span class="Constant">5</span>:address:shared:array:character
+    <span class="Constant">30</span>:array:character<span class="Special"> &lt;- </span>copy *<span class="Constant">6</span>:address:shared:array:character
+    <span class="Constant">40</span>:array:character<span class="Special"> &lt;- </span>copy *<span class="Constant">7</span>:address:shared:array:character
   ]
   memory-should-contain [
     <span class="Constant">3</span><span class="Special"> &lt;- </span><span class="Constant">4</span>  <span class="Comment"># length of result</span>
@@ -1237,7 +1234,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   ]
 ]
 
-<span class="muRecipe">recipe</span> split-first text:address:array:character, delim:character<span class="muRecipe"> -&gt; </span>x:address:array:character, y:address:array:character [
+<span class="muRecipe">recipe</span> split-first text:address:shared:array:character, delim:character<span class="muRecipe"> -&gt; </span>x:address:shared:array:character, y:address:shared:array:character [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   <span class="Comment"># empty text? return empty texts</span>
@@ -1245,22 +1242,22 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   <span class="Delimiter">{</span>
     empty?:boolean<span class="Special"> &lt;- </span>equal len, <span class="Constant">0</span>
     <span class="muControl">break-unless</span> empty?
-    x:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
-    y:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
+    x:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
+    y:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
     <span class="muControl">reply</span>
   <span class="Delimiter">}</span>
   idx:number<span class="Special"> &lt;- </span>find-next text, delim, <span class="Constant">0</span>
-  x:address:array:character<span class="Special"> &lt;- </span>copy text, <span class="Constant">0</span>, idx
+  x:address:shared:array:character<span class="Special"> &lt;- </span>copy-range text, <span class="Constant">0</span>, idx
   idx<span class="Special"> &lt;- </span>add idx, <span class="Constant">1</span>
-  y:address:array:character<span class="Special"> &lt;- </span>copy text, idx, len
+  y:address:shared:array:character<span class="Special"> &lt;- </span>copy-range text, idx, len
 ]
 
 <span class="muScenario">scenario</span> text-split-first [
   run [
-    <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[a/b]</span>
-    <span class="Constant">2</span>:address:array:character, <span class="Constant">3</span>:address:array:character<span class="Special"> &lt;- </span>split-first <span class="Constant">1</span>:address:array:character, <span class="Constant">47/slash</span>
-    <span class="Constant">10</span>:array:character<span class="Special"> &lt;- </span>copy *<span class="Constant">2</span>:address:array:character
-    <span class="Constant">20</span>:array:character<span class="Special"> &lt;- </span>copy *<span class="Constant">3</span>:address:array:character
+    <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[a/b]</span>
+    <span class="Constant">2</span>:address:shared:array:character, <span class="Constant">3</span>:address:shared:array:character<span class="Special"> &lt;- </span>split-first <span class="Constant">1</span>:address:shared:array:character, <span class="Constant">47/slash</span>
+    <span class="Constant">10</span>:array:character<span class="Special"> &lt;- </span>copy *<span class="Constant">2</span>:address:shared:array:character
+    <span class="Constant">20</span>:array:character<span class="Special"> &lt;- </span>copy *<span class="Constant">3</span>:address:shared:array:character
   ]
   memory-should-contain [
     <span class="Constant">10</span>:array:character<span class="Special"> &lt;- </span><span class="Constant">[a]</span>
@@ -1268,7 +1265,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   ]
 ]
 
-<span class="muRecipe">recipe</span> copy buf:address:array:character, start:number, end:number<span class="muRecipe"> -&gt; </span>result:address:array:character [
+<span class="muRecipe">recipe</span> copy-range buf:address:shared:array:character, start:number, end:number<span class="muRecipe"> -&gt; </span>result:address:shared:array:character [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   <span class="Comment"># if end is out of bounds, trim it</span>
@@ -1276,7 +1273,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   end:number<span class="Special"> &lt;- </span>min len, end
   <span class="Comment"># allocate space for result</span>
   len<span class="Special"> &lt;- </span>subtract end, start
-  result:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">character:type</span>, len
+  result:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">character:type</span>, len
   <span class="Comment"># copy start..end into result[curr-result]</span>
   src-idx:number<span class="Special"> &lt;- </span>copy start
   dest-idx:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
@@ -1294,9 +1291,9 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> text-copy-copies-partial-text [
   run [
-    <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
-    <span class="Constant">2</span>:address:array:character<span class="Special"> &lt;- </span>copy <span class="Constant">1</span>:address:array:character, <span class="Constant">1</span>, <span class="Constant">3</span>
-    <span class="Constant">3</span>:array:character<span class="Special"> &lt;- </span>copy *<span class="Constant">2</span>:address:array:character
+    <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
+    <span class="Constant">2</span>:address:shared:array:character<span class="Special"> &lt;- </span>copy-range <span class="Constant">1</span>:address:shared:array:character, <span class="Constant">1</span>, <span class="Constant">3</span>
+    <span class="Constant">3</span>:array:character<span class="Special"> &lt;- </span>copy *<span class="Constant">2</span>:address:shared:array:character
   ]
   memory-should-contain [
     <span class="Constant">3</span>:array:character<span class="Special"> &lt;- </span><span class="Constant">[bc]</span>
@@ -1305,9 +1302,9 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> text-copy-out-of-bounds [
   run [
-    <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
-    <span class="Constant">2</span>:address:array:character<span class="Special"> &lt;- </span>copy <span class="Constant">1</span>:address:array:character, <span class="Constant">2</span>, <span class="Constant">4</span>
-    <span class="Constant">3</span>:array:character<span class="Special"> &lt;- </span>copy *<span class="Constant">2</span>:address:array:character
+    <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
+    <span class="Constant">2</span>:address:shared:array:character<span class="Special"> &lt;- </span>copy-range <span class="Constant">1</span>:address:shared:array:character, <span class="Constant">2</span>, <span class="Constant">4</span>
+    <span class="Constant">3</span>:array:character<span class="Special"> &lt;- </span>copy *<span class="Constant">2</span>:address:shared:array:character
   ]
   memory-should-contain [
     <span class="Constant">3</span>:array:character<span class="Special"> &lt;- </span><span class="Constant">[c]</span>
@@ -1316,9 +1313,9 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> text-copy-out-of-bounds-2 [
   run [
-    <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
-    <span class="Constant">2</span>:address:array:character<span class="Special"> &lt;- </span>copy <span class="Constant">1</span>:address:array:character, <span class="Constant">3</span>, <span class="Constant">3</span>
-    <span class="Constant">3</span>:array:character<span class="Special"> &lt;- </span>copy *<span class="Constant">2</span>:address:array:character
+    <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
+    <span class="Constant">2</span>:address:shared:array:character<span class="Special"> &lt;- </span>copy-range <span class="Constant">1</span>:address:shared:array:character, <span class="Constant">3</span>, <span class="Constant">3</span>
+    <span class="Constant">3</span>:array:character<span class="Special"> &lt;- </span>copy *<span class="Constant">2</span>:address:shared:array:character
   ]
   memory-should-contain [
     <span class="Constant">3</span>:array:character<span class="Special"> &lt;- </span><span class="Constant">[]</span>
diff --git a/html/071channel.mu.html b/html/071channel.mu.html
index ec4fc68d..e1e14aaf 100644
--- a/html/071channel.mu.html
+++ b/html/071channel.mu.html
@@ -45,9 +45,9 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> channel [
   run [
-    <span class="Constant">1</span>:address:channel<span class="Special"> &lt;- </span>new-channel <span class="Constant">3/capacity</span>
-    <span class="Constant">1</span>:address:channel<span class="Special"> &lt;- </span>write <span class="Constant">1</span>:address:channel, <span class="Constant">34</span>
-    <span class="Constant">2</span>:character, <span class="Constant">1</span>:address:channel<span class="Special"> &lt;- </span>read <span class="Constant">1</span>:address:channel
+    <span class="Constant">1</span>:address:shared:channel<span class="Special"> &lt;- </span>new-channel <span class="Constant">3/capacity</span>
+    <span class="Constant">1</span>:address:shared:channel<span class="Special"> &lt;- </span>write <span class="Constant">1</span>:address:shared:channel, <span class="Constant">34</span>
+    <span class="Constant">2</span>:character, <span class="Constant">1</span>:address:shared:channel<span class="Special"> &lt;- </span>read <span class="Constant">1</span>:address:shared:channel
   ]
   memory-should-contain [
     <span class="Constant">2</span><span class="Special"> &lt;- </span><span class="Constant">34</span>
@@ -63,11 +63,10 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   <span class="Comment"># A circular buffer contains values from index first-full up to (but not</span>
   <span class="Comment"># including) index first-empty. The reader always modifies it at first-full,</span>
   <span class="Comment"># while the writer always modifies it at first-empty.</span>
-  data:address:array:character
+  data:address:shared:array:character
 ]
 
-<span class="Comment"># result:address:channel &lt;- new-channel capacity:number</span>
-<span class="muRecipe">recipe</span> new-channel capacity:number<span class="muRecipe"> -&gt; </span>result:address:channel [
+<span class="muRecipe">recipe</span> new-channel capacity:number<span class="muRecipe"> -&gt; </span>result:address:shared:channel [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   result<span class="Special"> &lt;- </span>new <span class="Constant">channel:type</span>
@@ -79,11 +78,11 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   *free<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
   <span class="Comment"># result.data = new location[ingredient+1]</span>
   capacity<span class="Special"> &lt;- </span>add capacity, <span class="Constant">1</span>  <span class="Comment"># unused slot for 'full?' below</span>
-  dest:address:address:array:character<span class="Special"> &lt;- </span>get-address *result, <span class="Constant">data:offset</span>
+  dest:address:address:shared:array:character<span class="Special"> &lt;- </span>get-address *result, <span class="Constant">data:offset</span>
   *dest<span class="Special"> &lt;- </span>new <span class="Constant">character:type</span>, capacity
 ]
 
-<span class="muRecipe">recipe</span> write chan:address:channel, val:character<span class="muRecipe"> -&gt; </span>chan:address:channel [
+<span class="muRecipe">recipe</span> write chan:address:shared:channel, val:character<span class="muRecipe"> -&gt; </span>chan:address:shared:channel [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   <span class="Delimiter">{</span>
@@ -94,7 +93,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     wait-for-location *full-address
   <span class="Delimiter">}</span>
   <span class="Comment"># store val</span>
-  circular-buffer:address:array:character<span class="Special"> &lt;- </span>get *chan, <span class="Constant">data:offset</span>
+  circular-buffer:address:shared:array:character<span class="Special"> &lt;- </span>get *chan, <span class="Constant">data:offset</span>
   free:address:number<span class="Special"> &lt;- </span>get-address *chan, <span class="Constant">first-free:offset</span>
   dest:address:character<span class="Special"> &lt;- </span>index-address *circular-buffer, *free
   *dest<span class="Special"> &lt;- </span>copy val
@@ -109,7 +108,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   <span class="Delimiter">}</span>
 ]
 
-<span class="muRecipe">recipe</span> read chan:address:channel<span class="muRecipe"> -&gt; </span>result:character, chan:address:channel [
+<span class="muRecipe">recipe</span> read chan:address:shared:channel<span class="muRecipe"> -&gt; </span>result:character, chan:address:shared:channel [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   <span class="Delimiter">{</span>
@@ -121,7 +120,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   <span class="Delimiter">}</span>
   <span class="Comment"># read result</span>
   full:address:number<span class="Special"> &lt;- </span>get-address *chan, <span class="Constant">first-full:offset</span>
-  circular-buffer:address:array:character<span class="Special"> &lt;- </span>get *chan, <span class="Constant">data:offset</span>
+  circular-buffer:address:shared:array:character<span class="Special"> &lt;- </span>get *chan, <span class="Constant">data:offset</span>
   result<span class="Special"> &lt;- </span>index *circular-buffer, *full
   <span class="Comment"># mark its slot as empty</span>
   *full<span class="Special"> &lt;- </span>add *full, <span class="Constant">1</span>
@@ -134,7 +133,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   <span class="Delimiter">}</span>
 ]
 
-<span class="muRecipe">recipe</span> clear-channel chan:address:channel<span class="muRecipe"> -&gt; </span>chan:address:channel [
+<span class="muRecipe">recipe</span> clear-channel chan:address:shared:channel<span class="muRecipe"> -&gt; </span>chan:address:shared:channel [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   <span class="Delimiter">{</span>
@@ -146,9 +145,9 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> channel-initialization [
   run [
-    <span class="Constant">1</span>:address:channel<span class="Special"> &lt;- </span>new-channel <span class="Constant">3/capacity</span>
-    <span class="Constant">2</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">1</span>:address:channel, <span class="Constant">first-full:offset</span>
-    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">1</span>:address:channel, <span class="Constant">first-free:offset</span>
+    <span class="Constant">1</span>:address:shared:channel<span class="Special"> &lt;- </span>new-channel <span class="Constant">3/capacity</span>
+    <span class="Constant">2</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">1</span>:address:shared:channel, <span class="Constant">first-full:offset</span>
+    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">1</span>:address:shared:channel, <span class="Constant">first-free:offset</span>
   ]
   memory-should-contain [
     <span class="Constant">2</span><span class="Special"> &lt;- </span><span class="Constant">0</span>  <span class="Comment"># first-full</span>
@@ -158,10 +157,10 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> channel-write-increments-free [
   run [
-    <span class="Constant">1</span>:address:channel<span class="Special"> &lt;- </span>new-channel <span class="Constant">3/capacity</span>
-    <span class="Constant">1</span>:address:channel<span class="Special"> &lt;- </span>write <span class="Constant">1</span>:address:channel, <span class="Constant">34</span>
-    <span class="Constant">2</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">1</span>:address:channel, <span class="Constant">first-full:offset</span>
-    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">1</span>:address:channel, <span class="Constant">first-free:offset</span>
+    <span class="Constant">1</span>:address:shared:channel<span class="Special"> &lt;- </span>new-channel <span class="Constant">3/capacity</span>
+    <span class="Constant">1</span>:address:shared:channel<span class="Special"> &lt;- </span>write <span class="Constant">1</span>:address:shared:channel, <span class="Constant">34</span>
+    <span class="Constant">2</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">1</span>:address:shared:channel, <span class="Constant">first-full:offset</span>
+    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">1</span>:address:shared:channel, <span class="Constant">first-free:offset</span>
   ]
   memory-should-contain [
     <span class="Constant">2</span><span class="Special"> &lt;- </span><span class="Constant">0</span>  <span class="Comment"># first-full</span>
@@ -171,11 +170,11 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> channel-read-increments-full [
   run [
-    <span class="Constant">1</span>:address:channel<span class="Special"> &lt;- </span>new-channel <span class="Constant">3/capacity</span>
-    <span class="Constant">1</span>:address:channel<span class="Special"> &lt;- </span>write <span class="Constant">1</span>:address:channel, <span class="Constant">34</span>
-    _, <span class="Constant">1</span>:address:channel<span class="Special"> &lt;- </span>read <span class="Constant">1</span>:address:channel
-    <span class="Constant">2</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">1</span>:address:channel, <span class="Constant">first-full:offset</span>
-    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">1</span>:address:channel, <span class="Constant">first-free:offset</span>
+    <span class="Constant">1</span>:address:shared:channel<span class="Special"> &lt;- </span>new-channel <span class="Constant">3/capacity</span>
+    <span class="Constant">1</span>:address:shared:channel<span class="Special"> &lt;- </span>write <span class="Constant">1</span>:address:shared:channel, <span class="Constant">34</span>
+    _, <span class="Constant">1</span>:address:shared:channel<span class="Special"> &lt;- </span>read <span class="Constant">1</span>:address:shared:channel
+    <span class="Constant">2</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">1</span>:address:shared:channel, <span class="Constant">first-full:offset</span>
+    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">1</span>:address:shared:channel, <span class="Constant">first-free:offset</span>
   ]
   memory-should-contain [
     <span class="Constant">2</span><span class="Special"> &lt;- </span><span class="Constant">1</span>  <span class="Comment"># first-full</span>
@@ -186,19 +185,19 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="muScenario">scenario</span> channel-wrap [
   run [
     <span class="Comment"># channel with just 1 slot</span>
-    <span class="Constant">1</span>:address:channel<span class="Special"> &lt;- </span>new-channel <span class="Constant">1/capacity</span>
+    <span class="Constant">1</span>:address:shared:channel<span class="Special"> &lt;- </span>new-channel <span class="Constant">1/capacity</span>
     <span class="Comment"># write and read a value</span>
-    <span class="Constant">1</span>:address:channel<span class="Special"> &lt;- </span>write <span class="Constant">1</span>:address:channel, <span class="Constant">34</span>
-    _, <span class="Constant">1</span>:address:channel<span class="Special"> &lt;- </span>read <span class="Constant">1</span>:address:channel
+    <span class="Constant">1</span>:address:shared:channel<span class="Special"> &lt;- </span>write <span class="Constant">1</span>:address:shared:channel, <span class="Constant">34</span>
+    _, <span class="Constant">1</span>:address:shared:channel<span class="Special"> &lt;- </span>read <span class="Constant">1</span>:address:shared:channel
     <span class="Comment"># first-free will now be 1</span>
-    <span class="Constant">2</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">1</span>:address:channel, <span class="Constant">first-free:offset</span>
-    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">1</span>:address:channel, <span class="Constant">first-free:offset</span>
+    <span class="Constant">2</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">1</span>:address:shared:channel, <span class="Constant">first-free:offset</span>
+    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">1</span>:address:shared:channel, <span class="Constant">first-free:offset</span>
     <span class="Comment"># write second value, verify that first-free wraps</span>
-    <span class="Constant">1</span>:address:channel<span class="Special"> &lt;- </span>write <span class="Constant">1</span>:address:channel, <span class="Constant">34</span>
-    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">1</span>:address:channel, <span class="Constant">first-free:offset</span>
+    <span class="Constant">1</span>:address:shared:channel<span class="Special"> &lt;- </span>write <span class="Constant">1</span>:address:shared:channel, <span class="Constant">34</span>
+    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">1</span>:address:shared:channel, <span class="Constant">first-free:offset</span>
     <span class="Comment"># read second value, verify that first-full wraps</span>
-    _, <span class="Constant">1</span>:address:channel<span class="Special"> &lt;- </span>read <span class="Constant">1</span>:address:channel
-    <span class="Constant">5</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">1</span>:address:channel, <span class="Constant">first-full:offset</span>
+    _, <span class="Constant">1</span>:address:shared:channel<span class="Special"> &lt;- </span>read <span class="Constant">1</span>:address:shared:channel
+    <span class="Constant">5</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">1</span>:address:shared:channel, <span class="Constant">first-full:offset</span>
   ]
   memory-should-contain [
     <span class="Constant">2</span><span class="Special"> &lt;- </span><span class="Constant">1</span>  <span class="Comment"># first-free after first write</span>
@@ -211,7 +210,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="SalientComment">## helpers</span>
 
 <span class="Comment"># An empty channel has first-empty and first-full both at the same value.</span>
-<span class="muRecipe">recipe</span> channel-empty? chan:address:channel<span class="muRecipe"> -&gt; </span>result:boolean [
+<span class="muRecipe">recipe</span> channel-empty? chan:address:shared:channel<span class="muRecipe"> -&gt; </span>result:boolean [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   <span class="Comment"># return chan.first-full == chan.first-free</span>
@@ -222,7 +221,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="Comment"># A full channel has first-empty just before first-full, wasting one slot.</span>
 <span class="Comment"># (Other alternatives: <a href="https://en.wikipedia.org/wiki/Circular_buffer#Full_.2F_Empty_Buffer_Distinction)">https://en.wikipedia.org/wiki/Circular_buffer#Full_.2F_Empty_Buffer_Distinction)</a></span>
-<span class="muRecipe">recipe</span> channel-full? chan:address:channel<span class="muRecipe"> -&gt; </span>result:boolean [
+<span class="muRecipe">recipe</span> channel-full? chan:address:shared:channel<span class="muRecipe"> -&gt; </span>result:boolean [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   <span class="Comment"># tmp = chan.first-free + 1</span>
@@ -240,19 +239,18 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   result<span class="Special"> &lt;- </span>equal full, tmp
 ]
 
-<span class="Comment"># result:number &lt;- channel-capacity chan:address:channel</span>
-<span class="muRecipe">recipe</span> channel-capacity chan:address:channel<span class="muRecipe"> -&gt; </span>result:number [
+<span class="muRecipe">recipe</span> channel-capacity chan:address:shared:channel<span class="muRecipe"> -&gt; </span>result:number [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
-  q:address:array:character<span class="Special"> &lt;- </span>get *chan, <span class="Constant">data:offset</span>
+  q:address:shared:array:character<span class="Special"> &lt;- </span>get *chan, <span class="Constant">data:offset</span>
   result<span class="Special"> &lt;- </span>length *q
 ]
 
 <span class="muScenario">scenario</span> channel-new-empty-not-full [
   run [
-    <span class="Constant">1</span>:address:channel<span class="Special"> &lt;- </span>new-channel <span class="Constant">3/capacity</span>
-    <span class="Constant">2</span>:boolean<span class="Special"> &lt;- </span>channel-empty? <span class="Constant">1</span>:address:channel
-    <span class="Constant">3</span>:boolean<span class="Special"> &lt;- </span>channel-full? <span class="Constant">1</span>:address:channel
+    <span class="Constant">1</span>:address:shared:channel<span class="Special"> &lt;- </span>new-channel <span class="Constant">3/capacity</span>
+    <span class="Constant">2</span>:boolean<span class="Special"> &lt;- </span>channel-empty? <span class="Constant">1</span>:address:shared:channel
+    <span class="Constant">3</span>:boolean<span class="Special"> &lt;- </span>channel-full? <span class="Constant">1</span>:address:shared:channel
   ]
   memory-should-contain [
     <span class="Constant">2</span><span class="Special"> &lt;- </span><span class="Constant">1</span>  <span class="Comment"># empty?</span>
@@ -262,10 +260,10 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> channel-write-not-empty [
   run [
-    <span class="Constant">1</span>:address:channel<span class="Special"> &lt;- </span>new-channel <span class="Constant">3/capacity</span>
-    <span class="Constant">1</span>:address:channel<span class="Special"> &lt;- </span>write <span class="Constant">1</span>:address:channel, <span class="Constant">34</span>
-    <span class="Constant">2</span>:boolean<span class="Special"> &lt;- </span>channel-empty? <span class="Constant">1</span>:address:channel
-    <span class="Constant">3</span>:boolean<span class="Special"> &lt;- </span>channel-full? <span class="Constant">1</span>:address:channel
+    <span class="Constant">1</span>:address:shared:channel<span class="Special"> &lt;- </span>new-channel <span class="Constant">3/capacity</span>
+    <span class="Constant">1</span>:address:shared:channel<span class="Special"> &lt;- </span>write <span class="Constant">1</span>:address:shared:channel, <span class="Constant">34</span>
+    <span class="Constant">2</span>:boolean<span class="Special"> &lt;- </span>channel-empty? <span class="Constant">1</span>:address:shared:channel
+    <span class="Constant">3</span>:boolean<span class="Special"> &lt;- </span>channel-full? <span class="Constant">1</span>:address:shared:channel
   ]
   memory-should-contain [
     <span class="Constant">2</span><span class="Special"> &lt;- </span><span class="Constant">0</span>  <span class="Comment"># empty?</span>
@@ -275,10 +273,10 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> channel-write-full [
   run [
-    <span class="Constant">1</span>:address:channel<span class="Special"> &lt;- </span>new-channel <span class="Constant">1/capacity</span>
-    <span class="Constant">1</span>:address:channel<span class="Special"> &lt;- </span>write <span class="Constant">1</span>:address:channel, <span class="Constant">34</span>
-    <span class="Constant">2</span>:boolean<span class="Special"> &lt;- </span>channel-empty? <span class="Constant">1</span>:address:channel
-    <span class="Constant">3</span>:boolean<span class="Special"> &lt;- </span>channel-full? <span class="Constant">1</span>:address:channel
+    <span class="Constant">1</span>:address:shared:channel<span class="Special"> &lt;- </span>new-channel <span class="Constant">1/capacity</span>
+    <span class="Constant">1</span>:address:shared:channel<span class="Special"> &lt;- </span>write <span class="Constant">1</span>:address:shared:channel, <span class="Constant">34</span>
+    <span class="Constant">2</span>:boolean<span class="Special"> &lt;- </span>channel-empty? <span class="Constant">1</span>:address:shared:channel
+    <span class="Constant">3</span>:boolean<span class="Special"> &lt;- </span>channel-full? <span class="Constant">1</span>:address:shared:channel
   ]
   memory-should-contain [
     <span class="Constant">2</span><span class="Special"> &lt;- </span><span class="Constant">0</span>  <span class="Comment"># empty?</span>
@@ -288,11 +286,11 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> channel-read-not-full [
   run [
-    <span class="Constant">1</span>:address:channel<span class="Special"> &lt;- </span>new-channel <span class="Constant">1/capacity</span>
-    <span class="Constant">1</span>:address:channel<span class="Special"> &lt;- </span>write <span class="Constant">1</span>:address:channel, <span class="Constant">34</span>
-    _, <span class="Constant">1</span>:address:channel<span class="Special"> &lt;- </span>read <span class="Constant">1</span>:address:channel
-    <span class="Constant">2</span>:boolean<span class="Special"> &lt;- </span>channel-empty? <span class="Constant">1</span>:address:channel
-    <span class="Constant">3</span>:boolean<span class="Special"> &lt;- </span>channel-full? <span class="Constant">1</span>:address:channel
+    <span class="Constant">1</span>:address:shared:channel<span class="Special"> &lt;- </span>new-channel <span class="Constant">1/capacity</span>
+    <span class="Constant">1</span>:address:shared:channel<span class="Special"> &lt;- </span>write <span class="Constant">1</span>:address:shared:channel, <span class="Constant">34</span>
+    _, <span class="Constant">1</span>:address:shared:channel<span class="Special"> &lt;- </span>read <span class="Constant">1</span>:address:shared:channel
+    <span class="Constant">2</span>:boolean<span class="Special"> &lt;- </span>channel-empty? <span class="Constant">1</span>:address:shared:channel
+    <span class="Constant">3</span>:boolean<span class="Special"> &lt;- </span>channel-full? <span class="Constant">1</span>:address:shared:channel
   ]
   memory-should-contain [
     <span class="Constant">2</span><span class="Special"> &lt;- </span><span class="Constant">1</span>  <span class="Comment"># empty?</span>
@@ -301,12 +299,12 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 ]
 
 <span class="Comment"># helper for channels of characters in particular</span>
-<span class="muRecipe">recipe</span> buffer-lines in:address:channel, out:address:channel<span class="muRecipe"> -&gt; </span>out:address:channel, in:address:channel [
+<span class="muRecipe">recipe</span> buffer-lines in:address:shared:channel, out:address:shared:channel<span class="muRecipe"> -&gt; </span>out:address:shared:channel, in:address:shared:channel [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   <span class="Comment"># repeat forever</span>
   <span class="Delimiter">{</span>
-    line:address:buffer<span class="Special"> &lt;- </span>new-buffer, <span class="Constant">30</span>
+    line:address:shared:buffer<span class="Special"> &lt;- </span>new-buffer <span class="Constant">30</span>
     <span class="Comment"># read characters from 'in' until newline, copy into line</span>
     <span class="Delimiter">{</span>
 <span class="Constant">      +next-character</span>
@@ -337,7 +335,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     <span class="Delimiter">}</span>
     <span class="Comment"># copy line into 'out'</span>
     i:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
-    line-contents:address:array:character<span class="Special"> &lt;- </span>get *line, <span class="Constant">data:offset</span>
+    line-contents:address:shared:array:character<span class="Special"> &lt;- </span>get *line, <span class="Constant">data:offset</span>
     max:number<span class="Special"> &lt;- </span>get *line, <span class="Constant">length:offset</span>
     <span class="Delimiter">{</span>
       done?:boolean<span class="Special"> &lt;- </span>greater-or-equal i, max
@@ -353,36 +351,36 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> buffer-lines-blocks-until-newline [
   run [
-    <span class="Constant">1</span>:address:channel/stdin<span class="Special"> &lt;- </span>new-channel <span class="Constant">10/capacity</span>
-    <span class="Constant">2</span>:address:channel/buffered-stdin<span class="Special"> &lt;- </span>new-channel <span class="Constant">10/capacity</span>
-    <span class="Constant">3</span>:boolean<span class="Special"> &lt;- </span>channel-empty? <span class="Constant">2</span>:address:channel/buffered-stdin
+    <span class="Constant">1</span>:address:shared:channel/stdin<span class="Special"> &lt;- </span>new-channel <span class="Constant">10/capacity</span>
+    <span class="Constant">2</span>:address:shared:channel/buffered-stdin<span class="Special"> &lt;- </span>new-channel <span class="Constant">10/capacity</span>
+    <span class="Constant">3</span>:boolean<span class="Special"> &lt;- </span>channel-empty? <span class="Constant">2</span>:address:shared:channel/buffered-stdin
     assert <span class="Constant">3</span>:boolean, [
 F buffer-lines-blocks-until-newline: channel should be empty <span class="muRecipe">after</span> init]
     <span class="Comment"># buffer stdin into buffered-stdin, try to read from buffered-stdin</span>
-    <span class="Constant">4</span>:number/buffer-routine<span class="Special"> &lt;- </span>start-running <span class="Constant">buffer-lines:recipe</span>, <span class="Constant">1</span>:address:channel/stdin, <span class="Constant">2</span>:address:channel/buffered-stdin
+    <span class="Constant">4</span>:number/buffer-routine<span class="Special"> &lt;- </span>start-running buffer-lines, <span class="Constant">1</span>:address:shared:channel/stdin, <span class="Constant">2</span>:address:shared:channel/buffered-stdin
     wait-for-routine <span class="Constant">4</span>:number/buffer-routine
-    <span class="Constant">5</span>:boolean<span class="Special"> &lt;- </span>channel-empty? <span class="Constant">2</span>:address:channel/buffered-stdin
+    <span class="Constant">5</span>:boolean<span class="Special"> &lt;- </span>channel-empty? <span class="Constant">2</span>:address:shared:channel/buffered-stdin
     assert <span class="Constant">5</span>:boolean, [
 F buffer-lines-blocks-until-newline: channel should be empty <span class="muRecipe">after</span> buffer-lines bring-up]
     <span class="Comment"># write 'a'</span>
-    <span class="Constant">1</span>:address:channel<span class="Special"> &lt;- </span>write <span class="Constant">1</span>:address:channel, <span class="Constant">97/a</span>
+    <span class="Constant">1</span>:address:shared:channel<span class="Special"> &lt;- </span>write <span class="Constant">1</span>:address:shared:channel, <span class="Constant">97/a</span>
     restart <span class="Constant">4</span>:number/buffer-routine
     wait-for-routine <span class="Constant">4</span>:number/buffer-routine
-    <span class="Constant">6</span>:boolean<span class="Special"> &lt;- </span>channel-empty? <span class="Constant">2</span>:address:channel/buffered-stdin
+    <span class="Constant">6</span>:boolean<span class="Special"> &lt;- </span>channel-empty? <span class="Constant">2</span>:address:shared:channel/buffered-stdin
     assert <span class="Constant">6</span>:boolean, [
 F buffer-lines-blocks-until-newline: channel should be empty <span class="muRecipe">after</span> writing 'a']
     <span class="Comment"># write 'b'</span>
-    <span class="Constant">1</span>:address:channel<span class="Special"> &lt;- </span>write <span class="Constant">1</span>:address:channel, <span class="Constant">98/b</span>
+    <span class="Constant">1</span>:address:shared:channel<span class="Special"> &lt;- </span>write <span class="Constant">1</span>:address:shared:channel, <span class="Constant">98/b</span>
     restart <span class="Constant">4</span>:number/buffer-routine
     wait-for-routine <span class="Constant">4</span>:number/buffer-routine
-    <span class="Constant">7</span>:boolean<span class="Special"> &lt;- </span>channel-empty? <span class="Constant">2</span>:address:channel/buffered-stdin
+    <span class="Constant">7</span>:boolean<span class="Special"> &lt;- </span>channel-empty? <span class="Constant">2</span>:address:shared:channel/buffered-stdin
     assert <span class="Constant">7</span>:boolean, [
 F buffer-lines-blocks-until-newline: channel should be empty <span class="muRecipe">after</span> writing 'b']
     <span class="Comment"># write newline</span>
-    <span class="Constant">1</span>:address:channel<span class="Special"> &lt;- </span>write <span class="Constant">1</span>:address:channel, <span class="Constant">10/newline</span>
+    <span class="Constant">1</span>:address:shared:channel<span class="Special"> &lt;- </span>write <span class="Constant">1</span>:address:shared:channel, <span class="Constant">10/newline</span>
     restart <span class="Constant">4</span>:number/buffer-routine
     wait-for-routine <span class="Constant">4</span>:number/buffer-routine
-    <span class="Constant">8</span>:boolean<span class="Special"> &lt;- </span>channel-empty? <span class="Constant">2</span>:address:channel/buffered-stdin
+    <span class="Constant">8</span>:boolean<span class="Special"> &lt;- </span>channel-empty? <span class="Constant">2</span>:address:shared:channel/buffered-stdin
     <span class="Constant">9</span>:boolean/completed?<span class="Special"> &lt;- </span>not <span class="Constant">8</span>:boolean
     assert <span class="Constant">9</span>:boolean/completed?, [
 F buffer-lines-blocks-until-newline: channel should contain data <span class="muRecipe">after</span> writing newline]
diff --git a/html/072array.mu.html b/html/072array.mu.html
index e4ab32a8..61b5e14e 100644
--- a/html/072array.mu.html
+++ b/html/072array.mu.html
@@ -33,8 +33,8 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <pre id='vimCodeElement'>
 <span class="muScenario">scenario</span> array-from-args [
   run [
-    <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new-array <span class="Constant">0</span>, <span class="Constant">1</span>, <span class="Constant">2</span>
-    <span class="Constant">2</span>:array:character<span class="Special"> &lt;- </span>copy *<span class="Constant">1</span>:address:array:character
+    <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new-array <span class="Constant">0</span>, <span class="Constant">1</span>, <span class="Constant">2</span>
+    <span class="Constant">2</span>:array:character<span class="Special"> &lt;- </span>copy *<span class="Constant">1</span>:address:shared:array:character
   ]
   memory-should-contain [
     <span class="Constant">2</span><span class="Special"> &lt;- </span><span class="Constant">3</span>  <span class="Comment"># array length</span>
@@ -45,7 +45,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 ]
 
 <span class="Comment"># create an array out of a list of scalar args</span>
-<span class="muRecipe">recipe</span> new-array [
+<span class="muRecipe">recipe</span> new-array<span class="muRecipe"> -&gt; </span>result:address:shared:array:character [
   <span class="Constant">local-scope</span>
   capacity:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
   <span class="Delimiter">{</span>
@@ -55,7 +55,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     capacity<span class="Special"> &lt;- </span>add capacity, <span class="Constant">1</span>
     <span class="muControl">loop</span>
   <span class="Delimiter">}</span>
-  result:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">character:type</span>, capacity
+  result<span class="Special"> &lt;- </span>new <span class="Constant">character:type</span>, capacity
   rewind-ingredients
   i:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
   <span class="Delimiter">{</span>
diff --git a/html/073list.mu.html b/html/073list.mu.html
index 2097a4e6..c184e73f 100644
--- a/html/073list.mu.html
+++ b/html/073list.mu.html
@@ -40,27 +40,27 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muData">container</span> list:_elem [
   value:_elem
-  next:address:list:_elem
+  next:address:shared:list:_elem
 ]
 
-<span class="muRecipe">recipe</span> push x:_elem, in:address:list:_elem<span class="muRecipe"> -&gt; </span>in:address:list:_elem [
+<span class="muRecipe">recipe</span> push x:_elem, in:address:shared:list:_elem<span class="muRecipe"> -&gt; </span>in:address:shared:list:_elem [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
-  result:address:list:_elem<span class="Special"> &lt;- </span>new <span class="Delimiter">{</span>(list _elem): type<span class="Delimiter">}</span>
+  result:address:shared:list:_elem<span class="Special"> &lt;- </span>new <span class="Delimiter">{</span>(list _elem): type<span class="Delimiter">}</span>
   val:address:_elem<span class="Special"> &lt;- </span>get-address *result, <span class="Constant">value:offset</span>
   *val<span class="Special"> &lt;- </span>copy x
-  next:address:address:list:_elem<span class="Special"> &lt;- </span>get-address *result, <span class="Constant">next:offset</span>
+  next:address:address:shared:list:_elem<span class="Special"> &lt;- </span>get-address *result, <span class="Constant">next:offset</span>
   *next<span class="Special"> &lt;- </span>copy in
   <span class="muControl">reply</span> result  <span class="Comment"># needed explicitly because we need to replace 'in' with 'result'</span>
 ]
 
-<span class="muRecipe">recipe</span> first in:address:list:_elem<span class="muRecipe"> -&gt; </span>result:_elem [
+<span class="muRecipe">recipe</span> first in:address:shared:list:_elem<span class="muRecipe"> -&gt; </span>result:_elem [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   result<span class="Special"> &lt;- </span>get *in, <span class="Constant">value:offset</span>
 ]
 
-<span class="muRecipe">recipe</span> rest in:address:list:_elem<span class="muRecipe"> -&gt; </span>result:address:list:_elem/contained-in:in [
+<span class="muRecipe">recipe</span> rest in:address:shared:list:_elem<span class="muRecipe"> -&gt; </span>result:address:shared:list:_elem/contained-in:in [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   result<span class="Special"> &lt;- </span>get *in, <span class="Constant">next:offset</span>
@@ -68,15 +68,15 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> list-handling [
   run [
-    <span class="Constant">1</span>:address:list:number<span class="Special"> &lt;- </span>push <span class="Constant">3</span>, <span class="Constant">0</span>
-    <span class="Constant">1</span>:address:list:number<span class="Special"> &lt;- </span>push <span class="Constant">4</span>, <span class="Constant">1</span>:address:list:number
-    <span class="Constant">1</span>:address:list:number<span class="Special"> &lt;- </span>push <span class="Constant">5</span>, <span class="Constant">1</span>:address:list:number
-    <span class="Constant">2</span>:number<span class="Special"> &lt;- </span>first <span class="Constant">1</span>:address:list:number
-    <span class="Constant">1</span>:address:list:number<span class="Special"> &lt;- </span>rest <span class="Constant">1</span>:address:list:number
-    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>first <span class="Constant">1</span>:address:list:number
-    <span class="Constant">1</span>:address:list:number<span class="Special"> &lt;- </span>rest <span class="Constant">1</span>:address:list:number
-    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>first <span class="Constant">1</span>:address:list:number
-    <span class="Constant">1</span>:address:list:number<span class="Special"> &lt;- </span>rest <span class="Constant">1</span>:address:list:number
+    <span class="Constant">1</span>:address:shared:list:number<span class="Special"> &lt;- </span>push <span class="Constant">3</span>, <span class="Constant">0</span>
+    <span class="Constant">1</span>:address:shared:list:number<span class="Special"> &lt;- </span>push <span class="Constant">4</span>, <span class="Constant">1</span>:address:shared:list:number
+    <span class="Constant">1</span>:address:shared:list:number<span class="Special"> &lt;- </span>push <span class="Constant">5</span>, <span class="Constant">1</span>:address:shared:list:number
+    <span class="Constant">2</span>:number<span class="Special"> &lt;- </span>first <span class="Constant">1</span>:address:shared:list:number
+    <span class="Constant">1</span>:address:shared:list:number<span class="Special"> &lt;- </span>rest <span class="Constant">1</span>:address:shared:list:number
+    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>first <span class="Constant">1</span>:address:shared:list:number
+    <span class="Constant">1</span>:address:shared:list:number<span class="Special"> &lt;- </span>rest <span class="Constant">1</span>:address:shared:list:number
+    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>first <span class="Constant">1</span>:address:shared:list:number
+    <span class="Constant">1</span>:address:shared:list:number<span class="Special"> &lt;- </span>rest <span class="Constant">1</span>:address:shared:list:number
   ]
   memory-should-contain [
     <span class="Constant">1</span><span class="Special"> &lt;- </span><span class="Constant">0</span>  <span class="Comment"># empty to empty, dust to dust..</span>
@@ -86,26 +86,26 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   ]
 ]
 
-<span class="muRecipe">recipe</span> to-text in:address:list:_elem<span class="muRecipe"> -&gt; </span>result:address:array:character [
+<span class="muRecipe">recipe</span> to-text in:address:shared:list:_elem<span class="muRecipe"> -&gt; </span>result:address:shared:array:character [
   <span class="Constant">local-scope</span>
 <span class="CommentedCode">#?   $print [to text: list], 10/newline</span>
   <span class="Constant">load-ingredients</span>
-  buf:address:buffer<span class="Special"> &lt;- </span>new-buffer <span class="Constant">80</span>
+  buf:address:shared:buffer<span class="Special"> &lt;- </span>new-buffer <span class="Constant">80</span>
   buf<span class="Special"> &lt;- </span>to-buffer in, buf
   result<span class="Special"> &lt;- </span>buffer-to-array buf
 ]
 
 <span class="Comment"># variant of 'to-text' which stops printing after a few elements (and so is robust to cycles)</span>
-<span class="muRecipe">recipe</span> to-text-line in:address:list:_elem<span class="muRecipe"> -&gt; </span>result:address:array:character [
+<span class="muRecipe">recipe</span> to-text-line in:address:shared:list:_elem<span class="muRecipe"> -&gt; </span>result:address:shared:array:character [
   <span class="Constant">local-scope</span>
 <span class="CommentedCode">#?   $print [to text line: list], 10/newline</span>
   <span class="Constant">load-ingredients</span>
-  buf:address:buffer<span class="Special"> &lt;- </span>new-buffer <span class="Constant">80</span>
+  buf:address:shared:buffer<span class="Special"> &lt;- </span>new-buffer <span class="Constant">80</span>
   buf<span class="Special"> &lt;- </span>to-buffer in, buf, <span class="Constant">6</span>  <span class="Comment"># max elements to display</span>
   result<span class="Special"> &lt;- </span>buffer-to-array buf
 ]
 
-<span class="muRecipe">recipe</span> to-buffer in:address:list:_elem, buf:address:buffer<span class="muRecipe"> -&gt; </span>buf:address:buffer [
+<span class="muRecipe">recipe</span> to-buffer in:address:shared:list:_elem, buf:address:shared:buffer<span class="muRecipe"> -&gt; </span>buf:address:shared:buffer [
   <span class="Constant">local-scope</span>
 <span class="CommentedCode">#?   $print [to buffer: list], 10/newline</span>
   <span class="Constant">load-ingredients</span>
@@ -118,13 +118,13 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   val:_elem<span class="Special"> &lt;- </span>get *in, <span class="Constant">value:offset</span>
   buf<span class="Special"> &lt;- </span>append buf, val
   <span class="Comment"># now prepare next</span>
-  next:address:list:_elem<span class="Special"> &lt;- </span>rest in
+  next:address:shared:list:_elem<span class="Special"> &lt;- </span>rest in
   nextn:number<span class="Special"> &lt;- </span>copy next
 <span class="CommentedCode">#?   buf &lt;- append buf, nextn</span>
   <span class="muControl">reply-unless</span> next
   space:character<span class="Special"> &lt;- </span>copy <span class="Constant">32/space</span>
   buf<span class="Special"> &lt;- </span>append buf, space:character
-  s:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[-&gt; ]</span>
+  s:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[-&gt; ]</span>
   n:number<span class="Special"> &lt;- </span>length *s
   buf<span class="Special"> &lt;- </span>append buf, s
   <span class="Comment"># and recurse</span>
@@ -143,13 +143,13 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     <span class="muControl">reply</span>
   <span class="Delimiter">}</span>
   <span class="Comment"># past recursion depth; insert ellipses and stop</span>
-  s:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[...]</span>
+  s:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[...]</span>
   append buf, s
 ]
 
 <span class="muScenario">scenario</span> stash-on-list-converts-to-text [
   run [
-    x:address:list:number<span class="Special"> &lt;- </span>push <span class="Constant">4</span>, <span class="Constant">0</span>
+    x:address:shared:list:number<span class="Special"> &lt;- </span>push <span class="Constant">4</span>, <span class="Constant">0</span>
     x<span class="Special"> &lt;- </span>push <span class="Constant">5</span>, x
     x<span class="Special"> &lt;- </span>push <span class="Constant">6</span>, x
     stash <span class="Constant">[foo foo]</span>, x
@@ -161,8 +161,8 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> stash-handles-list-with-cycle [
   run [
-    x:address:list:number<span class="Special"> &lt;- </span>push <span class="Constant">4</span>, <span class="Constant">0</span>
-    y:address:address:list:number<span class="Special"> &lt;- </span>get-address *x, <span class="Constant">next:offset</span>
+    x:address:shared:list:number<span class="Special"> &lt;- </span>push <span class="Constant">4</span>, <span class="Constant">0</span>
+    y:address:address:shared:list:number<span class="Special"> &lt;- </span>get-address *x, <span class="Constant">next:offset</span>
     *y<span class="Special"> &lt;- </span>copy x
     stash <span class="Constant">[foo foo]</span>, x
   ]
diff --git a/html/075duplex_list.mu.html b/html/075duplex_list.mu.html
index 4a0abcbb..d30afff6 100644
--- a/html/075duplex_list.mu.html
+++ b/html/075duplex_list.mu.html
@@ -36,42 +36,42 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muData">container</span> duplex-list:_elem [
   value:_elem
-  next:address:duplex-list:_elem
-  prev:address:duplex-list:_elem
+  next:address:shared:duplex-list:_elem
+  prev:address:shared:duplex-list:_elem
 ]
 
 <span class="Comment"># should I say in/contained-in:result, allow ingredients to refer to products?</span>
-<span class="muRecipe">recipe</span> push x:_elem, in:address:duplex-list:_elem<span class="muRecipe"> -&gt; </span>in:address:duplex-list:_elem [
+<span class="muRecipe">recipe</span> push x:_elem, in:address:shared:duplex-list:_elem<span class="muRecipe"> -&gt; </span>in:address:shared:duplex-list:_elem [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
-  result:address:duplex-list:_elem<span class="Special"> &lt;- </span>new <span class="Delimiter">{</span>(duplex-list _elem): type<span class="Delimiter">}</span>
+  result:address:shared:duplex-list:_elem<span class="Special"> &lt;- </span>new <span class="Delimiter">{</span>(duplex-list _elem): type<span class="Delimiter">}</span>
   val:address:_elem<span class="Special"> &lt;- </span>get-address *result, <span class="Constant">value:offset</span>
   *val<span class="Special"> &lt;- </span>copy x
-  next:address:address:duplex-list:_elem<span class="Special"> &lt;- </span>get-address *result, <span class="Constant">next:offset</span>
+  next:address:address:shared:duplex-list:_elem<span class="Special"> &lt;- </span>get-address *result, <span class="Constant">next:offset</span>
   *next<span class="Special"> &lt;- </span>copy in
   <span class="Delimiter">{</span>
     <span class="muControl">break-unless</span> in
-    prev:address:address:duplex-list:_elem<span class="Special"> &lt;- </span>get-address *in, <span class="Constant">prev:offset</span>
+    prev:address:address:shared:duplex-list:_elem<span class="Special"> &lt;- </span>get-address *in, <span class="Constant">prev:offset</span>
     *prev<span class="Special"> &lt;- </span>copy result
   <span class="Delimiter">}</span>
   <span class="muControl">reply</span> result  <span class="Comment"># needed explicitly because we need to replace 'in' with 'result'</span>
 ]
 
-<span class="muRecipe">recipe</span> first in:address:duplex-list:_elem<span class="muRecipe"> -&gt; </span>result:_elem [
+<span class="muRecipe">recipe</span> first in:address:shared:duplex-list:_elem<span class="muRecipe"> -&gt; </span>result:_elem [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   <span class="muControl">reply-unless</span> in, <span class="Constant">0</span>
   result<span class="Special"> &lt;- </span>get *in, <span class="Constant">value:offset</span>
 ]
 
-<span class="muRecipe">recipe</span> next in:address:duplex-list:_elem<span class="muRecipe"> -&gt; </span>result:address:duplex-list:_elem/contained-in:in [
+<span class="muRecipe">recipe</span> next in:address:shared:duplex-list:_elem<span class="muRecipe"> -&gt; </span>result:address:shared:duplex-list:_elem/contained-in:in [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   <span class="muControl">reply-unless</span> in, <span class="Constant">0</span>
   result<span class="Special"> &lt;- </span>get *in, <span class="Constant">next:offset</span>
 ]
 
-<span class="muRecipe">recipe</span> prev in:address:duplex-list:_elem<span class="muRecipe"> -&gt; </span>result:address:duplex-list:_elem/contained-in:in [
+<span class="muRecipe">recipe</span> prev in:address:shared:duplex-list:_elem<span class="muRecipe"> -&gt; </span>result:address:shared:duplex-list:_elem/contained-in:in [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   <span class="muControl">reply-unless</span> in, <span class="Constant">0</span>
@@ -84,24 +84,24 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     <span class="Comment"># reserve locations 0, 1 and 2 to check for missing null check</span>
     <span class="Constant">1</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">34</span>
     <span class="Constant">2</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">35</span>
-    <span class="Constant">3</span>:address:duplex-list:character<span class="Special"> &lt;- </span>push <span class="Constant">3</span>, <span class="Constant">0</span>
-    <span class="Constant">3</span>:address:duplex-list:character<span class="Special"> &lt;- </span>push <span class="Constant">4</span>, <span class="Constant">3</span>:address:duplex-list:character
-    <span class="Constant">3</span>:address:duplex-list:character<span class="Special"> &lt;- </span>push <span class="Constant">5</span>, <span class="Constant">3</span>:address:duplex-list:character
-    <span class="Constant">4</span>:address:duplex-list:character<span class="Special"> &lt;- </span>copy <span class="Constant">3</span>:address:duplex-list:character
-    <span class="Constant">5</span>:character<span class="Special"> &lt;- </span>first <span class="Constant">4</span>:address:duplex-list:character
-    <span class="Constant">4</span>:address:duplex-list:character<span class="Special"> &lt;- </span>next <span class="Constant">4</span>:address:duplex-list:character
-    <span class="Constant">6</span>:character<span class="Special"> &lt;- </span>first <span class="Constant">4</span>:address:duplex-list:character
-    <span class="Constant">4</span>:address:duplex-list:character<span class="Special"> &lt;- </span>next <span class="Constant">4</span>:address:duplex-list:character
-    <span class="Constant">7</span>:character<span class="Special"> &lt;- </span>first <span class="Constant">4</span>:address:duplex-list:character
-    <span class="Constant">8</span>:address:duplex-list:character<span class="Special"> &lt;- </span>next <span class="Constant">4</span>:address:duplex-list:character
-    <span class="Constant">9</span>:character<span class="Special"> &lt;- </span>first <span class="Constant">8</span>:address:duplex-list:character
-    <span class="Constant">10</span>:address:duplex-list:character<span class="Special"> &lt;- </span>next <span class="Constant">8</span>:address:duplex-list:character
-    <span class="Constant">11</span>:address:duplex-list:character<span class="Special"> &lt;- </span>prev <span class="Constant">8</span>:address:duplex-list:character
-    <span class="Constant">4</span>:address:duplex-list:character<span class="Special"> &lt;- </span>prev <span class="Constant">4</span>:address:duplex-list:character
-    <span class="Constant">12</span>:character<span class="Special"> &lt;- </span>first <span class="Constant">4</span>:address:duplex-list:character
-    <span class="Constant">4</span>:address:duplex-list:character<span class="Special"> &lt;- </span>prev <span class="Constant">4</span>:address:duplex-list:character
-    <span class="Constant">13</span>:character<span class="Special"> &lt;- </span>first <span class="Constant">4</span>:address:duplex-list:character
-    <span class="Constant">14</span>:boolean<span class="Special"> &lt;- </span>equal <span class="Constant">3</span>:address:duplex-list:character, <span class="Constant">4</span>:address:duplex-list:character
+    <span class="Constant">3</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>push <span class="Constant">3</span>, <span class="Constant">0</span>
+    <span class="Constant">3</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>push <span class="Constant">4</span>, <span class="Constant">3</span>:address:shared:duplex-list:character
+    <span class="Constant">3</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>push <span class="Constant">5</span>, <span class="Constant">3</span>:address:shared:duplex-list:character
+    <span class="Constant">4</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>copy <span class="Constant">3</span>:address:shared:duplex-list:character
+    <span class="Constant">5</span>:character<span class="Special"> &lt;- </span>first <span class="Constant">4</span>:address:shared:duplex-list:character
+    <span class="Constant">4</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>next <span class="Constant">4</span>:address:shared:duplex-list:character
+    <span class="Constant">6</span>:character<span class="Special"> &lt;- </span>first <span class="Constant">4</span>:address:shared:duplex-list:character
+    <span class="Constant">4</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>next <span class="Constant">4</span>:address:shared:duplex-list:character
+    <span class="Constant">7</span>:character<span class="Special"> &lt;- </span>first <span class="Constant">4</span>:address:shared:duplex-list:character
+    <span class="Constant">8</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>next <span class="Constant">4</span>:address:shared:duplex-list:character
+    <span class="Constant">9</span>:character<span class="Special"> &lt;- </span>first <span class="Constant">8</span>:address:shared:duplex-list:character
+    <span class="Constant">10</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>next <span class="Constant">8</span>:address:shared:duplex-list:character
+    <span class="Constant">11</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>prev <span class="Constant">8</span>:address:shared:duplex-list:character
+    <span class="Constant">4</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>prev <span class="Constant">4</span>:address:shared:duplex-list:character
+    <span class="Constant">12</span>:character<span class="Special"> &lt;- </span>first <span class="Constant">4</span>:address:shared:duplex-list:character
+    <span class="Constant">4</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>prev <span class="Constant">4</span>:address:shared:duplex-list:character
+    <span class="Constant">13</span>:character<span class="Special"> &lt;- </span>first <span class="Constant">4</span>:address:shared:duplex-list:character
+    <span class="Constant">14</span>:boolean<span class="Special"> &lt;- </span>equal <span class="Constant">3</span>:address:shared:duplex-list:character, <span class="Constant">4</span>:address:shared:duplex-list:character
   ]
   memory-should-contain [
     <span class="Constant">0</span><span class="Special"> &lt;- </span><span class="Constant">0</span>  <span class="Comment"># no modifications to null pointers</span>
@@ -121,15 +121,15 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 ]
 
 <span class="Comment"># insert 'x' after 'in'</span>
-<span class="muRecipe">recipe</span> insert x:_elem, in:address:duplex-list:_elem<span class="muRecipe"> -&gt; </span>in:address:duplex-list:_elem [
+<span class="muRecipe">recipe</span> insert x:_elem, in:address:shared:duplex-list:_elem<span class="muRecipe"> -&gt; </span>in:address:shared:duplex-list:_elem [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
-  new-node:address:duplex-list:_elem<span class="Special"> &lt;- </span>new <span class="Delimiter">{</span>(duplex-list _elem): type<span class="Delimiter">}</span>
+  new-node:address:shared:duplex-list:_elem<span class="Special"> &lt;- </span>new <span class="Delimiter">{</span>(duplex-list _elem): type<span class="Delimiter">}</span>
   val:address:_elem<span class="Special"> &lt;- </span>get-address *new-node, <span class="Constant">value:offset</span>
   *val<span class="Special"> &lt;- </span>copy x
-  next-node:address:duplex-list:_elem<span class="Special"> &lt;- </span>get *in, <span class="Constant">next:offset</span>
+  next-node:address:shared:duplex-list:_elem<span class="Special"> &lt;- </span>get *in, <span class="Constant">next:offset</span>
   <span class="Comment"># in.next = new-node</span>
-  y:address:address:duplex-list:_elem<span class="Special"> &lt;- </span>get-address *in, <span class="Constant">next:offset</span>
+  y:address:address:shared:duplex-list:_elem<span class="Special"> &lt;- </span>get-address *in, <span class="Constant">next:offset</span>
   *y<span class="Special"> &lt;- </span>copy new-node
   <span class="Comment"># new-node.prev = in</span>
   y<span class="Special"> &lt;- </span>get-address *new-node, <span class="Constant">prev:offset</span>
@@ -146,27 +146,27 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> inserting-into-duplex-list [
   run [
-    <span class="Constant">1</span>:address:duplex-list:character<span class="Special"> &lt;- </span>push <span class="Constant">3</span>, <span class="Constant">0</span>
-    <span class="Constant">1</span>:address:duplex-list:character<span class="Special"> &lt;- </span>push <span class="Constant">4</span>, <span class="Constant">1</span>:address:duplex-list:character
-    <span class="Constant">1</span>:address:duplex-list:character<span class="Special"> &lt;- </span>push <span class="Constant">5</span>, <span class="Constant">1</span>:address:duplex-list:character
-    <span class="Constant">2</span>:address:duplex-list:character<span class="Special"> &lt;- </span>next <span class="Constant">1</span>:address:duplex-list:character  <span class="Comment"># 2 points inside list</span>
-    <span class="Constant">2</span>:address:duplex-list:character<span class="Special"> &lt;- </span>insert <span class="Constant">6</span>, <span class="Constant">2</span>:address:duplex-list:character
+    <span class="Constant">1</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>push <span class="Constant">3</span>, <span class="Constant">0</span>
+    <span class="Constant">1</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>push <span class="Constant">4</span>, <span class="Constant">1</span>:address:shared:duplex-list:character
+    <span class="Constant">1</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>push <span class="Constant">5</span>, <span class="Constant">1</span>:address:shared:duplex-list:character
+    <span class="Constant">2</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>next <span class="Constant">1</span>:address:shared:duplex-list:character  <span class="Comment"># 2 points inside list</span>
+    <span class="Constant">2</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>insert <span class="Constant">6</span>, <span class="Constant">2</span>:address:shared:duplex-list:character
     <span class="Comment"># check structure like before</span>
-    <span class="Constant">2</span>:address:duplex-list:character<span class="Special"> &lt;- </span>copy <span class="Constant">1</span>:address:duplex-list:character
-    <span class="Constant">3</span>:character<span class="Special"> &lt;- </span>first <span class="Constant">2</span>:address:duplex-list:character
-    <span class="Constant">2</span>:address:duplex-list:character<span class="Special"> &lt;- </span>next <span class="Constant">2</span>:address:duplex-list:character
-    <span class="Constant">4</span>:character<span class="Special"> &lt;- </span>first <span class="Constant">2</span>:address:duplex-list:character
-    <span class="Constant">2</span>:address:duplex-list:character<span class="Special"> &lt;- </span>next <span class="Constant">2</span>:address:duplex-list:character
-    <span class="Constant">5</span>:character<span class="Special"> &lt;- </span>first <span class="Constant">2</span>:address:duplex-list:character
-    <span class="Constant">2</span>:address:duplex-list:character<span class="Special"> &lt;- </span>next <span class="Constant">2</span>:address:duplex-list:character
-    <span class="Constant">6</span>:character<span class="Special"> &lt;- </span>first <span class="Constant">2</span>:address:duplex-list:character
-    <span class="Constant">2</span>:address:duplex-list:character<span class="Special"> &lt;- </span>prev <span class="Constant">2</span>:address:duplex-list:character
-    <span class="Constant">7</span>:character<span class="Special"> &lt;- </span>first <span class="Constant">2</span>:address:duplex-list:character
-    <span class="Constant">2</span>:address:duplex-list:character<span class="Special"> &lt;- </span>prev <span class="Constant">2</span>:address:duplex-list:character
-    <span class="Constant">8</span>:character<span class="Special"> &lt;- </span>first <span class="Constant">2</span>:address:duplex-list:character
-    <span class="Constant">2</span>:address:duplex-list:character<span class="Special"> &lt;- </span>prev <span class="Constant">2</span>:address:duplex-list:character
-    <span class="Constant">9</span>:character<span class="Special"> &lt;- </span>first <span class="Constant">2</span>:address:duplex-list:character
-    <span class="Constant">10</span>:boolean<span class="Special"> &lt;- </span>equal <span class="Constant">1</span>:address:duplex-list:character, <span class="Constant">2</span>:address:duplex-list:character
+    <span class="Constant">2</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>copy <span class="Constant">1</span>:address:shared:duplex-list:character
+    <span class="Constant">3</span>:character<span class="Special"> &lt;- </span>first <span class="Constant">2</span>:address:shared:duplex-list:character
+    <span class="Constant">2</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>next <span class="Constant">2</span>:address:shared:duplex-list:character
+    <span class="Constant">4</span>:character<span class="Special"> &lt;- </span>first <span class="Constant">2</span>:address:shared:duplex-list:character
+    <span class="Constant">2</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>next <span class="Constant">2</span>:address:shared:duplex-list:character
+    <span class="Constant">5</span>:character<span class="Special"> &lt;- </span>first <span class="Constant">2</span>:address:shared:duplex-list:character
+    <span class="Constant">2</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>next <span class="Constant">2</span>:address:shared:duplex-list:character
+    <span class="Constant">6</span>:character<span class="Special"> &lt;- </span>first <span class="Constant">2</span>:address:shared:duplex-list:character
+    <span class="Constant">2</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>prev <span class="Constant">2</span>:address:shared:duplex-list:character
+    <span class="Constant">7</span>:character<span class="Special"> &lt;- </span>first <span class="Constant">2</span>:address:shared:duplex-list:character
+    <span class="Constant">2</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>prev <span class="Constant">2</span>:address:shared:duplex-list:character
+    <span class="Constant">8</span>:character<span class="Special"> &lt;- </span>first <span class="Constant">2</span>:address:shared:duplex-list:character
+    <span class="Constant">2</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>prev <span class="Constant">2</span>:address:shared:duplex-list:character
+    <span class="Constant">9</span>:character<span class="Special"> &lt;- </span>first <span class="Constant">2</span>:address:shared:duplex-list:character
+    <span class="Constant">10</span>:boolean<span class="Special"> &lt;- </span>equal <span class="Constant">1</span>:address:shared:duplex-list:character, <span class="Constant">2</span>:address:shared:duplex-list:character
   ]
   memory-should-contain [
     <span class="Constant">3</span><span class="Special"> &lt;- </span><span class="Constant">5</span>  <span class="Comment"># scanning next</span>
@@ -182,28 +182,28 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> inserting-at-end-of-duplex-list [
   run [
-    <span class="Constant">1</span>:address:duplex-list:character<span class="Special"> &lt;- </span>push <span class="Constant">3</span>, <span class="Constant">0</span>
-    <span class="Constant">1</span>:address:duplex-list:character<span class="Special"> &lt;- </span>push <span class="Constant">4</span>, <span class="Constant">1</span>:address:duplex-list:character
-    <span class="Constant">1</span>:address:duplex-list:character<span class="Special"> &lt;- </span>push <span class="Constant">5</span>, <span class="Constant">1</span>:address:duplex-list:character
-    <span class="Constant">2</span>:address:duplex-list:character<span class="Special"> &lt;- </span>next <span class="Constant">1</span>:address:duplex-list:character  <span class="Comment"># 2 points inside list</span>
-    <span class="Constant">2</span>:address:duplex-list:character<span class="Special"> &lt;- </span>next <span class="Constant">2</span>:address:duplex-list:character  <span class="Comment"># now at end of list</span>
-    <span class="Constant">2</span>:address:duplex-list:character<span class="Special"> &lt;- </span>insert <span class="Constant">6</span>, <span class="Constant">2</span>:address:duplex-list:character
+    <span class="Constant">1</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>push <span class="Constant">3</span>, <span class="Constant">0</span>
+    <span class="Constant">1</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>push <span class="Constant">4</span>, <span class="Constant">1</span>:address:shared:duplex-list:character
+    <span class="Constant">1</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>push <span class="Constant">5</span>, <span class="Constant">1</span>:address:shared:duplex-list:character
+    <span class="Constant">2</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>next <span class="Constant">1</span>:address:shared:duplex-list:character  <span class="Comment"># 2 points inside list</span>
+    <span class="Constant">2</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>next <span class="Constant">2</span>:address:shared:duplex-list:character  <span class="Comment"># now at end of list</span>
+    <span class="Constant">2</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>insert <span class="Constant">6</span>, <span class="Constant">2</span>:address:shared:duplex-list:character
     <span class="Comment"># check structure like before</span>
-    <span class="Constant">2</span>:address:duplex-list:character<span class="Special"> &lt;- </span>copy <span class="Constant">1</span>:address:duplex-list:character
-    <span class="Constant">3</span>:character<span class="Special"> &lt;- </span>first <span class="Constant">2</span>:address:duplex-list:character
-    <span class="Constant">2</span>:address:duplex-list:character<span class="Special"> &lt;- </span>next <span class="Constant">2</span>:address:duplex-list:character
-    <span class="Constant">4</span>:character<span class="Special"> &lt;- </span>first <span class="Constant">2</span>:address:duplex-list:character
-    <span class="Constant">2</span>:address:duplex-list:character<span class="Special"> &lt;- </span>next <span class="Constant">2</span>:address:duplex-list:character
-    <span class="Constant">5</span>:character<span class="Special"> &lt;- </span>first <span class="Constant">2</span>:address:duplex-list:character
-    <span class="Constant">2</span>:address:duplex-list:character<span class="Special"> &lt;- </span>next <span class="Constant">2</span>:address:duplex-list:character
-    <span class="Constant">6</span>:character<span class="Special"> &lt;- </span>first <span class="Constant">2</span>:address:duplex-list:character
-    <span class="Constant">2</span>:address:duplex-list:character<span class="Special"> &lt;- </span>prev <span class="Constant">2</span>:address:duplex-list:character
-    <span class="Constant">7</span>:character<span class="Special"> &lt;- </span>first <span class="Constant">2</span>:address:duplex-list:character
-    <span class="Constant">2</span>:address:duplex-list:character<span class="Special"> &lt;- </span>prev <span class="Constant">2</span>:address:duplex-list:character
-    <span class="Constant">8</span>:character<span class="Special"> &lt;- </span>first <span class="Constant">2</span>:address:duplex-list:character
-    <span class="Constant">2</span>:address:duplex-list:character<span class="Special"> &lt;- </span>prev <span class="Constant">2</span>:address:duplex-list:character
-    <span class="Constant">9</span>:character<span class="Special"> &lt;- </span>first <span class="Constant">2</span>:address:duplex-list:character
-    <span class="Constant">10</span>:boolean<span class="Special"> &lt;- </span>equal <span class="Constant">1</span>:address:duplex-list:character, <span class="Constant">2</span>:address:duplex-list:character
+    <span class="Constant">2</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>copy <span class="Constant">1</span>:address:shared:duplex-list:character
+    <span class="Constant">3</span>:character<span class="Special"> &lt;- </span>first <span class="Constant">2</span>:address:shared:duplex-list:character
+    <span class="Constant">2</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>next <span class="Constant">2</span>:address:shared:duplex-list:character
+    <span class="Constant">4</span>:character<span class="Special"> &lt;- </span>first <span class="Constant">2</span>:address:shared:duplex-list:character
+    <span class="Constant">2</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>next <span class="Constant">2</span>:address:shared:duplex-list:character
+    <span class="Constant">5</span>:character<span class="Special"> &lt;- </span>first <span class="Constant">2</span>:address:shared:duplex-list:character
+    <span class="Constant">2</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>next <span class="Constant">2</span>:address:shared:duplex-list:character
+    <span class="Constant">6</span>:character<span class="Special"> &lt;- </span>first <span class="Constant">2</span>:address:shared:duplex-list:character
+    <span class="Constant">2</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>prev <span class="Constant">2</span>:address:shared:duplex-list:character
+    <span class="Constant">7</span>:character<span class="Special"> &lt;- </span>first <span class="Constant">2</span>:address:shared:duplex-list:character
+    <span class="Constant">2</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>prev <span class="Constant">2</span>:address:shared:duplex-list:character
+    <span class="Constant">8</span>:character<span class="Special"> &lt;- </span>first <span class="Constant">2</span>:address:shared:duplex-list:character
+    <span class="Constant">2</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>prev <span class="Constant">2</span>:address:shared:duplex-list:character
+    <span class="Constant">9</span>:character<span class="Special"> &lt;- </span>first <span class="Constant">2</span>:address:shared:duplex-list:character
+    <span class="Constant">10</span>:boolean<span class="Special"> &lt;- </span>equal <span class="Constant">1</span>:address:shared:duplex-list:character, <span class="Constant">2</span>:address:shared:duplex-list:character
   ]
   memory-should-contain [
     <span class="Constant">3</span><span class="Special"> &lt;- </span><span class="Constant">5</span>  <span class="Comment"># scanning next</span>
@@ -219,26 +219,26 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> inserting-after-start-of-duplex-list [
   run [
-    <span class="Constant">1</span>:address:duplex-list:character<span class="Special"> &lt;- </span>push <span class="Constant">3</span>, <span class="Constant">0</span>
-    <span class="Constant">1</span>:address:duplex-list:character<span class="Special"> &lt;- </span>push <span class="Constant">4</span>, <span class="Constant">1</span>:address:duplex-list:character
-    <span class="Constant">1</span>:address:duplex-list:character<span class="Special"> &lt;- </span>push <span class="Constant">5</span>, <span class="Constant">1</span>:address:duplex-list:character
-    <span class="Constant">1</span>:address:duplex-list:character<span class="Special"> &lt;- </span>insert <span class="Constant">6</span>, <span class="Constant">1</span>:address:duplex-list:character
+    <span class="Constant">1</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>push <span class="Constant">3</span>, <span class="Constant">0</span>
+    <span class="Constant">1</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>push <span class="Constant">4</span>, <span class="Constant">1</span>:address:shared:duplex-list:character
+    <span class="Constant">1</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>push <span class="Constant">5</span>, <span class="Constant">1</span>:address:shared:duplex-list:character
+    <span class="Constant">1</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>insert <span class="Constant">6</span>, <span class="Constant">1</span>:address:shared:duplex-list:character
     <span class="Comment"># check structure like before</span>
-    <span class="Constant">2</span>:address:duplex-list:character<span class="Special"> &lt;- </span>copy <span class="Constant">1</span>:address:duplex-list:character
-    <span class="Constant">3</span>:character<span class="Special"> &lt;- </span>first <span class="Constant">2</span>:address:duplex-list:character
-    <span class="Constant">2</span>:address:duplex-list:character<span class="Special"> &lt;- </span>next <span class="Constant">2</span>:address:duplex-list:character
-    <span class="Constant">4</span>:character<span class="Special"> &lt;- </span>first <span class="Constant">2</span>:address:duplex-list:character
-    <span class="Constant">2</span>:address:duplex-list:character<span class="Special"> &lt;- </span>next <span class="Constant">2</span>:address:duplex-list:character
-    <span class="Constant">5</span>:character<span class="Special"> &lt;- </span>first <span class="Constant">2</span>:address:duplex-list:character
-    <span class="Constant">2</span>:address:duplex-list:character<span class="Special"> &lt;- </span>next <span class="Constant">2</span>:address:duplex-list:character
-    <span class="Constant">6</span>:character<span class="Special"> &lt;- </span>first <span class="Constant">2</span>:address:duplex-list:character
-    <span class="Constant">2</span>:address:duplex-list:character<span class="Special"> &lt;- </span>prev <span class="Constant">2</span>:address:duplex-list:character
-    <span class="Constant">7</span>:character<span class="Special"> &lt;- </span>first <span class="Constant">2</span>:address:duplex-list:character
-    <span class="Constant">2</span>:address:duplex-list:character<span class="Special"> &lt;- </span>prev <span class="Constant">2</span>:address:duplex-list:character
-    <span class="Constant">8</span>:character<span class="Special"> &lt;- </span>first <span class="Constant">2</span>:address:duplex-list:character
-    <span class="Constant">2</span>:address:duplex-list:character<span class="Special"> &lt;- </span>prev <span class="Constant">2</span>:address:duplex-list:character
-    <span class="Constant">9</span>:character<span class="Special"> &lt;- </span>first <span class="Constant">2</span>:address:duplex-list:character
-    <span class="Constant">10</span>:boolean<span class="Special"> &lt;- </span>equal <span class="Constant">1</span>:address:duplex-list:character, <span class="Constant">2</span>:address:duplex-list:character
+    <span class="Constant">2</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>copy <span class="Constant">1</span>:address:shared:duplex-list:character
+    <span class="Constant">3</span>:character<span class="Special"> &lt;- </span>first <span class="Constant">2</span>:address:shared:duplex-list:character
+    <span class="Constant">2</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>next <span class="Constant">2</span>:address:shared:duplex-list:character
+    <span class="Constant">4</span>:character<span class="Special"> &lt;- </span>first <span class="Constant">2</span>:address:shared:duplex-list:character
+    <span class="Constant">2</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>next <span class="Constant">2</span>:address:shared:duplex-list:character
+    <span class="Constant">5</span>:character<span class="Special"> &lt;- </span>first <span class="Constant">2</span>:address:shared:duplex-list:character
+    <span class="Constant">2</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>next <span class="Constant">2</span>:address:shared:duplex-list:character
+    <span class="Constant">6</span>:character<span class="Special"> &lt;- </span>first <span class="Constant">2</span>:address:shared:duplex-list:character
+    <span class="Constant">2</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>prev <span class="Constant">2</span>:address:shared:duplex-list:character
+    <span class="Constant">7</span>:character<span class="Special"> &lt;- </span>first <span class="Constant">2</span>:address:shared:duplex-list:character
+    <span class="Constant">2</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>prev <span class="Constant">2</span>:address:shared:duplex-list:character
+    <span class="Constant">8</span>:character<span class="Special"> &lt;- </span>first <span class="Constant">2</span>:address:shared:duplex-list:character
+    <span class="Constant">2</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>prev <span class="Constant">2</span>:address:shared:duplex-list:character
+    <span class="Constant">9</span>:character<span class="Special"> &lt;- </span>first <span class="Constant">2</span>:address:shared:duplex-list:character
+    <span class="Constant">10</span>:boolean<span class="Special"> &lt;- </span>equal <span class="Constant">1</span>:address:shared:duplex-list:character, <span class="Constant">2</span>:address:shared:duplex-list:character
   ]
   memory-should-contain [
     <span class="Constant">3</span><span class="Special"> &lt;- </span><span class="Constant">5</span>  <span class="Comment"># scanning next</span>
@@ -256,15 +256,15 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="Comment">#</span>
 <span class="Comment"># Returns null if and only if list is empty. Beware: in that case any other</span>
 <span class="Comment"># pointers to the head are now invalid.</span>
-<span class="muRecipe">recipe</span> remove x:address:duplex-list:_elem/contained-in:in, in:address:duplex-list:_elem<span class="muRecipe"> -&gt; </span>in:address:duplex-list:_elem [
+<span class="muRecipe">recipe</span> remove x:address:shared:duplex-list:_elem/contained-in:in, in:address:shared:duplex-list:_elem<span class="muRecipe"> -&gt; </span>in:address:shared:duplex-list:_elem [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   <span class="Comment"># if 'x' is null, return</span>
   <span class="muControl">reply-unless</span> x
-  next-node:address:duplex-list:_elem<span class="Special"> &lt;- </span>get *x, <span class="Constant">next:offset</span>
-  prev-node:address:duplex-list:_elem<span class="Special"> &lt;- </span>get *x, <span class="Constant">prev:offset</span>
+  next-node:address:shared:duplex-list:_elem<span class="Special"> &lt;- </span>get *x, <span class="Constant">next:offset</span>
+  prev-node:address:shared:duplex-list:_elem<span class="Special"> &lt;- </span>get *x, <span class="Constant">prev:offset</span>
   <span class="Comment"># null x's pointers</span>
-  tmp:address:address:duplex-list:_elem<span class="Special"> &lt;- </span>get-address *x, <span class="Constant">next:offset</span>
+  tmp:address:address:shared:duplex-list:_elem<span class="Special"> &lt;- </span>get-address *x, <span class="Constant">next:offset</span>
   *tmp<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
   tmp<span class="Special"> &lt;- </span>get-address *x, <span class="Constant">prev:offset</span>
   *tmp<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
@@ -288,21 +288,21 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> removing-from-duplex-list [
   run [
-    <span class="Constant">1</span>:address:duplex-list:character<span class="Special"> &lt;- </span>push <span class="Constant">3</span>, <span class="Constant">0</span>
-    <span class="Constant">1</span>:address:duplex-list:character<span class="Special"> &lt;- </span>push <span class="Constant">4</span>, <span class="Constant">1</span>:address:duplex-list:character
-    <span class="Constant">1</span>:address:duplex-list:character<span class="Special"> &lt;- </span>push <span class="Constant">5</span>, <span class="Constant">1</span>:address:duplex-list:character
-    <span class="Constant">2</span>:address:duplex-list:character<span class="Special"> &lt;- </span>next <span class="Constant">1</span>:address:duplex-list:character  <span class="Comment"># 2 points at second element</span>
-    <span class="Constant">1</span>:address:duplex-list:character<span class="Special"> &lt;- </span>remove <span class="Constant">2</span>:address:duplex-list:character, <span class="Constant">1</span>:address:duplex-list:character
-    <span class="Constant">3</span>:boolean<span class="Special"> &lt;- </span>equal <span class="Constant">2</span>:address:duplex-list:character, <span class="Constant">0</span>
+    <span class="Constant">1</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>push <span class="Constant">3</span>, <span class="Constant">0</span>
+    <span class="Constant">1</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>push <span class="Constant">4</span>, <span class="Constant">1</span>:address:shared:duplex-list:character
+    <span class="Constant">1</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>push <span class="Constant">5</span>, <span class="Constant">1</span>:address:shared:duplex-list:character
+    <span class="Constant">2</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>next <span class="Constant">1</span>:address:shared:duplex-list:character  <span class="Comment"># 2 points at second element</span>
+    <span class="Constant">1</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>remove <span class="Constant">2</span>:address:shared:duplex-list:character, <span class="Constant">1</span>:address:shared:duplex-list:character
+    <span class="Constant">3</span>:boolean<span class="Special"> &lt;- </span>equal <span class="Constant">2</span>:address:shared:duplex-list:character, <span class="Constant">0</span>
     <span class="Comment"># check structure like before</span>
-    <span class="Constant">2</span>:address:duplex-list:character<span class="Special"> &lt;- </span>copy <span class="Constant">1</span>:address:duplex-list:character
-    <span class="Constant">4</span>:character<span class="Special"> &lt;- </span>first <span class="Constant">2</span>:address:duplex-list:character
-    <span class="Constant">2</span>:address:duplex-list:character<span class="Special"> &lt;- </span>next <span class="Constant">2</span>:address:duplex-list:character
-    <span class="Constant">5</span>:character<span class="Special"> &lt;- </span>first <span class="Constant">2</span>:address:duplex-list:character
-    <span class="Constant">6</span>:address:duplex-list:character<span class="Special"> &lt;- </span>next <span class="Constant">2</span>:address:duplex-list:character
-    <span class="Constant">2</span>:address:duplex-list:character<span class="Special"> &lt;- </span>prev <span class="Constant">2</span>:address:duplex-list:character
-    <span class="Constant">7</span>:character<span class="Special"> &lt;- </span>first <span class="Constant">2</span>:address:duplex-list:character
-    <span class="Constant">8</span>:boolean<span class="Special"> &lt;- </span>equal <span class="Constant">1</span>:address:duplex-list:character, <span class="Constant">2</span>:address:duplex-list:character
+    <span class="Constant">2</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>copy <span class="Constant">1</span>:address:shared:duplex-list:character
+    <span class="Constant">4</span>:character<span class="Special"> &lt;- </span>first <span class="Constant">2</span>:address:shared:duplex-list:character
+    <span class="Constant">2</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>next <span class="Constant">2</span>:address:shared:duplex-list:character
+    <span class="Constant">5</span>:character<span class="Special"> &lt;- </span>first <span class="Constant">2</span>:address:shared:duplex-list:character
+    <span class="Constant">6</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>next <span class="Constant">2</span>:address:shared:duplex-list:character
+    <span class="Constant">2</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>prev <span class="Constant">2</span>:address:shared:duplex-list:character
+    <span class="Constant">7</span>:character<span class="Special"> &lt;- </span>first <span class="Constant">2</span>:address:shared:duplex-list:character
+    <span class="Constant">8</span>:boolean<span class="Special"> &lt;- </span>equal <span class="Constant">1</span>:address:shared:duplex-list:character, <span class="Constant">2</span>:address:shared:duplex-list:character
   ]
   memory-should-contain [
     <span class="Constant">3</span><span class="Special"> &lt;- </span><span class="Constant">0</span>  <span class="Comment"># remove returned non-null</span>
@@ -316,19 +316,19 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> removing-from-start-of-duplex-list [
   run [
-    <span class="Constant">1</span>:address:duplex-list:character<span class="Special"> &lt;- </span>push <span class="Constant">3</span>, <span class="Constant">0</span>
-    <span class="Constant">1</span>:address:duplex-list:character<span class="Special"> &lt;- </span>push <span class="Constant">4</span>, <span class="Constant">1</span>:address:duplex-list:character
-    <span class="Constant">1</span>:address:duplex-list:character<span class="Special"> &lt;- </span>push <span class="Constant">5</span>, <span class="Constant">1</span>:address:duplex-list:character
-    <span class="Constant">1</span>:address:duplex-list:character<span class="Special"> &lt;- </span>remove <span class="Constant">1</span>:address:duplex-list:character, <span class="Constant">1</span>:address:duplex-list:character
+    <span class="Constant">1</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>push <span class="Constant">3</span>, <span class="Constant">0</span>
+    <span class="Constant">1</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>push <span class="Constant">4</span>, <span class="Constant">1</span>:address:shared:duplex-list:character
+    <span class="Constant">1</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>push <span class="Constant">5</span>, <span class="Constant">1</span>:address:shared:duplex-list:character
+    <span class="Constant">1</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>remove <span class="Constant">1</span>:address:shared:duplex-list:character, <span class="Constant">1</span>:address:shared:duplex-list:character
     <span class="Comment"># check structure like before</span>
-    <span class="Constant">2</span>:address:duplex-list:character<span class="Special"> &lt;- </span>copy <span class="Constant">1</span>:address:duplex-list:character
-    <span class="Constant">3</span>:character<span class="Special"> &lt;- </span>first <span class="Constant">2</span>:address:duplex-list:character
-    <span class="Constant">2</span>:address:duplex-list:character<span class="Special"> &lt;- </span>next <span class="Constant">2</span>:address:duplex-list:character
-    <span class="Constant">4</span>:character<span class="Special"> &lt;- </span>first <span class="Constant">2</span>:address:duplex-list:character
-    <span class="Constant">5</span>:address:duplex-list:character<span class="Special"> &lt;- </span>next <span class="Constant">2</span>:address:duplex-list:character
-    <span class="Constant">2</span>:address:duplex-list:character<span class="Special"> &lt;- </span>prev <span class="Constant">2</span>:address:duplex-list:character
-    <span class="Constant">6</span>:character<span class="Special"> &lt;- </span>first <span class="Constant">2</span>:address:duplex-list:character
-    <span class="Constant">7</span>:boolean<span class="Special"> &lt;- </span>equal <span class="Constant">1</span>:address:duplex-list:character, <span class="Constant">2</span>:address:duplex-list:character
+    <span class="Constant">2</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>copy <span class="Constant">1</span>:address:shared:duplex-list:character
+    <span class="Constant">3</span>:character<span class="Special"> &lt;- </span>first <span class="Constant">2</span>:address:shared:duplex-list:character
+    <span class="Constant">2</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>next <span class="Constant">2</span>:address:shared:duplex-list:character
+    <span class="Constant">4</span>:character<span class="Special"> &lt;- </span>first <span class="Constant">2</span>:address:shared:duplex-list:character
+    <span class="Constant">5</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>next <span class="Constant">2</span>:address:shared:duplex-list:character
+    <span class="Constant">2</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>prev <span class="Constant">2</span>:address:shared:duplex-list:character
+    <span class="Constant">6</span>:character<span class="Special"> &lt;- </span>first <span class="Constant">2</span>:address:shared:duplex-list:character
+    <span class="Constant">7</span>:boolean<span class="Special"> &lt;- </span>equal <span class="Constant">1</span>:address:shared:duplex-list:character, <span class="Constant">2</span>:address:shared:duplex-list:character
   ]
   memory-should-contain [
     <span class="Constant">3</span><span class="Special"> &lt;- </span><span class="Constant">4</span>  <span class="Comment"># scanning next, skipping deleted element</span>
@@ -341,23 +341,23 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> removing-from-end-of-duplex-list [
   run [
-    <span class="Constant">1</span>:address:duplex-list:character<span class="Special"> &lt;- </span>push <span class="Constant">3</span>, <span class="Constant">0</span>
-    <span class="Constant">1</span>:address:duplex-list:character<span class="Special"> &lt;- </span>push <span class="Constant">4</span>, <span class="Constant">1</span>:address:duplex-list:character
-    <span class="Constant">1</span>:address:duplex-list:character<span class="Special"> &lt;- </span>push <span class="Constant">5</span>, <span class="Constant">1</span>:address:duplex-list:character
+    <span class="Constant">1</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>push <span class="Constant">3</span>, <span class="Constant">0</span>
+    <span class="Constant">1</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>push <span class="Constant">4</span>, <span class="Constant">1</span>:address:shared:duplex-list:character
+    <span class="Constant">1</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>push <span class="Constant">5</span>, <span class="Constant">1</span>:address:shared:duplex-list:character
     <span class="Comment"># delete last element</span>
-    <span class="Constant">2</span>:address:duplex-list:character<span class="Special"> &lt;- </span>next <span class="Constant">1</span>:address:duplex-list:character
-    <span class="Constant">2</span>:address:duplex-list:character<span class="Special"> &lt;- </span>next <span class="Constant">2</span>:address:duplex-list:character
-    <span class="Constant">1</span>:address:duplex-list:character<span class="Special"> &lt;- </span>remove <span class="Constant">2</span>:address:duplex-list:character, <span class="Constant">1</span>:address:duplex-list:character
-    <span class="Constant">3</span>:boolean<span class="Special"> &lt;- </span>equal <span class="Constant">2</span>:address:duplex-list:character, <span class="Constant">0</span>
+    <span class="Constant">2</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>next <span class="Constant">1</span>:address:shared:duplex-list:character
+    <span class="Constant">2</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>next <span class="Constant">2</span>:address:shared:duplex-list:character
+    <span class="Constant">1</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>remove <span class="Constant">2</span>:address:shared:duplex-list:character, <span class="Constant">1</span>:address:shared:duplex-list:character
+    <span class="Constant">3</span>:boolean<span class="Special"> &lt;- </span>equal <span class="Constant">2</span>:address:shared:duplex-list:character, <span class="Constant">0</span>
     <span class="Comment"># check structure like before</span>
-    <span class="Constant">2</span>:address:duplex-list:character<span class="Special"> &lt;- </span>copy <span class="Constant">1</span>:address:duplex-list:character
-    <span class="Constant">4</span>:character<span class="Special"> &lt;- </span>first <span class="Constant">2</span>:address:duplex-list:character
-    <span class="Constant">2</span>:address:duplex-list:character<span class="Special"> &lt;- </span>next <span class="Constant">2</span>:address:duplex-list:character
-    <span class="Constant">5</span>:character<span class="Special"> &lt;- </span>first <span class="Constant">2</span>:address:duplex-list:character
-    <span class="Constant">6</span>:address:duplex-list:character<span class="Special"> &lt;- </span>next <span class="Constant">2</span>:address:duplex-list:character
-    <span class="Constant">2</span>:address:duplex-list:character<span class="Special"> &lt;- </span>prev <span class="Constant">2</span>:address:duplex-list:character
-    <span class="Constant">7</span>:character<span class="Special"> &lt;- </span>first <span class="Constant">2</span>:address:duplex-list:character
-    <span class="Constant">8</span>:boolean<span class="Special"> &lt;- </span>equal <span class="Constant">1</span>:address:duplex-list:character, <span class="Constant">2</span>:address:duplex-list:character
+    <span class="Constant">2</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>copy <span class="Constant">1</span>:address:shared:duplex-list:character
+    <span class="Constant">4</span>:character<span class="Special"> &lt;- </span>first <span class="Constant">2</span>:address:shared:duplex-list:character
+    <span class="Constant">2</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>next <span class="Constant">2</span>:address:shared:duplex-list:character
+    <span class="Constant">5</span>:character<span class="Special"> &lt;- </span>first <span class="Constant">2</span>:address:shared:duplex-list:character
+    <span class="Constant">6</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>next <span class="Constant">2</span>:address:shared:duplex-list:character
+    <span class="Constant">2</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>prev <span class="Constant">2</span>:address:shared:duplex-list:character
+    <span class="Constant">7</span>:character<span class="Special"> &lt;- </span>first <span class="Constant">2</span>:address:shared:duplex-list:character
+    <span class="Constant">8</span>:boolean<span class="Special"> &lt;- </span>equal <span class="Constant">1</span>:address:shared:duplex-list:character, <span class="Constant">2</span>:address:shared:duplex-list:character
   ]
   memory-should-contain [
     <span class="Constant">3</span><span class="Special"> &lt;- </span><span class="Constant">0</span>  <span class="Comment"># remove returned non-null</span>
@@ -371,8 +371,8 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> removing-from-singleton-list [
   run [
-    <span class="Constant">1</span>:address:duplex-list:character<span class="Special"> &lt;- </span>push <span class="Constant">3</span>, <span class="Constant">0</span>
-    <span class="Constant">1</span>:address:duplex-list:character<span class="Special"> &lt;- </span>remove <span class="Constant">1</span>:address:duplex-list:character, <span class="Constant">1</span>:address:duplex-list:character
+    <span class="Constant">1</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>push <span class="Constant">3</span>, <span class="Constant">0</span>
+    <span class="Constant">1</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>remove <span class="Constant">1</span>:address:shared:duplex-list:character, <span class="Constant">1</span>:address:shared:duplex-list:character
   ]
   memory-should-contain [
     <span class="Constant">1</span><span class="Special"> &lt;- </span><span class="Constant">0</span>  <span class="Comment"># back to an empty list</span>
@@ -381,16 +381,16 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="Comment"># remove values between 'start' and 'end' (both exclusive)</span>
 <span class="Comment"># also clear pointers back out from start/end for hygiene</span>
-<span class="muRecipe">recipe</span> remove-between start:address:duplex-list:_elem, end:address:duplex-list:_elem/contained-in:start<span class="muRecipe"> -&gt; </span>start:address:duplex-list:_elem [
+<span class="muRecipe">recipe</span> remove-between start:address:shared:duplex-list:_elem, end:address:shared:duplex-list:_elem/contained-in:start<span class="muRecipe"> -&gt; </span>start:address:shared:duplex-list:_elem [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   <span class="muControl">reply-unless</span> start
   <span class="Comment"># start-&gt;next-&gt;prev = 0</span>
   <span class="Comment"># start-&gt;next = end</span>
-  next:address:address:duplex-list:_elem<span class="Special"> &lt;- </span>get-address *start, <span class="Constant">next:offset</span>
+  next:address:address:shared:duplex-list:_elem<span class="Special"> &lt;- </span>get-address *start, <span class="Constant">next:offset</span>
   nothing-to-delete?:boolean<span class="Special"> &lt;- </span>equal *next, end
   <span class="muControl">reply-if</span> nothing-to-delete?
-  prev:address:address:duplex-list:_elem<span class="Special"> &lt;- </span>get-address **next, <span class="Constant">prev:offset</span>
+  prev:address:address:shared:duplex-list:_elem<span class="Special"> &lt;- </span>get-address **next, <span class="Constant">prev:offset</span>
   *prev<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
   *next<span class="Special"> &lt;- </span>copy end
   <span class="muControl">reply-unless</span> end
@@ -404,25 +404,25 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> remove-range [
   <span class="Comment"># construct a duplex list with six elements [13, 14, 15, 16, 17, 18]</span>
-  <span class="Constant">1</span>:address:duplex-list:character<span class="Special"> &lt;- </span>push <span class="Constant">18</span>, <span class="Constant">0</span>
-  <span class="Constant">1</span>:address:duplex-list:character<span class="Special"> &lt;- </span>push <span class="Constant">17</span>, <span class="Constant">1</span>:address:duplex-list:character
-  <span class="Constant">1</span>:address:duplex-list:character<span class="Special"> &lt;- </span>push <span class="Constant">16</span>, <span class="Constant">1</span>:address:duplex-list:character
-  <span class="Constant">1</span>:address:duplex-list:character<span class="Special"> &lt;- </span>push <span class="Constant">15</span>, <span class="Constant">1</span>:address:duplex-list:character
-  <span class="Constant">1</span>:address:duplex-list:character<span class="Special"> &lt;- </span>push <span class="Constant">14</span>, <span class="Constant">1</span>:address:duplex-list:character
-  <span class="Constant">1</span>:address:duplex-list:character<span class="Special"> &lt;- </span>push <span class="Constant">13</span>, <span class="Constant">1</span>:address:duplex-list:character
+  <span class="Constant">1</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>push <span class="Constant">18</span>, <span class="Constant">0</span>
+  <span class="Constant">1</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>push <span class="Constant">17</span>, <span class="Constant">1</span>:address:shared:duplex-list:character
+  <span class="Constant">1</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>push <span class="Constant">16</span>, <span class="Constant">1</span>:address:shared:duplex-list:character
+  <span class="Constant">1</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>push <span class="Constant">15</span>, <span class="Constant">1</span>:address:shared:duplex-list:character
+  <span class="Constant">1</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>push <span class="Constant">14</span>, <span class="Constant">1</span>:address:shared:duplex-list:character
+  <span class="Constant">1</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>push <span class="Constant">13</span>, <span class="Constant">1</span>:address:shared:duplex-list:character
   run [
     <span class="Comment"># delete 16 onwards</span>
     <span class="Comment"># first pointer: to the third element</span>
-    <span class="Constant">2</span>:address:duplex-list:character<span class="Special"> &lt;- </span>next <span class="Constant">1</span>:address:duplex-list:character
-    <span class="Constant">2</span>:address:duplex-list:character<span class="Special"> &lt;- </span>next <span class="Constant">2</span>:address:duplex-list:character
-    <span class="Constant">2</span>:address:duplex-list:character<span class="Special"> &lt;- </span>remove-between <span class="Constant">2</span>:address:duplex-list:character, <span class="Constant">0</span>
+    <span class="Constant">2</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>next <span class="Constant">1</span>:address:shared:duplex-list:character
+    <span class="Constant">2</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>next <span class="Constant">2</span>:address:shared:duplex-list:character
+    <span class="Constant">2</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>remove-between <span class="Constant">2</span>:address:shared:duplex-list:character, <span class="Constant">0</span>
     <span class="Comment"># now check the list</span>
-    <span class="Constant">4</span>:character<span class="Special"> &lt;- </span>get *<span class="Constant">1</span>:address:duplex-list:character, <span class="Constant">value:offset</span>
-    <span class="Constant">5</span>:address:duplex-list:character<span class="Special"> &lt;- </span>next <span class="Constant">1</span>:address:duplex-list:character
-    <span class="Constant">6</span>:character<span class="Special"> &lt;- </span>get *<span class="Constant">5</span>:address:duplex-list:character, <span class="Constant">value:offset</span>
-    <span class="Constant">7</span>:address:duplex-list:character<span class="Special"> &lt;- </span>next <span class="Constant">5</span>:address:duplex-list:character
-    <span class="Constant">8</span>:character<span class="Special"> &lt;- </span>get *<span class="Constant">7</span>:address:duplex-list:character, <span class="Constant">value:offset</span>
-    <span class="Constant">9</span>:address:duplex-list:character<span class="Special"> &lt;- </span>next <span class="Constant">7</span>:address:duplex-list:character
+    <span class="Constant">4</span>:character<span class="Special"> &lt;- </span>get *<span class="Constant">1</span>:address:shared:duplex-list:character, <span class="Constant">value:offset</span>
+    <span class="Constant">5</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>next <span class="Constant">1</span>:address:shared:duplex-list:character
+    <span class="Constant">6</span>:character<span class="Special"> &lt;- </span>get *<span class="Constant">5</span>:address:shared:duplex-list:character, <span class="Constant">value:offset</span>
+    <span class="Constant">7</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>next <span class="Constant">5</span>:address:shared:duplex-list:character
+    <span class="Constant">8</span>:character<span class="Special"> &lt;- </span>get *<span class="Constant">7</span>:address:shared:duplex-list:character, <span class="Constant">value:offset</span>
+    <span class="Constant">9</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>next <span class="Constant">7</span>:address:shared:duplex-list:character
   ]
   memory-should-contain [
     <span class="Constant">4</span><span class="Special"> &lt;- </span><span class="Constant">13</span>
@@ -434,29 +434,29 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> remove-range-to-end [
   <span class="Comment"># construct a duplex list with six elements [13, 14, 15, 16, 17, 18]</span>
-  <span class="Constant">1</span>:address:duplex-list:character<span class="Special"> &lt;- </span>push <span class="Constant">18</span>, <span class="Constant">0</span>
-  <span class="Constant">1</span>:address:duplex-list:character<span class="Special"> &lt;- </span>push <span class="Constant">17</span>, <span class="Constant">1</span>:address:duplex-list:character
-  <span class="Constant">1</span>:address:duplex-list:character<span class="Special"> &lt;- </span>push <span class="Constant">16</span>, <span class="Constant">1</span>:address:duplex-list:character
-  <span class="Constant">1</span>:address:duplex-list:character<span class="Special"> &lt;- </span>push <span class="Constant">15</span>, <span class="Constant">1</span>:address:duplex-list:character
-  <span class="Constant">1</span>:address:duplex-list:character<span class="Special"> &lt;- </span>push <span class="Constant">14</span>, <span class="Constant">1</span>:address:duplex-list:character
-  <span class="Constant">1</span>:address:duplex-list:character<span class="Special"> &lt;- </span>push <span class="Constant">13</span>, <span class="Constant">1</span>:address:duplex-list:character
+  <span class="Constant">1</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>push <span class="Constant">18</span>, <span class="Constant">0</span>
+  <span class="Constant">1</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>push <span class="Constant">17</span>, <span class="Constant">1</span>:address:shared:duplex-list:character
+  <span class="Constant">1</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>push <span class="Constant">16</span>, <span class="Constant">1</span>:address:shared:duplex-list:character
+  <span class="Constant">1</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>push <span class="Constant">15</span>, <span class="Constant">1</span>:address:shared:duplex-list:character
+  <span class="Constant">1</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>push <span class="Constant">14</span>, <span class="Constant">1</span>:address:shared:duplex-list:character
+  <span class="Constant">1</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>push <span class="Constant">13</span>, <span class="Constant">1</span>:address:shared:duplex-list:character
   run [
     <span class="Comment"># delete 15, 16 and 17</span>
     <span class="Comment"># first pointer: to the third element</span>
-    <span class="Constant">2</span>:address:duplex-list:character<span class="Special"> &lt;- </span>next <span class="Constant">1</span>:address:duplex-list:character
+    <span class="Constant">2</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>next <span class="Constant">1</span>:address:shared:duplex-list:character
     <span class="Comment"># second pointer: to the fifth element</span>
-    <span class="Constant">3</span>:address:duplex-list:character<span class="Special"> &lt;- </span>next <span class="Constant">2</span>:address:duplex-list:character
-    <span class="Constant">3</span>:address:duplex-list:character<span class="Special"> &lt;- </span>next <span class="Constant">3</span>:address:duplex-list:character
-    <span class="Constant">3</span>:address:duplex-list:character<span class="Special"> &lt;- </span>next <span class="Constant">3</span>:address:duplex-list:character
-    <span class="Constant">3</span>:address:duplex-list:character<span class="Special"> &lt;- </span>next <span class="Constant">3</span>:address:duplex-list:character
-    remove-between <span class="Constant">2</span>:address:duplex-list:character, <span class="Constant">3</span>:address:duplex-list:character
+    <span class="Constant">3</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>next <span class="Constant">2</span>:address:shared:duplex-list:character
+    <span class="Constant">3</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>next <span class="Constant">3</span>:address:shared:duplex-list:character
+    <span class="Constant">3</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>next <span class="Constant">3</span>:address:shared:duplex-list:character
+    <span class="Constant">3</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>next <span class="Constant">3</span>:address:shared:duplex-list:character
+    remove-between <span class="Constant">2</span>:address:shared:duplex-list:character, <span class="Constant">3</span>:address:shared:duplex-list:character
     <span class="Comment"># now check the list</span>
-    <span class="Constant">4</span>:character<span class="Special"> &lt;- </span>get *<span class="Constant">1</span>:address:duplex-list:character, <span class="Constant">value:offset</span>
-    <span class="Constant">5</span>:address:duplex-list:character<span class="Special"> &lt;- </span>next <span class="Constant">1</span>:address:duplex-list:character
-    <span class="Constant">6</span>:character<span class="Special"> &lt;- </span>get *<span class="Constant">5</span>:address:duplex-list:character, <span class="Constant">value:offset</span>
-    <span class="Constant">7</span>:address:duplex-list:character<span class="Special"> &lt;- </span>next <span class="Constant">5</span>:address:duplex-list:character
-    <span class="Constant">8</span>:character<span class="Special"> &lt;- </span>get *<span class="Constant">7</span>:address:duplex-list:character, <span class="Constant">value:offset</span>
-    <span class="Constant">9</span>:address:duplex-list:character<span class="Special"> &lt;- </span>next <span class="Constant">7</span>:address:duplex-list:character
+    <span class="Constant">4</span>:character<span class="Special"> &lt;- </span>get *<span class="Constant">1</span>:address:shared:duplex-list:character, <span class="Constant">value:offset</span>
+    <span class="Constant">5</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>next <span class="Constant">1</span>:address:shared:duplex-list:character
+    <span class="Constant">6</span>:character<span class="Special"> &lt;- </span>get *<span class="Constant">5</span>:address:shared:duplex-list:character, <span class="Constant">value:offset</span>
+    <span class="Constant">7</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>next <span class="Constant">5</span>:address:shared:duplex-list:character
+    <span class="Constant">8</span>:character<span class="Special"> &lt;- </span>get *<span class="Constant">7</span>:address:shared:duplex-list:character, <span class="Constant">value:offset</span>
+    <span class="Constant">9</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>next <span class="Constant">7</span>:address:shared:duplex-list:character
   ]
   memory-should-contain [
     <span class="Constant">4</span><span class="Special"> &lt;- </span><span class="Constant">13</span>
@@ -468,18 +468,18 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> remove-range-empty [
   <span class="Comment"># construct a duplex list with six elements [13, 14, 15, 16, 17, 18]</span>
-  <span class="Constant">1</span>:address:duplex-list:character<span class="Special"> &lt;- </span>push <span class="Constant">14</span>, <span class="Constant">0</span>
-  <span class="Constant">1</span>:address:duplex-list:character<span class="Special"> &lt;- </span>push <span class="Constant">13</span>, <span class="Constant">1</span>:address:duplex-list:character
+  <span class="Constant">1</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>push <span class="Constant">14</span>, <span class="Constant">0</span>
+  <span class="Constant">1</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>push <span class="Constant">13</span>, <span class="Constant">1</span>:address:shared:duplex-list:character
   run [
     <span class="Comment"># delete 16 onwards</span>
     <span class="Comment"># first pointer: to the third element</span>
-    <span class="Constant">2</span>:address:duplex-list:character<span class="Special"> &lt;- </span>next <span class="Constant">1</span>:address:duplex-list:character
-    remove-between <span class="Constant">1</span>:address:duplex-list:character, <span class="Constant">2</span>:address:duplex-list:character
+    <span class="Constant">2</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>next <span class="Constant">1</span>:address:shared:duplex-list:character
+    remove-between <span class="Constant">1</span>:address:shared:duplex-list:character, <span class="Constant">2</span>:address:shared:duplex-list:character
     <span class="Comment"># now check the list</span>
-    <span class="Constant">4</span>:character<span class="Special"> &lt;- </span>get *<span class="Constant">1</span>:address:duplex-list:character, <span class="Constant">value:offset</span>
-    <span class="Constant">5</span>:address:duplex-list:character<span class="Special"> &lt;- </span>next <span class="Constant">1</span>:address:duplex-list:character
-    <span class="Constant">6</span>:character<span class="Special"> &lt;- </span>get *<span class="Constant">5</span>:address:duplex-list:character, <span class="Constant">value:offset</span>
-    <span class="Constant">7</span>:address:duplex-list:character<span class="Special"> &lt;- </span>next <span class="Constant">5</span>:address:duplex-list:character
+    <span class="Constant">4</span>:character<span class="Special"> &lt;- </span>get *<span class="Constant">1</span>:address:shared:duplex-list:character, <span class="Constant">value:offset</span>
+    <span class="Constant">5</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>next <span class="Constant">1</span>:address:shared:duplex-list:character
+    <span class="Constant">6</span>:character<span class="Special"> &lt;- </span>get *<span class="Constant">5</span>:address:shared:duplex-list:character, <span class="Constant">value:offset</span>
+    <span class="Constant">7</span>:address:shared:duplex-list:character<span class="Special"> &lt;- </span>next <span class="Constant">5</span>:address:shared:duplex-list:character
   ]
   memory-should-contain [
     <span class="Constant">4</span><span class="Special"> &lt;- </span><span class="Constant">13</span>
@@ -489,20 +489,20 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 ]
 
 <span class="Comment"># insert list beginning at 'new' after 'in'</span>
-<span class="muRecipe">recipe</span> insert-range in:address:duplex-list:_elem, start:address:duplex-list:_elem/contained-in:in<span class="muRecipe"> -&gt; </span>in:address:duplex-list:_elem [
+<span class="muRecipe">recipe</span> insert-range in:address:shared:duplex-list:_elem, start:address:shared:duplex-list:_elem/contained-in:in<span class="muRecipe"> -&gt; </span>in:address:shared:duplex-list:_elem [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   <span class="muControl">reply-unless</span> in
   <span class="muControl">reply-unless</span> start
-  end:address:duplex-list:_elem<span class="Special"> &lt;- </span>copy start
+  end:address:shared:duplex-list:_elem<span class="Special"> &lt;- </span>copy start
   <span class="Delimiter">{</span>
-    next:address:duplex-list:_elem<span class="Special"> &lt;- </span>next end/insert-range
+    next:address:shared:duplex-list:_elem<span class="Special"> &lt;- </span>next end/insert-range
     <span class="muControl">break-unless</span> next
     end<span class="Special"> &lt;- </span>copy next
     <span class="muControl">loop</span>
   <span class="Delimiter">}</span>
-  next:address:duplex-list:_elem<span class="Special"> &lt;- </span>next in
-  dest:address:address:duplex-list:_elem<span class="Special"> &lt;- </span>get-address *end, <span class="Constant">next:offset</span>
+  next:address:shared:duplex-list:_elem<span class="Special"> &lt;- </span>next in
+  dest:address:address:shared:duplex-list:_elem<span class="Special"> &lt;- </span>get-address *end, <span class="Constant">next:offset</span>
   *dest<span class="Special"> &lt;- </span>copy next
   <span class="Delimiter">{</span>
     <span class="muControl">break-unless</span> next
@@ -515,23 +515,23 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   *dest<span class="Special"> &lt;- </span>copy in
 ]
 
-<span class="muRecipe">recipe</span> append in:address:duplex-list:_elem, new:address:duplex-list:_elem/contained-in:in<span class="muRecipe"> -&gt; </span>in:address:duplex-list:_elem [
+<span class="muRecipe">recipe</span> append in:address:shared:duplex-list:_elem, new:address:shared:duplex-list:_elem/contained-in:in<span class="muRecipe"> -&gt; </span>in:address:shared:duplex-list:_elem [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
-  last:address:duplex-list:_elem<span class="Special"> &lt;- </span>last in
-  dest:address:address:duplex-list:_elem<span class="Special"> &lt;- </span>get-address *last, <span class="Constant">next:offset</span>
+  last:address:shared:duplex-list:_elem<span class="Special"> &lt;- </span>last in
+  dest:address:address:shared:duplex-list:_elem<span class="Special"> &lt;- </span>get-address *last, <span class="Constant">next:offset</span>
   *dest<span class="Special"> &lt;- </span>copy new
   <span class="muControl">reply-unless</span> new
   dest<span class="Special"> &lt;- </span>get-address *new, <span class="Constant">prev:offset</span>
   *dest<span class="Special"> &lt;- </span>copy last
 ]
 
-<span class="muRecipe">recipe</span> last in:address:duplex-list:_elem<span class="muRecipe"> -&gt; </span>result:address:duplex-list:_elem [
+<span class="muRecipe">recipe</span> last in:address:shared:duplex-list:_elem<span class="muRecipe"> -&gt; </span>result:address:shared:duplex-list:_elem [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   result<span class="Special"> &lt;- </span>copy in
   <span class="Delimiter">{</span>
-    next:address:duplex-list:_elem<span class="Special"> &lt;- </span>next result
+    next:address:shared:duplex-list:_elem<span class="Special"> &lt;- </span>next result
     <span class="muControl">break-unless</span> next
     result<span class="Special"> &lt;- </span>copy next
     <span class="muControl">loop</span>
@@ -539,7 +539,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 ]
 
 <span class="Comment"># helper for debugging</span>
-<span class="muRecipe">recipe</span> dump-from x:address:duplex-list:_elem [
+<span class="muRecipe">recipe</span> dump-from x:address:shared:duplex-list:_elem [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   $print x, <span class="Constant">[: ]</span>
diff --git a/html/076stream.mu.html b/html/076stream.mu.html
index 91861d7d..ec37fd4b 100644
--- a/html/076stream.mu.html
+++ b/html/076stream.mu.html
@@ -32,41 +32,41 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="Comment"># new type to help incrementally read texts (arrays of characters)</span>
 <span class="muData">container</span> stream [
   index:number
-  data:address:array:character
+  data:address:shared:array:character
 ]
 
-<span class="muRecipe">recipe</span> new-stream s:address:array:character<span class="muRecipe"> -&gt; </span>result:address:stream [
+<span class="muRecipe">recipe</span> new-stream s:address:shared:array:character<span class="muRecipe"> -&gt; </span>result:address:shared:stream [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   result<span class="Special"> &lt;- </span>new <span class="Constant">stream:type</span>
   i:address:number<span class="Special"> &lt;- </span>get-address *result, <span class="Constant">index:offset</span>
   *i<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
-  d:address:address:array:character<span class="Special"> &lt;- </span>get-address *result, <span class="Constant">data:offset</span>
+  d:address:address:shared:array:character<span class="Special"> &lt;- </span>get-address *result, <span class="Constant">data:offset</span>
   *d<span class="Special"> &lt;- </span>copy s
 ]
 
-<span class="muRecipe">recipe</span> rewind-stream in:address:stream<span class="muRecipe"> -&gt; </span>in:address:stream [
+<span class="muRecipe">recipe</span> rewind-stream in:address:shared:stream<span class="muRecipe"> -&gt; </span>in:address:shared:stream [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   x:address:number<span class="Special"> &lt;- </span>get-address *in, <span class="Constant">index:offset</span>
   *x<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
 ]
 
-<span class="muRecipe">recipe</span> read-line in:address:stream<span class="muRecipe"> -&gt; </span>result:address:array:character, in:address:stream [
+<span class="muRecipe">recipe</span> read-line in:address:shared:stream<span class="muRecipe"> -&gt; </span>result:address:shared:array:character, in:address:shared:stream [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   idx:address:number<span class="Special"> &lt;- </span>get-address *in, <span class="Constant">index:offset</span>
-  s:address:array:character<span class="Special"> &lt;- </span>get *in, <span class="Constant">data:offset</span>
+  s:address:shared:array:character<span class="Special"> &lt;- </span>get *in, <span class="Constant">data:offset</span>
   next-idx:number<span class="Special"> &lt;- </span>find-next s, <span class="Constant">10/newline</span>, *idx
-  result<span class="Special"> &lt;- </span>copy s, *idx, next-idx
+  result<span class="Special"> &lt;- </span>copy-range s, *idx, next-idx
   *idx<span class="Special"> &lt;- </span>add next-idx, <span class="Constant">1</span>  <span class="Comment"># skip newline</span>
 ]
 
-<span class="muRecipe">recipe</span> end-of-stream? in:address:stream<span class="muRecipe"> -&gt; </span>result:boolean [
+<span class="muRecipe">recipe</span> end-of-stream? in:address:shared:stream<span class="muRecipe"> -&gt; </span>result:boolean [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   idx:number<span class="Special"> &lt;- </span>get *in, <span class="Constant">index:offset</span>
-  s:address:array:character<span class="Special"> &lt;- </span>get *in, <span class="Constant">data:offset</span>
+  s:address:shared:array:character<span class="Special"> &lt;- </span>get *in, <span class="Constant">data:offset</span>
   len:number<span class="Special"> &lt;- </span>length *s
   result<span class="Special"> &lt;- </span>greater-or-equal idx, len
 ]
diff --git a/html/080display.cc.html b/html/080display.cc.html
index 88a10a41..6e605255 100644
--- a/html/080display.cc.html
+++ b/html/080display.cc.html
@@ -14,7 +14,6 @@ pre { white-space: pre-wrap; font-family: monospace; color: #eeeeee; background-
 body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 * { font-size: 1.05em; }
 .cSpecial { color: #008000; }
-.CommentedCode { color: #6c6c6c; }
 .Constant { color: #00a0a0; }
 .Comment { color: #9090ff; }
 .Delimiter { color: #a04060; }
@@ -447,7 +446,6 @@ case CHECK_FOR_INTERACTION: <span class="Delimiter">{</span>
     products<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">).</span>push_back<span class="Delimiter">(</span><span class="Comment">/*</span><span class="Comment">text event</span><span class="Comment">*/</span><span class="Constant">0</span><span class="Delimiter">);</span>
     if <span class="Delimiter">(</span>event<span class="Delimiter">.</span>key == TB_KEY_CTRL_C<span class="Delimiter">)</span> <span class="Delimiter">{</span>
       tb_shutdown<span class="Delimiter">();</span>
-<span class="CommentedCode">//?       LOG &lt;&lt; &quot;exit\n&quot;;</span>
       exit<span class="Delimiter">(</span><span class="Constant">1</span><span class="Delimiter">);</span>
     <span class="Delimiter">}</span>
     if <span class="Delimiter">(</span>event<span class="Delimiter">.</span>key == TB_KEY_BACKSPACE2<span class="Delimiter">)</span> event<span class="Delimiter">.</span>key = TB_KEY_BACKSPACE<span class="Delimiter">;</span>
diff --git a/html/081print.mu.html b/html/081print.mu.html
index 7bfdc7dc..4a25e071 100644
--- a/html/081print.mu.html
+++ b/html/081print.mu.html
@@ -20,6 +20,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 .Comment { color: #9090ff; }
 .Constant { color: #00a0a0; }
 .Special { color: #ff6060; }
+.CommentedCode { color: #6c6c6c; }
 .Delimiter { color: #a04060; }
 -->
 </style>
@@ -40,7 +41,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   num-columns:number
   cursor-row:number
   cursor-column:number
-  data:address:array:screen-cell
+  data:address:shared:array:screen-cell
 ]
 
 <span class="muData">container</span> screen-cell [
@@ -48,7 +49,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   color:number
 ]
 
-<span class="muRecipe">recipe</span> new-fake-screen w:number, h:number<span class="muRecipe"> -&gt; </span>result:address:screen [
+<span class="muRecipe">recipe</span> new-fake-screen w:number, h:number<span class="muRecipe"> -&gt; </span>result:address:shared:screen [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   result<span class="Special"> &lt;- </span>new <span class="Constant">screen:type</span>
@@ -61,19 +62,19 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   column:address:number<span class="Special"> &lt;- </span>get-address *result, <span class="Constant">cursor-column:offset</span>
   *column<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
   bufsize:number<span class="Special"> &lt;- </span>multiply *width, *height
-  buf:address:address:array:screen-cell<span class="Special"> &lt;- </span>get-address *result, <span class="Constant">data:offset</span>
+  buf:address:address:shared:array:screen-cell<span class="Special"> &lt;- </span>get-address *result, <span class="Constant">data:offset</span>
   *buf<span class="Special"> &lt;- </span>new <span class="Constant">screen-cell:type</span>, bufsize
   result<span class="Special"> &lt;- </span>clear-screen result
 ]
 
-<span class="muRecipe">recipe</span> clear-screen screen:address:screen<span class="muRecipe"> -&gt; </span>screen:address:screen [
+<span class="muRecipe">recipe</span> clear-screen screen:address:shared:screen<span class="muRecipe"> -&gt; </span>screen:address:shared:screen [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   <span class="Comment"># if x exists</span>
   <span class="Delimiter">{</span>
     <span class="muControl">break-unless</span> screen
     <span class="Comment"># clear fake screen</span>
-    buf:address:array:screen-cell<span class="Special"> &lt;- </span>get *screen, <span class="Constant">data:offset</span>
+    buf:address:shared:array:screen-cell<span class="Special"> &lt;- </span>get *screen, <span class="Constant">data:offset</span>
     max:number<span class="Special"> &lt;- </span>length *buf
     i:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
     <span class="Delimiter">{</span>
@@ -98,9 +99,9 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   clear-display
 ]
 
-<span class="muRecipe">recipe</span> sync-screen screen:address:screen<span class="muRecipe"> -&gt; </span>screen:address:screen [
+<span class="muRecipe">recipe</span> sync-screen screen:address:shared:screen<span class="muRecipe"> -&gt; </span>screen:address:shared:screen [
   <span class="Constant">local-scope</span>
-  screen:address:screen<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
+  <span class="Constant">load-ingredients</span>
   <span class="Delimiter">{</span>
     <span class="muControl">break-if</span> screen
     sync-display
@@ -108,11 +109,11 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   <span class="Comment"># do nothing for fake screens</span>
 ]
 
-<span class="muRecipe">recipe</span> fake-screen-is-empty? screen:address:screen<span class="muRecipe"> -&gt; </span>result:boolean [
+<span class="muRecipe">recipe</span> fake-screen-is-empty? screen:address:shared:screen<span class="muRecipe"> -&gt; </span>result:boolean [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   <span class="muControl">reply-unless</span> screen, <span class="Constant">1/true</span>
-  buf:address:array:screen-cell<span class="Special"> &lt;- </span>get *screen, <span class="Constant">data:offset</span>
+  buf:address:shared:array:screen-cell<span class="Special"> &lt;- </span>get *screen, <span class="Constant">data:offset</span>
   i:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
   len:number<span class="Special"> &lt;- </span>length *buf
   <span class="Delimiter">{</span>
@@ -128,7 +129,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   <span class="muControl">reply</span> <span class="Constant">1/true</span>
 ]
 
-<span class="muRecipe">recipe</span> print screen:address:screen, c:character<span class="muRecipe"> -&gt; </span>screen:address:screen [
+<span class="muRecipe">recipe</span> print screen:address:shared:screen, c:character<span class="muRecipe"> -&gt; </span>screen:address:shared:screen [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   color:number, color-found?:boolean<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
@@ -161,6 +162,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     <span class="muControl">reply-unless</span> legal?
     legal?<span class="Special"> &lt;- </span>lesser-than *column, width
     <span class="muControl">reply-unless</span> legal?
+<span class="CommentedCode">#?     $print [print-character (], *row, [, ], *column, [): ], c, 10/newline</span>
     <span class="Comment"># special-case: newline</span>
     <span class="Delimiter">{</span>
       newline?:boolean<span class="Special"> &lt;- </span>equal c, <span class="Constant">10/newline</span>
@@ -179,7 +181,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     <span class="Comment"># save character in fake screen</span>
     index:number<span class="Special"> &lt;- </span>multiply *row, width
     index<span class="Special"> &lt;- </span>add index, *column
-    buf:address:array:screen-cell<span class="Special"> &lt;- </span>get *screen, <span class="Constant">data:offset</span>
+    buf:address:shared:array:screen-cell<span class="Special"> &lt;- </span>get *screen, <span class="Constant">data:offset</span>
     len:number<span class="Special"> &lt;- </span>length *buf
     <span class="Comment"># special-case: backspace</span>
     <span class="Delimiter">{</span>
@@ -220,10 +222,11 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> print-character-at-top-left [
   run [
-    <span class="Constant">1</span>:address:screen<span class="Special"> &lt;- </span>new-fake-screen <span class="Constant">3/width</span>, <span class="Constant">2/height</span>
-    <span class="Constant">1</span>:address:screen<span class="Special"> &lt;- </span>print <span class="Constant">1</span>:address:screen, <span class="Constant">97</span>  <span class="Comment"># 'a'</span>
-    <span class="Constant">2</span>:address:array:screen-cell<span class="Special"> &lt;- </span>get *<span class="Constant">1</span>:address:screen, <span class="Constant">data:offset</span>
-    <span class="Constant">3</span>:array:screen-cell<span class="Special"> &lt;- </span>copy *<span class="Constant">2</span>:address:array:screen-cell
+    <span class="Constant">1</span>:address:shared:screen<span class="Special"> &lt;- </span>new-fake-screen <span class="Constant">3/width</span>, <span class="Constant">2/height</span>
+    <span class="Constant">11</span>:character<span class="Special"> &lt;- </span>copy <span class="Constant">97/a</span>
+    <span class="Constant">1</span>:address:shared:screen<span class="Special"> &lt;- </span>print <span class="Constant">1</span>:address:shared:screen, <span class="Constant">11</span>:character/a
+    <span class="Constant">2</span>:address:shared:array:screen-cell<span class="Special"> &lt;- </span>get *<span class="Constant">1</span>:address:shared:screen, <span class="Constant">data:offset</span>
+    <span class="Constant">3</span>:array:screen-cell<span class="Special"> &lt;- </span>copy *<span class="Constant">2</span>:address:shared:array:screen-cell
   ]
   memory-should-contain [
     <span class="Constant">3</span><span class="Special"> &lt;- </span><span class="Constant">6</span>  <span class="Comment"># width*height</span>
@@ -235,10 +238,11 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> print-character-in-color [
   run [
-    <span class="Constant">1</span>:address:screen<span class="Special"> &lt;- </span>new-fake-screen <span class="Constant">3/width</span>, <span class="Constant">2/height</span>
-    <span class="Constant">1</span>:address:screen<span class="Special"> &lt;- </span>print <span class="Constant">1</span>:address:screen, <span class="Constant">97/a</span>, <span class="Constant">1/red</span>
-    <span class="Constant">2</span>:address:array:screen-cell<span class="Special"> &lt;- </span>get *<span class="Constant">1</span>:address:screen, <span class="Constant">data:offset</span>
-    <span class="Constant">3</span>:array:screen-cell<span class="Special"> &lt;- </span>copy *<span class="Constant">2</span>:address:array:screen-cell
+    <span class="Constant">1</span>:address:shared:screen<span class="Special"> &lt;- </span>new-fake-screen <span class="Constant">3/width</span>, <span class="Constant">2/height</span>
+    <span class="Constant">11</span>:character<span class="Special"> &lt;- </span>copy <span class="Constant">97/a</span>
+    <span class="Constant">1</span>:address:shared:screen<span class="Special"> &lt;- </span>print <span class="Constant">1</span>:address:shared:screen, <span class="Constant">11</span>:character/a, <span class="Constant">1/red</span>
+    <span class="Constant">2</span>:address:shared:array:screen-cell<span class="Special"> &lt;- </span>get *<span class="Constant">1</span>:address:shared:screen, <span class="Constant">data:offset</span>
+    <span class="Constant">3</span>:array:screen-cell<span class="Special"> &lt;- </span>copy *<span class="Constant">2</span>:address:shared:array:screen-cell
   ]
   memory-should-contain [
     <span class="Constant">3</span><span class="Special"> &lt;- </span><span class="Constant">6</span>  <span class="Comment"># width*height</span>
@@ -250,12 +254,14 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> print-backspace-character [
   run [
-    <span class="Constant">1</span>:address:screen<span class="Special"> &lt;- </span>new-fake-screen <span class="Constant">3/width</span>, <span class="Constant">2/height</span>
-    <span class="Constant">1</span>:address:screen<span class="Special"> &lt;- </span>print <span class="Constant">1</span>:address:screen, <span class="Constant">97</span>  <span class="Comment"># 'a'</span>
-    <span class="Constant">1</span>:address:screen<span class="Special"> &lt;- </span>print <span class="Constant">1</span>:address:screen, <span class="Constant">8</span>  <span class="Comment"># backspace</span>
-    <span class="Constant">2</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">1</span>:address:screen, <span class="Constant">cursor-column:offset</span>
-    <span class="Constant">3</span>:address:array:screen-cell<span class="Special"> &lt;- </span>get *<span class="Constant">1</span>:address:screen, <span class="Constant">data:offset</span>
-    <span class="Constant">4</span>:array:screen-cell<span class="Special"> &lt;- </span>copy *<span class="Constant">3</span>:address:array:screen-cell
+    <span class="Constant">1</span>:address:shared:screen<span class="Special"> &lt;- </span>new-fake-screen <span class="Constant">3/width</span>, <span class="Constant">2/height</span>
+    <span class="Constant">11</span>:character<span class="Special"> &lt;- </span>copy <span class="Constant">97/a</span>
+    <span class="Constant">1</span>:address:shared:screen<span class="Special"> &lt;- </span>print <span class="Constant">1</span>:address:shared:screen, <span class="Constant">11</span>:character/a
+    <span class="Constant">12</span>:character<span class="Special"> &lt;- </span>copy <span class="Constant">8/backspace</span>
+    <span class="Constant">1</span>:address:shared:screen<span class="Special"> &lt;- </span>print <span class="Constant">1</span>:address:shared:screen, <span class="Constant">12</span>:character/backspace
+    <span class="Constant">2</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">1</span>:address:shared:screen, <span class="Constant">cursor-column:offset</span>
+    <span class="Constant">3</span>:address:shared:array:screen-cell<span class="Special"> &lt;- </span>get *<span class="Constant">1</span>:address:shared:screen, <span class="Constant">data:offset</span>
+    <span class="Constant">4</span>:array:screen-cell<span class="Special"> &lt;- </span>copy *<span class="Constant">3</span>:address:shared:array:screen-cell
   ]
   memory-should-contain [
     <span class="Constant">2</span><span class="Special"> &lt;- </span><span class="Constant">0</span>  <span class="Comment"># cursor column</span>
@@ -268,13 +274,16 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> print-extra-backspace-character [
   run [
-    <span class="Constant">1</span>:address:screen<span class="Special"> &lt;- </span>new-fake-screen <span class="Constant">3/width</span>, <span class="Constant">2/height</span>
-    <span class="Constant">1</span>:address:screen<span class="Special"> &lt;- </span>print <span class="Constant">1</span>:address:screen, <span class="Constant">97</span>  <span class="Comment"># 'a'</span>
-    <span class="Constant">1</span>:address:screen<span class="Special"> &lt;- </span>print <span class="Constant">1</span>:address:screen, <span class="Constant">8</span>  <span class="Comment"># backspace</span>
-    <span class="Constant">1</span>:address:screen<span class="Special"> &lt;- </span>print <span class="Constant">1</span>:address:screen, <span class="Constant">8</span>  <span class="Comment"># backspace</span>
-    <span class="Constant">2</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">1</span>:address:screen, <span class="Constant">cursor-column:offset</span>
-    <span class="Constant">3</span>:address:array:screen-cell<span class="Special"> &lt;- </span>get *<span class="Constant">1</span>:address:screen, <span class="Constant">data:offset</span>
-    <span class="Constant">4</span>:array:screen-cell<span class="Special"> &lt;- </span>copy *<span class="Constant">3</span>:address:array:screen-cell
+    <span class="Constant">1</span>:address:shared:screen<span class="Special"> &lt;- </span>new-fake-screen <span class="Constant">3/width</span>, <span class="Constant">2/height</span>
+    <span class="Constant">11</span>:character<span class="Special"> &lt;- </span>copy <span class="Constant">97/a</span>
+    <span class="Constant">1</span>:address:shared:screen<span class="Special"> &lt;- </span>print <span class="Constant">1</span>:address:shared:screen, <span class="Constant">11</span>:character/a
+    <span class="Constant">12</span>:character<span class="Special"> &lt;- </span>copy <span class="Constant">8/backspace</span>
+    <span class="Constant">1</span>:address:shared:screen<span class="Special"> &lt;- </span>print <span class="Constant">1</span>:address:shared:screen, <span class="Constant">12</span>:character/backspace
+    <span class="Constant">12</span>:character<span class="Special"> &lt;- </span>copy <span class="Constant">8/backspace</span>
+    <span class="Constant">1</span>:address:shared:screen<span class="Special"> &lt;- </span>print <span class="Constant">1</span>:address:shared:screen, <span class="Constant">12</span>:character/backspace
+    <span class="Constant">2</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">1</span>:address:shared:screen, <span class="Constant">cursor-column:offset</span>
+    <span class="Constant">3</span>:address:shared:array:screen-cell<span class="Special"> &lt;- </span>get *<span class="Constant">1</span>:address:shared:screen, <span class="Constant">data:offset</span>
+    <span class="Constant">4</span>:array:screen-cell<span class="Special"> &lt;- </span>copy *<span class="Constant">3</span>:address:shared:array:screen-cell
   ]
   memory-should-contain [
     <span class="Constant">2</span><span class="Special"> &lt;- </span><span class="Constant">0</span>  <span class="Comment"># cursor column</span>
@@ -287,13 +296,16 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> print-character-at-right-margin [
   run [
-    <span class="Constant">1</span>:address:screen<span class="Special"> &lt;- </span>new-fake-screen <span class="Constant">2/width</span>, <span class="Constant">2/height</span>
-    <span class="Constant">1</span>:address:screen<span class="Special"> &lt;- </span>print <span class="Constant">1</span>:address:screen, <span class="Constant">97</span>  <span class="Comment"># 'a'</span>
-    <span class="Constant">1</span>:address:screen<span class="Special"> &lt;- </span>print <span class="Constant">1</span>:address:screen, <span class="Constant">98</span>  <span class="Comment"># 'b'</span>
-    <span class="Constant">1</span>:address:screen<span class="Special"> &lt;- </span>print <span class="Constant">1</span>:address:screen, <span class="Constant">99</span>  <span class="Comment"># 'c'</span>
-    <span class="Constant">2</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">1</span>:address:screen, <span class="Constant">cursor-column:offset</span>
-    <span class="Constant">3</span>:address:array:screen-cell<span class="Special"> &lt;- </span>get *<span class="Constant">1</span>:address:screen, <span class="Constant">data:offset</span>
-    <span class="Constant">4</span>:array:screen-cell<span class="Special"> &lt;- </span>copy *<span class="Constant">3</span>:address:array:screen-cell
+    <span class="Constant">1</span>:address:shared:screen<span class="Special"> &lt;- </span>new-fake-screen <span class="Constant">2/width</span>, <span class="Constant">2/height</span>
+    <span class="Constant">11</span>:character<span class="Special"> &lt;- </span>copy <span class="Constant">97/a</span>
+    <span class="Constant">1</span>:address:shared:screen<span class="Special"> &lt;- </span>print <span class="Constant">1</span>:address:shared:screen, <span class="Constant">11</span>:character/a
+    <span class="Constant">12</span>:character<span class="Special"> &lt;- </span>copy <span class="Constant">98/b</span>
+    <span class="Constant">1</span>:address:shared:screen<span class="Special"> &lt;- </span>print <span class="Constant">1</span>:address:shared:screen, <span class="Constant">12</span>:character/b
+    <span class="Constant">13</span>:character<span class="Special"> &lt;- </span>copy <span class="Constant">99/b</span>
+    <span class="Constant">1</span>:address:shared:screen<span class="Special"> &lt;- </span>print <span class="Constant">1</span>:address:shared:screen, <span class="Constant">13</span>:character/c
+    <span class="Constant">2</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">1</span>:address:shared:screen, <span class="Constant">cursor-column:offset</span>
+    <span class="Constant">3</span>:address:shared:array:screen-cell<span class="Special"> &lt;- </span>get *<span class="Constant">1</span>:address:shared:screen, <span class="Constant">data:offset</span>
+    <span class="Constant">4</span>:array:screen-cell<span class="Special"> &lt;- </span>copy *<span class="Constant">3</span>:address:shared:array:screen-cell
   ]
   memory-should-contain [
     <span class="Constant">2</span><span class="Special"> &lt;- </span><span class="Constant">1</span>  <span class="Comment"># cursor column</span>
@@ -308,13 +320,15 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> print-newline-character [
   run [
-    <span class="Constant">1</span>:address:screen<span class="Special"> &lt;- </span>new-fake-screen <span class="Constant">3/width</span>, <span class="Constant">2/height</span>
-    <span class="Constant">1</span>:address:screen<span class="Special"> &lt;- </span>print <span class="Constant">1</span>:address:screen, <span class="Constant">97</span>  <span class="Comment"># 'a'</span>
-    <span class="Constant">1</span>:address:screen<span class="Special"> &lt;- </span>print <span class="Constant">1</span>:address:screen, <span class="Constant">10/newline</span>
-    <span class="Constant">2</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">1</span>:address:screen, <span class="Constant">cursor-row:offset</span>
-    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">1</span>:address:screen, <span class="Constant">cursor-column:offset</span>
-    <span class="Constant">4</span>:address:array:screen-cell<span class="Special"> &lt;- </span>get *<span class="Constant">1</span>:address:screen, <span class="Constant">data:offset</span>
-    <span class="Constant">5</span>:array:screen-cell<span class="Special"> &lt;- </span>copy *<span class="Constant">4</span>:address:array:screen-cell
+    <span class="Constant">1</span>:address:shared:screen<span class="Special"> &lt;- </span>new-fake-screen <span class="Constant">3/width</span>, <span class="Constant">2/height</span>
+    <span class="Constant">10</span>:character<span class="Special"> &lt;- </span>copy <span class="Constant">10/newline</span>
+    <span class="Constant">11</span>:character<span class="Special"> &lt;- </span>copy <span class="Constant">97/a</span>
+    <span class="Constant">1</span>:address:shared:screen<span class="Special"> &lt;- </span>print <span class="Constant">1</span>:address:shared:screen, <span class="Constant">11</span>:character/a
+    <span class="Constant">1</span>:address:shared:screen<span class="Special"> &lt;- </span>print <span class="Constant">1</span>:address:shared:screen, <span class="Constant">10</span>:character/newline
+    <span class="Constant">2</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">1</span>:address:shared:screen, <span class="Constant">cursor-row:offset</span>
+    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">1</span>:address:shared:screen, <span class="Constant">cursor-column:offset</span>
+    <span class="Constant">4</span>:address:shared:array:screen-cell<span class="Special"> &lt;- </span>get *<span class="Constant">1</span>:address:shared:screen, <span class="Constant">data:offset</span>
+    <span class="Constant">5</span>:array:screen-cell<span class="Special"> &lt;- </span>copy *<span class="Constant">4</span>:address:shared:array:screen-cell
   ]
   memory-should-contain [
     <span class="Constant">2</span><span class="Special"> &lt;- </span><span class="Constant">1</span>  <span class="Comment"># cursor row</span>
@@ -328,12 +342,13 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> print-newline-at-bottom-line [
   run [
-    <span class="Constant">1</span>:address:screen<span class="Special"> &lt;- </span>new-fake-screen <span class="Constant">3/width</span>, <span class="Constant">2/height</span>
-    <span class="Constant">1</span>:address:screen<span class="Special"> &lt;- </span>print <span class="Constant">1</span>:address:screen, <span class="Constant">10/newline</span>
-    <span class="Constant">1</span>:address:screen<span class="Special"> &lt;- </span>print <span class="Constant">1</span>:address:screen, <span class="Constant">10/newline</span>
-    <span class="Constant">1</span>:address:screen<span class="Special"> &lt;- </span>print <span class="Constant">1</span>:address:screen, <span class="Constant">10/newline</span>
-    <span class="Constant">2</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">1</span>:address:screen, <span class="Constant">cursor-row:offset</span>
-    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">1</span>:address:screen, <span class="Constant">cursor-column:offset</span>
+    <span class="Constant">1</span>:address:shared:screen<span class="Special"> &lt;- </span>new-fake-screen <span class="Constant">3/width</span>, <span class="Constant">2/height</span>
+    <span class="Constant">10</span>:character<span class="Special"> &lt;- </span>copy <span class="Constant">10/newline</span>
+    <span class="Constant">1</span>:address:shared:screen<span class="Special"> &lt;- </span>print <span class="Constant">1</span>:address:shared:screen, <span class="Constant">10</span>:character/newline
+    <span class="Constant">1</span>:address:shared:screen<span class="Special"> &lt;- </span>print <span class="Constant">1</span>:address:shared:screen, <span class="Constant">10</span>:character/newline
+    <span class="Constant">1</span>:address:shared:screen<span class="Special"> &lt;- </span>print <span class="Constant">1</span>:address:shared:screen, <span class="Constant">10</span>:character/newline
+    <span class="Constant">2</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">1</span>:address:shared:screen, <span class="Constant">cursor-row:offset</span>
+    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">1</span>:address:shared:screen, <span class="Constant">cursor-column:offset</span>
   ]
   memory-should-contain [
     <span class="Constant">2</span><span class="Special"> &lt;- </span><span class="Constant">1</span>  <span class="Comment"># cursor row</span>
@@ -343,37 +358,43 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> print-character-at-bottom-right [
   run [
-    <span class="Constant">1</span>:address:screen<span class="Special"> &lt;- </span>new-fake-screen <span class="Constant">2/width</span>, <span class="Constant">2/height</span>
-    <span class="Constant">1</span>:address:screen<span class="Special"> &lt;- </span>print <span class="Constant">1</span>:address:screen, <span class="Constant">10/newline</span>
-    <span class="Constant">1</span>:address:screen<span class="Special"> &lt;- </span>print <span class="Constant">1</span>:address:screen, <span class="Constant">97</span>  <span class="Comment"># 'a'</span>
-    <span class="Constant">1</span>:address:screen<span class="Special"> &lt;- </span>print <span class="Constant">1</span>:address:screen, <span class="Constant">98</span>  <span class="Comment"># 'b'</span>
-    <span class="Constant">1</span>:address:screen<span class="Special"> &lt;- </span>print <span class="Constant">1</span>:address:screen, <span class="Constant">99</span>  <span class="Comment"># 'c'</span>
-    <span class="Constant">1</span>:address:screen<span class="Special"> &lt;- </span>print <span class="Constant">1</span>:address:screen, <span class="Constant">10/newline</span>
-    <span class="Constant">1</span>:address:screen<span class="Special"> &lt;- </span>print <span class="Constant">1</span>:address:screen, <span class="Constant">100</span>  <span class="Comment"># 'd'</span>
-    <span class="Constant">2</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">1</span>:address:screen, <span class="Constant">cursor-row:offset</span>
-    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">1</span>:address:screen, <span class="Constant">cursor-column:offset</span>
-    <span class="Constant">4</span>:address:array:screen-cell<span class="Special"> &lt;- </span>get *<span class="Constant">1</span>:address:screen, <span class="Constant">data:offset</span>
-    <span class="Constant">5</span>:array:screen-cell<span class="Special"> &lt;- </span>copy *<span class="Constant">4</span>:address:array:screen-cell
+    <span class="Constant">1</span>:address:shared:screen<span class="Special"> &lt;- </span>new-fake-screen <span class="Constant">2/width</span>, <span class="Constant">2/height</span>
+    <span class="Constant">10</span>:character<span class="Special"> &lt;- </span>copy <span class="Constant">10/newline</span>
+    <span class="Constant">1</span>:address:shared:screen<span class="Special"> &lt;- </span>print <span class="Constant">1</span>:address:shared:screen, <span class="Constant">10</span>:character/newline
+    <span class="Constant">11</span>:character<span class="Special"> &lt;- </span>copy <span class="Constant">97/a</span>
+    <span class="Constant">1</span>:address:shared:screen<span class="Special"> &lt;- </span>print <span class="Constant">1</span>:address:shared:screen, <span class="Constant">11</span>:character/a
+    <span class="Constant">12</span>:character<span class="Special"> &lt;- </span>copy <span class="Constant">98/b</span>
+    <span class="Constant">1</span>:address:shared:screen<span class="Special"> &lt;- </span>print <span class="Constant">1</span>:address:shared:screen, <span class="Constant">12</span>:character/b
+    <span class="Constant">13</span>:character<span class="Special"> &lt;- </span>copy <span class="Constant">99/c</span>
+    <span class="Constant">1</span>:address:shared:screen<span class="Special"> &lt;- </span>print <span class="Constant">1</span>:address:shared:screen, <span class="Constant">13</span>:character/c
+    <span class="Constant">1</span>:address:shared:screen<span class="Special"> &lt;- </span>print <span class="Constant">1</span>:address:shared:screen, <span class="Constant">10</span>:character/newline
+    <span class="Constant">14</span>:character<span class="Special"> &lt;- </span>copy <span class="Constant">100/d</span>
+    <span class="Constant">1</span>:address:shared:screen<span class="Special"> &lt;- </span>print <span class="Constant">1</span>:address:shared:screen, <span class="Constant">14</span>:character/d
+    <span class="Constant">2</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">1</span>:address:shared:screen, <span class="Constant">cursor-row:offset</span>
+    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">1</span>:address:shared:screen, <span class="Constant">cursor-column:offset</span>
+    <span class="Constant">4</span>:address:shared:array:screen-cell<span class="Special"> &lt;- </span>get *<span class="Constant">1</span>:address:shared:screen, <span class="Constant">data:offset</span>
+    <span class="Constant">20</span>:array:screen-cell<span class="Special"> &lt;- </span>copy *<span class="Constant">4</span>:address:shared:array:screen-cell
   ]
   memory-should-contain [
     <span class="Constant">2</span><span class="Special"> &lt;- </span><span class="Constant">1</span>  <span class="Comment"># cursor row</span>
     <span class="Constant">3</span><span class="Special"> &lt;- </span><span class="Constant">1</span>  <span class="Comment"># cursor column</span>
-    <span class="Constant">5</span><span class="Special"> &lt;- </span><span class="Constant">4</span>  <span class="Comment"># width*height</span>
-    <span class="Constant">6</span><span class="Special"> &lt;- </span><span class="Constant">0</span>  <span class="Comment"># unused</span>
-    <span class="Constant">7</span><span class="Special"> &lt;- </span><span class="Constant">7</span>  <span class="Comment"># white</span>
-    <span class="Constant">8</span><span class="Special"> &lt;- </span><span class="Constant">0</span>  <span class="Comment"># unused</span>
-    <span class="Constant">9</span><span class="Special"> &lt;- </span><span class="Constant">7</span>  <span class="Comment"># white</span>
-    <span class="Constant">10</span><span class="Special"> &lt;- </span><span class="Constant">97</span> <span class="Comment"># 'a'</span>
-    <span class="Constant">11</span><span class="Special"> &lt;- </span><span class="Constant">7</span>  <span class="Comment"># white</span>
-    <span class="Constant">12</span><span class="Special"> &lt;- </span><span class="Constant">100</span>  <span class="Comment"># 'd' over 'b' and 'c' and newline</span>
-    <span class="Constant">13</span><span class="Special"> &lt;- </span><span class="Constant">7</span>  <span class="Comment"># white</span>
-    <span class="Constant">14</span><span class="Special"> &lt;- </span><span class="Constant">0</span>
+    <span class="Constant">20</span><span class="Special"> &lt;- </span><span class="Constant">4</span>  <span class="Comment"># width*height</span>
+    <span class="Constant">21</span><span class="Special"> &lt;- </span><span class="Constant">0</span>  <span class="Comment"># unused</span>
+    <span class="Constant">22</span><span class="Special"> &lt;- </span><span class="Constant">7</span>  <span class="Comment"># white</span>
+    <span class="Constant">23</span><span class="Special"> &lt;- </span><span class="Constant">0</span>  <span class="Comment"># unused</span>
+    <span class="Constant">24</span><span class="Special"> &lt;- </span><span class="Constant">7</span>  <span class="Comment"># white</span>
+    <span class="Constant">25</span><span class="Special"> &lt;- </span><span class="Constant">97</span> <span class="Comment"># 'a'</span>
+    <span class="Constant">26</span><span class="Special"> &lt;- </span><span class="Constant">7</span>  <span class="Comment"># white</span>
+    <span class="Constant">27</span><span class="Special"> &lt;- </span><span class="Constant">100</span>  <span class="Comment"># 'd' over 'b' and 'c' and newline</span>
+    <span class="Constant">28</span><span class="Special"> &lt;- </span><span class="Constant">7</span>  <span class="Comment"># white</span>
+    <span class="Constant">29</span><span class="Special"> &lt;- </span><span class="Constant">0</span>
   ]
 ]
 
-<span class="muRecipe">recipe</span> clear-line screen:address:screen<span class="muRecipe"> -&gt; </span>screen:address:screen [
+<span class="muRecipe">recipe</span> clear-line screen:address:shared:screen<span class="muRecipe"> -&gt; </span>screen:address:shared:screen [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
+  space:character<span class="Special"> &lt;- </span>copy <span class="Constant">0/nul</span>
   <span class="Comment"># if x exists, clear line in fake screen</span>
   <span class="Delimiter">{</span>
     <span class="muControl">break-unless</span> screen
@@ -385,7 +406,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
       right:number<span class="Special"> &lt;- </span>subtract width, <span class="Constant">1</span>
       done?:boolean<span class="Special"> &lt;- </span>greater-or-equal *column, right
       <span class="muControl">break-if</span> done?
-      print screen, <span class="Constant">[ ]</span>  <span class="Comment"># implicitly updates 'column'</span>
+      print screen, space  <span class="Comment"># implicitly updates 'column'</span>
       <span class="muControl">loop</span>
     <span class="Delimiter">}</span>
     <span class="Comment"># now back to where the cursor was</span>
@@ -396,7 +417,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   clear-line-on-display
 ]
 
-<span class="muRecipe">recipe</span> cursor-position screen:address:screen<span class="muRecipe"> -&gt; </span>row:number, column:number [
+<span class="muRecipe">recipe</span> cursor-position screen:address:shared:screen<span class="muRecipe"> -&gt; </span>row:number, column:number [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   <span class="Comment"># if x exists, lookup cursor in fake screen</span>
@@ -409,7 +430,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   row, column<span class="Special"> &lt;- </span>cursor-position-on-display
 ]
 
-<span class="muRecipe">recipe</span> move-cursor screen:address:screen, new-row:number, new-column:number<span class="muRecipe"> -&gt; </span>screen:address:screen [
+<span class="muRecipe">recipe</span> move-cursor screen:address:shared:screen, new-row:number, new-column:number<span class="muRecipe"> -&gt; </span>screen:address:shared:screen [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   <span class="Comment"># if x exists, move cursor in fake screen</span>
@@ -427,35 +448,36 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> clear-line-erases-printed-characters [
   run [
-    <span class="Constant">1</span>:address:screen<span class="Special"> &lt;- </span>new-fake-screen <span class="Constant">3/width</span>, <span class="Constant">2/height</span>
+    <span class="Constant">1</span>:address:shared:screen<span class="Special"> &lt;- </span>new-fake-screen <span class="Constant">3/width</span>, <span class="Constant">2/height</span>
     <span class="Comment"># print a character</span>
-    <span class="Constant">1</span>:address:screen<span class="Special"> &lt;- </span>print <span class="Constant">1</span>:address:screen, <span class="Constant">97</span>  <span class="Comment"># 'a'</span>
+    <span class="Constant">10</span>:character<span class="Special"> &lt;- </span>copy <span class="Constant">97/a</span>
+    <span class="Constant">1</span>:address:shared:screen<span class="Special"> &lt;- </span>print <span class="Constant">1</span>:address:shared:screen, <span class="Constant">10</span>:character/a
     <span class="Comment"># move cursor to start of line</span>
-    <span class="Constant">1</span>:address:screen<span class="Special"> &lt;- </span>move-cursor <span class="Constant">1</span>:address:screen, <span class="Constant">0/row</span>, <span class="Constant">0/column</span>
+    <span class="Constant">1</span>:address:shared:screen<span class="Special"> &lt;- </span>move-cursor <span class="Constant">1</span>:address:shared:screen, <span class="Constant">0/row</span>, <span class="Constant">0/column</span>
     <span class="Comment"># clear line</span>
-    <span class="Constant">1</span>:address:screen<span class="Special"> &lt;- </span>clear-line <span class="Constant">1</span>:address:screen
-    <span class="Constant">2</span>:address:array:screen-cell<span class="Special"> &lt;- </span>get *<span class="Constant">1</span>:address:screen, <span class="Constant">data:offset</span>
-    <span class="Constant">3</span>:array:screen-cell<span class="Special"> &lt;- </span>copy *<span class="Constant">2</span>:address:array:screen-cell
+    <span class="Constant">1</span>:address:shared:screen<span class="Special"> &lt;- </span>clear-line <span class="Constant">1</span>:address:shared:screen
+    <span class="Constant">2</span>:address:shared:array:screen-cell<span class="Special"> &lt;- </span>get *<span class="Constant">1</span>:address:shared:screen, <span class="Constant">data:offset</span>
+    <span class="Constant">20</span>:array:screen-cell<span class="Special"> &lt;- </span>copy *<span class="Constant">2</span>:address:shared:array:screen-cell
   ]
   <span class="Comment"># screen should be blank</span>
   memory-should-contain [
-    <span class="Constant">3</span><span class="Special"> &lt;- </span><span class="Constant">6</span>  <span class="Comment"># width*height</span>
-    <span class="Constant">4</span><span class="Special"> &lt;- </span><span class="Constant">0</span>
-    <span class="Constant">5</span><span class="Special"> &lt;- </span><span class="Constant">7</span>
-    <span class="Constant">6</span><span class="Special"> &lt;- </span><span class="Constant">0</span>
-    <span class="Constant">7</span><span class="Special"> &lt;- </span><span class="Constant">7</span>
-    <span class="Constant">8</span><span class="Special"> &lt;- </span><span class="Constant">0</span>
-    <span class="Constant">9</span><span class="Special"> &lt;- </span><span class="Constant">7</span>
-    <span class="Constant">10</span><span class="Special"> &lt;- </span><span class="Constant">0</span>
-    <span class="Constant">11</span><span class="Special"> &lt;- </span><span class="Constant">7</span>
-    <span class="Constant">12</span><span class="Special"> &lt;- </span><span class="Constant">0</span>
-    <span class="Constant">13</span><span class="Special"> &lt;- </span><span class="Constant">7</span>
-    <span class="Constant">14</span><span class="Special"> &lt;- </span><span class="Constant">0</span>
-    <span class="Constant">15</span><span class="Special"> &lt;- </span><span class="Constant">7</span>
+    <span class="Constant">20</span><span class="Special"> &lt;- </span><span class="Constant">6</span>  <span class="Comment"># width*height</span>
+    <span class="Constant">21</span><span class="Special"> &lt;- </span><span class="Constant">0</span>
+    <span class="Constant">22</span><span class="Special"> &lt;- </span><span class="Constant">7</span>
+    <span class="Constant">23</span><span class="Special"> &lt;- </span><span class="Constant">0</span>
+    <span class="Constant">24</span><span class="Special"> &lt;- </span><span class="Constant">7</span>
+    <span class="Constant">25</span><span class="Special"> &lt;- </span><span class="Constant">0</span>
+    <span class="Constant">26</span><span class="Special"> &lt;- </span><span class="Constant">7</span>
+    <span class="Constant">27</span><span class="Special"> &lt;- </span><span class="Constant">0</span>
+    <span class="Constant">28</span><span class="Special"> &lt;- </span><span class="Constant">7</span>
+    <span class="Constant">29</span><span class="Special"> &lt;- </span><span class="Constant">0</span>
+    <span class="Constant">30</span><span class="Special"> &lt;- </span><span class="Constant">7</span>
+    <span class="Constant">31</span><span class="Special"> &lt;- </span><span class="Constant">0</span>
+    <span class="Constant">32</span><span class="Special"> &lt;- </span><span class="Constant">7</span>
   ]
 ]
 
-<span class="muRecipe">recipe</span> cursor-down screen:address:screen<span class="muRecipe"> -&gt; </span>screen:address:screen [
+<span class="muRecipe">recipe</span> cursor-down screen:address:shared:screen<span class="muRecipe"> -&gt; </span>screen:address:shared:screen [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   <span class="Comment"># if x exists, move cursor in fake screen</span>
@@ -476,7 +498,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   move-cursor-down-on-display
 ]
 
-<span class="muRecipe">recipe</span> cursor-up screen:address:screen<span class="muRecipe"> -&gt; </span>screen:address:screen [
+<span class="muRecipe">recipe</span> cursor-up screen:address:shared:screen<span class="muRecipe"> -&gt; </span>screen:address:shared:screen [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   <span class="Comment"># if x exists, move cursor in fake screen</span>
@@ -495,7 +517,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   move-cursor-up-on-display
 ]
 
-<span class="muRecipe">recipe</span> cursor-right screen:address:screen<span class="muRecipe"> -&gt; </span>screen:address:screen [
+<span class="muRecipe">recipe</span> cursor-right screen:address:shared:screen<span class="muRecipe"> -&gt; </span>screen:address:shared:screen [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   <span class="Comment"># if x exists, move cursor in fake screen</span>
@@ -516,7 +538,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   move-cursor-right-on-display
 ]
 
-<span class="muRecipe">recipe</span> cursor-left screen:address:screen<span class="muRecipe"> -&gt; </span>screen:address:screen [
+<span class="muRecipe">recipe</span> cursor-left screen:address:shared:screen<span class="muRecipe"> -&gt; </span>screen:address:shared:screen [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   <span class="Comment"># if x exists, move cursor in fake screen</span>
@@ -535,7 +557,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   move-cursor-left-on-display
 ]
 
-<span class="muRecipe">recipe</span> cursor-to-start-of-line screen:address:screen<span class="muRecipe"> -&gt; </span>screen:address:screen [
+<span class="muRecipe">recipe</span> cursor-to-start-of-line screen:address:shared:screen<span class="muRecipe"> -&gt; </span>screen:address:shared:screen [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   row:number<span class="Special"> &lt;- </span>cursor-position screen
@@ -543,14 +565,14 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   screen<span class="Special"> &lt;- </span>move-cursor screen, row, column
 ]
 
-<span class="muRecipe">recipe</span> cursor-to-next-line screen:address:screen<span class="muRecipe"> -&gt; </span>screen:address:screen [
+<span class="muRecipe">recipe</span> cursor-to-next-line screen:address:shared:screen<span class="muRecipe"> -&gt; </span>screen:address:shared:screen [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   screen<span class="Special"> &lt;- </span>cursor-down screen
   screen<span class="Special"> &lt;- </span>cursor-to-start-of-line screen
 ]
 
-<span class="muRecipe">recipe</span> screen-width screen:address:screen<span class="muRecipe"> -&gt; </span>width:number [
+<span class="muRecipe">recipe</span> screen-width screen:address:shared:screen<span class="muRecipe"> -&gt; </span>width:number [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   <span class="Comment"># if x exists, move cursor in fake screen</span>
@@ -563,7 +585,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   width<span class="Special"> &lt;- </span>display-width
 ]
 
-<span class="muRecipe">recipe</span> screen-height screen:address:screen<span class="muRecipe"> -&gt; </span>height:number [
+<span class="muRecipe">recipe</span> screen-height screen:address:shared:screen<span class="muRecipe"> -&gt; </span>height:number [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   <span class="Comment"># if x exists, move cursor in fake screen</span>
@@ -576,7 +598,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   height<span class="Special"> &lt;- </span>display-height
 ]
 
-<span class="muRecipe">recipe</span> hide-cursor screen:address:screen<span class="muRecipe"> -&gt; </span>screen:address:screen [
+<span class="muRecipe">recipe</span> hide-cursor screen:address:shared:screen<span class="muRecipe"> -&gt; </span>screen:address:shared:screen [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   <span class="Comment"># if x exists (not real display), do nothing</span>
@@ -588,7 +610,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   hide-cursor-on-display
 ]
 
-<span class="muRecipe">recipe</span> show-cursor screen:address:screen<span class="muRecipe"> -&gt; </span>screen:address:screen [
+<span class="muRecipe">recipe</span> show-cursor screen:address:shared:screen<span class="muRecipe"> -&gt; </span>screen:address:shared:screen [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   <span class="Comment"># if x exists (not real display), do nothing</span>
@@ -600,7 +622,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   show-cursor-on-display
 ]
 
-<span class="muRecipe">recipe</span> hide-screen screen:address:screen<span class="muRecipe"> -&gt; </span>screen:address:screen [
+<span class="muRecipe">recipe</span> hide-screen screen:address:shared:screen<span class="muRecipe"> -&gt; </span>screen:address:shared:screen [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   <span class="Comment"># if x exists (not real display), do nothing</span>
@@ -613,7 +635,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   hide-display
 ]
 
-<span class="muRecipe">recipe</span> show-screen screen:address:screen<span class="muRecipe"> -&gt; </span>screen:address:screen [
+<span class="muRecipe">recipe</span> show-screen screen:address:shared:screen<span class="muRecipe"> -&gt; </span>screen:address:shared:screen [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   <span class="Comment"># if x exists (not real display), do nothing</span>
@@ -626,7 +648,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   show-display
 ]
 
-<span class="muRecipe">recipe</span> print screen:address:screen, s:address:array:character<span class="muRecipe"> -&gt; </span>screen:address:screen [
+<span class="muRecipe">recipe</span> print screen:address:shared:screen, s:address:shared:array:character<span class="muRecipe"> -&gt; </span>screen:address:shared:screen [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   color:number, color-found?:boolean<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
@@ -655,11 +677,11 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> print-text-stops-at-right-margin [
   run [
-    <span class="Constant">1</span>:address:screen<span class="Special"> &lt;- </span>new-fake-screen <span class="Constant">3/width</span>, <span class="Constant">2/height</span>
-    <span class="Constant">2</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abcd]</span>
-    <span class="Constant">1</span>:address:screen<span class="Special"> &lt;- </span>print <span class="Constant">1</span>:address:screen, <span class="Constant">2</span>:address:array:character
-    <span class="Constant">3</span>:address:array:screen-cell<span class="Special"> &lt;- </span>get *<span class="Constant">1</span>:address:screen, <span class="Constant">data:offset</span>
-    <span class="Constant">4</span>:array:screen-cell<span class="Special"> &lt;- </span>copy *<span class="Constant">3</span>:address:array:screen-cell
+    <span class="Constant">1</span>:address:shared:screen<span class="Special"> &lt;- </span>new-fake-screen <span class="Constant">3/width</span>, <span class="Constant">2/height</span>
+    <span class="Constant">2</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abcd]</span>
+    <span class="Constant">1</span>:address:shared:screen<span class="Special"> &lt;- </span>print <span class="Constant">1</span>:address:shared:screen, <span class="Constant">2</span>:address:shared:array:character
+    <span class="Constant">3</span>:address:shared:array:screen-cell<span class="Special"> &lt;- </span>get *<span class="Constant">1</span>:address:shared:screen, <span class="Constant">data:offset</span>
+    <span class="Constant">4</span>:array:screen-cell<span class="Special"> &lt;- </span>copy *<span class="Constant">3</span>:address:shared:array:screen-cell
   ]
   memory-should-contain [
     <span class="Constant">4</span><span class="Special"> &lt;- </span><span class="Constant">6</span>  <span class="Comment"># width*height</span>
@@ -673,10 +695,9 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   ]
 ]
 
-<span class="muRecipe">recipe</span> print-integer screen:address:screen, n:number<span class="muRecipe"> -&gt; </span>screen:address:screen [
+<span class="muRecipe">recipe</span> print-integer screen:address:shared:screen, n:number<span class="muRecipe"> -&gt; </span>screen:address:shared:screen [
   <span class="Constant">local-scope</span>
-  screen:address:screen<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
-  n:number<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
+  <span class="Constant">load-ingredients</span>
   color:number, color-found?:boolean<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
   <span class="Delimiter">{</span>
     <span class="Comment"># default color to white</span>
@@ -690,9 +711,48 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     bg-color<span class="Special"> &lt;- </span>copy <span class="Constant">0/black</span>
   <span class="Delimiter">}</span>
   <span class="Comment"># todo: other bases besides decimal</span>
-  s:address:array:character<span class="Special"> &lt;- </span>to-text n
+  s:address:shared:array:character<span class="Special"> &lt;- </span>to-text n
   screen<span class="Special"> &lt;- </span>print screen, s, color, bg-color
 ]
+
+<span class="Comment"># for now, we can only print integers</span>
+<span class="muRecipe">recipe</span> print screen:address:shared:screen, n:number<span class="muRecipe"> -&gt; </span>screen:address:shared:screen [
+  <span class="Constant">local-scope</span>
+  <span class="Constant">load-ingredients</span>
+  color:number, color-found?:boolean<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
+  <span class="Delimiter">{</span>
+    <span class="Comment"># default color to white</span>
+    <span class="muControl">break-if</span> color-found?
+    color<span class="Special"> &lt;- </span>copy <span class="Constant">7/white</span>
+  <span class="Delimiter">}</span>
+  bg-color:number, bg-color-found?:boolean<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
+  <span class="Delimiter">{</span>
+    <span class="Comment"># default bg-color to black</span>
+    <span class="muControl">break-if</span> bg-color-found?
+    bg-color<span class="Special"> &lt;- </span>copy <span class="Constant">0/black</span>
+  <span class="Delimiter">}</span>
+  screen<span class="Special"> &lt;- </span>print-integer screen, n, color, bg-color
+]
+
+<span class="Comment"># addresses</span>
+<span class="muRecipe">recipe</span> print screen:address:shared:screen, n:address:_elem<span class="muRecipe"> -&gt; </span>screen:address:shared:screen [
+  <span class="Constant">local-scope</span>
+  <span class="Constant">load-ingredients</span>
+  color:number, color-found?:boolean<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
+  <span class="Delimiter">{</span>
+    <span class="Comment"># default color to white</span>
+    <span class="muControl">break-if</span> color-found?
+    color<span class="Special"> &lt;- </span>copy <span class="Constant">7/white</span>
+  <span class="Delimiter">}</span>
+  bg-color:number, bg-color-found?:boolean<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
+  <span class="Delimiter">{</span>
+    <span class="Comment"># default bg-color to black</span>
+    <span class="muControl">break-if</span> bg-color-found?
+    bg-color<span class="Special"> &lt;- </span>copy <span class="Constant">0/black</span>
+  <span class="Delimiter">}</span>
+  n2:number<span class="Special"> &lt;- </span>copy n
+  screen<span class="Special"> &lt;- </span>print-integer screen, n2, color, bg-color
+]
 </pre>
 </body>
 </html>
diff --git a/html/082scenario_screen.cc.html b/html/082scenario_screen.cc.html
index 85ef4880..71522122 100644
--- a/html/082scenario_screen.cc.html
+++ b/html/082scenario_screen.cc.html
@@ -44,7 +44,8 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 scenario screen-in-scenario [
   assume-screen <span class="Constant">5</span>/width<span class="Delimiter">,</span> <span class="Constant">3</span>/height
   run [
-    screen:address:screen<span class="Special"> &lt;- </span>print screen:address:screen<span class="Delimiter">,</span> <span class="Constant">97</span>  <span class="Comment"># 'a'</span>
+    <span class="Constant">1</span>:character<span class="Special"> &lt;- </span>copy <span class="Constant">97</span>/a
+    screen:address:shared:screen<span class="Special"> &lt;- </span>print screen:address:shared:screen<span class="Delimiter">,</span> <span class="Constant">1</span>:character/a
   ]
   screen-should-contain [
   <span class="Comment">#  01234</span>
@@ -58,8 +59,10 @@ scenario screen-in-scenario [
 scenario screen-in-scenario-unicode-color [
   assume-screen <span class="Constant">5</span>/width<span class="Delimiter">,</span> <span class="Constant">3</span>/height
   run [
-    screen:address:screen<span class="Special"> &lt;- </span>print screen:address:screen<span class="Delimiter">,</span> <span class="Constant">955</span>/greek-small-lambda<span class="Delimiter">,</span> <span class="Constant">1</span>/red
-    screen:address:screen<span class="Special"> &lt;- </span>print screen:address:screen<span class="Delimiter">,</span> <span class="Constant">97</span>/a
+    <span class="Constant">1</span>:character<span class="Special"> &lt;- </span>copy <span class="Constant">955</span>/greek-small-lambda
+    screen:address:shared:screen<span class="Special"> &lt;- </span>print screen:address:shared:screen<span class="Delimiter">,</span> <span class="Constant">1</span>:character/lambda<span class="Delimiter">,</span> <span class="Constant">1</span>/red
+    <span class="Constant">2</span>:character<span class="Special"> &lt;- </span>copy <span class="Constant">97</span>/a
+    screen:address:shared:screen<span class="Special"> &lt;- </span>print screen:address:shared:screen<span class="Delimiter">,</span> <span class="Constant">2</span>:character/a
   ]
   screen-should-contain [
   <span class="Comment">#  01234</span>
@@ -74,8 +77,10 @@ scenario screen-in-scenario-unicode-color [
 scenario screen-in-scenario-color [
   assume-screen <span class="Constant">5</span>/width<span class="Delimiter">,</span> <span class="Constant">3</span>/height
   run [
-    screen:address:screen<span class="Special"> &lt;- </span>print screen:address:screen<span class="Delimiter">,</span> <span class="Constant">955</span>/greek-small-lambda<span class="Delimiter">,</span> <span class="Constant">1</span>/red
-    screen:address:screen<span class="Special"> &lt;- </span>print screen:address:screen<span class="Delimiter">,</span> <span class="Constant">97</span>/a<span class="Delimiter">,</span> <span class="Constant">7</span>/white
+    <span class="Constant">1</span>:character<span class="Special"> &lt;- </span>copy <span class="Constant">955</span>/greek-small-lambda
+    screen:address:shared:screen<span class="Special"> &lt;- </span>print screen:address:shared:screen<span class="Delimiter">,</span> <span class="Constant">1</span>:character/lambda<span class="Delimiter">,</span> <span class="Constant">1</span>/red
+    <span class="Constant">2</span>:character<span class="Special"> &lt;- </span>copy <span class="Constant">97</span>/a
+    screen:address:shared:screen<span class="Special"> &lt;- </span>print screen:address:shared:screen<span class="Delimiter">,</span> <span class="Constant">2</span>:character/a<span class="Delimiter">,</span> <span class="Constant">7</span>/white
   ]
   <span class="Comment"># screen-should-contain shows everything</span>
   screen-should-contain [
@@ -107,7 +112,8 @@ scenario screen-in-scenario-color [
 scenario screen-in-scenario-error [
   assume-screen <span class="Constant">5</span>/width<span class="Delimiter">,</span> <span class="Constant">3</span>/height
   run [
-    screen:address:screen<span class="Special"> &lt;- </span>print screen:address:screen<span class="Delimiter">,</span> <span class="Constant">97</span>  <span class="Comment"># 'a'</span>
+    <span class="Constant">1</span>:character<span class="Special"> &lt;- </span>copy <span class="Constant">97</span>/a
+    screen:address:shared:screen<span class="Special"> &lt;- </span>print screen:address:shared:screen<span class="Delimiter">,</span> <span class="Constant">1</span>:character/a
   ]
   screen-should-contain [
   <span class="Comment">#  01234</span>
@@ -125,7 +131,8 @@ scenario screen-in-scenario-error [
 scenario screen-in-scenario-color [
   assume-screen <span class="Constant">5</span>/width<span class="Delimiter">,</span> <span class="Constant">3</span>/height
   run [
-    screen:address:screen<span class="Special"> &lt;- </span>print screen:address:screen<span class="Delimiter">,</span> <span class="Constant">97</span>/a<span class="Delimiter">,</span> <span class="Constant">1</span>/red
+    <span class="Constant">1</span>:character<span class="Special"> &lt;- </span>copy <span class="Constant">97</span>/a
+    screen:address:shared:screen<span class="Special"> &lt;- </span>print screen:address:shared:screen<span class="Delimiter">,</span> <span class="Constant">1</span>:character/a<span class="Delimiter">,</span> <span class="Constant">1</span>/red
   ]
   screen-should-contain-in-color <span class="Constant">2</span>/green<span class="Delimiter">,</span> [
   <span class="Comment">#  01234</span>
@@ -174,11 +181,11 @@ Name[r][<span class="Constant">&quot;screen&quot;</span>] = SCREEN<span class="D
 
 <span class="Delimiter">:(before &quot;End Rewrite Instruction(curr, recipe result)&quot;)</span>
 <span class="Comment">// rewrite `assume-screen width, height` to</span>
-<span class="Comment">// `screen:address:screen &lt;- new-fake-screen width, height`</span>
+<span class="Comment">// `screen:address:shared:screen &lt;- new-fake-screen width, height`</span>
 if <span class="Delimiter">(</span>curr<span class="Delimiter">.</span>name == <span class="Constant">&quot;assume-screen&quot;</span><span class="Delimiter">)</span> <span class="Delimiter">{</span>
   curr<span class="Delimiter">.</span>name = <span class="Constant">&quot;new-fake-screen&quot;</span><span class="Delimiter">;</span>
   assert<span class="Delimiter">(</span>curr<span class="Delimiter">.</span>products<span class="Delimiter">.</span>empty<span class="Delimiter">());</span>
-  curr<span class="Delimiter">.</span>products<span class="Delimiter">.</span>push_back<span class="Delimiter">(</span>reagent<span class="Delimiter">(</span><span class="Constant">&quot;screen:address:screen&quot;</span><span class="Delimiter">));</span>
+  curr<span class="Delimiter">.</span>products<span class="Delimiter">.</span>push_back<span class="Delimiter">(</span>reagent<span class="Delimiter">(</span><span class="Constant">&quot;screen:address:shared:screen&quot;</span><span class="Delimiter">));</span>
   curr<span class="Delimiter">.</span>products<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">).</span>set_value<span class="Delimiter">(</span>SCREEN<span class="Delimiter">);</span>
 <span class="Delimiter">}</span>
 
@@ -235,18 +242,18 @@ struct raw_string_stream <span class="Delimiter">{</span>
 <span class="Delimiter">:(code)</span>
 void check_screen<span class="Delimiter">(</span>const string&amp; expected_contents<span class="Delimiter">,</span> const int color<span class="Delimiter">)</span> <span class="Delimiter">{</span>
   assert<span class="Delimiter">(</span>!current_call<span class="Delimiter">().</span>default_space<span class="Delimiter">);</span>  <span class="Comment">// not supported</span>
-  long long int screen_location = get_or_insert<span class="Delimiter">(</span>Memory<span class="Delimiter">,</span> SCREEN<span class="Delimiter">);</span>
+  long long int screen_location = get_or_insert<span class="Delimiter">(</span>Memory<span class="Delimiter">,</span> SCREEN<span class="Delimiter">)</span>+<span class="Comment">/*</span><span class="Comment">skip refcount</span><span class="Comment">*/</span><span class="Constant">1</span><span class="Delimiter">;</span>
   int data_offset = find_element_name<span class="Delimiter">(</span>get<span class="Delimiter">(</span>Type_ordinal<span class="Delimiter">,</span> <span class="Constant">&quot;screen&quot;</span><span class="Delimiter">),</span> <span class="Constant">&quot;data&quot;</span><span class="Delimiter">,</span> <span class="Constant">&quot;&quot;</span><span class="Delimiter">);</span>
   assert<span class="Delimiter">(</span>data_offset &gt;= <span class="Constant">0</span><span class="Delimiter">);</span>
-  long long int screen_data_location = screen_location+data_offset<span class="Delimiter">;</span>  <span class="Comment">// type: address:array:character</span>
-  long long int screen_data_start = get_or_insert<span class="Delimiter">(</span>Memory<span class="Delimiter">,</span> screen_data_location<span class="Delimiter">);</span>  <span class="Comment">// type: array:character</span>
+  long long int screen_data_location = screen_location+data_offset<span class="Delimiter">;</span>  <span class="Comment">// type: address:shared:array:character</span>
+  long long int screen_data_start = get_or_insert<span class="Delimiter">(</span>Memory<span class="Delimiter">,</span> screen_data_location<span class="Delimiter">)</span> + <span class="Comment">/*</span><span class="Comment">skip refcount</span><span class="Comment">*/</span><span class="Constant">1</span><span class="Delimiter">;</span>  <span class="Comment">// type: array:character</span>
   int width_offset = find_element_name<span class="Delimiter">(</span>get<span class="Delimiter">(</span>Type_ordinal<span class="Delimiter">,</span> <span class="Constant">&quot;screen&quot;</span><span class="Delimiter">),</span> <span class="Constant">&quot;num-columns&quot;</span><span class="Delimiter">,</span> <span class="Constant">&quot;&quot;</span><span class="Delimiter">);</span>
   long long int screen_width = get_or_insert<span class="Delimiter">(</span>Memory<span class="Delimiter">,</span> screen_location+width_offset<span class="Delimiter">);</span>
   int height_offset = find_element_name<span class="Delimiter">(</span>get<span class="Delimiter">(</span>Type_ordinal<span class="Delimiter">,</span> <span class="Constant">&quot;screen&quot;</span><span class="Delimiter">),</span> <span class="Constant">&quot;num-rows&quot;</span><span class="Delimiter">,</span> <span class="Constant">&quot;&quot;</span><span class="Delimiter">);</span>
   long long int screen_height = get_or_insert<span class="Delimiter">(</span>Memory<span class="Delimiter">,</span> screen_location+height_offset<span class="Delimiter">);</span>
   raw_string_stream cursor<span class="Delimiter">(</span>expected_contents<span class="Delimiter">);</span>
   <span class="Comment">// todo: too-long expected_contents should fail</span>
-  long long int addr = screen_data_start+<span class="Constant">1</span><span class="Delimiter">;</span>  <span class="Comment">// skip length</span>
+  long long int addr = screen_data_start+<span class="Comment">/*</span><span class="Comment">skip length</span><span class="Comment">*/</span><span class="Constant">1</span><span class="Delimiter">;</span>
   for <span class="Delimiter">(</span>long long int row = <span class="Constant">0</span><span class="Delimiter">;</span> row &lt; screen_height<span class="Delimiter">;</span> ++row<span class="Delimiter">)</span> <span class="Delimiter">{</span>
     cursor<span class="Delimiter">.</span>skip_whitespace_and_comments<span class="Delimiter">();</span>
     if <span class="Delimiter">(</span>cursor<span class="Delimiter">.</span>at_end<span class="Delimiter">())</span> <span class="Identifier">break</span><span class="Delimiter">;</span>
@@ -370,15 +377,15 @@ case _DUMP_SCREEN: <span class="Delimiter">{</span>
 <span class="Delimiter">:(code)</span>
 void dump_screen<span class="Delimiter">()</span> <span class="Delimiter">{</span>
   assert<span class="Delimiter">(</span>!current_call<span class="Delimiter">().</span>default_space<span class="Delimiter">);</span>  <span class="Comment">// not supported</span>
-  long long int screen_location = get_or_insert<span class="Delimiter">(</span>Memory<span class="Delimiter">,</span> SCREEN<span class="Delimiter">);</span>
+  long long int screen_location = get_or_insert<span class="Delimiter">(</span>Memory<span class="Delimiter">,</span> SCREEN<span class="Delimiter">)</span> + <span class="Comment">/*</span><span class="Comment">skip refcount</span><span class="Comment">*/</span><span class="Constant">1</span><span class="Delimiter">;</span>
   int width_offset = find_element_name<span class="Delimiter">(</span>get<span class="Delimiter">(</span>Type_ordinal<span class="Delimiter">,</span> <span class="Constant">&quot;screen&quot;</span><span class="Delimiter">),</span> <span class="Constant">&quot;num-columns&quot;</span><span class="Delimiter">,</span> <span class="Constant">&quot;&quot;</span><span class="Delimiter">);</span>
   long long int screen_width = get_or_insert<span class="Delimiter">(</span>Memory<span class="Delimiter">,</span> screen_location+width_offset<span class="Delimiter">);</span>
   int height_offset = find_element_name<span class="Delimiter">(</span>get<span class="Delimiter">(</span>Type_ordinal<span class="Delimiter">,</span> <span class="Constant">&quot;screen&quot;</span><span class="Delimiter">),</span> <span class="Constant">&quot;num-rows&quot;</span><span class="Delimiter">,</span> <span class="Constant">&quot;&quot;</span><span class="Delimiter">);</span>
   long long int screen_height = get_or_insert<span class="Delimiter">(</span>Memory<span class="Delimiter">,</span> screen_location+height_offset<span class="Delimiter">);</span>
   int data_offset = find_element_name<span class="Delimiter">(</span>get<span class="Delimiter">(</span>Type_ordinal<span class="Delimiter">,</span> <span class="Constant">&quot;screen&quot;</span><span class="Delimiter">),</span> <span class="Constant">&quot;data&quot;</span><span class="Delimiter">,</span> <span class="Constant">&quot;&quot;</span><span class="Delimiter">);</span>
   assert<span class="Delimiter">(</span>data_offset &gt;= <span class="Constant">0</span><span class="Delimiter">);</span>
-  long long int screen_data_location = screen_location+data_offset<span class="Delimiter">;</span>  <span class="Comment">// type: address:array:character</span>
-  long long int screen_data_start = get_or_insert<span class="Delimiter">(</span>Memory<span class="Delimiter">,</span> screen_data_location<span class="Delimiter">);</span>  <span class="Comment">// type: array:character</span>
+  long long int screen_data_location = screen_location+data_offset<span class="Delimiter">;</span>  <span class="Comment">// type: address:shared:array:character</span>
+  long long int screen_data_start = get_or_insert<span class="Delimiter">(</span>Memory<span class="Delimiter">,</span> screen_data_location<span class="Delimiter">)</span> + <span class="Comment">/*</span><span class="Comment">skip refcount</span><span class="Comment">*/</span><span class="Constant">1</span><span class="Delimiter">;</span>  <span class="Comment">// type: array:character</span>
   assert<span class="Delimiter">(</span>get_or_insert<span class="Delimiter">(</span>Memory<span class="Delimiter">,</span> screen_data_start<span class="Delimiter">)</span> == screen_width*screen_height<span class="Delimiter">);</span>
   long long int curr = screen_data_start+<span class="Constant">1</span><span class="Delimiter">;</span>  <span class="Comment">// skip length</span>
   for <span class="Delimiter">(</span>long long int row = <span class="Constant">0</span><span class="Delimiter">;</span> row &lt; screen_height<span class="Delimiter">;</span> ++row<span class="Delimiter">)</span> <span class="Delimiter">{</span>
diff --git a/html/083scenario_screen_test.mu.html b/html/083scenario_screen_test.mu.html
index 2fdd57bc..195d8a79 100644
--- a/html/083scenario_screen_test.mu.html
+++ b/html/083scenario_screen_test.mu.html
@@ -33,7 +33,8 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="muScenario">scenario</span> print-character-at-top-left-2 [
   assume-screen <span class="Constant">3/width</span>, <span class="Constant">2/height</span>
   run [
-    screen:address:screen<span class="Special"> &lt;- </span>print screen:address:screen, <span class="Constant">97/a</span>
+    <span class="Constant">1</span>:character<span class="Special"> &lt;- </span>copy <span class="Constant">97/a</span>
+    screen:address:shared:screen<span class="Special"> &lt;- </span>print screen:address:shared:screen, <span class="Constant">1</span>:character/a
   ]
   screen-should-contain [
    <span class="Constant"> .a  .</span>
@@ -45,11 +46,12 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   assume-screen <span class="Constant">5/width</span>, <span class="Constant">3/height</span>
   run [
     <span class="Comment"># print a character</span>
-    screen:address:screen<span class="Special"> &lt;- </span>print screen:address:screen, <span class="Constant">97/a</span>
+    <span class="Constant">1</span>:character<span class="Special"> &lt;- </span>copy <span class="Constant">97/a</span>
+    screen:address:shared:screen<span class="Special"> &lt;- </span>print screen:address:shared:screen, <span class="Constant">1</span>:character/a
     <span class="Comment"># move cursor to start of line</span>
-    screen:address:screen<span class="Special"> &lt;- </span>move-cursor screen:address:screen, <span class="Constant">0/row</span>, <span class="Constant">0/column</span>
+    screen:address:shared:screen<span class="Special"> &lt;- </span>move-cursor screen:address:shared:screen, <span class="Constant">0/row</span>, <span class="Constant">0/column</span>
     <span class="Comment"># clear line</span>
-    screen:address:screen<span class="Special"> &lt;- </span>clear-line screen:address:screen
+    screen:address:shared:screen<span class="Special"> &lt;- </span>clear-line screen:address:shared:screen
   ]
   screen-should-contain [
    <span class="Constant"> .     .</span>
diff --git a/html/084console.mu.html b/html/084console.mu.html
index 4065e18b..f608bafe 100644
--- a/html/084console.mu.html
+++ b/html/084console.mu.html
@@ -55,31 +55,31 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muData">container</span> console [
   current-event-index:number
-  events:address:array:event
+  events:address:shared:array:event
 ]
 
-<span class="muRecipe">recipe</span> new-fake-console events:address:array:event<span class="muRecipe"> -&gt; </span>result:address:console [
+<span class="muRecipe">recipe</span> new-fake-console events:address:shared:array:event<span class="muRecipe"> -&gt; </span>result:address:shared:console [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
-  result:address:console<span class="Special"> &lt;- </span>new <span class="Constant">console:type</span>
-  buf:address:address:array:event<span class="Special"> &lt;- </span>get-address *result, <span class="Constant">events:offset</span>
+  result:address:shared:console<span class="Special"> &lt;- </span>new <span class="Constant">console:type</span>
+  buf:address:address:shared:array:event<span class="Special"> &lt;- </span>get-address *result, <span class="Constant">events:offset</span>
   *buf<span class="Special"> &lt;- </span>copy events
   idx:address:number<span class="Special"> &lt;- </span>get-address *result, <span class="Constant">current-event-index:offset</span>
   *idx<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
 ]
 
-<span class="muRecipe">recipe</span> read-event console:address:console<span class="muRecipe"> -&gt; </span>result:event, console:address:console, found?:boolean, quit?:boolean [
+<span class="muRecipe">recipe</span> read-event console:address:shared:console<span class="muRecipe"> -&gt; </span>result:event, console:address:shared:console, found?:boolean, quit?:boolean [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   <span class="Delimiter">{</span>
     <span class="muControl">break-unless</span> console
     current-event-index:address:number<span class="Special"> &lt;- </span>get-address *console, <span class="Constant">current-event-index:offset</span>
-    buf:address:array:event<span class="Special"> &lt;- </span>get *console, <span class="Constant">events:offset</span>
+    buf:address:shared:array:event<span class="Special"> &lt;- </span>get *console, <span class="Constant">events:offset</span>
     <span class="Delimiter">{</span>
       max:number<span class="Special"> &lt;- </span>length *buf
       done?:boolean<span class="Special"> &lt;- </span>greater-or-equal *current-event-index, max
       <span class="muControl">break-unless</span> done?
-      dummy:address:event<span class="Special"> &lt;- </span>new <span class="Constant">event:type</span>
+      dummy:address:shared:event<span class="Special"> &lt;- </span>new <span class="Constant">event:type</span>
       <span class="muControl">reply</span> *dummy, console/same-as-ingredient:<span class="Constant">0</span>, <span class="Constant">1/found</span>, <span class="Constant">1/quit</span>
     <span class="Delimiter">}</span>
     result<span class="Special"> &lt;- </span>index *buf, *current-event-index
@@ -94,7 +94,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="Comment"># variant of read-event for just keyboard events. Discards everything that</span>
 <span class="Comment"># isn't unicode, so no arrow keys, page-up/page-down, etc. But you still get</span>
 <span class="Comment"># newlines, tabs, ctrl-d..</span>
-<span class="muRecipe">recipe</span> read-key console:address:console<span class="muRecipe"> -&gt; </span>result:character, console:address:console, found?:boolean, quit?:boolean [
+<span class="muRecipe">recipe</span> read-key console:address:shared:console<span class="muRecipe"> -&gt; </span>result:character, console:address:shared:console, found?:boolean, quit?:boolean [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   x:event, console, found?:boolean, quit?:boolean<span class="Special"> &lt;- </span>read-event console
@@ -105,7 +105,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   <span class="muControl">reply</span> *c, console/same-as-ingredient:<span class="Constant">0</span>, <span class="Constant">1/found</span>, <span class="Constant">0/quit</span>
 ]
 
-<span class="muRecipe">recipe</span> send-keys-to-channel console:address:console, chan:address:channel, screen:address:screen<span class="muRecipe"> -&gt; </span>console:address:console, chan:address:channel, screen:address:screen [
+<span class="muRecipe">recipe</span> send-keys-to-channel console:address:shared:console, chan:address:shared:channel, screen:address:shared:screen<span class="muRecipe"> -&gt; </span>console:address:shared:console, chan:address:shared:channel, screen:address:shared:screen [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   <span class="Delimiter">{</span>
@@ -119,7 +119,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   <span class="Delimiter">}</span>
 ]
 
-<span class="muRecipe">recipe</span> wait-for-event console:address:console<span class="muRecipe"> -&gt; </span>console:address:console [
+<span class="muRecipe">recipe</span> wait-for-event console:address:shared:console<span class="muRecipe"> -&gt; </span>console:address:shared:console [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   <span class="Delimiter">{</span>
@@ -129,7 +129,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 ]
 
 <span class="Comment"># use this helper to skip rendering if there's lots of other events queued up</span>
-<span class="muRecipe">recipe</span> has-more-events? console:address:console<span class="muRecipe"> -&gt; </span>result:boolean [
+<span class="muRecipe">recipe</span> has-more-events? console:address:shared:console<span class="muRecipe"> -&gt; </span>result:boolean [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   <span class="Delimiter">{</span>
diff --git a/html/085scenario_console.cc.html b/html/085scenario_console.cc.html
index 061712fa..24311448 100644
--- a/html/085scenario_console.cc.html
+++ b/html/085scenario_console.cc.html
@@ -43,10 +43,10 @@ scenario keyboard-in-scenario [
     type [abc]
   ]
   run [
-    <span class="Constant">1</span>:character<span class="Delimiter">,</span> console:address:console<span class="Delimiter">,</span> <span class="Constant">2</span>:boolean<span class="Special"> &lt;- </span>read-key console:address:console
-    <span class="Constant">3</span>:character<span class="Delimiter">,</span> console:address:console<span class="Delimiter">,</span> <span class="Constant">4</span>:boolean<span class="Special"> &lt;- </span>read-key console:address:console
-    <span class="Constant">5</span>:character<span class="Delimiter">,</span> console:address:console<span class="Delimiter">,</span> <span class="Constant">6</span>:boolean<span class="Special"> &lt;- </span>read-key console:address:console
-    <span class="Constant">7</span>:character<span class="Delimiter">,</span> console:address:console<span class="Delimiter">,</span> <span class="Constant">8</span>:boolean<span class="Delimiter">,</span> <span class="Constant">9</span>:boolean<span class="Special"> &lt;- </span>read-key console:address:console
+    <span class="Constant">1</span>:character<span class="Delimiter">,</span> console:address:shared:console<span class="Delimiter">,</span> <span class="Constant">2</span>:boolean<span class="Special"> &lt;- </span>read-key console:address:shared:console
+    <span class="Constant">3</span>:character<span class="Delimiter">,</span> console:address:shared:console<span class="Delimiter">,</span> <span class="Constant">4</span>:boolean<span class="Special"> &lt;- </span>read-key console:address:shared:console
+    <span class="Constant">5</span>:character<span class="Delimiter">,</span> console:address:shared:console<span class="Delimiter">,</span> <span class="Constant">6</span>:boolean<span class="Special"> &lt;- </span>read-key console:address:shared:console
+    <span class="Constant">7</span>:character<span class="Delimiter">,</span> console:address:shared:console<span class="Delimiter">,</span> <span class="Constant">8</span>:boolean<span class="Delimiter">,</span> <span class="Constant">9</span>:boolean<span class="Special"> &lt;- </span>read-key console:address:shared:console
   ]
   memory-should-contain [
     <span class="Constant">1</span><span class="Special"> &lt;- </span><span class="Constant">97</span>  <span class="Comment"># 'a'</span>
@@ -86,14 +86,16 @@ case ASSUME_CONSOLE: <span class="Delimiter">{</span>
   slurp_body<span class="Delimiter">(</span>in<span class="Delimiter">,</span> r<span class="Delimiter">);</span>
   long long int num_events = count_events<span class="Delimiter">(</span>r<span class="Delimiter">);</span>
   <span class="Comment">// initialize the events like in new-fake-console</span>
-  long long int size = num_events*size_of_event<span class="Delimiter">()</span> + <span class="Comment">/*</span><span class="Comment">space for length</span><span class="Comment">*/</span><span class="Constant">1</span><span class="Delimiter">;</span>
+  long long int size = <span class="Comment">/*</span><span class="Comment">space for refcount</span><span class="Comment">*/</span><span class="Constant">1</span> + <span class="Comment">/*</span><span class="Comment">space for length</span><span class="Comment">*/</span><span class="Constant">1</span> + num_events*size_of_event<span class="Delimiter">();</span>
   ensure_space<span class="Delimiter">(</span>size<span class="Delimiter">);</span>
   long long int event_data_address = Current_routine<span class="Delimiter">-&gt;</span>alloc<span class="Delimiter">;</span>
-  put<span class="Delimiter">(</span>Memory<span class="Delimiter">,</span> event_data_address<span class="Delimiter">,</span> num_events<span class="Delimiter">);</span>
-  ++Current_routine<span class="Delimiter">-&gt;</span>alloc<span class="Delimiter">;</span>
+  <span class="Comment">// store length</span>
+  put<span class="Delimiter">(</span>Memory<span class="Delimiter">,</span> Current_routine<span class="Delimiter">-&gt;</span>alloc+<span class="Comment">/*</span><span class="Comment">skip refcount</span><span class="Comment">*/</span><span class="Constant">1</span><span class="Delimiter">,</span> num_events<span class="Delimiter">);</span>
+  Current_routine<span class="Delimiter">-&gt;</span>alloc += <span class="Comment">/*</span><span class="Comment">skip refcount and length</span><span class="Comment">*/</span><span class="Constant">2</span><span class="Delimiter">;</span>
   for <span class="Delimiter">(</span>long long int i = <span class="Constant">0</span><span class="Delimiter">;</span> i &lt; SIZE<span class="Delimiter">(</span>r<span class="Delimiter">.</span>steps<span class="Delimiter">);</span> ++i<span class="Delimiter">)</span> <span class="Delimiter">{</span>
     const instruction&amp; curr = r<span class="Delimiter">.</span>steps<span class="Delimiter">.</span>at<span class="Delimiter">(</span>i<span class="Delimiter">);</span>
     if <span class="Delimiter">(</span>curr<span class="Delimiter">.</span>name == <span class="Constant">&quot;left-click&quot;</span><span class="Delimiter">)</span> <span class="Delimiter">{</span>
+      trace<span class="Delimiter">(</span><span class="Constant">9999</span><span class="Delimiter">,</span> <span class="Constant">&quot;mem&quot;</span><span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;storing 'left-click' event starting at &quot;</span> &lt;&lt; Current_routine<span class="Delimiter">-&gt;</span>alloc &lt;&lt; end<span class="Delimiter">();</span>
       put<span class="Delimiter">(</span>Memory<span class="Delimiter">,</span> Current_routine<span class="Delimiter">-&gt;</span>alloc<span class="Delimiter">,</span> <span class="Comment">/*</span><span class="Comment">tag for 'touch-event' variant of 'event' exclusive-container</span><span class="Comment">*/</span><span class="Constant">2</span><span class="Delimiter">);</span>
       put<span class="Delimiter">(</span>Memory<span class="Delimiter">,</span> Current_routine<span class="Delimiter">-&gt;</span>alloc+<span class="Constant">1</span>+<span class="Comment">/*</span><span class="Comment">offset of 'type' in 'mouse-event'</span><span class="Comment">*/</span><span class="Constant">0</span><span class="Delimiter">,</span> TB_KEY_MOUSE_LEFT<span class="Delimiter">);</span>
       put<span class="Delimiter">(</span>Memory<span class="Delimiter">,</span> Current_routine<span class="Delimiter">-&gt;</span>alloc+<span class="Constant">1</span>+<span class="Comment">/*</span><span class="Comment">offset of 'row' in 'mouse-event'</span><span class="Comment">*/</span><span class="Constant">1</span><span class="Delimiter">,</span> to_integer<span class="Delimiter">(</span>curr<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">).</span>name<span class="Delimiter">));</span>
@@ -101,6 +103,7 @@ case ASSUME_CONSOLE: <span class="Delimiter">{</span>
       Current_routine<span class="Delimiter">-&gt;</span>alloc += size_of_event<span class="Delimiter">();</span>
     <span class="Delimiter">}</span>
     else if <span class="Delimiter">(</span>curr<span class="Delimiter">.</span>name == <span class="Constant">&quot;press&quot;</span><span class="Delimiter">)</span> <span class="Delimiter">{</span>
+      trace<span class="Delimiter">(</span><span class="Constant">9999</span><span class="Delimiter">,</span> <span class="Constant">&quot;mem&quot;</span><span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;storing 'press' event starting at &quot;</span> &lt;&lt; Current_routine<span class="Delimiter">-&gt;</span>alloc &lt;&lt; end<span class="Delimiter">();</span>
       string key = curr<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">).</span>name<span class="Delimiter">;</span>
       if <span class="Delimiter">(</span>is_integer<span class="Delimiter">(</span>key<span class="Delimiter">))</span>
         put<span class="Delimiter">(</span>Memory<span class="Delimiter">,</span> Current_routine<span class="Delimiter">-&gt;</span>alloc+<span class="Constant">1</span><span class="Delimiter">,</span> to_integer<span class="Delimiter">(</span>key<span class="Delimiter">));</span>
@@ -121,15 +124,18 @@ case ASSUME_CONSOLE: <span class="Delimiter">{</span>
     else <span class="Delimiter">{</span>
       <span class="Comment">// keyboard input</span>
       assert<span class="Delimiter">(</span>curr<span class="Delimiter">.</span>name == <span class="Constant">&quot;type&quot;</span><span class="Delimiter">);</span>
+      trace<span class="Delimiter">(</span><span class="Constant">9999</span><span class="Delimiter">,</span> <span class="Constant">&quot;mem&quot;</span><span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;storing 'type' event starting at &quot;</span> &lt;&lt; Current_routine<span class="Delimiter">-&gt;</span>alloc &lt;&lt; end<span class="Delimiter">();</span>
       const string&amp; contents = curr<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">).</span>name<span class="Delimiter">;</span>
       const char* raw_contents = contents<span class="Delimiter">.</span>c_str<span class="Delimiter">();</span>
       long long int num_keyboard_events = unicode_length<span class="Delimiter">(</span>contents<span class="Delimiter">);</span>
       long long int curr = <span class="Constant">0</span><span class="Delimiter">;</span>
       for <span class="Delimiter">(</span>long long int i = <span class="Constant">0</span><span class="Delimiter">;</span> i &lt; num_keyboard_events<span class="Delimiter">;</span> ++i<span class="Delimiter">)</span> <span class="Delimiter">{</span>
+        trace<span class="Delimiter">(</span><span class="Constant">9999</span><span class="Delimiter">,</span> <span class="Constant">&quot;mem&quot;</span><span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;storing 'text' tag at &quot;</span> &lt;&lt; Current_routine<span class="Delimiter">-&gt;</span>alloc &lt;&lt; end<span class="Delimiter">();</span>
         put<span class="Delimiter">(</span>Memory<span class="Delimiter">,</span> Current_routine<span class="Delimiter">-&gt;</span>alloc<span class="Delimiter">,</span> <span class="Comment">/*</span><span class="Comment">tag for 'text' variant of 'event' exclusive-container</span><span class="Comment">*/</span><span class="Constant">0</span><span class="Delimiter">);</span>
         uint32_t curr_character<span class="Delimiter">;</span>
         assert<span class="Delimiter">(</span>curr &lt; SIZE<span class="Delimiter">(</span>contents<span class="Delimiter">));</span>
         tb_utf8_char_to_unicode<span class="Delimiter">(</span>&amp;curr_character<span class="Delimiter">,</span> &amp;raw_contents[curr]<span class="Delimiter">);</span>
+        trace<span class="Delimiter">(</span><span class="Constant">9999</span><span class="Delimiter">,</span> <span class="Constant">&quot;mem&quot;</span><span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;storing character &quot;</span> &lt;&lt; curr_character &lt;&lt; <span class="Constant">&quot; at &quot;</span> &lt;&lt; Current_routine<span class="Delimiter">-&gt;</span>alloc+<span class="Constant">1</span> &lt;&lt; end<span class="Delimiter">();</span>
         put<span class="Delimiter">(</span>Memory<span class="Delimiter">,</span> Current_routine<span class="Delimiter">-&gt;</span>alloc+<span class="Comment">/*</span><span class="Comment">skip exclusive container tag</span><span class="Comment">*/</span><span class="Constant">1</span><span class="Delimiter">,</span> curr_character<span class="Delimiter">);</span>
         curr += tb_utf8_char_length<span class="Delimiter">(</span>raw_contents[curr]<span class="Delimiter">);</span>
         Current_routine<span class="Delimiter">-&gt;</span>alloc += size_of_event<span class="Delimiter">();</span>
@@ -140,9 +146,11 @@ case ASSUME_CONSOLE: <span class="Delimiter">{</span>
   <span class="Comment">// wrap the array of events in a console object</span>
   ensure_space<span class="Delimiter">(</span>size_of_console<span class="Delimiter">());</span>
   put<span class="Delimiter">(</span>Memory<span class="Delimiter">,</span> CONSOLE<span class="Delimiter">,</span> Current_routine<span class="Delimiter">-&gt;</span>alloc<span class="Delimiter">);</span>
+  trace<span class="Delimiter">(</span><span class="Constant">9999</span><span class="Delimiter">,</span> <span class="Constant">&quot;mem&quot;</span><span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;storing console in &quot;</span> &lt;&lt; Current_routine<span class="Delimiter">-&gt;</span>alloc &lt;&lt; end<span class="Delimiter">();</span>
   Current_routine<span class="Delimiter">-&gt;</span>alloc += size_of_console<span class="Delimiter">();</span>
   long long int console_address = get_or_insert<span class="Delimiter">(</span>Memory<span class="Delimiter">,</span> CONSOLE<span class="Delimiter">);</span>
-  put<span class="Delimiter">(</span>Memory<span class="Delimiter">,</span> console_address+<span class="Comment">/*</span><span class="Comment">offset of 'data' in container 'events'</span><span class="Comment">*/</span><span class="Constant">1</span><span class="Delimiter">,</span> event_data_address<span class="Delimiter">);</span>
+  trace<span class="Delimiter">(</span><span class="Constant">9999</span><span class="Delimiter">,</span> <span class="Constant">&quot;mem&quot;</span><span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;storing console data in &quot;</span> &lt;&lt; console_address+<span class="Constant">2</span> &lt;&lt; end<span class="Delimiter">();</span>
+  put<span class="Delimiter">(</span>Memory<span class="Delimiter">,</span> console_address+<span class="Comment">/*</span><span class="Comment">skip refcount</span><span class="Comment">*/</span><span class="Constant">1</span>+<span class="Comment">/*</span><span class="Comment">offset of 'data' in container 'events'</span><span class="Comment">*/</span><span class="Constant">1</span><span class="Delimiter">,</span> event_data_address<span class="Delimiter">);</span>
   <span class="Identifier">break</span><span class="Delimiter">;</span>
 <span class="Delimiter">}</span>
 
@@ -216,15 +224,15 @@ scenario events-in-scenario [
   ]
   run [
     <span class="Comment"># 3 keyboard events; each event occupies 4 locations</span>
-    <span class="Constant">1</span>:event<span class="Special"> &lt;- </span>read-event console:address:console
-    <span class="Constant">5</span>:event<span class="Special"> &lt;- </span>read-event console:address:console
-    <span class="Constant">9</span>:event<span class="Special"> &lt;- </span>read-event console:address:console
+    <span class="Constant">1</span>:event<span class="Special"> &lt;- </span>read-event console:address:shared:console
+    <span class="Constant">5</span>:event<span class="Special"> &lt;- </span>read-event console:address:shared:console
+    <span class="Constant">9</span>:event<span class="Special"> &lt;- </span>read-event console:address:shared:console
     <span class="Comment"># mouse click</span>
-    <span class="Constant">13</span>:event<span class="Special"> &lt;- </span>read-event console:address:console
+    <span class="Constant">13</span>:event<span class="Special"> &lt;- </span>read-event console:address:shared:console
     <span class="Comment"># non-character keycode</span>
-    <span class="Constant">17</span>:event<span class="Special"> &lt;- </span>read-event console:address:console
+    <span class="Constant">17</span>:event<span class="Special"> &lt;- </span>read-event console:address:shared:console
     <span class="Comment"># final keyboard event</span>
-    <span class="Constant">21</span>:event<span class="Special"> &lt;- </span>read-event console:address:console
+    <span class="Constant">21</span>:event<span class="Special"> &lt;- </span>read-event console:address:shared:console
   ]
   memory-should-contain [
     <span class="Constant">1</span><span class="Special"> &lt;- </span><span class="Constant">0</span>  <span class="Comment"># 'text'</span>
@@ -313,7 +321,7 @@ long long int size_of_console<span class="Delimiter">()</span> <span class="Deli
   if <span class="Delimiter">(</span>result<span class="Delimiter">)</span> <span class="Identifier">return</span> result<span class="Delimiter">;</span>
   assert<span class="Delimiter">(</span>get<span class="Delimiter">(</span>Type_ordinal<span class="Delimiter">,</span> <span class="Constant">&quot;console&quot;</span><span class="Delimiter">));</span>
   type_tree* type = new type_tree<span class="Delimiter">(</span>get<span class="Delimiter">(</span>Type_ordinal<span class="Delimiter">,</span> <span class="Constant">&quot;console&quot;</span><span class="Delimiter">));</span>
-  result = size_of<span class="Delimiter">(</span>type<span class="Delimiter">);</span>
+  result = size_of<span class="Delimiter">(</span>type<span class="Delimiter">)</span>+<span class="Comment">/*</span><span class="Comment">refcount</span><span class="Comment">*/</span><span class="Constant">1</span><span class="Delimiter">;</span>
   delete type<span class="Delimiter">;</span>
   <span class="Identifier">return</span> result<span class="Delimiter">;</span>
 <span class="Delimiter">}</span>
diff --git a/html/086scenario_console_test.mu.html b/html/086scenario_console_test.mu.html
index 8f0c8685..f36290b3 100644
--- a/html/086scenario_console_test.mu.html
+++ b/html/086scenario_console_test.mu.html
@@ -37,10 +37,10 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     type <span class="Constant">[abc]</span>
   ]
   run [
-    <span class="Constant">1</span>:character, console:address:console, <span class="Constant">2</span>:boolean<span class="Special"> &lt;- </span>read-key console:address:console
-    <span class="Constant">3</span>:character, console:address:console, <span class="Constant">4</span>:boolean<span class="Special"> &lt;- </span>read-key console:address:console
-    <span class="Constant">5</span>:character, console:address:console, <span class="Constant">6</span>:boolean<span class="Special"> &lt;- </span>read-key console:address:console
-    <span class="Constant">7</span>:character, console:address:console, <span class="Constant">8</span>:boolean<span class="Special"> &lt;- </span>read-key console:address:console
+    <span class="Constant">1</span>:character, console:address:shared:console, <span class="Constant">2</span>:boolean<span class="Special"> &lt;- </span>read-key console:address:shared:console
+    <span class="Constant">3</span>:character, console:address:shared:console, <span class="Constant">4</span>:boolean<span class="Special"> &lt;- </span>read-key console:address:shared:console
+    <span class="Constant">5</span>:character, console:address:shared:console, <span class="Constant">6</span>:boolean<span class="Special"> &lt;- </span>read-key console:address:shared:console
+    <span class="Constant">7</span>:character, console:address:shared:console, <span class="Constant">8</span>:boolean<span class="Special"> &lt;- </span>read-key console:address:shared:console
   ]
   memory-should-contain [
     <span class="Constant">1</span><span class="Special"> &lt;- </span><span class="Constant">97</span>  <span class="Comment"># 'a'</span>
diff --git a/html/091run_interactive.cc.html b/html/091run_interactive.cc.html
index 703fd5c1..661ff83c 100644
--- a/html/091run_interactive.cc.html
+++ b/html/091run_interactive.cc.html
@@ -38,16 +38,16 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="Delimiter">:(scenario run_interactive_code)</span>
 recipe main [
   <span class="Constant">1</span>:number/<span class="Special">raw &lt;- </span>copy <span class="Constant">0</span>
-  <span class="Constant">2</span>:address:array:character<span class="Special"> &lt;- </span>new [<span class="Constant">1</span>:number/<span class="Special">raw &lt;- </span>copy <span class="Constant">34</span>]
-  run-interactive <span class="Constant">2</span>:address:array:character
+  <span class="Constant">2</span>:address:shared:array:character<span class="Special"> &lt;- </span>new [<span class="Constant">1</span>:number/<span class="Special">raw &lt;- </span>copy <span class="Constant">34</span>]
+  run-interactive <span class="Constant">2</span>:address:shared:array:character
   <span class="Constant">3</span>:number/<span class="Special">raw &lt;- </span>copy <span class="Constant">1</span>:number/<span class="Special">raw</span>
 ]
 <span class="traceContains">+mem: storing 34 in location 3</span>
 
 <span class="Delimiter">:(scenario run_interactive_empty)</span>
 recipe main [
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>/unsafe
-  <span class="Constant">2</span>:address:array:character<span class="Special"> &lt;- </span>run-interactive <span class="Constant">1</span>:address:array:character
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>/unsafe
+  <span class="Constant">2</span>:address:shared:array:character<span class="Special"> &lt;- </span>run-interactive <span class="Constant">1</span>:address:shared:array:character
 ]
 <span class="Comment"># result is null</span>
 <span class="traceContains">+mem: storing 0 in location 2</span>
@@ -122,7 +122,7 @@ bool run_interactive<span class="Delimiter">(</span>long long int address<span c
   <span class="Comment">// call run(string) but without the scheduling</span>
   load<span class="Delimiter">(</span>string<span class="Delimiter">(</span><span class="Constant">&quot;recipe! interactive [</span><span class="cSpecial">\n</span><span class="Constant">&quot;</span><span class="Delimiter">)</span> +
           <span class="Constant">&quot;local-scope</span><span class="cSpecial">\n</span><span class="Constant">&quot;</span> +
-          <span class="Constant">&quot;screen:address:screen &lt;- next-ingredient</span><span class="cSpecial">\n</span><span class="Constant">&quot;</span> +
+          <span class="Constant">&quot;screen:address:shared:screen &lt;- next-ingredient</span><span class="cSpecial">\n</span><span class="Constant">&quot;</span> +
           <span class="Constant">&quot;$start-tracking-products</span><span class="cSpecial">\n</span><span class="Constant">&quot;</span> +
           command + <span class="Constant">&quot;</span><span class="cSpecial">\n</span><span class="Constant">&quot;</span> +
           <span class="Constant">&quot;$stop-tracking-products</span><span class="cSpecial">\n</span><span class="Constant">&quot;</span> +
@@ -187,15 +187,15 @@ load<span class="Delimiter">(</span>string<span class="Delimiter">(</span>
 <span class="Constant">&quot;]</span><span class="cSpecial">\n</span><span class="Constant">&quot;</span> +
 <span class="Constant">&quot;recipe sandbox [</span><span class="cSpecial">\n</span><span class="Constant">&quot;</span> +
   <span class="Constant">&quot;local-scope</span><span class="cSpecial">\n</span><span class="Constant">&quot;</span> +
-  <span class="Constant">&quot;screen:address:screen/shared &lt;- new-fake-screen 30, 5</span><span class="cSpecial">\n</span><span class="Constant">&quot;</span> +
-  <span class="Constant">&quot;r:number/routine_id &lt;- start-running interactive:recipe, screen</span><span class="cSpecial">\n</span><span class="Constant">&quot;</span> +
+  <span class="Constant">&quot;screen:address:shared:screen &lt;- new-fake-screen 30, 5</span><span class="cSpecial">\n</span><span class="Constant">&quot;</span> +
+  <span class="Constant">&quot;r:number/routine_id &lt;- start-running interactive, screen</span><span class="cSpecial">\n</span><span class="Constant">&quot;</span> +
   <span class="Constant">&quot;limit-time r, 100000/instructions</span><span class="cSpecial">\n</span><span class="Constant">&quot;</span> +
   <span class="Constant">&quot;wait-for-routine r</span><span class="cSpecial">\n</span><span class="Constant">&quot;</span> +
   <span class="Constant">&quot;sandbox-state:number &lt;- routine-state r/routine_id</span><span class="cSpecial">\n</span><span class="Constant">&quot;</span> +
   <span class="Constant">&quot;completed?:boolean &lt;- equal sandbox-state, 1/completed</span><span class="cSpecial">\n</span><span class="Constant">&quot;</span> +
-  <span class="Constant">&quot;output:address:array:character &lt;- $most-recent-products</span><span class="cSpecial">\n</span><span class="Constant">&quot;</span> +
-  <span class="Constant">&quot;warnings:address:array:character &lt;- save-errors-warnings</span><span class="cSpecial">\n</span><span class="Constant">&quot;</span> +
-  <span class="Constant">&quot;stashes:address:array:character &lt;- save-app-trace</span><span class="cSpecial">\n</span><span class="Constant">&quot;</span> +
+  <span class="Constant">&quot;output:address:shared:array:character &lt;- $most-recent-products</span><span class="cSpecial">\n</span><span class="Constant">&quot;</span> +
+  <span class="Constant">&quot;warnings:address:shared:array:character &lt;- save-errors-warnings</span><span class="cSpecial">\n</span><span class="Constant">&quot;</span> +
+  <span class="Constant">&quot;stashes:address:shared:array:character &lt;- save-app-trace</span><span class="cSpecial">\n</span><span class="Constant">&quot;</span> +
   <span class="Constant">&quot;$cleanup-run-interactive</span><span class="cSpecial">\n</span><span class="Constant">&quot;</span> +
   <span class="Constant">&quot;reply output, warnings, screen, stashes, completed?</span><span class="cSpecial">\n</span><span class="Constant">&quot;</span> +
 <span class="Constant">&quot;]</span><span class="cSpecial">\n</span><span class="Constant">&quot;</span><span class="Delimiter">);</span>
@@ -208,10 +208,10 @@ Recently_added_recipes<span class="Delimiter">.</span>clear<span class="Delimite
 
 <span class="Delimiter">:(scenario run_interactive_comments)</span>
 recipe main [
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new [<span class="Comment"># ab</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new [<span class="Comment"># ab</span>
 add <span class="Constant">2</span><span class="Delimiter">,</span> <span class="Constant">2</span>]
-  <span class="Constant">2</span>:address:array:character<span class="Special"> &lt;- </span>run-interactive <span class="Constant">1</span>:address:array:character
-  <span class="Constant">3</span>:array:character<span class="Special"> &lt;- </span>copy *<span class="Constant">2</span>:address:array:character
+  <span class="Constant">2</span>:address:shared:array:character<span class="Special"> &lt;- </span>run-interactive <span class="Constant">1</span>:address:shared:array:character
+  <span class="Constant">3</span>:array:character<span class="Special"> &lt;- </span>copy *<span class="Constant">2</span>:address:shared:array:character
 ]
 <span class="traceContains">+mem: storing 52 in location 4</span>
 
@@ -305,9 +305,9 @@ case _CLEANUP_RUN_INTERACTIVE: <span class="Delimiter">{</span>
 <span class="Delimiter">:(scenario &quot;run_interactive_converts_result_to_text&quot;)</span>
 recipe main [
   <span class="Comment"># try to interactively add 2 and 2</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new [add <span class="Constant">2</span><span class="Delimiter">,</span> <span class="Constant">2</span>]
-  <span class="Constant">2</span>:address:array:character<span class="Special"> &lt;- </span>run-interactive <span class="Constant">1</span>:address:array:character
-  <span class="Constant">10</span>:array:character<span class="Special"> &lt;- </span>copy <span class="Constant">2</span>:address:array:character/lookup
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new [add <span class="Constant">2</span><span class="Delimiter">,</span> <span class="Constant">2</span>]
+  <span class="Constant">2</span>:address:shared:array:character<span class="Special"> &lt;- </span>run-interactive <span class="Constant">1</span>:address:shared:array:character
+  <span class="Constant">10</span>:array:character<span class="Special"> &lt;- </span>copy <span class="Constant">2</span>:address:shared:array:character/lookup
 ]
 <span class="Comment"># first letter in the output should be '4' in unicode</span>
 <span class="traceContains">+mem: storing 52 in location 11</span>
@@ -315,13 +315,13 @@ recipe main [
 <span class="Delimiter">:(scenario &quot;run_interactive_returns_text&quot;)</span>
 recipe main [
   <span class="Comment"># try to interactively add 2 and 2</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new [
-    x:address:array:character<span class="Special"> &lt;- </span>new [a]
-    y:address:array:character<span class="Special"> &lt;- </span>new [b]
-    z:address:array:character<span class="Special"> &lt;- </span>append x:address:array:character<span class="Delimiter">,</span> y:address:array:character
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new [
+    x:address:shared:array:character<span class="Special"> &lt;- </span>new [a]
+    y:address:shared:array:character<span class="Special"> &lt;- </span>new [b]
+    z:address:shared:array:character<span class="Special"> &lt;- </span>append x:address:shared:array:character<span class="Delimiter">,</span> y:address:shared:array:character
   ]
-  <span class="Constant">2</span>:address:array:character<span class="Special"> &lt;- </span>run-interactive <span class="Constant">1</span>:address:array:character
-  <span class="Constant">10</span>:array:character<span class="Special"> &lt;- </span>copy <span class="Constant">2</span>:address:array:character/lookup
+  <span class="Constant">2</span>:address:shared:array:character<span class="Special"> &lt;- </span>run-interactive <span class="Constant">1</span>:address:shared:array:character
+  <span class="Constant">10</span>:array:character<span class="Special"> &lt;- </span>copy <span class="Constant">2</span>:address:shared:array:character/lookup
 ]
 <span class="Comment"># output contains &quot;ab&quot;</span>
 <span class="traceContains">+mem: storing 97 in location 11</span>
@@ -330,10 +330,10 @@ recipe main [
 <span class="Delimiter">:(scenario &quot;run_interactive_returns_errors&quot;)</span>
 recipe main [
   <span class="Comment"># run a command that generates an error</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new [x:number<span class="Special"> &lt;- </span>copy <span class="Constant">34</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new [x:number<span class="Special"> &lt;- </span>copy <span class="Constant">34</span>
 get x:number<span class="Delimiter">,</span> foo:offset]
-  <span class="Constant">2</span>:address:array:character<span class="Delimiter">,</span> <span class="Constant">3</span>:address:array:character<span class="Special"> &lt;- </span>run-interactive <span class="Constant">1</span>:address:array:character
-  <span class="Constant">10</span>:array:character<span class="Special"> &lt;- </span>copy <span class="Constant">3</span>:address:array:character/lookup
+  <span class="Constant">2</span>:address:shared:array:character<span class="Delimiter">,</span> <span class="Constant">3</span>:address:shared:array:character<span class="Special"> &lt;- </span>run-interactive <span class="Constant">1</span>:address:shared:array:character
+  <span class="Constant">10</span>:array:character<span class="Special"> &lt;- </span>copy <span class="Constant">3</span>:address:shared:array:character/lookup
 ]
 <span class="Comment"># error should be &quot;unknown element foo in container number&quot;</span>
 <span class="traceContains">+mem: storing 117 in location 11</span>
@@ -345,10 +345,10 @@ get x:number<span class="Delimiter">,</span> foo:offset]
 <span class="Delimiter">:(scenario run_interactive_with_comment)</span>
 recipe main [
   <span class="Comment"># 2 instructions, with a comment after the first</span>
-  <span class="Constant">1</span>:address:array:number<span class="Special"> &lt;- </span>new [a:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>  <span class="Comment"># abc</span>
+  <span class="Constant">1</span>:address:shared:array:number<span class="Special"> &lt;- </span>new [a:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>  <span class="Comment"># abc</span>
 b:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
 ]
-  <span class="Constant">2</span>:address:array:character<span class="Delimiter">,</span> <span class="Constant">3</span>:address:array:character<span class="Special"> &lt;- </span>run-interactive <span class="Constant">1</span>:address:array:character
+  <span class="Constant">2</span>:address:shared:array:character<span class="Delimiter">,</span> <span class="Constant">3</span>:address:shared:array:character<span class="Special"> &lt;- </span>run-interactive <span class="Constant">1</span>:address:shared:array:character
 ]
 <span class="Comment"># no errors</span>
 <span class="traceContains">+mem: storing 0 in location 3</span>
@@ -365,8 +365,8 @@ void test_run_interactive_cleans_up_any_created_specializations<span class="Deli
   <span class="Comment">// run-interactive a call that specializes this recipe</span>
   run<span class="Delimiter">(</span><span class="Constant">&quot;recipe main [</span><span class="cSpecial">\n</span><span class="Constant">&quot;</span>
        <span class="Constant">&quot;  1:number/raw &lt;- copy 0</span><span class="cSpecial">\n</span><span class="Constant">&quot;</span>
-       <span class="Constant">&quot;  2:address:array:character &lt;- new [foo 1:number/raw]</span><span class="cSpecial">\n</span><span class="Constant">&quot;</span>
-       <span class="Constant">&quot;  run-interactive 2:address:array:character</span><span class="cSpecial">\n</span><span class="Constant">&quot;</span>
+       <span class="Constant">&quot;  2:address:shared:array:character &lt;- new [foo 1:number/raw]</span><span class="cSpecial">\n</span><span class="Constant">&quot;</span>
+       <span class="Constant">&quot;  run-interactive 2:address:shared:array:character</span><span class="cSpecial">\n</span><span class="Constant">&quot;</span>
        <span class="Constant">&quot;]</span><span class="cSpecial">\n</span><span class="Constant">&quot;</span><span class="Delimiter">);</span>
   assert<span class="Delimiter">(</span>SIZE<span class="Delimiter">(</span>Recently_added_recipes<span class="Delimiter">)</span> == <span class="Constant">2</span><span class="Delimiter">);</span>  <span class="Comment">// foo, main</span>
   <span class="Comment">// check that number of variants doesn't change</span>
@@ -512,7 +512,6 @@ case RELOAD: <span class="Delimiter">{</span>
     <span class="Delimiter">}</span>
   <span class="Delimiter">}</span>
   for <span class="Delimiter">(</span>long long int i = <span class="Constant">0</span><span class="Delimiter">;</span> i &lt; SIZE<span class="Delimiter">(</span>Recently_added_shape_shifting_recipes<span class="Delimiter">);</span> ++i<span class="Delimiter">)</span> <span class="Delimiter">{</span>
-<span class="CommentedCode">//?     LOG &lt;&lt; &quot;erasing &quot; &lt;&lt; get(Recipe, Recently_added_shape_shifting_recipes.at(i)).name &lt;&lt; '\n';</span>
     Recipe_ordinal<span class="Delimiter">.</span>erase<span class="Delimiter">(</span>get<span class="Delimiter">(</span>Recipe<span class="Delimiter">,</span> Recently_added_shape_shifting_recipes<span class="Delimiter">.</span>at<span class="Delimiter">(</span>i<span class="Delimiter">)).</span>name<span class="Delimiter">);</span>
     Recipe<span class="Delimiter">.</span>erase<span class="Delimiter">(</span>Recently_added_shape_shifting_recipes<span class="Delimiter">.</span>at<span class="Delimiter">(</span>i<span class="Delimiter">));</span>
   <span class="Delimiter">}</span>
@@ -539,7 +538,7 @@ case RELOAD: <span class="Delimiter">{</span>
 <span class="Delimiter">:(scenario reload_continues_past_error)</span>
 recipe main [
   local-scope
-  x:address:array:character<span class="Special"> &lt;- </span>new [recipe foo [
+  x:address:shared:array:character<span class="Special"> &lt;- </span>new [recipe foo [
   get <span class="Constant">1234</span>:number<span class="Delimiter">,</span> foo:offset
 ]]
   reload x
@@ -555,7 +554,7 @@ void test_reload_cleans_up_any_created_specializations<span class="Delimiter">()
   <span class="Comment">// a call that specializes this recipe</span>
   run<span class="Delimiter">(</span><span class="Constant">&quot;recipe main [</span><span class="cSpecial">\n</span><span class="Constant">&quot;</span>
       <span class="Constant">&quot;  local-scope</span><span class="cSpecial">\n</span><span class="Constant">&quot;</span>
-      <span class="Constant">&quot;  x:address:array:character &lt;- new [recipe foo x:_elem -&gt; n:number [</span><span class="cSpecial">\n</span><span class="Constant">&quot;</span>
+      <span class="Constant">&quot;  x:address:shared:array:character &lt;- new [recipe foo x:_elem -&gt; n:number [</span><span class="cSpecial">\n</span><span class="Constant">&quot;</span>
       <span class="Constant">&quot;local-scope</span><span class="cSpecial">\n</span><span class="Constant">&quot;</span>
       <span class="Constant">&quot;load-ingredients</span><span class="cSpecial">\n</span><span class="Constant">&quot;</span>
       <span class="Constant">&quot;reply 34</span><span class="cSpecial">\n</span><span class="Constant">&quot;</span>
diff --git a/html/channel.mu.html b/html/channel.mu.html
index 15a75d1f..98bd4066 100644
--- a/html/channel.mu.html
+++ b/html/channel.mu.html
@@ -32,7 +32,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <pre id='vimCodeElement'>
 <span class="Comment"># example program: communicating between routines using channels</span>
 
-<span class="muRecipe">recipe</span> producer chan:address:channel<span class="muRecipe"> -&gt; </span>chan:address:channel [
+<span class="muRecipe">recipe</span> producer chan:address:shared:channel<span class="muRecipe"> -&gt; </span>chan:address:shared:channel [
   <span class="Comment"># produce characters 1 to 5 on a channel</span>
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
@@ -44,19 +44,19 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     <span class="Comment"># other threads might get between these prints</span>
     $print <span class="Constant">[produce: ]</span>, n, <span class="Constant">[ </span>
 <span class="Constant">]</span>
-    chan:address:channel<span class="Special"> &lt;- </span>write chan, n
+    chan:address:shared:channel<span class="Special"> &lt;- </span>write chan, n
     n<span class="Special"> &lt;- </span>add n, <span class="Constant">1</span>
     <span class="muControl">loop</span>
   <span class="Delimiter">}</span>
 ]
 
-<span class="muRecipe">recipe</span> consumer chan:address:channel<span class="muRecipe"> -&gt; </span>chan:address:channel [
+<span class="muRecipe">recipe</span> consumer chan:address:shared:channel<span class="muRecipe"> -&gt; </span>chan:address:shared:channel [
   <span class="Comment"># consume and print integers from a channel</span>
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   <span class="Delimiter">{</span>
     <span class="Comment"># read an integer from the channel</span>
-    n:character, chan:address:channel<span class="Special"> &lt;- </span>read chan
+    n:character, chan:address:shared:channel<span class="Special"> &lt;- </span>read chan
     <span class="Comment"># other threads might get between these prints</span>
     $print <span class="Constant">[consume: ]</span>, n:character, <span class="Constant">[ </span>
 <span class="Constant">]</span>
@@ -66,10 +66,10 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muRecipe">recipe</span> main [
   <span class="Constant">local-scope</span>
-  chan:address:channel<span class="Special"> &lt;- </span>new-channel <span class="Constant">3</span>
+  chan:address:shared:channel<span class="Special"> &lt;- </span>new-channel <span class="Constant">3</span>
   <span class="Comment"># create two background 'routines' that communicate by a channel</span>
-  routine1:character<span class="Special"> &lt;- </span>start-running <span class="Constant">producer:recipe</span>, chan
-  routine2:character<span class="Special"> &lt;- </span>start-running <span class="Constant">consumer:recipe</span>, chan
+  routine1:number<span class="Special"> &lt;- </span>start-running producer, chan
+  routine2:number<span class="Special"> &lt;- </span>start-running consumer, chan
   wait-for-routine routine1
   wait-for-routine routine2
 ]
diff --git a/html/chessboard.mu.html b/html/chessboard.mu.html
index 16230411..2211f854 100644
--- a/html/chessboard.mu.html
+++ b/html/chessboard.mu.html
@@ -70,7 +70,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="Constant">]</span>
   ]
   run [
-    screen:address:screen, console:address:console<span class="Special"> &lt;- </span>chessboard screen:address:screen, console:address:console
+    screen:address:shared:screen, console:address:shared:console<span class="Special"> &lt;- </span>chessboard screen:address:shared:screen, console:address:shared:console
     <span class="Comment"># icon for the cursor</span>
     screen<span class="Special"> &lt;- </span>print screen, <span class="Constant">9251/␣</span>
   ]
@@ -102,18 +102,18 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="SalientComment">## Here's how 'chessboard' is implemented.</span>
 
-<span class="muRecipe">recipe</span> chessboard screen:address:screen, console:address:console<span class="muRecipe"> -&gt; </span>screen:address:screen, console:address:console [
+<span class="muRecipe">recipe</span> chessboard screen:address:shared:screen, console:address:shared:console<span class="muRecipe"> -&gt; </span>screen:address:shared:screen, console:address:shared:console [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
-  board:address:array:address:array:character<span class="Special"> &lt;- </span>initial-position
+  board:address:shared:array:address:shared:array:character<span class="Special"> &lt;- </span>initial-position
   <span class="Comment"># hook up stdin</span>
-  stdin:address:channel<span class="Special"> &lt;- </span>new-channel <span class="Constant">10/capacity</span>
-  start-running <span class="Constant">send-keys-to-channel:recipe</span>, console, stdin, screen
+  stdin:address:shared:channel<span class="Special"> &lt;- </span>new-channel <span class="Constant">10/capacity</span>
+  start-running send-keys-to-channel, console, stdin, screen
   <span class="Comment"># buffer lines in stdin</span>
-  buffered-stdin:address:channel<span class="Special"> &lt;- </span>new-channel <span class="Constant">10/capacity</span>
-  start-running <span class="Constant">buffer-lines:recipe</span>, stdin, buffered-stdin
+  buffered-stdin:address:shared:channel<span class="Special"> &lt;- </span>new-channel <span class="Constant">10/capacity</span>
+  start-running buffer-lines, stdin, buffered-stdin
   <span class="Delimiter">{</span>
-    msg:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[Stupid text-mode chessboard. White pieces in uppercase; black pieces in lowercase. No checking for legal moves.</span>
+    msg:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[Stupid text-mode chessboard. White pieces in uppercase; black pieces in lowercase. No checking for legal moves.</span>
 <span class="Constant">]</span>
     print screen, msg
     cursor-to-next-line screen
@@ -130,7 +130,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
       cursor-to-next-line screen
       msg<span class="Special"> &lt;- </span>new <span class="Constant">[move: ]</span>
       screen<span class="Special"> &lt;- </span>print screen, msg
-      m:address:move, quit:boolean, error:boolean<span class="Special"> &lt;- </span>read-move buffered-stdin, screen
+      m:address:shared:move, quit:boolean, error:boolean<span class="Special"> &lt;- </span>read-move buffered-stdin, screen
       <span class="muControl">break-if</span> quit, <span class="Constant">+quit:label</span>
       buffered-stdin<span class="Special"> &lt;- </span>clear-channel buffered-stdin  <span class="Comment"># cleanup after error. todo: test this?</span>
       <span class="muControl">loop-if</span> error
@@ -139,12 +139,13 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     screen<span class="Special"> &lt;- </span>clear-screen screen
     <span class="muControl">loop</span>
   <span class="Delimiter">}</span>
+  msg<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
 <span class="Constant">  +quit</span>
 ]
 
 <span class="SalientComment">## a board is an array of files, a file is an array of characters (squares)</span>
 
-<span class="muRecipe">recipe</span> new-board initial-position:address:array:character<span class="muRecipe"> -&gt; </span>board:address:array:address:array:character [
+<span class="muRecipe">recipe</span> new-board initial-position:address:shared:array:character<span class="muRecipe"> -&gt; </span>board:address:shared:array:address:shared:array:character [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   <span class="Comment"># assert(length(initial-position) == 64)</span>
@@ -152,19 +153,19 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   correct-length?:boolean<span class="Special"> &lt;- </span>equal len, <span class="Constant">64</span>
   assert correct-length?, <span class="Constant">[chessboard had incorrect size]</span>
   <span class="Comment"># board is an array of pointers to files; file is an array of characters</span>
-  board<span class="Special"> &lt;- </span>new <span class="Constant">location:type</span>, <span class="Constant">8</span>
+  board<span class="Special"> &lt;- </span>new <span class="Delimiter">{</span>(address shared array character): type<span class="Delimiter">}</span>, <span class="Constant">8</span>
   col:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
   <span class="Delimiter">{</span>
     done?:boolean<span class="Special"> &lt;- </span>equal col, <span class="Constant">8</span>
     <span class="muControl">break-if</span> done?
-    file:address:address:array:character<span class="Special"> &lt;- </span>index-address *board, col
+    file:address:address:shared:array:character<span class="Special"> &lt;- </span>index-address *board, col
     *file<span class="Special"> &lt;- </span>new-file initial-position, col
     col<span class="Special"> &lt;- </span>add col, <span class="Constant">1</span>
     <span class="muControl">loop</span>
   <span class="Delimiter">}</span>
 ]
 
-<span class="muRecipe">recipe</span> new-file position:address:array:character, index:number<span class="muRecipe"> -&gt; </span>result:address:array:character [
+<span class="muRecipe">recipe</span> new-file position:address:shared:array:character, index:number<span class="muRecipe"> -&gt; </span>result:address:shared:array:character [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   index<span class="Special"> &lt;- </span>multiply index, <span class="Constant">8</span>
@@ -181,10 +182,11 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   <span class="Delimiter">}</span>
 ]
 
-<span class="muRecipe">recipe</span> print-board screen:address:screen, board:address:array:address:array:character<span class="muRecipe"> -&gt; </span>screen:address:screen [
+<span class="muRecipe">recipe</span> print-board screen:address:shared:screen, board:address:shared:array:address:shared:array:character<span class="muRecipe"> -&gt; </span>screen:address:shared:screen [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   row:number<span class="Special"> &lt;- </span>copy <span class="Constant">7</span>  <span class="Comment"># start printing from the top of the board</span>
+  space:character<span class="Special"> &lt;- </span>copy <span class="Constant">32/space</span>
   <span class="Comment"># print each row</span>
   <span class="Delimiter">{</span>
     done?:boolean<span class="Special"> &lt;- </span>lesser-than row, <span class="Constant">0</span>
@@ -192,17 +194,17 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     <span class="Comment"># print rank number as a legend</span>
     rank:number<span class="Special"> &lt;- </span>add row, <span class="Constant">1</span>
     print-integer screen, rank
-    s:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[ | ]</span>
+    s:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[ | ]</span>
     print screen, s
     <span class="Comment"># print each square in the row</span>
     col:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
     <span class="Delimiter">{</span>
       done?:boolean<span class="Special"> &lt;- </span>equal col:number, <span class="Constant">8</span>
       <span class="muControl">break-if</span> done?:boolean
-      f:address:array:character<span class="Special"> &lt;- </span>index *board, col
+      f:address:shared:array:character<span class="Special"> &lt;- </span>index *board, col
       c:character<span class="Special"> &lt;- </span>index *f, row
       print screen, c
-      print screen, <span class="Constant">32/space</span>
+      print screen, space
       col<span class="Special"> &lt;- </span>add col, <span class="Constant">1</span>
       <span class="muControl">loop</span>
     <span class="Delimiter">}</span>
@@ -219,7 +221,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   screen<span class="Special"> &lt;- </span>cursor-to-next-line screen
 ]
 
-<span class="muRecipe">recipe</span> initial-position<span class="muRecipe"> -&gt; </span>board:address:array:address:array:character [
+<span class="muRecipe">recipe</span> initial-position<span class="muRecipe"> -&gt; </span>board:address:shared:array:address:shared:array:character [
   <span class="Constant">local-scope</span>
   <span class="Comment"># layout in memory (in raster order):</span>
   <span class="Comment">#   R P _ _ _ _ p r</span>
@@ -230,7 +232,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   <span class="Comment">#   B P _ _ _ _ p B</span>
   <span class="Comment">#   N P _ _ _ _ p n</span>
   <span class="Comment">#   R P _ _ _ _ p r</span>
-  initial-position:address:array:character<span class="Special"> &lt;- </span>new-array <span class="Constant">82/R</span>, <span class="Constant">80/P</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">112/p</span>, <span class="Constant">114/r</span>, <span class="Constant">78/N</span>, <span class="Constant">80/P</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">112/p</span>, <span class="Constant">110/n</span>, <span class="Constant">66/B</span>, <span class="Constant">80/P</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">112/p</span>, <span class="Constant">98/b</span>, <span class="Constant">81/Q</span>, <span class="Constant">80/P</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">112/p</span>, <span class="Constant">113/q</span>, <span class="Constant">75/K</span>, <span class="Constant">80/P</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">112/p</span>, <span class="Constant">107/k</span>, <span class="Constant">66/B</span>, <span class="Constant">80/P</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">112/p</span>, <span class="Constant">98/b</span>, <span class="Constant">78/N</span>, <span class="Constant">80/P</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">112/p</span>, <span class="Constant">110/n</span>, <span class="Constant">82/R</span>, <span class="Constant">80/P</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">112/p</span>, <span class="Constant">114/r</span>
+  initial-position:address:shared:array:character<span class="Special"> &lt;- </span>new-array <span class="Constant">82/R</span>, <span class="Constant">80/P</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">112/p</span>, <span class="Constant">114/r</span>, <span class="Constant">78/N</span>, <span class="Constant">80/P</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">112/p</span>, <span class="Constant">110/n</span>, <span class="Constant">66/B</span>, <span class="Constant">80/P</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">112/p</span>, <span class="Constant">98/b</span>, <span class="Constant">81/Q</span>, <span class="Constant">80/P</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">112/p</span>, <span class="Constant">113/q</span>, <span class="Constant">75/K</span>, <span class="Constant">80/P</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">112/p</span>, <span class="Constant">107/k</span>, <span class="Constant">66/B</span>, <span class="Constant">80/P</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">112/p</span>, <span class="Constant">98/b</span>, <span class="Constant">78/N</span>, <span class="Constant">80/P</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">112/p</span>, <span class="Constant">110/n</span>, <span class="Constant">82/R</span>, <span class="Constant">80/P</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">32/blank</span>, <span class="Constant">112/p</span>, <span class="Constant">114/r</span>
 <span class="CommentedCode">#?       82/R, 80/P, 32/blank, 32/blank, 32/blank, 32/blank, 112/p, 114/r,</span>
 <span class="CommentedCode">#?       78/N, 80/P, 32/blank, 32/blank, 32/blank, 32/blank, 112/p, 110/n,</span>
 <span class="CommentedCode">#?       66/B, 80/P, 32/blank, 32/blank, 32/blank, 32/blank, 112/p, 98/b, </span>
@@ -245,8 +247,8 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="muScenario">scenario</span> printing-the-board [
   assume-screen <span class="Constant">30/width</span>, <span class="Constant">12/height</span>
   run [
-    <span class="Constant">1</span>:address:array:address:array:character/board<span class="Special"> &lt;- </span>initial-position
-    screen:address:screen<span class="Special"> &lt;- </span>print-board screen:address:screen, <span class="Constant">1</span>:address:array:address:array:character/board
+    <span class="Constant">1</span>:address:shared:array:address:shared:array:character/board<span class="Special"> &lt;- </span>initial-position
+    screen:address:shared:screen<span class="Special"> &lt;- </span>print-board screen:address:shared:screen, <span class="Constant">1</span>:address:shared:array:address:shared:array:character/board
   ]
   screen-should-contain [
   <span class="Comment">#  012345678901234567890123456789</span>
@@ -276,14 +278,14 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 ]
 
 <span class="Comment"># prints only error messages to screen</span>
-<span class="muRecipe">recipe</span> read-move stdin:address:channel, screen:address:screen<span class="muRecipe"> -&gt; </span>result:address:move, quit?:boolean, error?:boolean, stdin:address:channel, screen:address:screen [
+<span class="muRecipe">recipe</span> read-move stdin:address:shared:channel, screen:address:shared:screen<span class="muRecipe"> -&gt; </span>result:address:shared:move, quit?:boolean, error?:boolean, stdin:address:shared:channel, screen:address:shared:screen [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   from-file:number, quit?:boolean, error?:boolean<span class="Special"> &lt;- </span>read-file stdin, screen
   <span class="muControl">reply-if</span> quit?, <span class="Constant">0/dummy</span>, quit?, error?
   <span class="muControl">reply-if</span> error?, <span class="Constant">0/dummy</span>, quit?, error?
   <span class="Comment"># construct the move object</span>
-  result:address:move<span class="Special"> &lt;- </span>new <span class="Constant">move:type</span>
+  result:address:shared:move<span class="Special"> &lt;- </span>new <span class="Constant">move:type</span>
   x:address:number<span class="Special"> &lt;- </span>get-address *result, <span class="Constant">from-file:offset</span>
   *x<span class="Special"> &lt;- </span>copy from-file
   x<span class="Special"> &lt;- </span>get-address *result, <span class="Constant">from-rank:offset</span>
@@ -306,7 +308,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 ]
 
 <span class="Comment"># valid values for file: 0-7</span>
-<span class="muRecipe">recipe</span> read-file stdin:address:channel, screen:address:screen<span class="muRecipe"> -&gt; </span>file:number, quit:boolean, error:boolean, stdin:address:channel, screen:address:screen [
+<span class="muRecipe">recipe</span> read-file stdin:address:shared:channel, screen:address:shared:screen<span class="muRecipe"> -&gt; </span>file:number, quit:boolean, error:boolean, stdin:address:shared:channel, screen:address:shared:screen [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   c:character, stdin<span class="Special"> &lt;- </span>read stdin
@@ -328,7 +330,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   <span class="Delimiter">{</span>
     newline?:boolean<span class="Special"> &lt;- </span>equal c, <span class="Constant">10/newline</span>
     <span class="muControl">break-unless</span> newline?
-    error-message:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[that's not enough]</span>
+    error-message:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[that's not enough]</span>
     print screen, error-message
     <span class="muControl">reply</span> <span class="Constant">0/dummy</span>, <span class="Constant">0/quit</span>, <span class="Constant">1/error</span>
   <span class="Delimiter">}</span>
@@ -337,7 +339,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   <span class="Delimiter">{</span>
     above-min:boolean<span class="Special"> &lt;- </span>greater-or-equal file, <span class="Constant">0</span>
     <span class="muControl">break-if</span> above-min
-    error-message:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[file too low: ]</span>
+    error-message:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[file too low: ]</span>
     print screen, error-message
     print screen, c
     cursor-to-next-line screen
@@ -355,7 +357,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 ]
 
 <span class="Comment"># valid values: 0-7, -1 (quit), -2 (error)</span>
-<span class="muRecipe">recipe</span> read-rank stdin:address:channel, screen:address:screen<span class="muRecipe"> -&gt; </span>rank:number, quit?:boolean, error?:boolean, stdin:address:channel, screen:address:screen [
+<span class="muRecipe">recipe</span> read-rank stdin:address:shared:channel, screen:address:shared:screen<span class="muRecipe"> -&gt; </span>rank:number, quit?:boolean, error?:boolean, stdin:address:shared:channel, screen:address:shared:screen [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   c:character, stdin<span class="Special"> &lt;- </span>read stdin
@@ -372,7 +374,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   <span class="Delimiter">{</span>
     newline?:boolean<span class="Special"> &lt;- </span>equal c, <span class="Constant">10</span>  <span class="Comment"># newline</span>
     <span class="muControl">break-unless</span> newline?
-    error-message:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[that's not enough]</span>
+    error-message:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[that's not enough]</span>
     print screen, error-message
     <span class="muControl">reply</span> <span class="Constant">0/dummy</span>, <span class="Constant">0/quit</span>, <span class="Constant">1/error</span>
   <span class="Delimiter">}</span>
@@ -399,14 +401,14 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="Comment"># read a character from the given channel and check that it's what we expect</span>
 <span class="Comment"># return true on error</span>
-<span class="muRecipe">recipe</span> expect-from-channel stdin:address:channel, expected:character, screen:address:screen<span class="muRecipe"> -&gt; </span>result:boolean, stdin:address:channel, screen:address:screen [
+<span class="muRecipe">recipe</span> expect-from-channel stdin:address:shared:channel, expected:character, screen:address:shared:screen<span class="muRecipe"> -&gt; </span>result:boolean, stdin:address:shared:channel, screen:address:shared:screen [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   c:character, stdin<span class="Special"> &lt;- </span>read stdin
   <span class="Delimiter">{</span>
     match?:boolean<span class="Special"> &lt;- </span>equal c, expected
     <span class="muControl">break-if</span> match?
-    s:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[expected character not found]</span>
+    s:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[expected character not found]</span>
     print screen, s
   <span class="Delimiter">}</span>
   result<span class="Special"> &lt;- </span>not match?
@@ -415,8 +417,8 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="muScenario">scenario</span> read-move-blocking [
   assume-screen <span class="Constant">20/width</span>, <span class="Constant">2/height</span>
   run [
-    <span class="Constant">1</span>:address:channel<span class="Special"> &lt;- </span>new-channel <span class="Constant">2</span>
-    <span class="Constant">2</span>:number/routine<span class="Special"> &lt;- </span>start-running <span class="Constant">read-move:recipe</span>, <span class="Constant">1</span>:address:channel, screen:address:screen
+    <span class="Constant">1</span>:address:shared:channel<span class="Special"> &lt;- </span>new-channel <span class="Constant">2</span>
+    <span class="Constant">2</span>:number/routine<span class="Special"> &lt;- </span>start-running read-move, <span class="Constant">1</span>:address:shared:channel, screen:address:shared:screen
     <span class="Comment"># 'read-move' is waiting for input</span>
     wait-for-routine <span class="Constant">2</span>:number
     <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>routine-state <span class="Constant">2</span>:number/id
@@ -424,7 +426,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     assert <span class="Constant">4</span>:boolean/waiting?, [
 F read-move-blocking: routine failed to pause <span class="muRecipe">after</span> coming up (<span class="muRecipe">before</span> any keys were pressed)]
     <span class="Comment"># press 'a'</span>
-    <span class="Constant">1</span>:address:channel<span class="Special"> &lt;- </span>write <span class="Constant">1</span>:address:channel, <span class="Constant">97/a</span>
+    <span class="Constant">1</span>:address:shared:channel<span class="Special"> &lt;- </span>write <span class="Constant">1</span>:address:shared:channel, <span class="Constant">97/a</span>
     restart <span class="Constant">2</span>:number/routine
     <span class="Comment"># 'read-move' still waiting for input</span>
     wait-for-routine <span class="Constant">2</span>:number
@@ -433,7 +435,7 @@ F read-move-blocking: routine failed to pause <span class="muRecipe">after</span
     assert <span class="Constant">4</span>:boolean/waiting?, [
 F read-move-blocking: routine failed to pause <span class="muRecipe">after</span> rank 'a']
     <span class="Comment"># press '2'</span>
-    <span class="Constant">1</span>:address:channel<span class="Special"> &lt;- </span>write <span class="Constant">1</span>:address:channel, <span class="Constant">50/'2'</span>
+    <span class="Constant">1</span>:address:shared:channel<span class="Special"> &lt;- </span>write <span class="Constant">1</span>:address:shared:channel, <span class="Constant">50/'2'</span>
     restart <span class="Constant">2</span>:number/routine
     <span class="Comment"># 'read-move' still waiting for input</span>
     wait-for-routine <span class="Constant">2</span>:number
@@ -442,7 +444,7 @@ F read-move-blocking: routine failed to pause <span class="muRecipe">after</span
     assert <span class="Constant">4</span>:boolean/waiting?, [
 F read-move-blocking: routine failed to pause <span class="muRecipe">after</span> file 'a2']
     <span class="Comment"># press '-'</span>
-    <span class="Constant">1</span>:address:channel<span class="Special"> &lt;- </span>write <span class="Constant">1</span>:address:channel, <span class="Constant">45/'-'</span>
+    <span class="Constant">1</span>:address:shared:channel<span class="Special"> &lt;- </span>write <span class="Constant">1</span>:address:shared:channel, <span class="Constant">45/'-'</span>
     restart <span class="Constant">2</span>:number/routine
     <span class="Comment"># 'read-move' still waiting for input</span>
     wait-for-routine <span class="Constant">2</span>:number
@@ -451,7 +453,7 @@ F read-move-blocking: routine failed to pause <span class="muRecipe">after</span
     assert <span class="Constant">4</span>:boolean/waiting?/routine-state, [
 F read-move-blocking: routine failed to pause <span class="muRecipe">after</span> hyphen 'a2-']
     <span class="Comment"># press 'a'</span>
-    <span class="Constant">1</span>:address:channel<span class="Special"> &lt;- </span>write <span class="Constant">1</span>:address:channel, <span class="Constant">97/a</span>
+    <span class="Constant">1</span>:address:shared:channel<span class="Special"> &lt;- </span>write <span class="Constant">1</span>:address:shared:channel, <span class="Constant">97/a</span>
     restart <span class="Constant">2</span>:number/routine
     <span class="Comment"># 'read-move' still waiting for input</span>
     wait-for-routine <span class="Constant">2</span>:number
@@ -460,7 +462,7 @@ F read-move-blocking: routine failed to pause <span class="muRecipe">after</span
     assert <span class="Constant">4</span>:boolean/waiting?/routine-state, [
 F read-move-blocking: routine failed to pause <span class="muRecipe">after</span> rank 'a2-a']
     <span class="Comment"># press '4'</span>
-    <span class="Constant">1</span>:address:channel<span class="Special"> &lt;- </span>write <span class="Constant">1</span>:address:channel, <span class="Constant">52/'4'</span>
+    <span class="Constant">1</span>:address:shared:channel<span class="Special"> &lt;- </span>write <span class="Constant">1</span>:address:shared:channel, <span class="Constant">52/'4'</span>
     restart <span class="Constant">2</span>:number/routine
     <span class="Comment"># 'read-move' still waiting for input</span>
     wait-for-routine <span class="Constant">2</span>:number
@@ -469,7 +471,7 @@ F read-move-blocking: routine failed to pause <span class="muRecipe">after</span
     assert <span class="Constant">4</span>:boolean/waiting?, [
 F read-move-blocking: routine failed to pause <span class="muRecipe">after</span> file 'a2-a4']
     <span class="Comment"># press 'newline'</span>
-    <span class="Constant">1</span>:address:channel<span class="Special"> &lt;- </span>write <span class="Constant">1</span>:address:channel, <span class="Constant">10</span>  <span class="Comment"># newline</span>
+    <span class="Constant">1</span>:address:shared:channel<span class="Special"> &lt;- </span>write <span class="Constant">1</span>:address:shared:channel, <span class="Constant">10</span>  <span class="Comment"># newline</span>
     restart <span class="Constant">2</span>:number/routine
     <span class="Comment"># 'read-move' now completes</span>
     wait-for-routine <span class="Constant">2</span>:number
@@ -487,8 +489,8 @@ F read-move-blocking: routine failed to terminate on newline]
 <span class="muScenario">scenario</span> read-move-quit [
   assume-screen <span class="Constant">20/width</span>, <span class="Constant">2/height</span>
   run [
-    <span class="Constant">1</span>:address:channel<span class="Special"> &lt;- </span>new-channel <span class="Constant">2</span>
-    <span class="Constant">2</span>:number/routine<span class="Special"> &lt;- </span>start-running <span class="Constant">read-move:recipe</span>, <span class="Constant">1</span>:address:channel, screen:address:screen
+    <span class="Constant">1</span>:address:shared:channel<span class="Special"> &lt;- </span>new-channel <span class="Constant">2</span>
+    <span class="Constant">2</span>:number/routine<span class="Special"> &lt;- </span>start-running read-move, <span class="Constant">1</span>:address:shared:channel, screen:address:shared:screen
     <span class="Comment"># 'read-move' is waiting for input</span>
     wait-for-routine <span class="Constant">2</span>:number
     <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>routine-state <span class="Constant">2</span>:number/id
@@ -496,7 +498,7 @@ F read-move-blocking: routine failed to terminate on newline]
     assert <span class="Constant">4</span>:boolean/waiting?, [
 F read-move-quit: routine failed to pause <span class="muRecipe">after</span> coming up (<span class="muRecipe">before</span> any keys were pressed)]
     <span class="Comment"># press 'q'</span>
-    <span class="Constant">1</span>:address:channel<span class="Special"> &lt;- </span>write <span class="Constant">1</span>:address:channel, <span class="Constant">113/q</span>
+    <span class="Constant">1</span>:address:shared:channel<span class="Special"> &lt;- </span>write <span class="Constant">1</span>:address:shared:channel, <span class="Constant">113/q</span>
     restart <span class="Constant">2</span>:number/routine
     <span class="Comment"># 'read-move' completes</span>
     wait-for-routine <span class="Constant">2</span>:number
@@ -514,15 +516,15 @@ F read-move-quit: routine failed to terminate on 'q']
 <span class="muScenario">scenario</span> read-move-illegal-file [
   assume-screen <span class="Constant">20/width</span>, <span class="Constant">2/height</span>
   run [
-    <span class="Constant">1</span>:address:channel<span class="Special"> &lt;- </span>new-channel <span class="Constant">2</span>
-    <span class="Constant">2</span>:number/routine<span class="Special"> &lt;- </span>start-running <span class="Constant">read-move:recipe</span>, <span class="Constant">1</span>:address:channel, screen:address:screen
+    <span class="Constant">1</span>:address:shared:channel<span class="Special"> &lt;- </span>new-channel <span class="Constant">2</span>
+    <span class="Constant">2</span>:number/routine<span class="Special"> &lt;- </span>start-running read-move, <span class="Constant">1</span>:address:shared:channel, screen:address:shared:screen
     <span class="Comment"># 'read-move' is waiting for input</span>
     wait-for-routine <span class="Constant">2</span>:number
     <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>routine-state <span class="Constant">2</span>:number/id
     <span class="Constant">4</span>:boolean/waiting?<span class="Special"> &lt;- </span>equal <span class="Constant">3</span>:number/routine-state, <span class="Constant">3/waiting</span>
     assert <span class="Constant">4</span>:boolean/waiting?, [
 F read-move-file: routine failed to pause <span class="muRecipe">after</span> coming up (<span class="muRecipe">before</span> any keys were pressed)]
-    <span class="Constant">1</span>:address:channel<span class="Special"> &lt;- </span>write <span class="Constant">1</span>:address:channel, <span class="Constant">50/'2'</span>
+    <span class="Constant">1</span>:address:shared:channel<span class="Special"> &lt;- </span>write <span class="Constant">1</span>:address:shared:channel, <span class="Constant">50/'2'</span>
     restart <span class="Constant">2</span>:number/routine
     wait-for-routine <span class="Constant">2</span>:number
   ]
@@ -535,16 +537,16 @@ F read-move-file: routine failed to pause <span class="muRecipe">after</span> co
 <span class="muScenario">scenario</span> read-move-illegal-rank [
   assume-screen <span class="Constant">20/width</span>, <span class="Constant">2/height</span>
   run [
-    <span class="Constant">1</span>:address:channel<span class="Special"> &lt;- </span>new-channel <span class="Constant">2</span>
-    <span class="Constant">2</span>:number/routine<span class="Special"> &lt;- </span>start-running <span class="Constant">read-move:recipe</span>, <span class="Constant">1</span>:address:channel, screen:address:screen
+    <span class="Constant">1</span>:address:shared:channel<span class="Special"> &lt;- </span>new-channel <span class="Constant">2</span>
+    <span class="Constant">2</span>:number/routine<span class="Special"> &lt;- </span>start-running read-move, <span class="Constant">1</span>:address:shared:channel, screen:address:shared:screen
     <span class="Comment"># 'read-move' is waiting for input</span>
     wait-for-routine <span class="Constant">2</span>:number
     <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>routine-state <span class="Constant">2</span>:number/id
     <span class="Constant">4</span>:boolean/waiting?<span class="Special"> &lt;- </span>equal <span class="Constant">3</span>:number/routine-state, <span class="Constant">3/waiting</span>
     assert <span class="Constant">4</span>:boolean/waiting?, [
 F read-move-file: routine failed to pause <span class="muRecipe">after</span> coming up (<span class="muRecipe">before</span> any keys were pressed)]
-    <span class="Constant">1</span>:address:channel<span class="Special"> &lt;- </span>write <span class="Constant">1</span>:address:channel, <span class="Constant">97/a</span>
-    <span class="Constant">1</span>:address:channel<span class="Special"> &lt;- </span>write <span class="Constant">1</span>:address:channel, <span class="Constant">97/a</span>
+    <span class="Constant">1</span>:address:shared:channel<span class="Special"> &lt;- </span>write <span class="Constant">1</span>:address:shared:channel, <span class="Constant">97/a</span>
+    <span class="Constant">1</span>:address:shared:channel<span class="Special"> &lt;- </span>write <span class="Constant">1</span>:address:shared:channel, <span class="Constant">97/a</span>
     restart <span class="Constant">2</span>:number/routine
     wait-for-routine <span class="Constant">2</span>:number
   ]
@@ -557,16 +559,16 @@ F read-move-file: routine failed to pause <span class="muRecipe">after</span> co
 <span class="muScenario">scenario</span> read-move-empty [
   assume-screen <span class="Constant">20/width</span>, <span class="Constant">2/height</span>
   run [
-    <span class="Constant">1</span>:address:channel<span class="Special"> &lt;- </span>new-channel <span class="Constant">2</span>
-    <span class="Constant">2</span>:number/routine<span class="Special"> &lt;- </span>start-running <span class="Constant">read-move:recipe</span>, <span class="Constant">1</span>:address:channel, screen:address:screen
+    <span class="Constant">1</span>:address:shared:channel<span class="Special"> &lt;- </span>new-channel <span class="Constant">2</span>
+    <span class="Constant">2</span>:number/routine<span class="Special"> &lt;- </span>start-running read-move, <span class="Constant">1</span>:address:shared:channel, screen:address:shared:screen
     <span class="Comment"># 'read-move' is waiting for input</span>
     wait-for-routine <span class="Constant">2</span>:number
     <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>routine-state <span class="Constant">2</span>:number/id
     <span class="Constant">4</span>:boolean/waiting?<span class="Special"> &lt;- </span>equal <span class="Constant">3</span>:number/routine-state, <span class="Constant">3/waiting</span>
     assert <span class="Constant">4</span>:boolean/waiting?, [
 F read-move-file: routine failed to pause <span class="muRecipe">after</span> coming up (<span class="muRecipe">before</span> any keys were pressed)]
-    <span class="Constant">1</span>:address:channel<span class="Special"> &lt;- </span>write <span class="Constant">1</span>:address:channel, <span class="Constant">10/newline</span>
-    <span class="Constant">1</span>:address:channel<span class="Special"> &lt;- </span>write <span class="Constant">1</span>:address:channel, <span class="Constant">97/a</span>
+    <span class="Constant">1</span>:address:shared:channel<span class="Special"> &lt;- </span>write <span class="Constant">1</span>:address:shared:channel, <span class="Constant">10/newline</span>
+    <span class="Constant">1</span>:address:shared:channel<span class="Special"> &lt;- </span>write <span class="Constant">1</span>:address:shared:channel, <span class="Constant">97/a</span>
     restart <span class="Constant">2</span>:number/routine
     wait-for-routine <span class="Constant">2</span>:number
   ]
@@ -576,14 +578,14 @@ F read-move-file: routine failed to pause <span class="muRecipe">after</span> co
   ]
 ]
 
-<span class="muRecipe">recipe</span> make-move board:address:array:address:array:character, m:address:move<span class="muRecipe"> -&gt; </span>board:address:array:address:array:character [
+<span class="muRecipe">recipe</span> make-move board:address:shared:array:address:shared:array:character, m:address:shared:move<span class="muRecipe"> -&gt; </span>board:address:shared:array:address:shared:array:character [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   from-file:number<span class="Special"> &lt;- </span>get *m, <span class="Constant">from-file:offset</span>
   from-rank:number<span class="Special"> &lt;- </span>get *m, <span class="Constant">from-rank:offset</span>
   to-file:number<span class="Special"> &lt;- </span>get *m, <span class="Constant">to-file:offset</span>
   to-rank:number<span class="Special"> &lt;- </span>get *m, <span class="Constant">to-rank:offset</span>
-  f:address:array:character<span class="Special"> &lt;- </span>index *board, from-file
+  f:address:shared:array:character<span class="Special"> &lt;- </span>index *board, from-file
   src:address:character/square<span class="Special"> &lt;- </span>index-address *f, from-rank
   f<span class="Special"> &lt;- </span>index *board, to-file
   dest:address:character/square<span class="Special"> &lt;- </span>index-address *f, to-rank
@@ -594,18 +596,18 @@ F read-move-file: routine failed to pause <span class="muRecipe">after</span> co
 <span class="muScenario">scenario</span> making-a-move [
   assume-screen <span class="Constant">30/width</span>, <span class="Constant">12/height</span>
   run [
-    <span class="Constant">2</span>:address:array:address:array:character/board<span class="Special"> &lt;- </span>initial-position
-    <span class="Constant">3</span>:address:move<span class="Special"> &lt;- </span>new <span class="Constant">move:type</span>
-    <span class="Constant">4</span>:address:number<span class="Special"> &lt;- </span>get-address *<span class="Constant">3</span>:address:move, <span class="Constant">from-file:offset</span>
+    <span class="Constant">2</span>:address:shared:array:address:shared:array:character/board<span class="Special"> &lt;- </span>initial-position
+    <span class="Constant">3</span>:address:shared:move<span class="Special"> &lt;- </span>new <span class="Constant">move:type</span>
+    <span class="Constant">4</span>:address:number<span class="Special"> &lt;- </span>get-address *<span class="Constant">3</span>:address:shared:move, <span class="Constant">from-file:offset</span>
     *<span class="Constant">4</span>:address:number<span class="Special"> &lt;- </span>copy <span class="Constant">6/g</span>
-    <span class="Constant">5</span>:address:number<span class="Special"> &lt;- </span>get-address *<span class="Constant">3</span>:address:move, <span class="Constant">from-rank:offset</span>
+    <span class="Constant">5</span>:address:number<span class="Special"> &lt;- </span>get-address *<span class="Constant">3</span>:address:shared:move, <span class="Constant">from-rank:offset</span>
     *<span class="Constant">5</span>:address:number<span class="Special"> &lt;- </span>copy <span class="Constant">1/'2'</span>
-    <span class="Constant">6</span>:address:number<span class="Special"> &lt;- </span>get-address *<span class="Constant">3</span>:address:move, <span class="Constant">to-file:offset</span>
+    <span class="Constant">6</span>:address:number<span class="Special"> &lt;- </span>get-address *<span class="Constant">3</span>:address:shared:move, <span class="Constant">to-file:offset</span>
     *<span class="Constant">6</span>:address:number<span class="Special"> &lt;- </span>copy <span class="Constant">6/g</span>
-    <span class="Constant">7</span>:address:number<span class="Special"> &lt;- </span>get-address *<span class="Constant">3</span>:address:move, <span class="Constant">to-rank:offset</span>
+    <span class="Constant">7</span>:address:number<span class="Special"> &lt;- </span>get-address *<span class="Constant">3</span>:address:shared:move, <span class="Constant">to-rank:offset</span>
     *<span class="Constant">7</span>:address:number<span class="Special"> &lt;- </span>copy <span class="Constant">3/'4'</span>
-    <span class="Constant">2</span>:address:array:address:array:character/board<span class="Special"> &lt;- </span>make-move <span class="Constant">2</span>:address:array:address:array:character/board, <span class="Constant">3</span>:address:move
-    screen:address:screen<span class="Special"> &lt;- </span>print-board screen:address:screen, <span class="Constant">2</span>:address:array:address:array:character/board
+    <span class="Constant">2</span>:address:shared:array:address:shared:array:character/board<span class="Special"> &lt;- </span>make-move <span class="Constant">2</span>:address:shared:array:address:shared:array:character/board, <span class="Constant">3</span>:address:shared:move
+    screen:address:shared:screen<span class="Special"> &lt;- </span>print-board screen:address:shared:screen, <span class="Constant">2</span>:address:shared:array:address:shared:array:character/board
   ]
   screen-should-contain [
   <span class="Comment">#  012345678901234567890123456789</span>
diff --git a/html/counters.mu.html b/html/counters.mu.html
index 495def81..e73a5581 100644
--- a/html/counters.mu.html
+++ b/html/counters.mu.html
@@ -31,24 +31,24 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="Comment"># example program: maintain multiple counters with isolated lexical scopes</span>
 <span class="Comment"># (spaces)</span>
 
-<span class="muRecipe">recipe</span> new-counter n:number<span class="muRecipe"> -&gt; </span><span class="Constant">default-space</span>:address:array:location [
+<span class="muRecipe">recipe</span> new-counter n:number<span class="muRecipe"> -&gt; </span><span class="Constant">default-space</span>:address:shared:array:location [
   <span class="Constant">default-space</span><span class="Special"> &lt;- </span>new <span class="Constant">location:type</span>, <span class="Constant">30</span>
   <span class="Constant">load-ingredients</span>
 ]
 
-<span class="muRecipe">recipe</span> increment-counter outer:address:array:location/names:new-counter, x:number<span class="muRecipe"> -&gt; </span>n:number/space:<span class="Constant">1</span> [
+<span class="muRecipe">recipe</span> increment-counter outer:address:shared:array:location/names:new-counter, x:number<span class="muRecipe"> -&gt; </span>n:number/space:<span class="Constant">1</span> [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
-  <span class="Constant">0</span>:address:array:location/names:new-counter<span class="Special"> &lt;- </span>copy outer  <span class="Comment"># setup outer space; it *must* come from 'new-counter'</span>
+  <span class="Constant">0</span>:address:shared:array:location/names:new-counter<span class="Special"> &lt;- </span>copy outer  <span class="Comment"># setup outer space; it *must* come from 'new-counter'</span>
   n/space:<span class="Constant">1</span><span class="Special"> &lt;- </span>add n/space:<span class="Constant">1</span>, x
 ]
 
 <span class="muRecipe">recipe</span> main [
   <span class="Constant">local-scope</span>
   <span class="Comment"># counter A</span>
-  a:address:array:location<span class="Special"> &lt;- </span>new-counter <span class="Constant">34</span>
+  a:address:shared:array:location<span class="Special"> &lt;- </span>new-counter <span class="Constant">34</span>
   <span class="Comment"># counter B</span>
-  b:address:array:location<span class="Special"> &lt;- </span>new-counter <span class="Constant">23</span>
+  b:address:shared:array:location<span class="Special"> &lt;- </span>new-counter <span class="Constant">23</span>
   <span class="Comment"># increment both by 2 but in different ways</span>
   increment-counter a, <span class="Constant">1</span>
   b-value:number<span class="Special"> &lt;- </span>increment-counter b, <span class="Constant">2</span>
diff --git a/html/edit/001-editor.mu.html b/html/edit/001-editor.mu.html
index 11d1cb9d..ec683ce7 100644
--- a/html/edit/001-editor.mu.html
+++ b/html/edit/001-editor.mu.html
@@ -37,7 +37,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="Comment"># temporary main for this layer: just render the given text at the given</span>
 <span class="Comment"># screen dimensions, then stop</span>
-<span class="muRecipe">recipe!</span> main text:address:array:character [
+<span class="muRecipe">recipe!</span> main text:address:shared:array:character [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   open-console
@@ -51,8 +51,8 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="muScenario">scenario</span> editor-initially-prints-text-to-screen [
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
   run [
-    <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
-    new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+    <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
+    new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
   ]
   screen-should-contain [
     <span class="Comment"># top line of screen reserved for menu</span>
@@ -64,16 +64,17 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muData">container</span> editor-data [
   <span class="Comment"># editable text: doubly linked list of characters (head contains a special sentinel)</span>
-  data:address:duplex-list:character
-  top-of-screen:address:duplex-list:character
-  bottom-of-screen:address:duplex-list:character
+  data:address:shared:duplex-list:character
+  top-of-screen:address:shared:duplex-list:character
+  bottom-of-screen:address:shared:duplex-list:character
   <span class="Comment"># location before cursor inside data</span>
-  before-cursor:address:duplex-list:character
+  before-cursor:address:shared:duplex-list:character
 
   <span class="Comment"># raw bounds of display area on screen</span>
   <span class="Comment"># always displays from row 1 (leaving row 0 for a menu) and at most until bottom of screen</span>
   left:number
   right:number
+  bottom:number
   <span class="Comment"># raw screen coordinates of cursor</span>
   cursor-row:number
   cursor-column:number
@@ -82,7 +83,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="Comment"># creates a new editor widget and renders its initial appearance to screen</span>
 <span class="Comment">#   top/left/right constrain the screen area available to the new editor</span>
 <span class="Comment">#   right is exclusive</span>
-<span class="muRecipe">recipe</span> new-editor s:address:array:character, screen:address:screen, left:number, right:number<span class="muRecipe"> -&gt; </span>result:address:editor-data, screen:address:screen [
+<span class="muRecipe">recipe</span> new-editor s:address:shared:array:character, screen:address:shared:screen, left:number, right:number<span class="muRecipe"> -&gt; </span>result:address:shared:editor-data, screen:address:shared:screen [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   <span class="Comment"># no clipping of bounds</span>
@@ -98,11 +99,11 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   *x<span class="Special"> &lt;- </span>copy <span class="Constant">1/top</span>
   x<span class="Special"> &lt;- </span>get-address *result, <span class="Constant">cursor-column:offset</span>
   *x<span class="Special"> &lt;- </span>copy left
-  init:address:address:duplex-list:character<span class="Special"> &lt;- </span>get-address *result, <span class="Constant">data:offset</span>
+  init:address:address:shared:duplex-list:character<span class="Special"> &lt;- </span>get-address *result, <span class="Constant">data:offset</span>
   *init<span class="Special"> &lt;- </span>push <span class="Constant">167/§</span>, <span class="Constant">0/tail</span>
-  top-of-screen:address:address:duplex-list:character<span class="Special"> &lt;- </span>get-address *result, <span class="Constant">top-of-screen:offset</span>
+  top-of-screen:address:address:shared:duplex-list:character<span class="Special"> &lt;- </span>get-address *result, <span class="Constant">top-of-screen:offset</span>
   *top-of-screen<span class="Special"> &lt;- </span>copy *init
-  y:address:address:duplex-list:character<span class="Special"> &lt;- </span>get-address *result, <span class="Constant">before-cursor:offset</span>
+  y:address:address:shared:duplex-list:character<span class="Special"> &lt;- </span>get-address *result, <span class="Constant">before-cursor:offset</span>
   *y<span class="Special"> &lt;- </span>copy *init
   result<span class="Special"> &lt;- </span>insert-text result, s
   <span class="Comment"># initialize cursor to top of screen</span>
@@ -113,7 +114,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="Constant">  &lt;editor-initialization&gt;</span>
 ]
 
-<span class="muRecipe">recipe</span> insert-text editor:address:editor-data, text:address:array:character<span class="muRecipe"> -&gt; </span>editor:address:editor-data [
+<span class="muRecipe">recipe</span> insert-text editor:address:shared:editor-data, text:address:shared:array:character<span class="muRecipe"> -&gt; </span>editor:address:shared:editor-data [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   <span class="Comment"># early exit if text is empty</span>
@@ -122,7 +123,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   <span class="muControl">reply-unless</span> len, editor/same-as-ingredient:<span class="Constant">0</span>
   idx:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
   <span class="Comment"># now we can start appending the rest, character by character</span>
-  curr:address:duplex-list:character<span class="Special"> &lt;- </span>get *editor, <span class="Constant">data:offset</span>
+  curr:address:shared:duplex-list:character<span class="Special"> &lt;- </span>get *editor, <span class="Constant">data:offset</span>
   <span class="Delimiter">{</span>
     done?:boolean<span class="Special"> &lt;- </span>greater-or-equal idx, len
     <span class="muControl">break-if</span> done?
@@ -139,8 +140,8 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="muScenario">scenario</span> editor-initializes-without-data [
   assume-screen <span class="Constant">5/width</span>, <span class="Constant">3/height</span>
   run [
-    <span class="Constant">1</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">0/data</span>, screen:address:screen, <span class="Constant">2/left</span>, <span class="Constant">5/right</span>
-    <span class="Constant">2</span>:editor-data<span class="Special"> &lt;- </span>copy *<span class="Constant">1</span>:address:editor-data
+    <span class="Constant">1</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">0/data</span>, screen:address:shared:screen, <span class="Constant">2/left</span>, <span class="Constant">5/right</span>
+    <span class="Constant">2</span>:editor-data<span class="Special"> &lt;- </span>copy *<span class="Constant">1</span>:address:shared:editor-data
   ]
   memory-should-contain [
     <span class="Comment"># 2 (data) &lt;- just the § sentinel</span>
@@ -149,8 +150,9 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     <span class="Comment"># 5 (before cursor) &lt;- the § sentinel</span>
     <span class="Constant">6</span><span class="Special"> &lt;- </span><span class="Constant">2</span>  <span class="Comment"># left</span>
     <span class="Constant">7</span><span class="Special"> &lt;- </span><span class="Constant">4</span>  <span class="Comment"># right  (inclusive)</span>
-    <span class="Constant">8</span><span class="Special"> &lt;- </span><span class="Constant">1</span>  <span class="Comment"># cursor row</span>
-    <span class="Constant">9</span><span class="Special"> &lt;- </span><span class="Constant">2</span>  <span class="Comment"># cursor column</span>
+    <span class="Constant">8</span><span class="Special"> &lt;- </span><span class="Constant">1</span>  <span class="Comment"># bottom</span>
+    <span class="Constant">9</span><span class="Special"> &lt;- </span><span class="Constant">1</span>  <span class="Comment"># cursor row</span>
+    <span class="Constant">10</span><span class="Special"> &lt;- </span><span class="Constant">2</span>  <span class="Comment"># cursor column</span>
   ]
   screen-should-contain [
    <span class="Constant"> .     .</span>
@@ -162,7 +164,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="Comment"># Assumes cursor should be at coordinates (cursor-row, cursor-column) and</span>
 <span class="Comment"># updates before-cursor to match. Might also move coordinates if they're</span>
 <span class="Comment"># outside text.</span>
-<span class="muRecipe">recipe</span> render screen:address:screen, editor:address:editor-data<span class="muRecipe"> -&gt; </span>last-row:number, last-column:number, screen:address:screen, editor:address:editor-data [
+<span class="muRecipe">recipe</span> render screen:address:shared:screen, editor:address:shared:editor-data<span class="muRecipe"> -&gt; </span>last-row:number, last-column:number, screen:address:shared:screen, editor:address:shared:editor-data [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   <span class="muControl">reply-unless</span> editor, <span class="Constant">1/top</span>, <span class="Constant">0/left</span>, screen/same-as-ingredient:<span class="Constant">0</span>, editor/same-as-ingredient:<span class="Constant">1</span>
@@ -170,8 +172,8 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   screen-height:number<span class="Special"> &lt;- </span>screen-height screen
   right:number<span class="Special"> &lt;- </span>get *editor, <span class="Constant">right:offset</span>
   <span class="Comment"># traversing editor</span>
-  curr:address:duplex-list:character<span class="Special"> &lt;- </span>get *editor, <span class="Constant">top-of-screen:offset</span>
-  prev:address:duplex-list:character<span class="Special"> &lt;- </span>copy curr  <span class="Comment"># just in case curr becomes null and we can't compute prev</span>
+  curr:address:shared:duplex-list:character<span class="Special"> &lt;- </span>get *editor, <span class="Constant">top-of-screen:offset</span>
+  prev:address:shared:duplex-list:character<span class="Special"> &lt;- </span>copy curr  <span class="Comment"># just in case curr becomes null and we can't compute prev</span>
   curr<span class="Special"> &lt;- </span>next curr
   <span class="Comment"># traversing screen</span>
 <span class="Constant">  +render-loop-initialization</span>
@@ -180,7 +182,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   column:number<span class="Special"> &lt;- </span>copy left
   cursor-row:address:number<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">cursor-row:offset</span>
   cursor-column:address:number<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">cursor-column:offset</span>
-  before-cursor:address:address:duplex-list:character<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">before-cursor:offset</span>
+  before-cursor:address:address:shared:duplex-list:character<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">before-cursor:offset</span>
   screen<span class="Special"> &lt;- </span>move-cursor screen, row, column
   <span class="Delimiter">{</span>
 <span class="Constant">    +next-character</span>
@@ -228,7 +230,8 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
       at-right?:boolean<span class="Special"> &lt;- </span>equal column, right
       <span class="muControl">break-unless</span> at-right?
       <span class="Comment"># print wrap icon</span>
-      print screen, <span class="Constant">8617/loop-back-to-left</span>, <span class="Constant">245/grey</span>
+      wrap-icon:character<span class="Special"> &lt;- </span>copy <span class="Constant">8617/loop-back-to-left</span>
+      print screen, wrap-icon, <span class="Constant">245/grey</span>
       column<span class="Special"> &lt;- </span>copy left
       row<span class="Special"> &lt;- </span>add row, <span class="Constant">1</span>
       screen<span class="Special"> &lt;- </span>move-cursor screen, row, column
@@ -242,7 +245,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     <span class="muControl">loop</span>
   <span class="Delimiter">}</span>
   <span class="Comment"># save first character off-screen</span>
-  bottom-of-screen:address:address:duplex-list:character<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">bottom-of-screen:offset</span>
+  bottom-of-screen:address:address:shared:duplex-list:character<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">bottom-of-screen:offset</span>
   *bottom-of-screen<span class="Special"> &lt;- </span>copy curr
   <span class="Comment"># is cursor to the right of the last line? move to end</span>
   <span class="Delimiter">{</span>
@@ -256,22 +259,31 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     *cursor-column<span class="Special"> &lt;- </span>copy column
     *before-cursor<span class="Special"> &lt;- </span>copy prev
   <span class="Delimiter">}</span>
+  bottom:address:number<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">bottom:offset</span>
+  *bottom<span class="Special"> &lt;- </span>copy row
   <span class="muControl">reply</span> row, column, screen/same-as-ingredient:<span class="Constant">0</span>, editor/same-as-ingredient:<span class="Constant">1</span>
 ]
 
-<span class="muRecipe">recipe</span> clear-line-delimited screen:address:screen, column:number, right:number<span class="muRecipe"> -&gt; </span>screen:address:screen [
+<span class="muRecipe">recipe</span> clear-line-delimited screen:address:shared:screen, column:number, right:number<span class="muRecipe"> -&gt; </span>screen:address:shared:screen [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
+  space:character<span class="Special"> &lt;- </span>copy <span class="Constant">32/space</span>
+  bg-color:number, bg-color-found?:boolean<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
+  <span class="Delimiter">{</span>
+    <span class="Comment"># default bg-color to black</span>
+    <span class="muControl">break-if</span> bg-color-found?
+    bg-color<span class="Special"> &lt;- </span>copy <span class="Constant">0/black</span>
+  <span class="Delimiter">}</span>
   <span class="Delimiter">{</span>
     done?:boolean<span class="Special"> &lt;- </span>greater-than column, right
     <span class="muControl">break-if</span> done?
-    screen<span class="Special"> &lt;- </span>print screen, <span class="Constant">32/space</span>
+    screen<span class="Special"> &lt;- </span>print screen, space, <span class="Constant">7/white</span>, bg-color  <span class="Comment"># foreground color is mostly unused except if the cursor shows up at this cell</span>
     column<span class="Special"> &lt;- </span>add column, <span class="Constant">1</span>
     <span class="muControl">loop</span>
   <span class="Delimiter">}</span>
 ]
 
-<span class="muRecipe">recipe</span> clear-screen-from screen:address:screen, row:number, column:number, left:number, right:number<span class="muRecipe"> -&gt; </span>screen:address:screen [
+<span class="muRecipe">recipe</span> clear-screen-from screen:address:shared:screen, row:number, column:number, left:number, right:number<span class="muRecipe"> -&gt; </span>screen:address:shared:screen [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   <span class="Comment"># if it's the real screen, use the optimized primitive</span>
@@ -287,7 +299,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   <span class="muControl">reply</span> screen/same-as-ingredient:<span class="Constant">0</span>
 ]
 
-<span class="muRecipe">recipe</span> clear-rest-of-screen screen:address:screen, row:number, left:number, right:number<span class="muRecipe"> -&gt; </span>screen:address:screen [
+<span class="muRecipe">recipe</span> clear-rest-of-screen screen:address:shared:screen, row:number, left:number, right:number<span class="muRecipe"> -&gt; </span>screen:address:shared:screen [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   row<span class="Special"> &lt;- </span>add row, <span class="Constant">1</span>
@@ -306,9 +318,9 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="muScenario">scenario</span> editor-initially-prints-multiple-lines [
   assume-screen <span class="Constant">5/width</span>, <span class="Constant">5/height</span>
   run [
-    s:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
+    s:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
 <span class="Constant">def]</span>
-    new-editor s:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
+    new-editor s:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
   ]
   screen-should-contain [
    <span class="Constant"> .     .</span>
@@ -321,8 +333,8 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="muScenario">scenario</span> editor-initially-handles-offsets [
   assume-screen <span class="Constant">5/width</span>, <span class="Constant">5/height</span>
   run [
-    s:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
-    new-editor s:address:array:character, screen:address:screen, <span class="Constant">1/left</span>, <span class="Constant">5/right</span>
+    s:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
+    new-editor s:address:shared:array:character, screen:address:shared:screen, <span class="Constant">1/left</span>, <span class="Constant">5/right</span>
   ]
   screen-should-contain [
    <span class="Constant"> .     .</span>
@@ -334,9 +346,9 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="muScenario">scenario</span> editor-initially-prints-multiple-lines-at-offset [
   assume-screen <span class="Constant">5/width</span>, <span class="Constant">5/height</span>
   run [
-    s:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
+    s:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
 <span class="Constant">def]</span>
-    new-editor s:address:array:character, screen:address:screen, <span class="Constant">1/left</span>, <span class="Constant">5/right</span>
+    new-editor s:address:shared:array:character, screen:address:shared:screen, <span class="Constant">1/left</span>, <span class="Constant">5/right</span>
   ]
   screen-should-contain [
    <span class="Constant"> .     .</span>
@@ -349,8 +361,8 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="muScenario">scenario</span> editor-initially-wraps-long-lines [
   assume-screen <span class="Constant">5/width</span>, <span class="Constant">5/height</span>
   run [
-    s:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc def]</span>
-    new-editor s:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
+    s:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc def]</span>
+    new-editor s:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
   ]
   screen-should-contain [
    <span class="Constant"> .     .</span>
@@ -369,8 +381,8 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="muScenario">scenario</span> editor-initially-wraps-barely-long-lines [
   assume-screen <span class="Constant">5/width</span>, <span class="Constant">5/height</span>
   run [
-    s:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abcde]</span>
-    new-editor s:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
+    s:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abcde]</span>
+    new-editor s:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
   ]
   <span class="Comment"># still wrap, even though the line would fit. We need room to click on the</span>
   <span class="Comment"># end of the line</span>
@@ -391,10 +403,10 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="muScenario">scenario</span> editor-initializes-empty-text [
   assume-screen <span class="Constant">5/width</span>, <span class="Constant">5/height</span>
   run [
-    <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
-    <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
-    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+    <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
+    <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
+    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   ]
   screen-should-contain [
    <span class="Constant"> .     .</span>
@@ -412,10 +424,10 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="muScenario">scenario</span> render-colors-comments [
   assume-screen <span class="Constant">5/width</span>, <span class="Constant">5/height</span>
   run [
-    s:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
+    s:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
 <span class="Constant"># de</span>
 <span class="Constant">f]</span>
-    new-editor s:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
+    new-editor s:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
   ]
   screen-should-contain [
    <span class="Constant"> .     .</span>
@@ -493,10 +505,10 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="muScenario">scenario</span> render-colors-assignment [
   assume-screen <span class="Constant">8/width</span>, <span class="Constant">5/height</span>
   run [
-    s:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
+    s:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
 <span class="Constant">d &lt;- e</span>
 <span class="Constant">f]</span>
-    new-editor s:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">8/right</span>
+    new-editor s:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">8/right</span>
   ]
   screen-should-contain [
    <span class="Constant"> .        .</span>
diff --git a/html/edit/002-typing.mu.html b/html/edit/002-typing.mu.html
index 2585450c..e36c71db 100644
--- a/html/edit/002-typing.mu.html
+++ b/html/edit/002-typing.mu.html
@@ -37,16 +37,16 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="Comment"># temporary main: interactive editor</span>
 <span class="Comment"># hit ctrl-c to exit</span>
-<span class="muRecipe">recipe!</span> main text:address:array:character [
+<span class="muRecipe">recipe!</span> main text:address:shared:array:character [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   open-console
-  editor:address:editor-data<span class="Special"> &lt;- </span>new-editor text, <span class="Constant">0/screen</span>, <span class="Constant">5/left</span>, <span class="Constant">45/right</span>
+  editor:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor text, <span class="Constant">0/screen</span>, <span class="Constant">5/left</span>, <span class="Constant">45/right</span>
   editor-event-loop <span class="Constant">0/screen</span>, <span class="Constant">0/console</span>, editor
   close-console
 ]
 
-<span class="muRecipe">recipe</span> editor-event-loop screen:address:screen, console:address:console, editor:address:editor-data<span class="muRecipe"> -&gt; </span>screen:address:screen, console:address:console, editor:address:editor-data [
+<span class="muRecipe">recipe</span> editor-event-loop screen:address:shared:screen, console:address:shared:console, editor:address:shared:editor-data<span class="muRecipe"> -&gt; </span>screen:address:shared:screen, console:address:shared:console, editor:address:shared:editor-data [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   <span class="Delimiter">{</span>
@@ -55,7 +55,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     cursor-row:number<span class="Special"> &lt;- </span>get *editor, <span class="Constant">cursor-row:offset</span>
     cursor-column:number<span class="Special"> &lt;- </span>get *editor, <span class="Constant">cursor-column:offset</span>
     screen<span class="Special"> &lt;- </span>move-cursor screen, cursor-row, cursor-column
-    e:event, console:address:console, found?:boolean, quit?:boolean<span class="Special"> &lt;- </span>read-event console
+    e:event, console:address:shared:console, found?:boolean, quit?:boolean<span class="Special"> &lt;- </span>read-event console
     <span class="muControl">loop-unless</span> found?
     <span class="muControl">break-if</span> quit?  <span class="Comment"># only in tests</span>
     trace <span class="Constant">10</span>, <span class="Constant">[app]</span>, <span class="Constant">[next-event]</span>
@@ -80,7 +80,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 ]
 
 <span class="Comment"># process click, return if it was on current editor</span>
-<span class="muRecipe">recipe</span> move-cursor-in-editor screen:address:screen, editor:address:editor-data, t:touch-event<span class="muRecipe"> -&gt; </span>in-focus?:boolean, editor:address:editor-data [
+<span class="muRecipe">recipe</span> move-cursor-in-editor screen:address:shared:screen, editor:address:shared:editor-data, t:touch-event<span class="muRecipe"> -&gt; </span>in-focus?:boolean, editor:address:shared:editor-data [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   <span class="muControl">reply-unless</span> editor, <span class="Constant">0/false</span>
@@ -105,7 +105,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="Comment"># Variant of 'render' that only moves the cursor (coordinates and</span>
 <span class="Comment"># before-cursor). If it's past the end of a line, it 'slides' it left. If it's</span>
 <span class="Comment"># past the last line it positions at end of last line.</span>
-<span class="muRecipe">recipe</span> snap-cursor screen:address:screen, editor:address:editor-data, target-row:number, target-column:number<span class="muRecipe"> -&gt; </span>editor:address:editor-data [
+<span class="muRecipe">recipe</span> snap-cursor screen:address:shared:screen, editor:address:shared:editor-data, target-row:number, target-column:number<span class="muRecipe"> -&gt; </span>editor:address:shared:editor-data [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   <span class="muControl">reply-unless</span> editor
@@ -113,8 +113,8 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   right:number<span class="Special"> &lt;- </span>get *editor, <span class="Constant">right:offset</span>
   screen-height:number<span class="Special"> &lt;- </span>screen-height screen
   <span class="Comment"># count newlines until screen row</span>
-  curr:address:duplex-list:character<span class="Special"> &lt;- </span>get *editor, <span class="Constant">top-of-screen:offset</span>
-  prev:address:duplex-list:character<span class="Special"> &lt;- </span>copy curr  <span class="Comment"># just in case curr becomes null and we can't compute prev</span>
+  curr:address:shared:duplex-list:character<span class="Special"> &lt;- </span>get *editor, <span class="Constant">top-of-screen:offset</span>
+  prev:address:shared:duplex-list:character<span class="Special"> &lt;- </span>copy curr  <span class="Comment"># just in case curr becomes null and we can't compute prev</span>
   curr<span class="Special"> &lt;- </span>next curr
   row:number<span class="Special"> &lt;- </span>copy <span class="Constant">1/top</span>
   column:number<span class="Special"> &lt;- </span>copy left
@@ -122,7 +122,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   *cursor-row<span class="Special"> &lt;- </span>copy target-row
   cursor-column:address:number<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">cursor-column:offset</span>
   *cursor-column<span class="Special"> &lt;- </span>copy target-column
-  before-cursor:address:address:duplex-list:character<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">before-cursor:offset</span>
+  before-cursor:address:address:shared:duplex-list:character<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">before-cursor:offset</span>
   <span class="Delimiter">{</span>
 <span class="Constant">    +next-character</span>
     <span class="muControl">break-unless</span> curr
@@ -190,7 +190,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="Comment"># Process an event 'e' and try to minimally update the screen.</span>
 <span class="Comment"># Set 'go-render?' to true to indicate the caller must perform a non-minimal update.</span>
-<span class="muRecipe">recipe</span> handle-keyboard-event screen:address:screen, editor:address:editor-data, e:event<span class="muRecipe"> -&gt; </span>screen:address:screen, editor:address:editor-data, go-render?:boolean [
+<span class="muRecipe">recipe</span> handle-keyboard-event screen:address:shared:screen, editor:address:shared:editor-data, e:event<span class="muRecipe"> -&gt; </span>screen:address:shared:screen, editor:address:shared:editor-data, go-render?:boolean [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   go-render?<span class="Special"> &lt;- </span>copy <span class="Constant">0/false</span>
@@ -199,7 +199,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   screen-height:number<span class="Special"> &lt;- </span>screen-height screen
   left:number<span class="Special"> &lt;- </span>get *editor, <span class="Constant">left:offset</span>
   right:number<span class="Special"> &lt;- </span>get *editor, <span class="Constant">right:offset</span>
-  before-cursor:address:address:duplex-list:character<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">before-cursor:offset</span>
+  before-cursor:address:address:shared:duplex-list:character<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">before-cursor:offset</span>
   cursor-row:address:number<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">cursor-row:offset</span>
   cursor-column:address:number<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">cursor-column:offset</span>
   save-row:number<span class="Special"> &lt;- </span>copy *cursor-row
@@ -230,10 +230,10 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   <span class="muControl">reply</span>
 ]
 
-<span class="muRecipe">recipe</span> insert-at-cursor editor:address:editor-data, c:character, screen:address:screen<span class="muRecipe"> -&gt; </span>editor:address:editor-data, screen:address:screen, go-render?:boolean [
+<span class="muRecipe">recipe</span> insert-at-cursor editor:address:shared:editor-data, c:character, screen:address:shared:screen<span class="muRecipe"> -&gt; </span>editor:address:shared:editor-data, screen:address:shared:screen, go-render?:boolean [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
-  before-cursor:address:address:duplex-list:character<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">before-cursor:offset</span>
+  before-cursor:address:address:shared:duplex-list:character<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">before-cursor:offset</span>
   insert c, *before-cursor
   *before-cursor<span class="Special"> &lt;- </span>next *before-cursor
   cursor-row:address:number<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">cursor-row:offset</span>
@@ -248,7 +248,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="Constant">  &lt;insert-character-special-case&gt;</span>
   <span class="Comment"># but mostly we'll just move the cursor right</span>
   *cursor-column<span class="Special"> &lt;- </span>add *cursor-column, <span class="Constant">1</span>
-  next:address:duplex-list:character<span class="Special"> &lt;- </span>next *before-cursor
+  next:address:shared:duplex-list:character<span class="Special"> &lt;- </span>next *before-cursor
   <span class="Delimiter">{</span>
     <span class="Comment"># at end of all text? no need to scroll? just print the character and leave</span>
     at-end?:boolean<span class="Special"> &lt;- </span>equal next, <span class="Constant">0/null</span>
@@ -268,7 +268,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     <span class="muControl">break-unless</span> next
     at-right?:boolean<span class="Special"> &lt;- </span>greater-or-equal *cursor-column, screen-width
     <span class="muControl">break-if</span> at-right?
-    curr:address:duplex-list:character<span class="Special"> &lt;- </span>copy *before-cursor
+    curr:address:shared:duplex-list:character<span class="Special"> &lt;- </span>copy *before-cursor
     move-cursor screen, save-row, save-column
     curr-column:number<span class="Special"> &lt;- </span>copy save-column
     <span class="Delimiter">{</span>
@@ -294,7 +294,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 ]
 
 <span class="Comment"># helper for tests</span>
-<span class="muRecipe">recipe</span> editor-render screen:address:screen, editor:address:editor-data<span class="muRecipe"> -&gt; </span>screen:address:screen, editor:address:editor-data [
+<span class="muRecipe">recipe</span> editor-render screen:address:shared:screen, editor:address:shared:editor-data<span class="muRecipe"> -&gt; </span>screen:address:shared:screen, editor:address:shared:editor-data [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   left:number<span class="Special"> &lt;- </span>get *editor, <span class="Constant">left:offset</span>
@@ -309,12 +309,12 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> editor-handles-empty-event-queue [
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
-  editor-render screen, <span class="Constant">2</span>:address:editor-data
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+  editor-render screen, <span class="Constant">2</span>:address:shared:editor-data
   assume-console <span class="Constant">[]</span>
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   screen-should-contain [
    <span class="Constant"> .          .</span>
@@ -326,17 +326,17 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> editor-handles-mouse-clicks [
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
-  editor-render screen, <span class="Constant">2</span>:address:editor-data
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+  editor-render screen, <span class="Constant">2</span>:address:shared:editor-data
 <span class="Constant">  $clear-trace</span>
   assume-console [
     left-click <span class="Constant">1</span>, <span class="Constant">1</span>  <span class="Comment"># on the 'b'</span>
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
-    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
+    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   ]
   screen-should-contain [
    <span class="Constant"> .          .</span>
@@ -353,16 +353,16 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> editor-handles-mouse-clicks-outside-text [
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
 <span class="Constant">  $clear-trace</span>
   assume-console [
     left-click <span class="Constant">1</span>, <span class="Constant">7</span>  <span class="Comment"># last line, to the right of text</span>
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
-    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
+    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   ]
   memory-should-contain [
     <span class="Constant">3</span><span class="Special"> &lt;- </span><span class="Constant">1</span>  <span class="Comment"># cursor row</span>
@@ -373,17 +373,17 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> editor-handles-mouse-clicks-outside-text-2 [
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
 <span class="Constant">def]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
 <span class="Constant">  $clear-trace</span>
   assume-console [
     left-click <span class="Constant">1</span>, <span class="Constant">7</span>  <span class="Comment"># interior line, to the right of text</span>
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
-    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
+    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   ]
   memory-should-contain [
     <span class="Constant">3</span><span class="Special"> &lt;- </span><span class="Constant">1</span>  <span class="Comment"># cursor row</span>
@@ -394,17 +394,17 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> editor-handles-mouse-clicks-outside-text-3 [
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
 <span class="Constant">def]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
 <span class="Constant">  $clear-trace</span>
   assume-console [
     left-click <span class="Constant">3</span>, <span class="Constant">7</span>  <span class="Comment"># below text</span>
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
-    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
+    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   ]
   memory-should-contain [
     <span class="Constant">3</span><span class="Special"> &lt;- </span><span class="Constant">2</span>  <span class="Comment"># cursor row</span>
@@ -415,19 +415,19 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> editor-handles-mouse-clicks-outside-column [
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
   <span class="Comment"># editor occupies only left half of screen</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
-  editor-render screen, <span class="Constant">2</span>:address:editor-data
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
+  editor-render screen, <span class="Constant">2</span>:address:shared:editor-data
 <span class="Constant">  $clear-trace</span>
   assume-console [
     <span class="Comment"># click on right half of screen</span>
     left-click <span class="Constant">3</span>, <span class="Constant">8</span>
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
-    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
+    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   ]
   screen-should-contain [
    <span class="Constant"> .          .</span>
@@ -444,18 +444,18 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> editor-handles-mouse-clicks-in-menu-area [
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
-  editor-render screen, <span class="Constant">2</span>:address:editor-data
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
+  editor-render screen, <span class="Constant">2</span>:address:shared:editor-data
 <span class="Constant">  $clear-trace</span>
   assume-console [
     <span class="Comment"># click on first, 'menu' row</span>
     left-click <span class="Constant">0</span>, <span class="Constant">3</span>
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
-    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
+    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   ]
   <span class="Comment"># no change to cursor</span>
   memory-should-contain [
@@ -466,15 +466,15 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> editor-inserts-characters-into-empty-editor [
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
-  editor-render screen, <span class="Constant">2</span>:address:editor-data
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
+  editor-render screen, <span class="Constant">2</span>:address:shared:editor-data
 <span class="Constant">  $clear-trace</span>
   assume-console [
     type <span class="Constant">[abc]</span>
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   screen-should-contain [
    <span class="Constant"> .          .</span>
@@ -487,9 +487,9 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> editor-inserts-characters-at-cursor [
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
-  editor-render screen, <span class="Constant">2</span>:address:editor-data
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+  editor-render screen, <span class="Constant">2</span>:address:shared:editor-data
 <span class="Constant">  $clear-trace</span>
   <span class="Comment"># type two letters at different places</span>
   assume-console [
@@ -498,7 +498,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     type <span class="Constant">[d]</span>
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   screen-should-contain [
    <span class="Constant"> .          .</span>
@@ -511,16 +511,16 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> editor-inserts-characters-at-cursor-2 [
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
-  editor-render screen, <span class="Constant">2</span>:address:editor-data
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+  editor-render screen, <span class="Constant">2</span>:address:shared:editor-data
 <span class="Constant">  $clear-trace</span>
   assume-console [
     left-click <span class="Constant">1</span>, <span class="Constant">5</span>  <span class="Comment"># right of last line</span>
     type <span class="Constant">[d]</span>
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   screen-should-contain [
    <span class="Constant"> .          .</span>
@@ -533,17 +533,17 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> editor-inserts-characters-at-cursor-5 [
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
 <span class="Constant">d]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
-  editor-render screen, <span class="Constant">2</span>:address:editor-data
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+  editor-render screen, <span class="Constant">2</span>:address:shared:editor-data
 <span class="Constant">  $clear-trace</span>
   assume-console [
     left-click <span class="Constant">1</span>, <span class="Constant">5</span>  <span class="Comment"># right of non-last line</span>
     type <span class="Constant">[e]</span>
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   screen-should-contain [
    <span class="Constant"> .          .</span>
@@ -557,16 +557,16 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> editor-inserts-characters-at-cursor-3 [
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
-  editor-render screen, <span class="Constant">2</span>:address:editor-data
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+  editor-render screen, <span class="Constant">2</span>:address:shared:editor-data
 <span class="Constant">  $clear-trace</span>
   assume-console [
     left-click <span class="Constant">3</span>, <span class="Constant">5</span>  <span class="Comment"># below all text</span>
     type <span class="Constant">[d]</span>
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   screen-should-contain [
    <span class="Constant"> .          .</span>
@@ -579,17 +579,17 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> editor-inserts-characters-at-cursor-4 [
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
 <span class="Constant">d]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
-  editor-render screen, <span class="Constant">2</span>:address:editor-data
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+  editor-render screen, <span class="Constant">2</span>:address:shared:editor-data
 <span class="Constant">  $clear-trace</span>
   assume-console [
     left-click <span class="Constant">3</span>, <span class="Constant">5</span>  <span class="Comment"># below all text</span>
     type <span class="Constant">[e]</span>
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   screen-should-contain [
    <span class="Constant"> .          .</span>
@@ -603,17 +603,17 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> editor-inserts-characters-at-cursor-6 [
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
 <span class="Constant">d]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
-  editor-render screen, <span class="Constant">2</span>:address:editor-data
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+  editor-render screen, <span class="Constant">2</span>:address:shared:editor-data
 <span class="Constant">  $clear-trace</span>
   assume-console [
     left-click <span class="Constant">3</span>, <span class="Constant">5</span>  <span class="Comment"># below all text</span>
     type <span class="Constant">[ef]</span>
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   screen-should-contain [
    <span class="Constant"> .          .</span>
@@ -627,14 +627,14 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> editor-moves-cursor-after-inserting-characters [
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[ab]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
-  editor-render screen, <span class="Constant">2</span>:address:editor-data
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[ab]</span>
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
+  editor-render screen, <span class="Constant">2</span>:address:shared:editor-data
   assume-console [
     type <span class="Constant">[01]</span>
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   screen-should-contain [
    <span class="Constant"> .          .</span>
@@ -648,15 +648,15 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> editor-wraps-line-on-insert [
   assume-screen <span class="Constant">5/width</span>, <span class="Constant">5/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
-  editor-render screen, <span class="Constant">2</span>:address:editor-data
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
+  editor-render screen, <span class="Constant">2</span>:address:shared:editor-data
   <span class="Comment"># type a letter</span>
   assume-console [
     type <span class="Constant">[e]</span>
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   <span class="Comment"># no wrap yet</span>
   screen-should-contain [
@@ -671,7 +671,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     type <span class="Constant">[f]</span>
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   <span class="Comment"># now wrap</span>
   screen-should-contain [
@@ -686,19 +686,19 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="muScenario">scenario</span> editor-wraps-line-on-insert-2 [
   <span class="Comment"># create an editor with some text</span>
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abcdefg</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abcdefg</span>
 <span class="Constant">defg]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
-  editor-render screen, <span class="Constant">2</span>:address:editor-data
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
+  editor-render screen, <span class="Constant">2</span>:address:shared:editor-data
   <span class="Comment"># type more text at the start</span>
   assume-console [
     left-click <span class="Constant">3</span>, <span class="Constant">0</span>
     type <span class="Constant">[abc]</span>
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
-    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
+    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   ]
   <span class="Comment"># cursor is not wrapped</span>
   memory-should-contain [
@@ -738,16 +738,16 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> editor-wraps-cursor-after-inserting-characters [
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abcde]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abcde]</span>
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
   assume-console [
     left-click <span class="Constant">1</span>, <span class="Constant">4</span>  <span class="Comment"># line is full; no wrap icon yet</span>
     type <span class="Constant">[f]</span>
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
-    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
+    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   ]
   screen-should-contain [
    <span class="Constant"> .          .</span>
@@ -764,16 +764,16 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> editor-wraps-cursor-after-inserting-characters-2 [
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abcde]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abcde]</span>
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
   assume-console [
     left-click <span class="Constant">1</span>, <span class="Constant">3</span>  <span class="Comment"># right before the wrap icon</span>
     type <span class="Constant">[f]</span>
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
-    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
+    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   ]
   screen-should-contain [
    <span class="Constant"> .          .</span>
@@ -790,16 +790,16 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> editor-wraps-cursor-to-left-margin [
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abcde]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">2/left</span>, <span class="Constant">7/right</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abcde]</span>
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">2/left</span>, <span class="Constant">7/right</span>
   assume-console [
     left-click <span class="Constant">1</span>, <span class="Constant">5</span>  <span class="Comment"># line is full; no wrap icon yet</span>
     type <span class="Constant">[01]</span>
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
-    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
+    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   ]
   screen-should-contain [
    <span class="Constant"> .          .</span>
@@ -827,14 +827,14 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> editor-moves-cursor-down-after-inserting-newline [
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
   assume-console [
     type <span class="Constant">[0</span>
 <span class="Constant">1]</span>
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   screen-should-contain [
    <span class="Constant"> .          .</span>
@@ -857,12 +857,12 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   <span class="Delimiter">}</span>
 ]
 
-<span class="muRecipe">recipe</span> insert-new-line-and-indent editor:address:editor-data, screen:address:screen<span class="muRecipe"> -&gt; </span>editor:address:editor-data, screen:address:screen, go-render?:boolean [
+<span class="muRecipe">recipe</span> insert-new-line-and-indent editor:address:shared:editor-data, screen:address:shared:screen<span class="muRecipe"> -&gt; </span>editor:address:shared:editor-data, screen:address:shared:screen, go-render?:boolean [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   cursor-row:address:number<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">cursor-row:offset</span>
   cursor-column:address:number<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">cursor-column:offset</span>
-  before-cursor:address:address:duplex-list:character<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">before-cursor:offset</span>
+  before-cursor:address:address:shared:duplex-list:character<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">before-cursor:offset</span>
   left:number<span class="Special"> &lt;- </span>get *editor, <span class="Constant">left:offset</span>
   right:number<span class="Special"> &lt;- </span>get *editor, <span class="Constant">right:offset</span>
   screen-height:number<span class="Special"> &lt;- </span>screen-height screen
@@ -882,8 +882,8 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   <span class="Comment"># indent if necessary</span>
   indent?:boolean<span class="Special"> &lt;- </span>get *editor, <span class="Constant">indent?:offset</span>
   <span class="muControl">reply-unless</span> indent?
-  d:address:duplex-list:character<span class="Special"> &lt;- </span>get *editor, <span class="Constant">data:offset</span>
-  end-of-previous-line:address:duplex-list:character<span class="Special"> &lt;- </span>prev *before-cursor
+  d:address:shared:duplex-list:character<span class="Special"> &lt;- </span>get *editor, <span class="Constant">data:offset</span>
+  end-of-previous-line:address:shared:duplex-list:character<span class="Special"> &lt;- </span>prev *before-cursor
   indent:number<span class="Special"> &lt;- </span>line-indent end-of-previous-line, d
   i:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
   <span class="Delimiter">{</span>
@@ -897,7 +897,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="Comment"># takes a pointer 'curr' into the doubly-linked list and its sentinel, counts</span>
 <span class="Comment"># the number of spaces at the start of the line containing 'curr'.</span>
-<span class="muRecipe">recipe</span> line-indent curr:address:duplex-list:character, start:address:duplex-list:character<span class="muRecipe"> -&gt; </span>result:number [
+<span class="muRecipe">recipe</span> line-indent curr:address:shared:duplex-list:character, start:address:shared:duplex-list:character<span class="muRecipe"> -&gt; </span>result:number [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   result:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
@@ -929,14 +929,14 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> editor-moves-cursor-down-after-inserting-newline-2 [
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">1/left</span>, <span class="Constant">10/right</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">1/left</span>, <span class="Constant">10/right</span>
   assume-console [
     type <span class="Constant">[0</span>
 <span class="Constant">1]</span>
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   screen-should-contain [
    <span class="Constant"> .          .</span>
@@ -949,8 +949,8 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> editor-clears-previous-line-completely-after-inserting-newline [
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abcde]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abcde]</span>
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
   assume-console [
     press enter
   ]
@@ -962,7 +962,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
    <span class="Constant"> .          .</span>
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   <span class="Comment"># line should be fully cleared</span>
   screen-should-contain [
@@ -976,10 +976,10 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> editor-inserts-indent-after-newline [
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">10/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[ab</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[ab</span>
 <span class="Constant">  cd</span>
 <span class="Constant">ef]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
   <span class="Comment"># position cursor after 'cd' and hit 'newline'</span>
   assume-console [
     left-click <span class="Constant">2</span>, <span class="Constant">8</span>
@@ -987,9 +987,9 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 ]
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
-    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
+    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   ]
   <span class="Comment"># cursor should be below start of previous line</span>
   memory-should-contain [
@@ -1000,10 +1000,10 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> editor-skips-indent-around-paste [
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">10/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[ab</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[ab</span>
 <span class="Constant">  cd</span>
 <span class="Constant">ef]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
   <span class="Comment"># position cursor after 'cd' and hit 'newline' surrounded by paste markers</span>
   assume-console [
     left-click <span class="Constant">2</span>, <span class="Constant">8</span>
@@ -1012,9 +1012,9 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     press <span class="Constant">65506</span>  <span class="Comment"># end paste</span>
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
-    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
+    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   ]
   <span class="Comment"># cursor should be below start of previous line</span>
   memory-should-contain [
@@ -1047,7 +1047,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="SalientComment">## helpers</span>
 
-<span class="muRecipe">recipe</span> draw-horizontal screen:address:screen, row:number, x:number, right:number<span class="muRecipe"> -&gt; </span>screen:address:screen [
+<span class="muRecipe">recipe</span> draw-horizontal screen:address:shared:screen, row:number, x:number, right:number<span class="muRecipe"> -&gt; </span>screen:address:shared:screen [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   style:character, style-found?:boolean<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
diff --git a/html/edit/003-shortcuts.mu.html b/html/edit/003-shortcuts.mu.html
index 0f7a60da..243635b0 100644
--- a/html/edit/003-shortcuts.mu.html
+++ b/html/edit/003-shortcuts.mu.html
@@ -41,14 +41,14 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="muScenario">scenario</span> editor-inserts-two-spaces-on-tab [
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
   <span class="Comment"># just one character in final line</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[ab</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[ab</span>
 <span class="Constant">cd]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
   assume-console [
     press tab
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   screen-should-contain [
    <span class="Constant"> .          .</span>
@@ -74,18 +74,18 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> editor-handles-backspace-key [
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
-  editor-render screen, <span class="Constant">2</span>:address:editor-data
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+  editor-render screen, <span class="Constant">2</span>:address:shared:editor-data
 <span class="Constant">  $clear-trace</span>
   assume-console [
     left-click <span class="Constant">1</span>, <span class="Constant">1</span>
     press backspace
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
-    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-    <span class="Constant">5</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
+    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+    <span class="Constant">5</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   ]
   screen-should-contain [
    <span class="Constant"> .          .</span>
@@ -105,7 +105,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     delete-previous-character?:boolean<span class="Special"> &lt;- </span>equal *c, <span class="Constant">8/backspace</span>
     <span class="muControl">break-unless</span> delete-previous-character?
 <span class="Constant">    &lt;backspace-character-begin&gt;</span>
-    editor, screen, go-render?:boolean, backspaced-cell:address:duplex-list:character<span class="Special"> &lt;- </span>delete-before-cursor editor, screen
+    editor, screen, go-render?:boolean, backspaced-cell:address:shared:duplex-list:character<span class="Special"> &lt;- </span>delete-before-cursor editor, screen
 <span class="Constant">    &lt;backspace-character-end&gt;</span>
     <span class="muControl">reply</span>
   <span class="Delimiter">}</span>
@@ -114,19 +114,19 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="Comment"># return values:</span>
 <span class="Comment">#   go-render? - whether caller needs to update the screen</span>
 <span class="Comment">#   backspaced-cell - value deleted (or 0 if nothing was deleted) so we can save it for undo, etc.</span>
-<span class="muRecipe">recipe</span> delete-before-cursor editor:address:editor-data, screen:address:screen<span class="muRecipe"> -&gt; </span>editor:address:editor-data, screen:address:screen, go-render?:boolean, backspaced-cell:address:duplex-list:character [
+<span class="muRecipe">recipe</span> delete-before-cursor editor:address:shared:editor-data, screen:address:shared:screen<span class="muRecipe"> -&gt; </span>editor:address:shared:editor-data, screen:address:shared:screen, go-render?:boolean, backspaced-cell:address:shared:duplex-list:character [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
-  before-cursor:address:address:duplex-list:character<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">before-cursor:offset</span>
-  data:address:duplex-list:character<span class="Special"> &lt;- </span>get *editor, <span class="Constant">data:offset</span>
+  before-cursor:address:address:shared:duplex-list:character<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">before-cursor:offset</span>
+  data:address:shared:duplex-list:character<span class="Special"> &lt;- </span>get *editor, <span class="Constant">data:offset</span>
   <span class="Comment"># if at start of text (before-cursor at § sentinel), return</span>
-  prev:address:duplex-list:character<span class="Special"> &lt;- </span>prev *before-cursor
+  prev:address:shared:duplex-list:character<span class="Special"> &lt;- </span>prev *before-cursor
   go-render?, backspaced-cell<span class="Special"> &lt;- </span>copy <span class="Constant">0/no-more-render</span>, <span class="Constant">0/nothing-deleted</span>
   <span class="muControl">reply-unless</span> prev
   trace <span class="Constant">10</span>, <span class="Constant">[app]</span>, <span class="Constant">[delete-before-cursor]</span>
   original-row:number<span class="Special"> &lt;- </span>get *editor, <span class="Constant">cursor-row:offset</span>
   editor, scroll?:boolean<span class="Special"> &lt;- </span>move-cursor-coordinates-left editor
-  backspaced-cell:address:duplex-list:character<span class="Special"> &lt;- </span>copy *before-cursor
+  backspaced-cell:address:shared:duplex-list:character<span class="Special"> &lt;- </span>copy *before-cursor
   data<span class="Special"> &lt;- </span>remove *before-cursor, data  <span class="Comment"># will also neatly trim next/prev pointers in backspaced-cell/*before-cursor</span>
   *before-cursor<span class="Special"> &lt;- </span>copy prev
   go-render?<span class="Special"> &lt;- </span>copy <span class="Constant">1/true</span>
@@ -140,7 +140,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   <span class="muControl">reply-unless</span> same-row?
   left:number<span class="Special"> &lt;- </span>get *editor, <span class="Constant">left:offset</span>
   right:number<span class="Special"> &lt;- </span>get *editor, <span class="Constant">right:offset</span>
-  curr:address:duplex-list:character<span class="Special"> &lt;- </span>next *before-cursor
+  curr:address:shared:duplex-list:character<span class="Special"> &lt;- </span>next *before-cursor
   screen<span class="Special"> &lt;- </span>move-cursor screen, cursor-row, cursor-column
   curr-column:number<span class="Special"> &lt;- </span>copy cursor-column
   <span class="Delimiter">{</span>
@@ -159,14 +159,15 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     <span class="muControl">loop</span>
   <span class="Delimiter">}</span>
   <span class="Comment"># we're guaranteed not to be at the right margin</span>
-  screen<span class="Special"> &lt;- </span>print screen, <span class="Constant">32/space</span>
+  space:character<span class="Special"> &lt;- </span>copy <span class="Constant">32/space</span>
+  screen<span class="Special"> &lt;- </span>print screen, space
   go-render?<span class="Special"> &lt;- </span>copy <span class="Constant">0/false</span>
 ]
 
-<span class="muRecipe">recipe</span> move-cursor-coordinates-left editor:address:editor-data<span class="muRecipe"> -&gt; </span>editor:address:editor-data, go-render?:boolean [
+<span class="muRecipe">recipe</span> move-cursor-coordinates-left editor:address:shared:editor-data<span class="muRecipe"> -&gt; </span>editor:address:shared:editor-data, go-render?:boolean [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
-  before-cursor:address:duplex-list:character<span class="Special"> &lt;- </span>get *editor, <span class="Constant">before-cursor:offset</span>
+  before-cursor:address:shared:duplex-list:character<span class="Special"> &lt;- </span>get *editor, <span class="Constant">before-cursor:offset</span>
   cursor-row:address:number<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">cursor-row:offset</span>
   cursor-column:address:number<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">cursor-column:offset</span>
   left:number<span class="Special"> &lt;- </span>get *editor, <span class="Constant">left:offset</span>
@@ -198,7 +199,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     <span class="muControl">break-unless</span> previous-character-is-newline?
     <span class="Comment"># compute length of previous line</span>
     trace <span class="Constant">10</span>, <span class="Constant">[app]</span>, <span class="Constant">[switching to previous line]</span>
-    d:address:duplex-list:character<span class="Special"> &lt;- </span>get *editor, <span class="Constant">data:offset</span>
+    d:address:shared:duplex-list:character<span class="Special"> &lt;- </span>get *editor, <span class="Constant">data:offset</span>
     end-of-line:number<span class="Special"> &lt;- </span>previous-line-length before-cursor, d
     *cursor-column<span class="Special"> &lt;- </span>add left, end-of-line
     <span class="muControl">reply</span>
@@ -211,7 +212,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="Comment"># takes a pointer 'curr' into the doubly-linked list and its sentinel, counts</span>
 <span class="Comment"># the length of the previous line before the 'curr' pointer.</span>
-<span class="muRecipe">recipe</span> previous-line-length curr:address:duplex-list:character, start:address:duplex-list:character<span class="muRecipe"> -&gt; </span>result:number [
+<span class="muRecipe">recipe</span> previous-line-length curr:address:shared:duplex-list:character, start:address:shared:duplex-list:character<span class="muRecipe"> -&gt; </span>result:number [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   result:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
@@ -234,17 +235,17 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="muScenario">scenario</span> editor-clears-last-line-on-backspace [
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
   <span class="Comment"># just one character in final line</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[ab</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[ab</span>
 <span class="Constant">cd]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
   assume-console [
     left-click <span class="Constant">2</span>, <span class="Constant">0</span>  <span class="Comment"># cursor at only character in final line</span>
     press backspace
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
-    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-    <span class="Constant">5</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
+    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+    <span class="Constant">5</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   ]
   screen-should-contain [
    <span class="Constant"> .          .</span>
@@ -261,10 +262,10 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="muScenario">scenario</span> editor-joins-and-wraps-lines-on-backspace [
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
   <span class="Comment"># initialize editor with two long-ish but non-wrapping lines</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc def</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc def</span>
 <span class="Constant">ghi jkl]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
-  editor-render screen, <span class="Constant">2</span>:address:editor-data
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+  editor-render screen, <span class="Constant">2</span>:address:shared:editor-data
 <span class="Constant">  $clear-trace</span>
   <span class="Comment"># position the cursor at the start of the second and hit backspace</span>
   assume-console [
@@ -272,7 +273,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     press backspace
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   <span class="Comment"># resulting single line should wrap correctly</span>
   screen-should-contain [
@@ -287,9 +288,9 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="muScenario">scenario</span> editor-wraps-long-lines-on-backspace [
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
   <span class="Comment"># initialize editor in part of the screen with a long line</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc def ghij]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">8/right</span>
-  editor-render screen, <span class="Constant">2</span>:address:editor-data
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc def ghij]</span>
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">8/right</span>
+  editor-render screen, <span class="Constant">2</span>:address:shared:editor-data
   <span class="Comment"># confirm that it wraps</span>
   screen-should-contain [
    <span class="Constant"> .          .</span>
@@ -304,7 +305,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     press backspace
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   <span class="Comment"># resulting single line should wrap correctly and not overflow its bounds</span>
   screen-should-contain [
@@ -320,15 +321,15 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> editor-handles-delete-key [
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
-  editor-render screen, <span class="Constant">2</span>:address:editor-data
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+  editor-render screen, <span class="Constant">2</span>:address:shared:editor-data
 <span class="Constant">  $clear-trace</span>
   assume-console [
     press delete
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   screen-should-contain [
    <span class="Constant"> .          .</span>
@@ -342,7 +343,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     press delete
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   screen-should-contain [
    <span class="Constant"> .          .</span>
@@ -358,18 +359,18 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     delete-next-character?:boolean<span class="Special"> &lt;- </span>equal *k, <span class="Constant">65522/delete</span>
     <span class="muControl">break-unless</span> delete-next-character?
 <span class="Constant">    &lt;delete-character-begin&gt;</span>
-    editor, screen, go-render?:boolean, deleted-cell:address:duplex-list:character<span class="Special"> &lt;- </span>delete-at-cursor editor, screen
+    editor, screen, go-render?:boolean, deleted-cell:address:shared:duplex-list:character<span class="Special"> &lt;- </span>delete-at-cursor editor, screen
 <span class="Constant">    &lt;delete-character-end&gt;</span>
     <span class="muControl">reply</span>
   <span class="Delimiter">}</span>
 ]
 
-<span class="muRecipe">recipe</span> delete-at-cursor editor:address:editor-data, screen:address:screen<span class="muRecipe"> -&gt; </span>editor:address:editor-data, screen:address:screen, go-render?:boolean, deleted-cell:address:duplex-list:character [
+<span class="muRecipe">recipe</span> delete-at-cursor editor:address:shared:editor-data, screen:address:shared:screen<span class="muRecipe"> -&gt; </span>editor:address:shared:editor-data, screen:address:shared:screen, go-render?:boolean, deleted-cell:address:shared:duplex-list:character [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
-  before-cursor:address:address:duplex-list:character<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">before-cursor:offset</span>
-  data:address:duplex-list:character<span class="Special"> &lt;- </span>get *editor, <span class="Constant">data:offset</span>
-  deleted-cell:address:duplex-list:character<span class="Special"> &lt;- </span>next *before-cursor
+  before-cursor:address:address:shared:duplex-list:character<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">before-cursor:offset</span>
+  data:address:shared:duplex-list:character<span class="Special"> &lt;- </span>get *editor, <span class="Constant">data:offset</span>
+  deleted-cell:address:shared:duplex-list:character<span class="Special"> &lt;- </span>next *before-cursor
   go-render?<span class="Special"> &lt;- </span>copy <span class="Constant">0/false</span>
   <span class="muControl">reply-unless</span> deleted-cell
   currc:character<span class="Special"> &lt;- </span>get *deleted-cell, <span class="Constant">value:offset</span>
@@ -378,7 +379,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   go-render?<span class="Special"> &lt;- </span>copy <span class="Constant">1/true</span>
   <span class="muControl">reply-if</span> deleted-newline?
   <span class="Comment"># wasn't a newline? render rest of line</span>
-  curr:address:duplex-list:character<span class="Special"> &lt;- </span>next *before-cursor  <span class="Comment"># refresh after remove above</span>
+  curr:address:shared:duplex-list:character<span class="Special"> &lt;- </span>next *before-cursor  <span class="Comment"># refresh after remove above</span>
   cursor-row:address:number<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">cursor-row:offset</span>
   cursor-column:address:number<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">cursor-column:offset</span>
   screen<span class="Special"> &lt;- </span>move-cursor screen, *cursor-row, *cursor-column
@@ -400,7 +401,8 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     <span class="muControl">loop</span>
   <span class="Delimiter">}</span>
   <span class="Comment"># we're guaranteed not to be at the right margin</span>
-  screen<span class="Special"> &lt;- </span>print screen, <span class="Constant">32/space</span>
+  space:character<span class="Special"> &lt;- </span>copy <span class="Constant">32/space</span>
+  screen<span class="Special"> &lt;- </span>print screen, space
   go-render?<span class="Special"> &lt;- </span>copy <span class="Constant">0/false</span>
 ]
 
@@ -408,16 +410,16 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> editor-moves-cursor-right-with-key [
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
-  editor-render screen, <span class="Constant">2</span>:address:editor-data
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+  editor-render screen, <span class="Constant">2</span>:address:shared:editor-data
 <span class="Constant">  $clear-trace</span>
   assume-console [
     press right-arrow
     type <span class="Constant">[0]</span>
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   screen-should-contain [
    <span class="Constant"> .          .</span>
@@ -433,7 +435,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     move-to-next-character?:boolean<span class="Special"> &lt;- </span>equal *k, <span class="Constant">65514/right-arrow</span>
     <span class="muControl">break-unless</span> move-to-next-character?
     <span class="Comment"># if not at end of text</span>
-    next-cursor:address:duplex-list:character<span class="Special"> &lt;- </span>next *before-cursor
+    next-cursor:address:shared:duplex-list:character<span class="Special"> &lt;- </span>next *before-cursor
     <span class="muControl">break-unless</span> next-cursor
     <span class="Comment"># scan to next character</span>
 <span class="Constant">    &lt;move-cursor-begin&gt;</span>
@@ -446,10 +448,10 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   <span class="Delimiter">}</span>
 ]
 
-<span class="muRecipe">recipe</span> move-cursor-coordinates-right editor:address:editor-data, screen-height:number<span class="muRecipe"> -&gt; </span>editor:address:editor-data, go-render?:boolean [
+<span class="muRecipe">recipe</span> move-cursor-coordinates-right editor:address:shared:editor-data, screen-height:number<span class="muRecipe"> -&gt; </span>editor:address:shared:editor-data, go-render?:boolean [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
-  before-cursor:address:duplex-list:character<span class="Special"> &lt;- </span>get *editor <span class="Constant">before-cursor:offset</span>
+  before-cursor:address:shared:duplex-list:character<span class="Special"> &lt;- </span>get *editor <span class="Constant">before-cursor:offset</span>
   cursor-row:address:number<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">cursor-row:offset</span>
   cursor-column:address:number<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">cursor-column:offset</span>
   left:number<span class="Special"> &lt;- </span>get *editor, <span class="Constant">left:offset</span>
@@ -476,7 +478,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     at-wrap?:boolean<span class="Special"> &lt;- </span>equal *cursor-column, wrap-column
     <span class="muControl">break-unless</span> at-wrap?
     <span class="Comment"># and if next character isn't newline</span>
-    next:address:duplex-list:character<span class="Special"> &lt;- </span>next before-cursor
+    next:address:shared:duplex-list:character<span class="Special"> &lt;- </span>next before-cursor
     <span class="muControl">break-unless</span> next
     next-character:character<span class="Special"> &lt;- </span>get *next, <span class="Constant">value:offset</span>
     newline?:boolean<span class="Special"> &lt;- </span>equal next-character, <span class="Constant">10/newline</span>
@@ -497,10 +499,10 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> editor-moves-cursor-to-next-line-with-right-arrow [
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
 <span class="Constant">d]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
-  editor-render screen, <span class="Constant">2</span>:address:editor-data
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+  editor-render screen, <span class="Constant">2</span>:address:shared:editor-data
 <span class="Constant">  $clear-trace</span>
   <span class="Comment"># type right-arrow a few times to get to start of second line</span>
   assume-console [
@@ -510,7 +512,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     press right-arrow  <span class="Comment"># next line</span>
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   check-trace-count-for-label <span class="Constant">0</span>, <span class="Constant">[print-character]</span>
   <span class="Comment"># type something and ensure it goes where it should</span>
@@ -518,7 +520,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     type <span class="Constant">[0]</span>
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   screen-should-contain [
    <span class="Constant"> .          .</span>
@@ -532,10 +534,10 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> editor-moves-cursor-to-next-line-with-right-arrow-2 [
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
 <span class="Constant">d]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">1/left</span>, <span class="Constant">10/right</span>
-  editor-render screen, <span class="Constant">2</span>:address:editor-data
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">1/left</span>, <span class="Constant">10/right</span>
+  editor-render screen, <span class="Constant">2</span>:address:shared:editor-data
   assume-console [
     press right-arrow
     press right-arrow
@@ -544,7 +546,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     type <span class="Constant">[0]</span>
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   screen-should-contain [
    <span class="Constant"> .          .</span>
@@ -557,18 +559,18 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> editor-moves-cursor-to-next-wrapped-line-with-right-arrow [
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abcdef]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
-  editor-render screen, <span class="Constant">2</span>:address:editor-data
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abcdef]</span>
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
+  editor-render screen, <span class="Constant">2</span>:address:shared:editor-data
 <span class="Constant">  $clear-trace</span>
   assume-console [
     left-click <span class="Constant">1</span>, <span class="Constant">3</span>
     press right-arrow
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
-    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
+    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   ]
   screen-should-contain [
    <span class="Constant"> .          .</span>
@@ -587,9 +589,9 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="muScenario">scenario</span> editor-moves-cursor-to-next-wrapped-line-with-right-arrow-2 [
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
   <span class="Comment"># line just barely wrapping</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abcde]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
-  editor-render screen, <span class="Constant">2</span>:address:editor-data
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abcde]</span>
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
+  editor-render screen, <span class="Constant">2</span>:address:shared:editor-data
 <span class="Constant">  $clear-trace</span>
   <span class="Comment"># position cursor at last character before wrap and hit right-arrow</span>
   assume-console [
@@ -597,9 +599,9 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     press right-arrow
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
-    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
+    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   ]
   memory-should-contain [
     <span class="Constant">3</span><span class="Special"> &lt;- </span><span class="Constant">2</span>
@@ -610,9 +612,9 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     press right-arrow
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
-    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
+    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   ]
   memory-should-contain [
     <span class="Constant">3</span><span class="Special"> &lt;- </span><span class="Constant">2</span>
@@ -623,18 +625,18 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> editor-moves-cursor-to-next-wrapped-line-with-right-arrow-3 [
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abcdef]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">1/left</span>, <span class="Constant">6/right</span>
-  editor-render screen, <span class="Constant">2</span>:address:editor-data
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abcdef]</span>
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">1/left</span>, <span class="Constant">6/right</span>
+  editor-render screen, <span class="Constant">2</span>:address:shared:editor-data
 <span class="Constant">  $clear-trace</span>
   assume-console [
     left-click <span class="Constant">1</span>, <span class="Constant">4</span>
     press right-arrow
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
-    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
+    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   ]
   screen-should-contain [
    <span class="Constant"> .          .</span>
@@ -652,10 +654,10 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> editor-moves-cursor-to-next-line-with-right-arrow-at-end-of-line [
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
 <span class="Constant">d]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
-  editor-render screen, <span class="Constant">2</span>:address:editor-data
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+  editor-render screen, <span class="Constant">2</span>:address:shared:editor-data
 <span class="Constant">  $clear-trace</span>
   <span class="Comment"># move to end of line, press right-arrow, type a character</span>
   assume-console [
@@ -664,7 +666,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     type <span class="Constant">[0]</span>
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   <span class="Comment"># new character should be in next line</span>
   screen-should-contain [
@@ -683,9 +685,9 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> editor-moves-cursor-left-with-key [
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
-  editor-render screen, <span class="Constant">2</span>:address:editor-data
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+  editor-render screen, <span class="Constant">2</span>:address:shared:editor-data
 <span class="Constant">  $clear-trace</span>
   assume-console [
     left-click <span class="Constant">1</span>, <span class="Constant">2</span>
@@ -693,7 +695,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     type <span class="Constant">[0]</span>
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   screen-should-contain [
    <span class="Constant"> .          .</span>
@@ -710,7 +712,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     <span class="muControl">break-unless</span> move-to-previous-character?
     trace <span class="Constant">10</span>, <span class="Constant">[app]</span>, <span class="Constant">[left arrow]</span>
     <span class="Comment"># if not at start of text (before-cursor at § sentinel)</span>
-    prev:address:duplex-list:character<span class="Special"> &lt;- </span>prev *before-cursor
+    prev:address:shared:duplex-list:character<span class="Special"> &lt;- </span>prev *before-cursor
     go-render?<span class="Special"> &lt;- </span>copy <span class="Constant">0/false</span>
     <span class="muControl">reply-unless</span> prev
 <span class="Constant">    &lt;move-cursor-begin&gt;</span>
@@ -725,10 +727,10 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="muScenario">scenario</span> editor-moves-cursor-to-previous-line-with-left-arrow-at-start-of-line [
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
   <span class="Comment"># initialize editor with two lines</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
 <span class="Constant">d]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
-  editor-render screen, <span class="Constant">2</span>:address:editor-data
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+  editor-render screen, <span class="Constant">2</span>:address:shared:editor-data
 <span class="Constant">  $clear-trace</span>
   <span class="Comment"># position cursor at start of second line (so there's no previous newline)</span>
   assume-console [
@@ -736,9 +738,9 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     press left-arrow
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
-    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
+    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   ]
   memory-should-contain [
     <span class="Constant">3</span><span class="Special"> &lt;- </span><span class="Constant">1</span>
@@ -750,11 +752,11 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="muScenario">scenario</span> editor-moves-cursor-to-previous-line-with-left-arrow-at-start-of-line-2 [
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
   <span class="Comment"># initialize editor with three lines</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
 <span class="Constant">def</span>
 <span class="Constant">g]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
-  editor-render screen, <span class="Constant">2</span>:address:editor-data
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+  editor-render screen, <span class="Constant">2</span>:address:shared:editor-data
 <span class="Constant">  $clear-trace</span>
   <span class="Comment"># position cursor further down (so there's a newline before the character at</span>
   <span class="Comment"># the cursor)</span>
@@ -764,7 +766,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     type <span class="Constant">[0]</span>
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   screen-should-contain [
    <span class="Constant"> .          .</span>
@@ -778,11 +780,11 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> editor-moves-cursor-to-previous-line-with-left-arrow-at-start-of-line-3 [
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
 <span class="Constant">def</span>
 <span class="Constant">g]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
-  editor-render screen, <span class="Constant">2</span>:address:editor-data
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+  editor-render screen, <span class="Constant">2</span>:address:shared:editor-data
 <span class="Constant">  $clear-trace</span>
   <span class="Comment"># position cursor at start of text, press left-arrow, then type a character</span>
   assume-console [
@@ -791,7 +793,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     type <span class="Constant">[0]</span>
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   <span class="Comment"># left-arrow should have had no effect</span>
   screen-should-contain [
@@ -807,11 +809,11 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="muScenario">scenario</span> editor-moves-cursor-to-previous-line-with-left-arrow-at-start-of-line-4 [
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
   <span class="Comment"># initialize editor with text containing an empty line</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
 
 d]
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
-  editor-render screen, <span class="Constant">2</span>:address:editor-data
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+  editor-render screen, <span class="Constant">2</span>:address:shared:editor-data
 <span class="Constant">  $clear-trace</span>
   <span class="Comment"># position cursor right after empty line</span>
   assume-console [
@@ -820,7 +822,7 @@ d]
     type <span class="Constant">[0]</span>
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   screen-should-contain [
    <span class="Constant"> .          .</span>
@@ -835,9 +837,9 @@ d]
 <span class="muScenario">scenario</span> editor-moves-across-screen-lines-across-wrap-with-left-arrow [
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
   <span class="Comment"># initialize editor with text containing an empty line</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abcdef]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
-  editor-render screen, <span class="Constant">2</span>:address:editor-data
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abcdef]</span>
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
+  editor-render screen, <span class="Constant">2</span>:address:shared:editor-data
 <span class="Constant">  $clear-trace</span>
   screen-should-contain [
    <span class="Constant"> .          .</span>
@@ -852,9 +854,9 @@ d]
     press left-arrow
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
-    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
+    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   ]
   memory-should-contain [
     <span class="Constant">3</span><span class="Special"> &lt;- </span><span class="Constant">1</span>  <span class="Comment"># previous row</span>
@@ -869,19 +871,19 @@ d]
 
 <span class="muScenario">scenario</span> editor-moves-to-previous-line-with-up-arrow [
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
 <span class="Constant">def]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
-  editor-render screen, <span class="Constant">2</span>:address:editor-data
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+  editor-render screen, <span class="Constant">2</span>:address:shared:editor-data
 <span class="Constant">  $clear-trace</span>
   assume-console [
     left-click <span class="Constant">2</span>, <span class="Constant">1</span>
     press up-arrow
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
-    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
+    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   ]
   memory-should-contain [
     <span class="Constant">3</span><span class="Special"> &lt;- </span><span class="Constant">1</span>
@@ -892,7 +894,7 @@ d]
     type <span class="Constant">[0]</span>
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   screen-should-contain [
    <span class="Constant"> .          .</span>
@@ -915,12 +917,12 @@ d]
   <span class="Delimiter">}</span>
 ]
 
-<span class="muRecipe">recipe</span> move-to-previous-line editor:address:editor-data<span class="muRecipe"> -&gt; </span>editor:address:editor-data, go-render?:boolean [
+<span class="muRecipe">recipe</span> move-to-previous-line editor:address:shared:editor-data<span class="muRecipe"> -&gt; </span>editor:address:shared:editor-data, go-render?:boolean [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   cursor-row:address:number<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">cursor-row:offset</span>
   cursor-column:address:number<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">cursor-column:offset</span>
-  before-cursor:address:address:duplex-list:character<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">before-cursor:offset</span>
+  before-cursor:address:address:shared:duplex-list:character<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">before-cursor:offset</span>
   left:number<span class="Special"> &lt;- </span>get *editor, <span class="Constant">left:offset</span>
   right:number<span class="Special"> &lt;- </span>get *editor, <span class="Constant">right:offset</span>
   already-at-top?:boolean<span class="Special"> &lt;- </span>lesser-or-equal *cursor-row, <span class="Constant">1/top</span>
@@ -930,13 +932,13 @@ d]
     <span class="Comment"># if not at newline, move to start of line (previous newline)</span>
     <span class="Comment"># then scan back another line</span>
     <span class="Comment"># if either step fails, give up without modifying cursor or coordinates</span>
-    curr:address:duplex-list:character<span class="Special"> &lt;- </span>copy *before-cursor
+    curr:address:shared:duplex-list:character<span class="Special"> &lt;- </span>copy *before-cursor
     <span class="Delimiter">{</span>
-      old:address:duplex-list:character<span class="Special"> &lt;- </span>copy curr
+      old:address:shared:duplex-list:character<span class="Special"> &lt;- </span>copy curr
       c2:character<span class="Special"> &lt;- </span>get *curr, <span class="Constant">value:offset</span>
       at-newline?:boolean<span class="Special"> &lt;- </span>equal c2, <span class="Constant">10/newline</span>
       <span class="muControl">break-if</span> at-newline?
-      curr:address:duplex-list:character<span class="Special"> &lt;- </span>before-previous-line curr, editor
+      curr:address:shared:duplex-list:character<span class="Special"> &lt;- </span>before-previous-line curr, editor
       no-motion?:boolean<span class="Special"> &lt;- </span>equal curr, old
       go-render?<span class="Special"> &lt;- </span>copy <span class="Constant">0/false</span>
       <span class="muControl">reply-if</span> no-motion?
@@ -956,7 +958,7 @@ d]
     <span class="Delimiter">{</span>
       done?:boolean<span class="Special"> &lt;- </span>greater-or-equal *cursor-column, target-column
       <span class="muControl">break-if</span> done?
-      curr:address:duplex-list:character<span class="Special"> &lt;- </span>next *before-cursor
+      curr:address:shared:duplex-list:character<span class="Special"> &lt;- </span>next *before-cursor
       <span class="muControl">break-unless</span> curr
       currc:character<span class="Special"> &lt;- </span>get *curr, <span class="Constant">value:offset</span>
       at-newline?:boolean<span class="Special"> &lt;- </span>equal currc, <span class="Constant">10/newline</span>
@@ -980,19 +982,19 @@ d]
 
 <span class="muScenario">scenario</span> editor-adjusts-column-at-previous-line [
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[ab</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[ab</span>
 <span class="Constant">def]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
-  editor-render screen, <span class="Constant">2</span>:address:editor-data
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+  editor-render screen, <span class="Constant">2</span>:address:shared:editor-data
 <span class="Constant">  $clear-trace</span>
   assume-console [
     left-click <span class="Constant">2</span>, <span class="Constant">3</span>
     press up-arrow
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
-    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
+    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   ]
   memory-should-contain [
     <span class="Constant">3</span><span class="Special"> &lt;- </span><span class="Constant">1</span>
@@ -1003,7 +1005,7 @@ d]
     type <span class="Constant">[0]</span>
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   screen-should-contain [
    <span class="Constant"> .          .</span>
@@ -1016,19 +1018,19 @@ d]
 
 <span class="muScenario">scenario</span> editor-adjusts-column-at-empty-line [
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new [
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new [
 def]
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
-  editor-render screen, <span class="Constant">2</span>:address:editor-data
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+  editor-render screen, <span class="Constant">2</span>:address:shared:editor-data
 <span class="Constant">  $clear-trace</span>
   assume-console [
     left-click <span class="Constant">2</span>, <span class="Constant">3</span>
     press up-arrow
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
-    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
+    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   ]
   memory-should-contain [
     <span class="Constant">3</span><span class="Special"> &lt;- </span><span class="Constant">1</span>
@@ -1039,7 +1041,7 @@ def]
     type <span class="Constant">[0]</span>
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   screen-should-contain [
    <span class="Constant"> .          .</span>
@@ -1053,11 +1055,11 @@ def]
 <span class="muScenario">scenario</span> editor-moves-to-previous-line-from-left-margin [
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
   <span class="Comment"># start out with three lines</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
 <span class="Constant">def</span>
 <span class="Constant">ghi]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
-  editor-render screen, <span class="Constant">2</span>:address:editor-data
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+  editor-render screen, <span class="Constant">2</span>:address:shared:editor-data
 <span class="Constant">  $clear-trace</span>
   <span class="Comment"># click on the third line and hit up-arrow, so you end up just after a newline</span>
   assume-console [
@@ -1065,9 +1067,9 @@ def]
     press up-arrow
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
-    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
+    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   ]
   memory-should-contain [
     <span class="Constant">3</span><span class="Special"> &lt;- </span><span class="Constant">2</span>
@@ -1078,7 +1080,7 @@ def]
     type <span class="Constant">[0]</span>
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   screen-should-contain [
    <span class="Constant"> .          .</span>
@@ -1093,19 +1095,19 @@ def]
 
 <span class="muScenario">scenario</span> editor-moves-to-next-line-with-down-arrow [
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
 <span class="Constant">def]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
-  editor-render screen, <span class="Constant">2</span>:address:editor-data
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+  editor-render screen, <span class="Constant">2</span>:address:shared:editor-data
 <span class="Constant">  $clear-trace</span>
   <span class="Comment"># cursor starts out at (1, 0)</span>
   assume-console [
     press down-arrow
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
-    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
+    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   ]
   <span class="Comment"># ..and ends at (2, 0)</span>
   memory-should-contain [
@@ -1117,7 +1119,7 @@ def]
     type <span class="Constant">[0]</span>
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   screen-should-contain [
    <span class="Constant"> .          .</span>
@@ -1140,12 +1142,12 @@ def]
   <span class="Delimiter">}</span>
 ]
 
-<span class="muRecipe">recipe</span> move-to-next-line editor:address:editor-data, screen-height:number<span class="muRecipe"> -&gt; </span>editor:address:editor-data, go-render?:boolean [
+<span class="muRecipe">recipe</span> move-to-next-line editor:address:shared:editor-data, screen-height:number<span class="muRecipe"> -&gt; </span>editor:address:shared:editor-data, go-render?:boolean [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   cursor-row:address:number<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">cursor-row:offset</span>
   cursor-column:address:number<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">cursor-column:offset</span>
-  before-cursor:address:address:duplex-list:character<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">before-cursor:offset</span>
+  before-cursor:address:address:shared:duplex-list:character<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">before-cursor:offset</span>
   left:number<span class="Special"> &lt;- </span>get *editor, <span class="Constant">left:offset</span>
   right:number<span class="Special"> &lt;- </span>get *editor, <span class="Constant">right:offset</span>
   last-line:number<span class="Special"> &lt;- </span>subtract screen-height, <span class="Constant">1</span>
@@ -1155,7 +1157,7 @@ def]
     <span class="muControl">break-if</span> already-at-bottom?
     <span class="Comment"># scan to start of next line, then to right column or until end of line</span>
     max:number<span class="Special"> &lt;- </span>subtract right, left
-    next-line:address:duplex-list:character<span class="Special"> &lt;- </span>before-start-of-next-line *before-cursor, max
+    next-line:address:shared:duplex-list:character<span class="Special"> &lt;- </span>before-start-of-next-line *before-cursor, max
     <span class="Delimiter">{</span>
       <span class="Comment"># already at end of buffer? try to scroll up (so we can see more</span>
       <span class="Comment"># warnings or sandboxes below)</span>
@@ -1173,7 +1175,7 @@ def]
     <span class="Delimiter">{</span>
       done?:boolean<span class="Special"> &lt;- </span>greater-or-equal *cursor-column, target-column
       <span class="muControl">break-if</span> done?
-      curr:address:duplex-list:character<span class="Special"> &lt;- </span>next *before-cursor
+      curr:address:shared:duplex-list:character<span class="Special"> &lt;- </span>next *before-cursor
       <span class="muControl">break-unless</span> curr
       currc:character<span class="Special"> &lt;- </span>get *curr, <span class="Constant">value:offset</span>
       at-newline?:boolean<span class="Special"> &lt;- </span>equal currc, <span class="Constant">10/newline</span>
@@ -1193,19 +1195,19 @@ def]
 
 <span class="muScenario">scenario</span> editor-adjusts-column-at-next-line [
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
 <span class="Constant">de]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
-  editor-render screen, <span class="Constant">2</span>:address:editor-data
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+  editor-render screen, <span class="Constant">2</span>:address:shared:editor-data
 <span class="Constant">  $clear-trace</span>
   assume-console [
     left-click <span class="Constant">1</span>, <span class="Constant">3</span>
     press down-arrow
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
-    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
+    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   ]
   memory-should-contain [
     <span class="Constant">3</span><span class="Special"> &lt;- </span><span class="Constant">2</span>
@@ -1216,7 +1218,7 @@ def]
     type <span class="Constant">[0]</span>
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   screen-should-contain [
    <span class="Constant"> .          .</span>
@@ -1231,10 +1233,10 @@ def]
 
 <span class="muScenario">scenario</span> editor-moves-to-start-of-line-with-ctrl-a [
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[123</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[123</span>
 <span class="Constant">456]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
-  editor-render screen, <span class="Constant">2</span>:address:editor-data
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+  editor-render screen, <span class="Constant">2</span>:address:shared:editor-data
 <span class="Constant">  $clear-trace</span>
   <span class="Comment"># start on second line, press ctrl-a</span>
   assume-console [
@@ -1242,9 +1244,9 @@ def]
     press ctrl-a
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
-    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-    <span class="Constant">5</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
+    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+    <span class="Constant">5</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   ]
   <span class="Comment"># cursor moves to start of line</span>
   memory-should-contain [
@@ -1280,7 +1282,7 @@ def]
   <span class="Delimiter">}</span>
 ]
 
-<span class="muRecipe">recipe</span> move-to-start-of-line editor:address:editor-data<span class="muRecipe"> -&gt; </span>editor:address:editor-data [
+<span class="muRecipe">recipe</span> move-to-start-of-line editor:address:shared:editor-data<span class="muRecipe"> -&gt; </span>editor:address:shared:editor-data [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   <span class="Comment"># update cursor column</span>
@@ -1288,8 +1290,8 @@ def]
   cursor-column:address:number<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">cursor-column:offset</span>
   *cursor-column<span class="Special"> &lt;- </span>copy left
   <span class="Comment"># update before-cursor</span>
-  before-cursor:address:address:duplex-list:character<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">before-cursor:offset</span>
-  init:address:duplex-list:character<span class="Special"> &lt;- </span>get *editor, <span class="Constant">data:offset</span>
+  before-cursor:address:address:shared:duplex-list:character<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">before-cursor:offset</span>
+  init:address:shared:duplex-list:character<span class="Special"> &lt;- </span>get *editor, <span class="Constant">data:offset</span>
   <span class="Comment"># while not at start of line, move </span>
   <span class="Delimiter">{</span>
     at-start-of-text?:boolean<span class="Special"> &lt;- </span>equal *before-cursor, init
@@ -1305,10 +1307,10 @@ def]
 
 <span class="muScenario">scenario</span> editor-moves-to-start-of-line-with-ctrl-a-2 [
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[123</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[123</span>
 <span class="Constant">456]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
-  editor-render screen, <span class="Constant">2</span>:address:editor-data
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+  editor-render screen, <span class="Constant">2</span>:address:shared:editor-data
 <span class="Constant">  $clear-trace</span>
   <span class="Comment"># start on first line (no newline before), press ctrl-a</span>
   assume-console [
@@ -1316,9 +1318,9 @@ def]
     press ctrl-a
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
-    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-    <span class="Constant">5</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
+    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+    <span class="Constant">5</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   ]
   <span class="Comment"># cursor moves to start of line</span>
   memory-should-contain [
@@ -1330,9 +1332,9 @@ def]
 
 <span class="muScenario">scenario</span> editor-moves-to-start-of-line-with-home [
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[123</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[123</span>
 <span class="Constant">456]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
 <span class="Constant">  $clear-trace</span>
   <span class="Comment"># start on second line, press 'home'</span>
   assume-console [
@@ -1340,9 +1342,9 @@ def]
     press home
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
-    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
+    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   ]
   <span class="Comment"># cursor moves to start of line</span>
   memory-should-contain [
@@ -1354,10 +1356,10 @@ def]
 
 <span class="muScenario">scenario</span> editor-moves-to-start-of-line-with-home-2 [
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[123</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[123</span>
 <span class="Constant">456]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
-  editor-render screen, <span class="Constant">2</span>:address:editor-data
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+  editor-render screen, <span class="Constant">2</span>:address:shared:editor-data
 <span class="Constant">  $clear-trace</span>
   <span class="Comment"># start on first line (no newline before), press 'home'</span>
   assume-console [
@@ -1365,9 +1367,9 @@ def]
     press home
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
-    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
+    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   ]
   <span class="Comment"># cursor moves to start of line</span>
   memory-should-contain [
@@ -1381,10 +1383,10 @@ def]
 
 <span class="muScenario">scenario</span> editor-moves-to-end-of-line-with-ctrl-e [
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[123</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[123</span>
 <span class="Constant">456]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
-  editor-render screen, <span class="Constant">2</span>:address:editor-data
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+  editor-render screen, <span class="Constant">2</span>:address:shared:editor-data
 <span class="Constant">  $clear-trace</span>
   <span class="Comment"># start on first line, press ctrl-e</span>
   assume-console [
@@ -1392,9 +1394,9 @@ def]
     press ctrl-e
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
-    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-    <span class="Constant">5</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
+    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+    <span class="Constant">5</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   ]
   <span class="Comment"># cursor moves to end of line</span>
   memory-should-contain [
@@ -1407,9 +1409,9 @@ def]
     type <span class="Constant">[z]</span>
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
-    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-    <span class="Constant">5</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
+    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+    <span class="Constant">5</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   ]
   memory-should-contain [
     <span class="Constant">4</span><span class="Special"> &lt;- </span><span class="Constant">1</span>
@@ -1451,14 +1453,14 @@ def]
   <span class="Delimiter">}</span>
 ]
 
-<span class="muRecipe">recipe</span> move-to-end-of-line editor:address:editor-data<span class="muRecipe"> -&gt; </span>editor:address:editor-data [
+<span class="muRecipe">recipe</span> move-to-end-of-line editor:address:shared:editor-data<span class="muRecipe"> -&gt; </span>editor:address:shared:editor-data [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
-  before-cursor:address:address:duplex-list:character<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">before-cursor:offset</span>
+  before-cursor:address:address:shared:duplex-list:character<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">before-cursor:offset</span>
   cursor-column:address:number<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">cursor-column:offset</span>
   <span class="Comment"># while not at start of line, move </span>
   <span class="Delimiter">{</span>
-    next:address:duplex-list:character<span class="Special"> &lt;- </span>next *before-cursor
+    next:address:shared:duplex-list:character<span class="Special"> &lt;- </span>next *before-cursor
     <span class="muControl">break-unless</span> next  <span class="Comment"># end of text</span>
     nextc:character<span class="Special"> &lt;- </span>get *next, <span class="Constant">value:offset</span>
     at-end-of-line?:boolean<span class="Special"> &lt;- </span>equal nextc, <span class="Constant">10/newline</span>
@@ -1471,10 +1473,10 @@ def]
 
 <span class="muScenario">scenario</span> editor-moves-to-end-of-line-with-ctrl-e-2 [
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[123</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[123</span>
 <span class="Constant">456]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
-  editor-render screen, <span class="Constant">2</span>:address:editor-data
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+  editor-render screen, <span class="Constant">2</span>:address:shared:editor-data
 <span class="Constant">  $clear-trace</span>
   <span class="Comment"># start on second line (no newline after), press ctrl-e</span>
   assume-console [
@@ -1482,9 +1484,9 @@ def]
     press ctrl-e
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
-    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-    <span class="Constant">5</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
+    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+    <span class="Constant">5</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   ]
   <span class="Comment"># cursor moves to end of line</span>
   memory-should-contain [
@@ -1496,10 +1498,10 @@ def]
 
 <span class="muScenario">scenario</span> editor-moves-to-end-of-line-with-end [
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[123</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[123</span>
 <span class="Constant">456]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
-  editor-render screen, <span class="Constant">2</span>:address:editor-data
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+  editor-render screen, <span class="Constant">2</span>:address:shared:editor-data
 <span class="Constant">  $clear-trace</span>
   <span class="Comment"># start on first line, press 'end'</span>
   assume-console [
@@ -1507,9 +1509,9 @@ def]
     press end
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
-    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
+    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   ]
   <span class="Comment"># cursor moves to end of line</span>
   memory-should-contain [
@@ -1521,10 +1523,10 @@ def]
 
 <span class="muScenario">scenario</span> editor-moves-to-end-of-line-with-end-2 [
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[123</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[123</span>
 <span class="Constant">456]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
-  editor-render screen, <span class="Constant">2</span>:address:editor-data
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+  editor-render screen, <span class="Constant">2</span>:address:shared:editor-data
 <span class="Constant">  $clear-trace</span>
   <span class="Comment"># start on second line (no newline after), press 'end'</span>
   assume-console [
@@ -1532,9 +1534,9 @@ def]
     press end
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
-    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
+    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   ]
   <span class="Comment"># cursor moves to end of line</span>
   memory-should-contain [
@@ -1548,16 +1550,16 @@ def]
 
 <span class="muScenario">scenario</span> editor-deletes-to-start-of-line-with-ctrl-u [
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[123</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[123</span>
 <span class="Constant">456]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
   <span class="Comment"># start on second line, press ctrl-u</span>
   assume-console [
     left-click <span class="Constant">2</span>, <span class="Constant">2</span>
     press ctrl-u
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   <span class="Comment"># cursor deletes to start of line</span>
   screen-should-contain [
@@ -1574,21 +1576,21 @@ def]
     delete-to-start-of-line?:boolean<span class="Special"> &lt;- </span>equal *c, <span class="Constant">21/ctrl-u</span>
     <span class="muControl">break-unless</span> delete-to-start-of-line?
 <span class="Constant">    &lt;delete-to-start-of-line-begin&gt;</span>
-    deleted-cells:address:duplex-list:character<span class="Special"> &lt;- </span>delete-to-start-of-line editor
+    deleted-cells:address:shared:duplex-list:character<span class="Special"> &lt;- </span>delete-to-start-of-line editor
 <span class="Constant">    &lt;delete-to-start-of-line-end&gt;</span>
     go-render?<span class="Special"> &lt;- </span>copy <span class="Constant">1/true</span>
     <span class="muControl">reply</span>
   <span class="Delimiter">}</span>
 ]
 
-<span class="muRecipe">recipe</span> delete-to-start-of-line editor:address:editor-data<span class="muRecipe"> -&gt; </span>result:address:duplex-list:character, editor:address:editor-data [
+<span class="muRecipe">recipe</span> delete-to-start-of-line editor:address:shared:editor-data<span class="muRecipe"> -&gt; </span>result:address:shared:duplex-list:character, editor:address:shared:editor-data [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   <span class="Comment"># compute range to delete</span>
-  init:address:duplex-list:character<span class="Special"> &lt;- </span>get *editor, <span class="Constant">data:offset</span>
-  before-cursor:address:address:duplex-list:character<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">before-cursor:offset</span>
-  start:address:duplex-list:character<span class="Special"> &lt;- </span>copy *before-cursor
-  end:address:duplex-list:character<span class="Special"> &lt;- </span>next *before-cursor
+  init:address:shared:duplex-list:character<span class="Special"> &lt;- </span>get *editor, <span class="Constant">data:offset</span>
+  before-cursor:address:address:shared:duplex-list:character<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">before-cursor:offset</span>
+  start:address:shared:duplex-list:character<span class="Special"> &lt;- </span>copy *before-cursor
+  end:address:shared:duplex-list:character<span class="Special"> &lt;- </span>next *before-cursor
   <span class="Delimiter">{</span>
     at-start-of-text?:boolean<span class="Special"> &lt;- </span>equal start, init
     <span class="muControl">break-if</span> at-start-of-text?
@@ -1600,7 +1602,7 @@ def]
     <span class="muControl">loop</span>
   <span class="Delimiter">}</span>
   <span class="Comment"># snip it out</span>
-  result:address:duplex-list:character<span class="Special"> &lt;- </span>next start
+  result:address:shared:duplex-list:character<span class="Special"> &lt;- </span>next start
   remove-between start, end
   <span class="Comment"># adjust cursor</span>
   *before-cursor<span class="Special"> &lt;- </span>copy start
@@ -1611,16 +1613,16 @@ def]
 
 <span class="muScenario">scenario</span> editor-deletes-to-start-of-line-with-ctrl-u-2 [
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[123</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[123</span>
 <span class="Constant">456]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
   <span class="Comment"># start on first line (no newline before), press ctrl-u</span>
   assume-console [
     left-click <span class="Constant">1</span>, <span class="Constant">2</span>
     press ctrl-u
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   <span class="Comment"># cursor deletes to start of line</span>
   screen-should-contain [
@@ -1634,16 +1636,16 @@ def]
 
 <span class="muScenario">scenario</span> editor-deletes-to-start-of-line-with-ctrl-u-3 [
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[123</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[123</span>
 <span class="Constant">456]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
   <span class="Comment"># start past end of line, press ctrl-u</span>
   assume-console [
     left-click <span class="Constant">1</span>, <span class="Constant">3</span>
     press ctrl-u
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   <span class="Comment"># cursor deletes to start of line</span>
   screen-should-contain [
@@ -1657,16 +1659,16 @@ def]
 
 <span class="muScenario">scenario</span> editor-deletes-to-start-of-final-line-with-ctrl-u [
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[123</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[123</span>
 <span class="Constant">456]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
   <span class="Comment"># start past end of final line, press ctrl-u</span>
   assume-console [
     left-click <span class="Constant">2</span>, <span class="Constant">3</span>
     press ctrl-u
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   <span class="Comment"># cursor deletes to start of line</span>
   screen-should-contain [
@@ -1682,16 +1684,16 @@ def]
 
 <span class="muScenario">scenario</span> editor-deletes-to-end-of-line-with-ctrl-k [
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[123</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[123</span>
 <span class="Constant">456]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
   <span class="Comment"># start on first line, press ctrl-k</span>
   assume-console [
     left-click <span class="Constant">1</span>, <span class="Constant">1</span>
     press ctrl-k
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   <span class="Comment"># cursor deletes to end of line</span>
   screen-should-contain [
@@ -1708,19 +1710,19 @@ def]
     delete-to-end-of-line?:boolean<span class="Special"> &lt;- </span>equal *c, <span class="Constant">11/ctrl-k</span>
     <span class="muControl">break-unless</span> delete-to-end-of-line?
 <span class="Constant">    &lt;delete-to-end-of-line-begin&gt;</span>
-    deleted-cells:address:duplex-list:character<span class="Special"> &lt;- </span>delete-to-end-of-line editor
+    deleted-cells:address:shared:duplex-list:character<span class="Special"> &lt;- </span>delete-to-end-of-line editor
 <span class="Constant">    &lt;delete-to-end-of-line-end&gt;</span>
     go-render?<span class="Special"> &lt;- </span>copy <span class="Constant">1/true</span>
     <span class="muControl">reply</span>
   <span class="Delimiter">}</span>
 ]
 
-<span class="muRecipe">recipe</span> delete-to-end-of-line editor:address:editor-data<span class="muRecipe"> -&gt; </span>result:address:duplex-list:character, editor:address:editor-data [
+<span class="muRecipe">recipe</span> delete-to-end-of-line editor:address:shared:editor-data<span class="muRecipe"> -&gt; </span>result:address:shared:duplex-list:character, editor:address:shared:editor-data [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   <span class="Comment"># compute range to delete</span>
-  start:address:duplex-list:character<span class="Special"> &lt;- </span>get *editor, <span class="Constant">before-cursor:offset</span>
-  end:address:duplex-list:character<span class="Special"> &lt;- </span>next start
+  start:address:shared:duplex-list:character<span class="Special"> &lt;- </span>get *editor, <span class="Constant">before-cursor:offset</span>
+  end:address:shared:duplex-list:character<span class="Special"> &lt;- </span>next start
   <span class="Delimiter">{</span>
     at-end-of-text?:boolean<span class="Special"> &lt;- </span>equal end, <span class="Constant">0/null</span>
     <span class="muControl">break-if</span> at-end-of-text?
@@ -1737,16 +1739,16 @@ def]
 
 <span class="muScenario">scenario</span> editor-deletes-to-end-of-line-with-ctrl-k-2 [
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[123</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[123</span>
 <span class="Constant">456]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
   <span class="Comment"># start on second line (no newline after), press ctrl-k</span>
   assume-console [
     left-click <span class="Constant">2</span>, <span class="Constant">1</span>
     press ctrl-k
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   <span class="Comment"># cursor deletes to end of line</span>
   screen-should-contain [
@@ -1760,16 +1762,16 @@ def]
 
 <span class="muScenario">scenario</span> editor-deletes-to-end-of-line-with-ctrl-k-3 [
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[123</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[123</span>
 <span class="Constant">456]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
   <span class="Comment"># start at end of line</span>
   assume-console [
     left-click <span class="Constant">1</span>, <span class="Constant">2</span>
     press ctrl-k
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   <span class="Comment"># cursor deletes just last character</span>
   screen-should-contain [
@@ -1783,16 +1785,16 @@ def]
 
 <span class="muScenario">scenario</span> editor-deletes-to-end-of-line-with-ctrl-k-4 [
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[123</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[123</span>
 <span class="Constant">456]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
   <span class="Comment"># start past end of line</span>
   assume-console [
     left-click <span class="Constant">1</span>, <span class="Constant">3</span>
     press ctrl-k
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   <span class="Comment"># cursor deletes nothing</span>
   screen-should-contain [
@@ -1806,16 +1808,16 @@ def]
 
 <span class="muScenario">scenario</span> editor-deletes-to-end-of-line-with-ctrl-k-5 [
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[123</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[123</span>
 <span class="Constant">456]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
   <span class="Comment"># start at end of text</span>
   assume-console [
     left-click <span class="Constant">2</span>, <span class="Constant">2</span>
     press ctrl-k
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   <span class="Comment"># cursor deletes just the final character</span>
   screen-should-contain [
@@ -1829,16 +1831,16 @@ def]
 
 <span class="muScenario">scenario</span> editor-deletes-to-end-of-line-with-ctrl-k-6 [
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[123</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[123</span>
 <span class="Constant">456]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
   <span class="Comment"># start past end of text</span>
   assume-console [
     left-click <span class="Constant">2</span>, <span class="Constant">3</span>
     press ctrl-k
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   <span class="Comment"># cursor deletes nothing</span>
   screen-should-contain [
@@ -1856,11 +1858,11 @@ def]
   <span class="Comment"># screen has 1 line for menu + 3 lines</span>
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">4/height</span>
   <span class="Comment"># initialize editor with &gt;3 lines</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[a</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[a</span>
 <span class="Constant">b</span>
 <span class="Constant">c</span>
 <span class="Constant">d]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
   screen-should-contain [
    <span class="Constant"> .          .</span>
    <span class="Constant"> .a         .</span>
@@ -1873,7 +1875,7 @@ def]
     press down-arrow
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   <span class="Comment"># screen slides by one line</span>
   screen-should-contain [
@@ -1886,11 +1888,11 @@ def]
 
 <span class="muRecipe">after</span> <span class="Constant">&lt;scroll-down&gt;</span> [
   trace <span class="Constant">10</span>, <span class="Constant">[app]</span>, <span class="Constant">[scroll down]</span>
-  top-of-screen:address:address:duplex-list:character<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">top-of-screen:offset</span>
+  top-of-screen:address:address:shared:duplex-list:character<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">top-of-screen:offset</span>
   left:number<span class="Special"> &lt;- </span>get *editor, <span class="Constant">left:offset</span>
   right:number<span class="Special"> &lt;- </span>get *editor, <span class="Constant">right:offset</span>
   max:number<span class="Special"> &lt;- </span>subtract right, left
-  old-top:address:duplex-list:character<span class="Special"> &lt;- </span>copy *top-of-screen
+  old-top:address:shared:duplex-list:character<span class="Special"> &lt;- </span>copy *top-of-screen
   *top-of-screen<span class="Special"> &lt;- </span>before-start-of-next-line *top-of-screen, max
   no-movement?:boolean<span class="Special"> &lt;- </span>equal old-top, *top-of-screen
   go-render?<span class="Special"> &lt;- </span>copy <span class="Constant">0/false</span>
@@ -1900,11 +1902,11 @@ def]
 <span class="Comment"># takes a pointer into the doubly-linked list, scans ahead at most 'max'</span>
 <span class="Comment"># positions until the next newline</span>
 <span class="Comment"># beware: never return null pointer.</span>
-<span class="muRecipe">recipe</span> before-start-of-next-line original:address:duplex-list:character, max:number<span class="muRecipe"> -&gt; </span>curr:address:duplex-list:character [
+<span class="muRecipe">recipe</span> before-start-of-next-line original:address:shared:duplex-list:character, max:number<span class="muRecipe"> -&gt; </span>curr:address:shared:duplex-list:character [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   count:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
-  curr:address:duplex-list:character<span class="Special"> &lt;- </span>copy original
+  curr:address:shared:duplex-list:character<span class="Special"> &lt;- </span>copy original
   <span class="Comment"># skip the initial newline if it exists</span>
   <span class="Delimiter">{</span>
     c:character<span class="Special"> &lt;- </span>get *curr, <span class="Constant">value:offset</span>
@@ -1933,11 +1935,11 @@ def]
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">4/height</span>
   <span class="Comment"># initialize editor with a long, wrapped line and more than a screen of</span>
   <span class="Comment"># other lines</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abcdef</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abcdef</span>
 <span class="Constant">g</span>
 <span class="Constant">h</span>
 <span class="Constant">i]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
   screen-should-contain [
    <span class="Constant"> .          .</span>
    <span class="Constant"> .abcd↩     .</span>
@@ -1950,7 +1952,7 @@ def]
     press down-arrow
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   <span class="Comment"># screen shows partial wrapped line</span>
   screen-should-contain [
@@ -1965,18 +1967,18 @@ def]
   <span class="Comment"># screen has 1 line for menu + 3 lines</span>
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">4/height</span>
   <span class="Comment"># editor starts with a long line wrapping twice</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abcdefghij</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abcdefghij</span>
 <span class="Constant">k</span>
 <span class="Constant">l</span>
 <span class="Constant">m]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
   <span class="Comment"># position cursor at last line, then try to move further down</span>
   assume-console [
     left-click <span class="Constant">3</span>, <span class="Constant">0</span>
     press down-arrow
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   <span class="Comment"># screen shows partial wrapped line containing a wrap icon</span>
   screen-should-contain [
@@ -1990,7 +1992,7 @@ def]
     press down-arrow
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   <span class="Comment"># screen shows partial wrapped line</span>
   screen-should-contain [
@@ -2005,19 +2007,19 @@ def]
   <span class="Comment"># screen has 1 line for menu + 3 lines</span>
   assume-screen <span class="Constant">5/width</span>, <span class="Constant">4/height</span>
   <span class="Comment"># editor contains a long line in the third line</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[a</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[a</span>
 <span class="Constant">b</span>
 <span class="Constant">cdef]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
   <span class="Comment"># position cursor at end, type a character</span>
   assume-console [
     left-click <span class="Constant">3</span>, <span class="Constant">4</span>
     type <span class="Constant">[g]</span>
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
-    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
+    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   ]
   <span class="Comment"># screen scrolls</span>
   screen-should-contain [
@@ -2035,19 +2037,19 @@ def]
 <span class="muScenario">scenario</span> editor-scrolls-down-on-newline [
   assume-screen <span class="Constant">5/width</span>, <span class="Constant">4/height</span>
   <span class="Comment"># position cursor after last line and type newline</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[a</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[a</span>
 <span class="Constant">b</span>
 <span class="Constant">c]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
   assume-console [
     left-click <span class="Constant">3</span>, <span class="Constant">4</span>
     type [
 ]
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
-    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
+    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   ]
   <span class="Comment"># screen scrolls</span>
   screen-should-contain [
@@ -2066,19 +2068,19 @@ def]
   <span class="Comment"># screen has 1 line for menu + 3 lines</span>
   assume-screen <span class="Constant">5/width</span>, <span class="Constant">4/height</span>
   <span class="Comment"># editor contains a wrapped line</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[a</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[a</span>
 <span class="Constant">b</span>
 <span class="Constant">cdefgh]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
   <span class="Comment"># position cursor at end of screen and try to move right</span>
   assume-console [
     left-click <span class="Constant">3</span>, <span class="Constant">3</span>
     press right-arrow
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
-    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
+    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   ]
   <span class="Comment"># screen scrolls</span>
   screen-should-contain [
@@ -2097,20 +2099,20 @@ def]
   <span class="Comment"># screen has 1 line for menu + 3 lines</span>
   assume-screen <span class="Constant">5/width</span>, <span class="Constant">4/height</span>
   <span class="Comment"># editor contains more lines than can fit on screen</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[a</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[a</span>
 <span class="Constant">b</span>
 <span class="Constant">c</span>
 <span class="Constant">d]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
   <span class="Comment"># position cursor at end of screen and try to move right</span>
   assume-console [
     left-click <span class="Constant">3</span>, <span class="Constant">3</span>
     press right-arrow
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
-    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
+    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   ]
   <span class="Comment"># screen scrolls</span>
   screen-should-contain [
@@ -2127,10 +2129,10 @@ def]
 
 <span class="muScenario">scenario</span> editor-scrolls-at-end-on-down-arrow [
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
 <span class="Constant">de]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
-  editor-render screen, <span class="Constant">2</span>:address:editor-data
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+  editor-render screen, <span class="Constant">2</span>:address:shared:editor-data
 <span class="Constant">  $clear-trace</span>
   <span class="Comment"># try to move down past end of text</span>
   assume-console [
@@ -2138,9 +2140,9 @@ def]
     press down-arrow
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
-    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
+    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   ]
   <span class="Comment"># screen should scroll, moving cursor to end of text</span>
   memory-should-contain [
@@ -2151,7 +2153,7 @@ def]
     type <span class="Constant">[0]</span>
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   screen-should-contain [
    <span class="Constant"> .          .</span>
@@ -2166,9 +2168,9 @@ def]
     press down-arrow
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
-    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
+    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   ]
   <span class="Comment"># screen stops scrolling because cursor is already at top</span>
   memory-should-contain [
@@ -2180,7 +2182,7 @@ def]
     type <span class="Constant">[1]</span>
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   screen-should-contain [
    <span class="Constant"> .          .</span>
@@ -2194,14 +2196,14 @@ def]
   <span class="Comment"># screen has 1 line for menu + 3 lines</span>
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">4/height</span>
   <span class="Comment"># initialize editor with a few pages of lines</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[a</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[a</span>
 <span class="Constant">b</span>
 <span class="Constant">c</span>
 <span class="Constant">d</span>
 <span class="Constant">e</span>
 <span class="Constant">f</span>
 <span class="Constant">g]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
   <span class="Comment"># scroll down one page and one line</span>
   assume-console [
     press page-down
@@ -2209,7 +2211,7 @@ def]
     press down-arrow
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   <span class="Comment"># screen scrolls down 3 lines</span>
   screen-should-contain [
@@ -2226,11 +2228,11 @@ def]
   <span class="Comment"># screen has 1 line for menu + 3 lines</span>
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">4/height</span>
   <span class="Comment"># initialize editor with &gt;3 lines</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[a</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[a</span>
 <span class="Constant">b</span>
 <span class="Constant">c</span>
 <span class="Constant">d]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
   screen-should-contain [
    <span class="Constant"> .          .</span>
    <span class="Constant"> .a         .</span>
@@ -2243,7 +2245,7 @@ def]
     press up-arrow
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   <span class="Comment"># screen slides by one line</span>
   screen-should-contain [
@@ -2256,8 +2258,8 @@ def]
 
 <span class="muRecipe">after</span> <span class="Constant">&lt;scroll-up&gt;</span> [
   trace <span class="Constant">10</span>, <span class="Constant">[app]</span>, <span class="Constant">[scroll up]</span>
-  top-of-screen:address:address:duplex-list:character<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">top-of-screen:offset</span>
-  old-top:address:duplex-list:character<span class="Special"> &lt;- </span>copy *top-of-screen
+  top-of-screen:address:address:shared:duplex-list:character<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">top-of-screen:offset</span>
+  old-top:address:shared:duplex-list:character<span class="Special"> &lt;- </span>copy *top-of-screen
   *top-of-screen<span class="Special"> &lt;- </span>before-previous-line *top-of-screen, editor
   no-movement?:boolean<span class="Special"> &lt;- </span>equal old-top, *top-of-screen
   go-render?<span class="Special"> &lt;- </span>copy <span class="Constant">0/false</span>
@@ -2267,7 +2269,7 @@ def]
 <span class="Comment"># takes a pointer into the doubly-linked list, scans back to before start of</span>
 <span class="Comment"># previous *wrapped* line</span>
 <span class="Comment"># beware: never return null pointer</span>
-<span class="muRecipe">recipe</span> before-previous-line curr:address:duplex-list:character, editor:address:editor-data<span class="muRecipe"> -&gt; </span>curr:address:duplex-list:character [
+<span class="muRecipe">recipe</span> before-previous-line curr:address:shared:duplex-list:character, editor:address:shared:editor-data<span class="muRecipe"> -&gt; </span>curr:address:shared:duplex-list:character [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   c:character<span class="Special"> &lt;- </span>get *curr, <span class="Constant">value:offset</span>
@@ -2277,12 +2279,12 @@ def]
   left:number<span class="Special"> &lt;- </span>get *editor, <span class="Constant">left:offset</span>
   right:number<span class="Special"> &lt;- </span>get *editor, <span class="Constant">right:offset</span>
   max-line-length:number<span class="Special"> &lt;- </span>subtract right, left, <span class="Constant">-1/exclusive-right</span>, <span class="Constant">1/wrap-icon</span>
-  sentinel:address:duplex-list:character<span class="Special"> &lt;- </span>get *editor, <span class="Constant">data:offset</span>
+  sentinel:address:shared:duplex-list:character<span class="Special"> &lt;- </span>get *editor, <span class="Constant">data:offset</span>
   len:number<span class="Special"> &lt;- </span>previous-line-length curr, sentinel
   <span class="Delimiter">{</span>
     <span class="muControl">break-if</span> len
     <span class="Comment"># empty line; just skip this newline</span>
-    prev:address:duplex-list:character<span class="Special"> &lt;- </span>prev curr
+    prev:address:shared:duplex-list:character<span class="Special"> &lt;- </span>prev curr
     <span class="muControl">reply-unless</span> prev, curr
     <span class="muControl">reply</span> prev
   <span class="Delimiter">}</span>
@@ -2298,7 +2300,7 @@ def]
   <span class="Delimiter">{</span>
     done?:boolean<span class="Special"> &lt;- </span>greater-or-equal count, max
     <span class="muControl">break-if</span> done?
-    prev:address:duplex-list:character<span class="Special"> &lt;- </span>prev curr
+    prev:address:shared:duplex-list:character<span class="Special"> &lt;- </span>prev curr
     <span class="muControl">break-unless</span> prev
     curr<span class="Special"> &lt;- </span>copy prev
     count<span class="Special"> &lt;- </span>add count, <span class="Constant">1</span>
@@ -2312,11 +2314,11 @@ def]
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">4/height</span>
   <span class="Comment"># initialize editor with a long, wrapped line and more than a screen of</span>
   <span class="Comment"># other lines</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abcdef</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abcdef</span>
 <span class="Constant">g</span>
 <span class="Constant">h</span>
 <span class="Constant">i]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
   screen-should-contain [
    <span class="Constant"> .          .</span>
    <span class="Constant"> .abcd↩     .</span>
@@ -2328,7 +2330,7 @@ def]
     press page-down
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   screen-should-contain [
    <span class="Constant"> .          .</span>
@@ -2341,7 +2343,7 @@ def]
     press up-arrow
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   <span class="Comment"># screen shows partial wrapped line</span>
   screen-should-contain [
@@ -2356,17 +2358,17 @@ def]
   <span class="Comment"># screen has 1 line for menu + 4 lines</span>
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
   <span class="Comment"># editor starts with a long line wrapping twice, occupying 3 of the 4 lines</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abcdefghij</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abcdefghij</span>
 <span class="Constant">k</span>
 <span class="Constant">l</span>
 <span class="Constant">m]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
   <span class="Comment"># position cursor at top of second page</span>
   assume-console [
     press page-down
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   screen-should-contain [
    <span class="Constant"> .          .</span>
@@ -2380,7 +2382,7 @@ def]
     press up-arrow
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   <span class="Comment"># screen shows partial wrapped line</span>
   screen-should-contain [
@@ -2395,7 +2397,7 @@ def]
     press up-arrow
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   <span class="Comment"># screen shows partial wrapped line</span>
   screen-should-contain [
@@ -2410,7 +2412,7 @@ def]
     press up-arrow
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   <span class="Comment"># screen shows partial wrapped line</span>
   screen-should-contain [
@@ -2429,11 +2431,11 @@ def]
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">4/height</span>
   <span class="Comment"># initialize editor with a long, wrapped line and more than a screen of</span>
   <span class="Comment"># other lines</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abcdef</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abcdef</span>
 <span class="Constant">g</span>
 <span class="Constant">h</span>
 <span class="Constant">i]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">6/right</span>
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">6/right</span>
   screen-should-contain [
    <span class="Constant"> .          .</span>
    <span class="Constant"> .abcde↩    .</span>
@@ -2445,7 +2447,7 @@ def]
     press page-down
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   screen-should-contain [
    <span class="Constant"> .          .</span>
@@ -2458,7 +2460,7 @@ def]
     press up-arrow
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   <span class="Comment"># screen shows partial wrapped line</span>
   screen-should-contain [
@@ -2473,18 +2475,18 @@ def]
 <span class="muScenario">scenario</span> editor-scrolls-up-past-wrapped-line-using-arrow-keys-4 [
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">4/height</span>
   <span class="Comment"># initialize editor with some lines around an empty line</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[a</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[a</span>
 <span class="Constant">b</span>
 
 c
 d
 e]
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">6/right</span>
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">6/right</span>
   assume-console [
     press page-down
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   screen-should-contain [
    <span class="Constant"> .          .</span>
@@ -2496,7 +2498,7 @@ e]
     press page-down
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   screen-should-contain [
    <span class="Constant"> .          .</span>
@@ -2508,7 +2510,7 @@ e]
     press page-up
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   screen-should-contain [
    <span class="Constant"> .          .</span>
@@ -2522,18 +2524,18 @@ e]
   <span class="Comment"># screen has 1 line for menu + 3 lines</span>
   assume-screen <span class="Constant">5/width</span>, <span class="Constant">4/height</span>
   <span class="Comment"># editor contains &gt;3 lines</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[a</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[a</span>
 <span class="Constant">b</span>
 <span class="Constant">c</span>
 <span class="Constant">d</span>
 <span class="Constant">e]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
   <span class="Comment"># position cursor at top of second page</span>
   assume-console [
     press page-down
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   screen-should-contain [
    <span class="Constant"> .     .</span>
@@ -2546,9 +2548,9 @@ e]
     press left-arrow
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
-    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
+    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   ]
   <span class="Comment"># screen scrolls</span>
   screen-should-contain [
@@ -2567,11 +2569,11 @@ e]
   <span class="Comment"># screen has 1 line for menu + 3 lines</span>
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">4/height</span>
   <span class="Comment"># initialize editor with &gt;3 lines</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[a</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[a</span>
 <span class="Constant">b</span>
 <span class="Constant">c</span>
 <span class="Constant">d]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
   screen-should-contain [
    <span class="Constant"> .          .</span>
    <span class="Constant"> .a         .</span>
@@ -2586,7 +2588,7 @@ e]
     press up-arrow
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   <span class="Comment"># screen slides by one line</span>
   screen-should-contain [
@@ -2600,7 +2602,7 @@ e]
     press up-arrow
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   <span class="Comment"># screen remains unchanged</span>
   screen-should-contain [
@@ -2615,11 +2617,11 @@ e]
 
 <span class="muScenario">scenario</span> editor-can-scroll [
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">4/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[a</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[a</span>
 <span class="Constant">b</span>
 <span class="Constant">c</span>
 <span class="Constant">d]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
   screen-should-contain [
    <span class="Constant"> .          .</span>
    <span class="Constant"> .a         .</span>
@@ -2631,7 +2633,7 @@ e]
     press page-down
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   <span class="Comment"># screen shows next page</span>
   screen-should-contain [
@@ -2646,8 +2648,8 @@ e]
   <span class="Delimiter">{</span>
     page-down?:boolean<span class="Special"> &lt;- </span>equal *c, <span class="Constant">6/ctrl-f</span>
     <span class="muControl">break-unless</span> page-down?
-    top-of-screen:address:address:duplex-list:character<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">top-of-screen:offset</span>
-    old-top:address:duplex-list:character<span class="Special"> &lt;- </span>copy *top-of-screen
+    top-of-screen:address:address:shared:duplex-list:character<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">top-of-screen:offset</span>
+    old-top:address:shared:duplex-list:character<span class="Special"> &lt;- </span>copy *top-of-screen
 <span class="Constant">    &lt;move-cursor-begin&gt;</span>
     page-down editor
     undo-coalesce-tag:number<span class="Special"> &lt;- </span>copy <span class="Constant">0/never</span>
@@ -2662,8 +2664,8 @@ e]
   <span class="Delimiter">{</span>
     page-down?:boolean<span class="Special"> &lt;- </span>equal *k, <span class="Constant">65518/page-down</span>
     <span class="muControl">break-unless</span> page-down?
-    top-of-screen:address:address:duplex-list:character<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">top-of-screen:offset</span>
-    old-top:address:duplex-list:character<span class="Special"> &lt;- </span>copy *top-of-screen
+    top-of-screen:address:address:shared:duplex-list:character<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">top-of-screen:offset</span>
+    old-top:address:shared:duplex-list:character<span class="Special"> &lt;- </span>copy *top-of-screen
 <span class="Constant">    &lt;move-cursor-begin&gt;</span>
     page-down editor
     undo-coalesce-tag:number<span class="Special"> &lt;- </span>copy <span class="Constant">0/never</span>
@@ -2676,14 +2678,14 @@ e]
 
 <span class="Comment"># page-down skips entire wrapped lines, so it can't scroll past lines</span>
 <span class="Comment"># taking up the entire screen</span>
-<span class="muRecipe">recipe</span> page-down editor:address:editor-data<span class="muRecipe"> -&gt; </span>editor:address:editor-data [
+<span class="muRecipe">recipe</span> page-down editor:address:shared:editor-data<span class="muRecipe"> -&gt; </span>editor:address:shared:editor-data [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   <span class="Comment"># if editor contents don't overflow screen, do nothing</span>
-  bottom-of-screen:address:duplex-list:character<span class="Special"> &lt;- </span>get *editor, <span class="Constant">bottom-of-screen:offset</span>
+  bottom-of-screen:address:shared:duplex-list:character<span class="Special"> &lt;- </span>get *editor, <span class="Constant">bottom-of-screen:offset</span>
   <span class="muControl">reply-unless</span> bottom-of-screen
   <span class="Comment"># if not, position cursor at final character</span>
-  before-cursor:address:address:duplex-list:character<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">before-cursor:offset</span>
+  before-cursor:address:address:shared:duplex-list:character<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">before-cursor:offset</span>
   *before-cursor<span class="Special"> &lt;- </span>prev bottom-of-screen
   <span class="Comment"># keep one line in common with previous page</span>
   <span class="Delimiter">{</span>
@@ -2694,16 +2696,16 @@ e]
   <span class="Delimiter">}</span>
   <span class="Comment"># move cursor and top-of-screen to start of that line</span>
   move-to-start-of-line editor
-  top-of-screen:address:address:duplex-list:character<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">top-of-screen:offset</span>
+  top-of-screen:address:address:shared:duplex-list:character<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">top-of-screen:offset</span>
   *top-of-screen<span class="Special"> &lt;- </span>copy *before-cursor
 ]
 
 <span class="muScenario">scenario</span> editor-does-not-scroll-past-end [
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">4/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[a</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[a</span>
 <span class="Constant">b]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
-  editor-render screen, <span class="Constant">2</span>:address:editor-data
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+  editor-render screen, <span class="Constant">2</span>:address:shared:editor-data
   screen-should-contain [
    <span class="Constant"> .          .</span>
    <span class="Constant"> .a         .</span>
@@ -2715,7 +2717,7 @@ e]
     press page-down
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   <span class="Comment"># screen remains unmodified</span>
   screen-should-contain [
@@ -2730,11 +2732,11 @@ e]
   <span class="Comment"># screen has 1 line for menu + 3 lines for text</span>
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">4/height</span>
   <span class="Comment"># editor contains a long last line</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[a</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[a</span>
 <span class="Constant">b</span>
 <span class="Constant">cdefgh]</span>
   <span class="Comment"># editor screen triggers wrap of last line</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">4/right</span>
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">4/right</span>
   <span class="Comment"># some part of last line is not displayed</span>
   screen-should-contain [
    <span class="Constant"> .          .</span>
@@ -2747,7 +2749,7 @@ e]
     press page-down
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   <span class="Comment"># screen shows entire wrapped line</span>
   screen-should-contain [
@@ -2763,9 +2765,9 @@ e]
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">4/height</span>
   <span class="Comment"># editor contains a very long line that occupies last two lines of screen</span>
   <span class="Comment"># and still has something left over</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[a</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[a</span>
 <span class="Constant">bcdefgh]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">4/right</span>
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">4/right</span>
   <span class="Comment"># some part of last line is not displayed</span>
   screen-should-contain [
    <span class="Constant"> .          .</span>
@@ -2778,7 +2780,7 @@ e]
     press page-down
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   <span class="Comment"># screen shows entire wrapped line</span>
   screen-should-contain [
@@ -2793,11 +2795,11 @@ e]
 
 <span class="muScenario">scenario</span> editor-can-scroll-up [
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">4/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[a</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[a</span>
 <span class="Constant">b</span>
 <span class="Constant">c</span>
 <span class="Constant">d]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
   screen-should-contain [
    <span class="Constant"> .          .</span>
    <span class="Constant"> .a         .</span>
@@ -2809,7 +2811,7 @@ e]
     press page-down
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   <span class="Comment"># screen shows next page</span>
   screen-should-contain [
@@ -2823,7 +2825,7 @@ e]
     press page-up
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   <span class="Comment"># screen shows original page again</span>
   screen-should-contain [
@@ -2838,8 +2840,8 @@ e]
   <span class="Delimiter">{</span>
     page-up?:boolean<span class="Special"> &lt;- </span>equal *c, <span class="Constant">2/ctrl-b</span>
     <span class="muControl">break-unless</span> page-up?
-    top-of-screen:address:address:duplex-list:character<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">top-of-screen:offset</span>
-    old-top:address:duplex-list:character<span class="Special"> &lt;- </span>copy *top-of-screen
+    top-of-screen:address:address:shared:duplex-list:character<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">top-of-screen:offset</span>
+    old-top:address:shared:duplex-list:character<span class="Special"> &lt;- </span>copy *top-of-screen
 <span class="Constant">    &lt;move-cursor-begin&gt;</span>
     editor<span class="Special"> &lt;- </span>page-up editor, screen-height
     undo-coalesce-tag:number<span class="Special"> &lt;- </span>copy <span class="Constant">0/never</span>
@@ -2854,8 +2856,8 @@ e]
   <span class="Delimiter">{</span>
     page-up?:boolean<span class="Special"> &lt;- </span>equal *k, <span class="Constant">65519/page-up</span>
     <span class="muControl">break-unless</span> page-up?
-    top-of-screen:address:address:duplex-list:character<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">top-of-screen:offset</span>
-    old-top:address:duplex-list:character<span class="Special"> &lt;- </span>copy *top-of-screen
+    top-of-screen:address:address:shared:duplex-list:character<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">top-of-screen:offset</span>
+    old-top:address:shared:duplex-list:character<span class="Special"> &lt;- </span>copy *top-of-screen
 <span class="Constant">    &lt;move-cursor-begin&gt;</span>
     editor<span class="Special"> &lt;- </span>page-up editor, screen-height
     undo-coalesce-tag:number<span class="Special"> &lt;- </span>copy <span class="Constant">0/never</span>
@@ -2867,16 +2869,16 @@ e]
   <span class="Delimiter">}</span>
 ]
 
-<span class="muRecipe">recipe</span> page-up editor:address:editor-data, screen-height:number<span class="muRecipe"> -&gt; </span>editor:address:editor-data [
+<span class="muRecipe">recipe</span> page-up editor:address:shared:editor-data, screen-height:number<span class="muRecipe"> -&gt; </span>editor:address:shared:editor-data [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   max:number<span class="Special"> &lt;- </span>subtract screen-height, <span class="Constant">1/menu-bar</span>, <span class="Constant">1/overlapping-line</span>
   count:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
-  top-of-screen:address:address:duplex-list:character<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">top-of-screen:offset</span>
+  top-of-screen:address:address:shared:duplex-list:character<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">top-of-screen:offset</span>
   <span class="Delimiter">{</span>
     done?:boolean<span class="Special"> &lt;- </span>greater-or-equal count, max
     <span class="muControl">break-if</span> done?
-    prev:address:duplex-list:character<span class="Special"> &lt;- </span>before-previous-line *top-of-screen, editor
+    prev:address:shared:duplex-list:character<span class="Special"> &lt;- </span>before-previous-line *top-of-screen, editor
     <span class="muControl">break-unless</span> prev
     *top-of-screen<span class="Special"> &lt;- </span>copy prev
     count<span class="Special"> &lt;- </span>add count, <span class="Constant">1</span>
@@ -2888,7 +2890,7 @@ e]
   <span class="Comment"># screen has 1 line for menu + 3 lines</span>
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">4/height</span>
   <span class="Comment"># initialize editor with 8 lines</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[a</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[a</span>
 <span class="Constant">b</span>
 <span class="Constant">c</span>
 <span class="Constant">d</span>
@@ -2896,7 +2898,7 @@ e]
 <span class="Constant">f</span>
 <span class="Constant">g</span>
 <span class="Constant">h]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
   screen-should-contain [
    <span class="Constant"> .          .</span>
    <span class="Constant"> .a         .</span>
@@ -2909,7 +2911,7 @@ e]
     press page-down
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   <span class="Comment"># screen shows third page</span>
   screen-should-contain [
@@ -2923,7 +2925,7 @@ e]
     press page-up
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   <span class="Comment"># screen shows second page</span>
   screen-should-contain [
@@ -2937,7 +2939,7 @@ e]
     press page-up
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   <span class="Comment"># screen shows original page again</span>
   screen-should-contain [
@@ -2952,7 +2954,7 @@ e]
   <span class="Comment"># screen has 1 line for menu + 5 lines for text</span>
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">6/height</span>
   <span class="Comment"># editor contains a long line in the first page</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[a</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[a</span>
 <span class="Constant">b</span>
 <span class="Constant">cdefgh</span>
 <span class="Constant">i</span>
@@ -2963,7 +2965,7 @@ e]
 <span class="Constant">n</span>
 <span class="Constant">o]</span>
   <span class="Comment"># editor screen triggers wrap of last line</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">4/right</span>
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">4/right</span>
   <span class="Comment"># some part of last line is not displayed</span>
   screen-should-contain [
    <span class="Constant"> .          .</span>
@@ -2980,7 +2982,7 @@ e]
     press down-arrow
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   <span class="Comment"># screen shows entire wrapped line</span>
   screen-should-contain [
@@ -2996,7 +2998,7 @@ e]
     press page-up
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   <span class="Comment"># screen resets</span>
   screen-should-contain [
@@ -3014,9 +3016,9 @@ e]
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">4/height</span>
   <span class="Comment"># editor contains a very long line that occupies last two lines of screen</span>
   <span class="Comment"># and still has something left over</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[a</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[a</span>
 <span class="Constant">bcdefgh]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">4/right</span>
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">4/right</span>
   <span class="Comment"># some part of last line is not displayed</span>
   screen-should-contain [
    <span class="Constant"> .          .</span>
@@ -3029,7 +3031,7 @@ e]
     press page-down
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   <span class="Comment"># screen shows entire wrapped line</span>
   screen-should-contain [
@@ -3043,7 +3045,7 @@ e]
     press page-up
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   <span class="Comment"># screen resets</span>
   screen-should-contain [
@@ -3057,7 +3059,7 @@ e]
 <span class="muScenario">scenario</span> editor-can-scroll-up-past-nonempty-lines [
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">4/height</span>
   <span class="Comment"># text with empty line in second screen</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[axx</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[axx</span>
 <span class="Constant">bxx</span>
 <span class="Constant">cxx</span>
 <span class="Constant">dxx</span>
@@ -3066,7 +3068,7 @@ e]
 <span class="Constant">gxx</span>
 <span class="Constant">hxx</span>
 <span class="Constant">]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">4/right</span>
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">4/right</span>
   screen-should-contain [
    <span class="Constant"> .          .</span>
    <span class="Constant"> .axx       .</span>
@@ -3077,7 +3079,7 @@ e]
     press page-down
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   screen-should-contain [
    <span class="Constant"> .          .</span>
@@ -3089,7 +3091,7 @@ e]
     press page-down
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   screen-should-contain [
    <span class="Constant"> .          .</span>
@@ -3102,7 +3104,7 @@ e]
     press page-up
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   screen-should-contain [
    <span class="Constant"> .          .</span>
@@ -3115,7 +3117,7 @@ e]
 <span class="muScenario">scenario</span> editor-can-scroll-up-past-empty-lines [
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">4/height</span>
   <span class="Comment"># text with empty line in second screen</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[axy</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[axy</span>
 <span class="Constant">bxy</span>
 <span class="Constant">cxy</span>
 
@@ -3124,7 +3126,7 @@ exy
 fxy
 gxy
 ]
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">4/right</span>
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">4/right</span>
   screen-should-contain [
    <span class="Constant"> .          .</span>
    <span class="Constant"> .axy       .</span>
@@ -3135,7 +3137,7 @@ gxy
     press page-down
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   screen-should-contain [
    <span class="Constant"> .          .</span>
@@ -3147,7 +3149,7 @@ gxy
     press page-down
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   screen-should-contain [
    <span class="Constant"> .          .</span>
@@ -3160,7 +3162,7 @@ gxy
     press page-up
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   screen-should-contain [
    <span class="Constant"> .          .</span>
diff --git a/html/edit/004-programming-environment.mu.html b/html/edit/004-programming-environment.mu.html
index 7b632086..adcb7c8c 100644
--- a/html/edit/004-programming-environment.mu.html
+++ b/html/edit/004-programming-environment.mu.html
@@ -20,6 +20,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 .Comment { color: #9090ff; }
 .Constant { color: #00a0a0; }
 .SalientComment { color: #00ffff; }
+.CommentedCode { color: #6c6c6c; }
 .Delimiter { color: #a04060; }
 .muScenario { color: #00af00; }
 -->
@@ -41,22 +42,22 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="muRecipe">recipe!</span> main [
   <span class="Constant">local-scope</span>
   open-console
-  initial-recipe:address:array:character<span class="Special"> &lt;- </span>restore <span class="Constant">[recipes.mu]</span>
-  initial-sandbox:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
+  initial-recipe:address:shared:array:character<span class="Special"> &lt;- </span>restore <span class="Constant">[recipes.mu]</span>
+  initial-sandbox:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
   hide-screen <span class="Constant">0/screen</span>
-  env:address:programming-environment-data<span class="Special"> &lt;- </span>new-programming-environment <span class="Constant">0/screen</span>, initial-recipe, initial-sandbox
+  env:address:shared:programming-environment-data<span class="Special"> &lt;- </span>new-programming-environment <span class="Constant">0/screen</span>, initial-recipe, initial-sandbox
   render-all <span class="Constant">0/screen</span>, env
   event-loop <span class="Constant">0/screen</span>, <span class="Constant">0/console</span>, env
   <span class="Comment"># never gets here</span>
 ]
 
 <span class="muData">container</span> programming-environment-data [
-  recipes:address:editor-data
-  current-sandbox:address:editor-data
+  recipes:address:shared:editor-data
+  current-sandbox:address:shared:editor-data
   sandbox-in-focus?:boolean  <span class="Comment"># false =&gt; cursor in recipes; true =&gt; cursor in current-sandbox</span>
 ]
 
-<span class="muRecipe">recipe</span> new-programming-environment screen:address:screen, initial-recipe-contents:address:array:character, initial-sandbox-contents:address:array:character<span class="muRecipe"> -&gt; </span>result:address:programming-environment-data, screen:address:screen [
+<span class="muRecipe">recipe</span> new-programming-environment screen:address:shared:screen, initial-recipe-contents:address:shared:array:character, initial-sandbox-contents:address:shared:array:character<span class="muRecipe"> -&gt; </span>result:address:shared:programming-environment-data, screen:address:shared:screen [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   width:number<span class="Special"> &lt;- </span>screen-width screen
@@ -68,25 +69,26 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   button-on-screen?:boolean<span class="Special"> &lt;- </span>greater-or-equal button-start, <span class="Constant">0</span>
   assert button-on-screen?, <span class="Constant">[screen too narrow for menu]</span>
   screen<span class="Special"> &lt;- </span>move-cursor screen, <span class="Constant">0/row</span>, button-start
-  run-button:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[ run (F4) ]</span>
+  run-button:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[ run (F4) ]</span>
   print screen, run-button, <span class="Constant">255/white</span>, <span class="Constant">161/reddish</span>
   <span class="Comment"># dotted line down the middle</span>
   divider:number, _<span class="Special"> &lt;- </span>divide-with-remainder width, <span class="Constant">2</span>
   draw-vertical screen, divider, <span class="Constant">1/top</span>, height, <span class="Constant">9482/vertical-dotted</span>
   <span class="Comment"># recipe editor on the left</span>
-  recipes:address:address:editor-data<span class="Special"> &lt;- </span>get-address *result, <span class="Constant">recipes:offset</span>
+  recipes:address:address:shared:editor-data<span class="Special"> &lt;- </span>get-address *result, <span class="Constant">recipes:offset</span>
   *recipes<span class="Special"> &lt;- </span>new-editor initial-recipe-contents, screen, <span class="Constant">0/left</span>, divider/right
   <span class="Comment"># sandbox editor on the right</span>
   new-left:number<span class="Special"> &lt;- </span>add divider, <span class="Constant">1</span>
-  current-sandbox:address:address:editor-data<span class="Special"> &lt;- </span>get-address *result, <span class="Constant">current-sandbox:offset</span>
+  current-sandbox:address:address:shared:editor-data<span class="Special"> &lt;- </span>get-address *result, <span class="Constant">current-sandbox:offset</span>
   *current-sandbox<span class="Special"> &lt;- </span>new-editor initial-sandbox-contents, screen, new-left, width/right
+<span class="Constant">  &lt;programming-environment-initialization&gt;</span>
 ]
 
-<span class="muRecipe">recipe</span> event-loop screen:address:screen, console:address:console, env:address:programming-environment-data<span class="muRecipe"> -&gt; </span>screen:address:screen, console:address:console, env:address:programming-environment-data [
+<span class="muRecipe">recipe</span> event-loop screen:address:shared:screen, console:address:shared:console, env:address:shared:programming-environment-data<span class="muRecipe"> -&gt; </span>screen:address:shared:screen, console:address:shared:console, env:address:shared:programming-environment-data [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
-  recipes:address:editor-data<span class="Special"> &lt;- </span>get *env, <span class="Constant">recipes:offset</span>
-  current-sandbox:address:editor-data<span class="Special"> &lt;- </span>get *env, <span class="Constant">current-sandbox:offset</span>
+  recipes:address:shared:editor-data<span class="Special"> &lt;- </span>get *env, <span class="Constant">recipes:offset</span>
+  current-sandbox:address:shared:editor-data<span class="Special"> &lt;- </span>get *env, <span class="Constant">current-sandbox:offset</span>
   sandbox-in-focus?:address:boolean<span class="Special"> &lt;- </span>get-address *env, <span class="Constant">sandbox-in-focus?:offset</span>
   <span class="Comment"># if we fall behind we'll stop updating the screen, but then we have to</span>
   <span class="Comment"># render the entire screen when we catch up.</span>
@@ -125,7 +127,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
       <span class="Comment"># send to both editors</span>
       _<span class="Special"> &lt;- </span>move-cursor-in-editor screen, recipes, *t
       *sandbox-in-focus?<span class="Special"> &lt;- </span>move-cursor-in-editor screen, current-sandbox, *t
-      screen<span class="Special"> &lt;- </span>update-cursor screen, recipes, current-sandbox, *sandbox-in-focus?
+      screen<span class="Special"> &lt;- </span>update-cursor screen, recipes, current-sandbox, *sandbox-in-focus?, env
       <span class="muControl">loop</span> <span class="Constant">+next-event:label</span>
     <span class="Delimiter">}</span>
     <span class="Comment"># 'resize' event - redraw editor</span>
@@ -207,21 +209,21 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
         <span class="Delimiter">}</span>
       <span class="Delimiter">}</span>
 <span class="Constant">      +finish-event</span>
-      screen<span class="Special"> &lt;- </span>update-cursor screen, recipes, current-sandbox, *sandbox-in-focus?
+      screen<span class="Special"> &lt;- </span>update-cursor screen, recipes, current-sandbox, *sandbox-in-focus?, env
       show-screen screen
     <span class="Delimiter">}</span>
     <span class="muControl">loop</span>
   <span class="Delimiter">}</span>
 ]
 
-<span class="muRecipe">recipe</span> resize screen:address:screen, env:address:programming-environment-data<span class="muRecipe"> -&gt; </span>env:address:programming-environment-data, screen:address:screen [
+<span class="muRecipe">recipe</span> resize screen:address:shared:screen, env:address:shared:programming-environment-data<span class="muRecipe"> -&gt; </span>env:address:shared:programming-environment-data, screen:address:shared:screen [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   clear-screen screen  <span class="Comment"># update screen dimensions</span>
   width:number<span class="Special"> &lt;- </span>screen-width screen
   divider:number, _<span class="Special"> &lt;- </span>divide-with-remainder width, <span class="Constant">2</span>
   <span class="Comment"># update recipe editor</span>
-  recipes:address:editor-data<span class="Special"> &lt;- </span>get *env, <span class="Constant">recipes:offset</span>
+  recipes:address:shared:editor-data<span class="Special"> &lt;- </span>get *env, <span class="Constant">recipes:offset</span>
   right:address:number<span class="Special"> &lt;- </span>get-address *recipes, <span class="Constant">right:offset</span>
   *right<span class="Special"> &lt;- </span>subtract divider, <span class="Constant">1</span>
   <span class="Comment"># reset cursor (later we'll try to preserve its position)</span>
@@ -230,7 +232,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   cursor-column:address:number<span class="Special"> &lt;- </span>get-address *recipes, <span class="Constant">cursor-column:offset</span>
   *cursor-column<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
   <span class="Comment"># update sandbox editor</span>
-  current-sandbox:address:editor-data<span class="Special"> &lt;- </span>get *env, <span class="Constant">current-sandbox:offset</span>
+  current-sandbox:address:shared:editor-data<span class="Special"> &lt;- </span>get *env, <span class="Constant">current-sandbox:offset</span>
   left:address:number<span class="Special"> &lt;- </span>get-address *current-sandbox, <span class="Constant">left:offset</span>
   right:address:number<span class="Special"> &lt;- </span>get-address *current-sandbox, <span class="Constant">right:offset</span>
   *left<span class="Special"> &lt;- </span>add divider, <span class="Constant">1</span>
@@ -246,9 +248,9 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
   assume-screen <span class="Constant">30/width</span>, <span class="Constant">5/height</span>
   <span class="Comment"># initialize both halves of screen</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
-  <span class="Constant">2</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[def]</span>
-  <span class="Constant">3</span>:address:programming-environment-data<span class="Special"> &lt;- </span>new-programming-environment screen:address:screen, <span class="Constant">1</span>:address:array:character, <span class="Constant">2</span>:address:array:character
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
+  <span class="Constant">2</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[def]</span>
+  <span class="Constant">3</span>:address:shared:programming-environment-data<span class="Special"> &lt;- </span>new-programming-environment screen:address:shared:screen, <span class="Constant">1</span>:address:shared:array:character, <span class="Constant">2</span>:address:shared:array:character
   <span class="Comment"># focus on both sides</span>
   assume-console [
     left-click <span class="Constant">1</span>, <span class="Constant">1</span>
@@ -256,11 +258,11 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   ]
   <span class="Comment"># check cursor column in each</span>
   run [
-    event-loop screen:address:screen, console:address:console, <span class="Constant">3</span>:address:programming-environment-data
-    <span class="Constant">4</span>:address:editor-data<span class="Special"> &lt;- </span>get *<span class="Constant">3</span>:address:programming-environment-data, <span class="Constant">recipes:offset</span>
-    <span class="Constant">5</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">4</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
-    <span class="Constant">6</span>:address:editor-data<span class="Special"> &lt;- </span>get *<span class="Constant">3</span>:address:programming-environment-data, <span class="Constant">current-sandbox:offset</span>
-    <span class="Constant">7</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">6</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+    event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">3</span>:address:shared:programming-environment-data
+    <span class="Constant">4</span>:address:shared:editor-data<span class="Special"> &lt;- </span>get *<span class="Constant">3</span>:address:shared:programming-environment-data, <span class="Constant">recipes:offset</span>
+    <span class="Constant">5</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">4</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
+    <span class="Constant">6</span>:address:shared:editor-data<span class="Special"> &lt;- </span>get *<span class="Constant">3</span>:address:shared:programming-environment-data, <span class="Constant">current-sandbox:offset</span>
+    <span class="Constant">7</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">6</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   ]
   memory-should-contain [
     <span class="Constant">5</span><span class="Special"> &lt;- </span><span class="Constant">1</span>
@@ -272,10 +274,10 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
   assume-screen <span class="Constant">30/width</span>, <span class="Constant">5/height</span>
   <span class="Comment"># initialize both halves of screen</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
-  <span class="Constant">2</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[def]</span>
-  <span class="Constant">3</span>:address:programming-environment-data<span class="Special"> &lt;- </span>new-programming-environment screen:address:screen, <span class="Constant">1</span>:address:array:character, <span class="Constant">2</span>:address:array:character
-  render-all screen, <span class="Constant">3</span>:address:programming-environment-data
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
+  <span class="Constant">2</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[def]</span>
+  <span class="Constant">3</span>:address:shared:programming-environment-data<span class="Special"> &lt;- </span>new-programming-environment screen:address:shared:screen, <span class="Constant">1</span>:address:shared:array:character, <span class="Constant">2</span>:address:shared:array:character
+  render-all screen, <span class="Constant">3</span>:address:shared:programming-environment-data
   <span class="Comment"># type one letter in each of them</span>
   assume-console [
     left-click <span class="Constant">1</span>, <span class="Constant">1</span>
@@ -284,11 +286,11 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     type <span class="Constant">[1]</span>
   ]
   run [
-    event-loop screen:address:screen, console:address:console, <span class="Constant">3</span>:address:programming-environment-data
-    <span class="Constant">4</span>:address:editor-data<span class="Special"> &lt;- </span>get *<span class="Constant">3</span>:address:programming-environment-data, <span class="Constant">recipes:offset</span>
-    <span class="Constant">5</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">4</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
-    <span class="Constant">6</span>:address:editor-data<span class="Special"> &lt;- </span>get *<span class="Constant">3</span>:address:programming-environment-data, <span class="Constant">current-sandbox:offset</span>
-    <span class="Constant">7</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">6</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+    event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">3</span>:address:shared:programming-environment-data
+    <span class="Constant">4</span>:address:shared:editor-data<span class="Special"> &lt;- </span>get *<span class="Constant">3</span>:address:shared:programming-environment-data, <span class="Constant">recipes:offset</span>
+    <span class="Constant">5</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">4</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
+    <span class="Constant">6</span>:address:shared:editor-data<span class="Special"> &lt;- </span>get *<span class="Constant">3</span>:address:shared:programming-environment-data, <span class="Constant">current-sandbox:offset</span>
+    <span class="Constant">7</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">6</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   ]
   screen-should-contain [
    <span class="Constant"> .           run (F4)           .  # this line has a different background, but we don't test that yet</span>
@@ -302,7 +304,8 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   ]
   <span class="Comment"># show the cursor at the right window</span>
   run [
-    print screen:address:screen, <span class="Constant">9251/␣/cursor</span>
+    <span class="Constant">8</span>:character/cursor<span class="Special"> &lt;- </span>copy <span class="Constant">9251/␣</span>
+    print screen:address:shared:screen, <span class="Constant">8</span>:character/cursor
   ]
   screen-should-contain [
    <span class="Constant"> .           run (F4)           .</span>
@@ -316,10 +319,10 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
   assume-screen <span class="Constant">60/width</span>, <span class="Constant">10/height</span>
   run [
-    <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
-    <span class="Constant">2</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[def]</span>
-    <span class="Constant">3</span>:address:programming-environment-data<span class="Special"> &lt;- </span>new-programming-environment screen:address:screen, <span class="Constant">1</span>:address:array:character, <span class="Constant">2</span>:address:array:character
-    render-all screen, <span class="Constant">3</span>:address:programming-environment-data
+    <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
+    <span class="Constant">2</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[def]</span>
+    <span class="Constant">3</span>:address:shared:programming-environment-data<span class="Special"> &lt;- </span>new-programming-environment screen:address:shared:screen, <span class="Constant">1</span>:address:shared:array:character, <span class="Constant">2</span>:address:shared:array:character
+    render-all screen, <span class="Constant">3</span>:address:shared:programming-environment-data
   ]
   <span class="Comment"># divider isn't messed up</span>
   screen-should-contain [
@@ -334,15 +337,16 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="muScenario">scenario</span> editor-in-focus-keeps-cursor [
   trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
   assume-screen <span class="Constant">30/width</span>, <span class="Constant">5/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
-  <span class="Constant">2</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[def]</span>
-  <span class="Constant">3</span>:address:programming-environment-data<span class="Special"> &lt;- </span>new-programming-environment screen:address:screen, <span class="Constant">1</span>:address:array:character, <span class="Constant">2</span>:address:array:character
-  render-all screen, <span class="Constant">3</span>:address:programming-environment-data
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
+  <span class="Constant">2</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[def]</span>
+  <span class="Constant">3</span>:address:shared:programming-environment-data<span class="Special"> &lt;- </span>new-programming-environment screen:address:shared:screen, <span class="Constant">1</span>:address:shared:array:character, <span class="Constant">2</span>:address:shared:array:character
+  render-all screen, <span class="Constant">3</span>:address:shared:programming-environment-data
   <span class="Comment"># initialize programming environment and highlight cursor</span>
   assume-console <span class="Constant">[]</span>
   run [
-    event-loop screen:address:screen, console:address:console, <span class="Constant">3</span>:address:programming-environment-data
-    print screen:address:screen, <span class="Constant">9251/␣/cursor</span>
+    event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">3</span>:address:shared:programming-environment-data
+    <span class="Constant">4</span>:character/cursor<span class="Special"> &lt;- </span>copy <span class="Constant">9251/␣</span>
+    print screen:address:shared:screen, <span class="Constant">4</span>:character/cursor
   ]
   <span class="Comment"># is cursor at the right place?</span>
   screen-should-contain [
@@ -356,8 +360,9 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     type <span class="Constant">[z]</span>
   ]
   run [
-    event-loop screen:address:screen, console:address:console, <span class="Constant">3</span>:address:programming-environment-data
-    print screen:address:screen, <span class="Constant">9251/␣/cursor</span>
+    event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">3</span>:address:shared:programming-environment-data
+    <span class="Constant">4</span>:character/cursor<span class="Special"> &lt;- </span>copy <span class="Constant">9251/␣</span>
+    print screen:address:shared:screen, <span class="Constant">4</span>:character/cursor
   ]
   <span class="Comment"># cursor should still be right</span>
   screen-should-contain [
@@ -372,11 +377,11 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
   assume-screen <span class="Constant">30/width</span>, <span class="Constant">5/height</span>
   <span class="Comment"># initialize sandbox side with two lines</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
-  <span class="Constant">2</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
+  <span class="Constant">2</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
 <span class="Constant">def]</span>
-  <span class="Constant">3</span>:address:programming-environment-data<span class="Special"> &lt;- </span>new-programming-environment screen:address:screen, <span class="Constant">1</span>:address:array:character, <span class="Constant">2</span>:address:array:character
-  render-all screen, <span class="Constant">3</span>:address:programming-environment-data
+  <span class="Constant">3</span>:address:shared:programming-environment-data<span class="Special"> &lt;- </span>new-programming-environment screen:address:shared:screen, <span class="Constant">1</span>:address:shared:array:character, <span class="Constant">2</span>:address:shared:array:character
+  render-all screen, <span class="Constant">3</span>:address:shared:programming-environment-data
   screen-should-contain [
    <span class="Constant"> .           run (F4)           .</span>
    <span class="Constant"> .               ┊abc           .</span>
@@ -390,8 +395,9 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     press backspace
   ]
   run [
-    event-loop screen:address:screen, console:address:console, <span class="Constant">3</span>:address:programming-environment-data
-    print screen:address:screen, <span class="Constant">9251/␣/cursor</span>
+    event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">3</span>:address:shared:programming-environment-data
+    <span class="Constant">4</span>:character/cursor<span class="Special"> &lt;- </span>copy <span class="Constant">9251/␣</span>
+    print screen:address:shared:screen, <span class="Constant">4</span>:character/cursor
   ]
   <span class="Comment"># cursor moves to end of old line</span>
   screen-should-contain [
@@ -402,7 +408,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   ]
 ]
 
-<span class="muRecipe">recipe</span> render-all screen:address:screen, env:address:programming-environment-data<span class="muRecipe"> -&gt; </span>screen:address:screen [
+<span class="muRecipe">recipe</span> render-all screen:address:shared:screen, env:address:shared:programming-environment-data<span class="muRecipe"> -&gt; </span>screen:address:shared:screen [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   trace <span class="Constant">10</span>, <span class="Constant">[app]</span>, <span class="Constant">[render all]</span>
@@ -410,12 +416,14 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   <span class="Comment"># top menu</span>
   trace <span class="Constant">11</span>, <span class="Constant">[app]</span>, <span class="Constant">[render top menu]</span>
   width:number<span class="Special"> &lt;- </span>screen-width screen
+<span class="CommentedCode">#?   $print [draw menu], 10/newline</span>
   draw-horizontal screen, <span class="Constant">0</span>, <span class="Constant">0/left</span>, width, <span class="Constant">32/space</span>, <span class="Constant">0/black</span>, <span class="Constant">238/grey</span>
+<span class="CommentedCode">#?   $print [draw menu end], 10/newline</span>
   button-start:number<span class="Special"> &lt;- </span>subtract width, <span class="Constant">20</span>
   button-on-screen?:boolean<span class="Special"> &lt;- </span>greater-or-equal button-start, <span class="Constant">0</span>
   assert button-on-screen?, <span class="Constant">[screen too narrow for menu]</span>
   screen<span class="Special"> &lt;- </span>move-cursor screen, <span class="Constant">0/row</span>, button-start
-  run-button:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[ run (F4) ]</span>
+  run-button:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[ run (F4) ]</span>
   print screen, run-button, <span class="Constant">255/white</span>, <span class="Constant">161/reddish</span>
   <span class="Comment"># dotted line down the middle</span>
   trace <span class="Constant">11</span>, <span class="Constant">[app]</span>, <span class="Constant">[render divider]</span>
@@ -427,19 +435,19 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   screen<span class="Special"> &lt;- </span>render-sandbox-side screen, env
 <span class="Constant">  &lt;render-components-end&gt;</span>
   <span class="Comment">#</span>
-  recipes:address:editor-data<span class="Special"> &lt;- </span>get *env, <span class="Constant">recipes:offset</span>
-  current-sandbox:address:editor-data<span class="Special"> &lt;- </span>get *env, <span class="Constant">current-sandbox:offset</span>
+  recipes:address:shared:editor-data<span class="Special"> &lt;- </span>get *env, <span class="Constant">recipes:offset</span>
+  current-sandbox:address:shared:editor-data<span class="Special"> &lt;- </span>get *env, <span class="Constant">current-sandbox:offset</span>
   sandbox-in-focus?:boolean<span class="Special"> &lt;- </span>get *env, <span class="Constant">sandbox-in-focus?:offset</span>
-  screen<span class="Special"> &lt;- </span>update-cursor screen, recipes, current-sandbox, sandbox-in-focus?
+  screen<span class="Special"> &lt;- </span>update-cursor screen, recipes, current-sandbox, sandbox-in-focus?, env
   <span class="Comment">#</span>
   show-screen screen
 ]
 
-<span class="muRecipe">recipe</span> render-recipes screen:address:screen, env:address:programming-environment-data<span class="muRecipe"> -&gt; </span>screen:address:screen [
+<span class="muRecipe">recipe</span> render-recipes screen:address:shared:screen, env:address:shared:programming-environment-data<span class="muRecipe"> -&gt; </span>screen:address:shared:screen [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   trace <span class="Constant">11</span>, <span class="Constant">[app]</span>, <span class="Constant">[render recipes]</span>
-  recipes:address:editor-data<span class="Special"> &lt;- </span>get *env, <span class="Constant">recipes:offset</span>
+  recipes:address:shared:editor-data<span class="Special"> &lt;- </span>get *env, <span class="Constant">recipes:offset</span>
   <span class="Comment"># render recipes</span>
   left:number<span class="Special"> &lt;- </span>get *recipes, <span class="Constant">left:offset</span>
   right:number<span class="Special"> &lt;- </span>get *recipes, <span class="Constant">right:offset</span>
@@ -454,10 +462,10 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 ]
 
 <span class="Comment"># replaced in a later layer</span>
-<span class="muRecipe">recipe</span> render-sandbox-side screen:address:screen, env:address:programming-environment-data<span class="muRecipe"> -&gt; </span>screen:address:screen [
+<span class="muRecipe">recipe</span> render-sandbox-side screen:address:shared:screen, env:address:shared:programming-environment-data<span class="muRecipe"> -&gt; </span>screen:address:shared:screen [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
-  current-sandbox:address:editor-data<span class="Special"> &lt;- </span>get *env, <span class="Constant">current-sandbox:offset</span>
+  current-sandbox:address:shared:editor-data<span class="Special"> &lt;- </span>get *env, <span class="Constant">current-sandbox:offset</span>
   left:number<span class="Special"> &lt;- </span>get *current-sandbox, <span class="Constant">left:offset</span>
   right:number<span class="Special"> &lt;- </span>get *current-sandbox, <span class="Constant">right:offset</span>
   row:number, column:number, screen, current-sandbox<span class="Special"> &lt;- </span>render screen, current-sandbox
@@ -469,9 +477,10 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   clear-screen-from screen, row, left, left, right
 ]
 
-<span class="muRecipe">recipe</span> update-cursor screen:address:screen, recipes:address:editor-data, current-sandbox:address:editor-data, sandbox-in-focus?:boolean<span class="muRecipe"> -&gt; </span>screen:address:screen [
+<span class="muRecipe">recipe</span> update-cursor screen:address:shared:screen, recipes:address:shared:editor-data, current-sandbox:address:shared:editor-data, sandbox-in-focus?:boolean, env:address:shared:programming-environment-data<span class="muRecipe"> -&gt; </span>screen:address:shared:screen [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
+<span class="Constant">  &lt;update-cursor-special-cases&gt;</span>
   <span class="Delimiter">{</span>
     <span class="muControl">break-if</span> sandbox-in-focus?
     cursor-row:number<span class="Special"> &lt;- </span>get *recipes, <span class="Constant">cursor-row:offset</span>
@@ -487,7 +496,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="Comment"># print a text 's' to 'editor' in 'color' starting at 'row'</span>
 <span class="Comment"># clear rest of last line, move cursor to next line</span>
-<span class="muRecipe">recipe</span> render screen:address:screen, s:address:array:character, left:number, right:number, color:number, row:number<span class="muRecipe"> -&gt; </span>row:number, screen:address:screen [
+<span class="muRecipe">recipe</span> render screen:address:shared:screen, s:address:shared:array:character, left:number, right:number, color:number, row:number<span class="muRecipe"> -&gt; </span>row:number, screen:address:shared:screen [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   <span class="muControl">reply-unless</span> s
@@ -508,7 +517,8 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
       at-right?:boolean<span class="Special"> &lt;- </span>equal column, right
       <span class="muControl">break-unless</span> at-right?
       <span class="Comment"># print wrap icon</span>
-      print screen, <span class="Constant">8617/loop-back-to-left</span>, <span class="Constant">245/grey</span>
+      wrap-icon:character<span class="Special"> &lt;- </span>copy <span class="Constant">8617/loop-back-to-left</span>
+      print screen, wrap-icon, <span class="Constant">245/grey</span>
       column<span class="Special"> &lt;- </span>copy left
       row<span class="Special"> &lt;- </span>add row, <span class="Constant">1</span>
       screen<span class="Special"> &lt;- </span>move-cursor screen, row, column
@@ -523,7 +533,8 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
       <span class="Delimiter">{</span>
         done?:boolean<span class="Special"> &lt;- </span>greater-than column, right
         <span class="muControl">break-if</span> done?
-        print screen, <span class="Constant">32/space</span>
+        space:character<span class="Special"> &lt;- </span>copy <span class="Constant">32/space</span>
+        print screen, space
         column<span class="Special"> &lt;- </span>add column, <span class="Constant">1</span>
         <span class="muControl">loop</span>
       <span class="Delimiter">}</span>
@@ -546,7 +557,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 ]
 
 <span class="Comment"># like 'render' for texts, but with colorization for comments like in the editor</span>
-<span class="muRecipe">recipe</span> render-code screen:address:screen, s:address:array:character, left:number, right:number, row:number<span class="muRecipe"> -&gt; </span>row:number, screen:address:screen [
+<span class="muRecipe">recipe</span> render-code screen:address:shared:screen, s:address:shared:array:character, left:number, right:number, row:number<span class="muRecipe"> -&gt; </span>row:number, screen:address:shared:screen [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   <span class="muControl">reply-unless</span> s
@@ -569,7 +580,8 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
       at-right?:boolean<span class="Special"> &lt;- </span>equal column, right
       <span class="muControl">break-unless</span> at-right?
       <span class="Comment"># print wrap icon</span>
-      print screen, <span class="Constant">8617/loop-back-to-left</span>, <span class="Constant">245/grey</span>
+      wrap-icon:character<span class="Special"> &lt;- </span>copy <span class="Constant">8617/loop-back-to-left</span>
+      print screen, wrap-icon, <span class="Constant">245/grey</span>
       column<span class="Special"> &lt;- </span>copy left
       row<span class="Special"> &lt;- </span>add row, <span class="Constant">1</span>
       screen<span class="Special"> &lt;- </span>move-cursor screen, row, column
@@ -584,7 +596,8 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
       <span class="Delimiter">{</span>
         done?:boolean<span class="Special"> &lt;- </span>greater-than column, right
         <span class="muControl">break-if</span> done?
-        print screen, <span class="Constant">32/space</span>
+        space:character<span class="Special"> &lt;- </span>copy <span class="Constant">32/space</span>
+        print screen, space
         column<span class="Special"> &lt;- </span>add column, <span class="Constant">1</span>
         <span class="muControl">loop</span>
       <span class="Delimiter">}</span>
@@ -612,7 +625,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   <span class="Delimiter">{</span>
     redraw-screen?:boolean<span class="Special"> &lt;- </span>equal *c, <span class="Constant">12/ctrl-l</span>
     <span class="muControl">break-unless</span> redraw-screen?
-    screen<span class="Special"> &lt;- </span>render-all screen, env:address:programming-environment-data
+    screen<span class="Special"> &lt;- </span>render-all screen, env:address:shared:programming-environment-data
     sync-screen screen
     <span class="muControl">loop</span> <span class="Constant">+next-event:label</span>
   <span class="Delimiter">}</span>
@@ -626,14 +639,14 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     switch-side?:boolean<span class="Special"> &lt;- </span>equal *c, <span class="Constant">14/ctrl-n</span>
     <span class="muControl">break-unless</span> switch-side?
     *sandbox-in-focus?<span class="Special"> &lt;- </span>not *sandbox-in-focus?
-    screen<span class="Special"> &lt;- </span>update-cursor screen, recipes, current-sandbox, *sandbox-in-focus?
+    screen<span class="Special"> &lt;- </span>update-cursor screen, recipes, current-sandbox, *sandbox-in-focus?, env
     <span class="muControl">loop</span> <span class="Constant">+next-event:label</span>
   <span class="Delimiter">}</span>
 ]
 
 <span class="SalientComment">## helpers</span>
 
-<span class="muRecipe">recipe</span> draw-vertical screen:address:screen, col:number, y:number, bottom:number<span class="muRecipe"> -&gt; </span>screen:address:screen [
+<span class="muRecipe">recipe</span> draw-vertical screen:address:shared:screen, col:number, y:number, bottom:number<span class="muRecipe"> -&gt; </span>screen:address:shared:screen [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   style:character, style-found?:boolean<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
diff --git a/html/edit/005-sandbox.mu.html b/html/edit/005-sandbox.mu.html
index 0b3e3926..c079109e 100644
--- a/html/edit/005-sandbox.mu.html
+++ b/html/edit/005-sandbox.mu.html
@@ -43,10 +43,10 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="muRecipe">recipe!</span> main [
   <span class="Constant">local-scope</span>
   open-console
-  initial-recipe:address:array:character<span class="Special"> &lt;- </span>restore <span class="Constant">[recipes.mu]</span>
-  initial-sandbox:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
+  initial-recipe:address:shared:array:character<span class="Special"> &lt;- </span>restore <span class="Constant">[recipes.mu]</span>
+  initial-sandbox:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
   hide-screen <span class="Constant">0/screen</span>
-  env:address:programming-environment-data<span class="Special"> &lt;- </span>new-programming-environment <span class="Constant">0/screen</span>, initial-recipe, initial-sandbox
+  env:address:shared:programming-environment-data<span class="Special"> &lt;- </span>new-programming-environment <span class="Constant">0/screen</span>, initial-recipe, initial-sandbox
   env<span class="Special"> &lt;- </span>restore-sandboxes env
   render-all <span class="Constant">0/screen</span>, env
   event-loop <span class="Constant">0/screen</span>, <span class="Constant">0/console</span>, env
@@ -54,42 +54,50 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 ]
 
 <span class="muData">container</span> programming-environment-data [
-  sandbox:address:sandbox-data  <span class="Comment"># list of sandboxes, from top to bottom</span>
+  sandbox:address:shared:sandbox-data  <span class="Comment"># list of sandboxes, from top to bottom</span>
+  render-from:number
+  number-of-sandboxes:number
+]
+
+<span class="muRecipe">after</span> <span class="Constant">&lt;programming-environment-initialization&gt;</span> [
+  render-from:address:number<span class="Special"> &lt;- </span>get-address *result, <span class="Constant">render-from:offset</span>
+  *render-from<span class="Special"> &lt;- </span>copy <span class="Constant">-1</span>
 ]
 
 <span class="muData">container</span> sandbox-data [
-  data:address:array:character
-  response:address:array:character
-  expected-response:address:array:character
+  data:address:shared:array:character
+  response:address:shared:array:character
+  expected-response:address:shared:array:character
   <span class="Comment"># coordinates to track clicks</span>
+  <span class="Comment"># constraint: will be 0 for sandboxes at positions before env.render-from</span>
   starting-row-on-screen:number
   code-ending-row-on-screen:number  <span class="Comment"># past end of code</span>
   response-starting-row-on-screen:number
-  screen:address:screen  <span class="Comment"># prints in the sandbox go here</span>
-  next-sandbox:address:sandbox-data
+  screen:address:shared:screen  <span class="Comment"># prints in the sandbox go here</span>
+  next-sandbox:address:shared:sandbox-data
 ]
 
 <span class="muScenario">scenario</span> run-and-show-results [
   trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
   assume-screen <span class="Constant">100/width</span>, <span class="Constant">15/height</span>
   <span class="Comment"># recipe editor is empty</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
   <span class="Comment"># sandbox editor contains an instruction without storing outputs</span>
-  <span class="Constant">2</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[divide-with-remainder 11, 3]</span>
-  <span class="Constant">3</span>:address:programming-environment-data<span class="Special"> &lt;- </span>new-programming-environment screen:address:screen, <span class="Constant">1</span>:address:array:character, <span class="Constant">2</span>:address:array:character
+  <span class="Constant">2</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[divide-with-remainder 11, 3]</span>
+  <span class="Constant">3</span>:address:shared:programming-environment-data<span class="Special"> &lt;- </span>new-programming-environment screen:address:shared:screen, <span class="Constant">1</span>:address:shared:array:character, <span class="Constant">2</span>:address:shared:array:character
   <span class="Comment"># run the code in the editors</span>
   assume-console [
     press F4
   ]
   run [
-    event-loop screen:address:screen, console:address:console, <span class="Constant">3</span>:address:programming-environment-data
+    event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">3</span>:address:shared:programming-environment-data
   ]
   <span class="Comment"># check that screen prints the results</span>
   screen-should-contain [
    <span class="Constant"> .                                                                                 run (F4)           .</span>
    <span class="Constant"> .                                                  ┊                                                 .</span>
 <span class="Constant">    .┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┊━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━.</span>
-   <span class="Constant"> .                                                  ┊                                                x.</span>
+   <span class="Constant"> .                                                  ┊0                                               x.</span>
    <span class="Constant"> .                                                  ┊divide-with-remainder 11, 3                      .</span>
    <span class="Constant"> .                                                  ┊3                                                .</span>
    <span class="Constant"> .                                                  ┊2                                                .</span>
@@ -118,6 +126,13 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
    <span class="Constant"> .                                                  ┊━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━.</span>
    <span class="Constant"> .                                                  ┊                                                 .</span>
   ]
+  <span class="Comment"># sandbox title in reverse video</span>
+  screen-should-contain-in-color <span class="Constant">240/dark-grey</span>, [
+   <span class="Constant"> .                                                                                                    .</span>
+   <span class="Constant"> .                                                                                                    .</span>
+   <span class="Constant"> .                                                                                                    .</span>
+   <span class="Constant"> .                                                   0                                                .</span>
+  ]
   <span class="Comment"># run another command</span>
   assume-console [
     left-click <span class="Constant">1</span>, <span class="Constant">80</span>
@@ -125,18 +140,18 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     press F4
   ]
   run [
-    event-loop screen:address:screen, console:address:console, <span class="Constant">3</span>:address:programming-environment-data
+    event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">3</span>:address:shared:programming-environment-data
   ]
   <span class="Comment"># check that screen prints the results</span>
   screen-should-contain [
    <span class="Constant"> .                                                                                 run (F4)           .</span>
    <span class="Constant"> .                                                  ┊                                                 .</span>
 <span class="Constant">    .┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┊━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━.</span>
-   <span class="Constant"> .                                                  ┊                                                x.</span>
+   <span class="Constant"> .                                                  ┊0                                               x.</span>
    <span class="Constant"> .                                                  ┊add 2, 2                                         .</span>
    <span class="Constant"> .                                                  ┊4                                                .</span>
    <span class="Constant"> .                                                  ┊━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━.</span>
-   <span class="Constant"> .                                                  ┊                                                x.</span>
+   <span class="Constant"> .                                                  ┊1                                               x.</span>
    <span class="Constant"> .                                                  ┊divide-with-remainder 11, 3                      .</span>
    <span class="Constant"> .                                                  ┊3                                                .</span>
    <span class="Constant"> .                                                  ┊2                                                .</span>
@@ -151,105 +166,113 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     do-run?:boolean<span class="Special"> &lt;- </span>equal *k, <span class="Constant">65532/F4</span>
     <span class="muControl">break-unless</span> do-run?
 <span class="CommentedCode">#?     $log [F4 pressed]</span>
-    status:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[running...  ]</span>
+    status:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[running...       ]</span>
     screen<span class="Special"> &lt;- </span>update-status screen, status, <span class="Constant">245/grey</span>
     error?:boolean, env, screen<span class="Special"> &lt;- </span>run-sandboxes env, screen
     <span class="Comment"># F4 might update warnings and results on both sides</span>
+<span class="CommentedCode">#?     $print [render-all begin], 10/newline</span>
     screen<span class="Special"> &lt;- </span>render-all screen, env
+<span class="CommentedCode">#?     $print [render-all end], 10/newline</span>
     <span class="Delimiter">{</span>
       <span class="muControl">break-if</span> error?
-      status:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[            ]</span>
+      status:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[                 ]</span>
       screen<span class="Special"> &lt;- </span>update-status screen, status, <span class="Constant">245/grey</span>
     <span class="Delimiter">}</span>
-    screen<span class="Special"> &lt;- </span>update-cursor screen, recipes, current-sandbox, *sandbox-in-focus?
+    screen<span class="Special"> &lt;- </span>update-cursor screen, recipes, current-sandbox, *sandbox-in-focus?, env
     <span class="muControl">loop</span> <span class="Constant">+next-event:label</span>
   <span class="Delimiter">}</span>
 ]
 
-<span class="muRecipe">recipe</span> run-sandboxes env:address:programming-environment-data, screen:address:screen<span class="muRecipe"> -&gt; </span>errors-found?:boolean, env:address:programming-environment-data, screen:address:screen [
+<span class="muRecipe">recipe</span> run-sandboxes env:address:shared:programming-environment-data, screen:address:shared:screen<span class="muRecipe"> -&gt; </span>errors-found?:boolean, env:address:shared:programming-environment-data, screen:address:shared:screen [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   errors-found?:boolean, env, screen<span class="Special"> &lt;- </span>update-recipes env, screen
   <span class="muControl">reply-if</span> errors-found?
   <span class="Comment"># check contents of right editor (sandbox)</span>
-  current-sandbox:address:editor-data<span class="Special"> &lt;- </span>get *env, <span class="Constant">current-sandbox:offset</span>
+<span class="Constant">  &lt;run-sandboxes-begin&gt;</span>
+  current-sandbox:address:shared:editor-data<span class="Special"> &lt;- </span>get *env, <span class="Constant">current-sandbox:offset</span>
   <span class="Delimiter">{</span>
-    sandbox-contents:address:array:character<span class="Special"> &lt;- </span>editor-contents current-sandbox
+    sandbox-contents:address:shared:array:character<span class="Special"> &lt;- </span>editor-contents current-sandbox
     <span class="muControl">break-unless</span> sandbox-contents
     <span class="Comment"># if contents exist, first save them</span>
     <span class="Comment"># run them and turn them into a new sandbox-data</span>
-    new-sandbox:address:sandbox-data<span class="Special"> &lt;- </span>new <span class="Constant">sandbox-data:type</span>
-    data:address:address:array:character<span class="Special"> &lt;- </span>get-address *new-sandbox, <span class="Constant">data:offset</span>
+    new-sandbox:address:shared:sandbox-data<span class="Special"> &lt;- </span>new <span class="Constant">sandbox-data:type</span>
+    data:address:address:shared:array:character<span class="Special"> &lt;- </span>get-address *new-sandbox, <span class="Constant">data:offset</span>
     *data<span class="Special"> &lt;- </span>copy sandbox-contents
     <span class="Comment"># push to head of sandbox list</span>
-    dest:address:address:sandbox-data<span class="Special"> &lt;- </span>get-address *env, <span class="Constant">sandbox:offset</span>
-    next:address:address:sandbox-data<span class="Special"> &lt;- </span>get-address *new-sandbox, <span class="Constant">next-sandbox:offset</span>
+    dest:address:address:shared:sandbox-data<span class="Special"> &lt;- </span>get-address *env, <span class="Constant">sandbox:offset</span>
+    next:address:address:shared:sandbox-data<span class="Special"> &lt;- </span>get-address *new-sandbox, <span class="Constant">next-sandbox:offset</span>
     *next<span class="Special"> &lt;- </span>copy *dest
     *dest<span class="Special"> &lt;- </span>copy new-sandbox
+    <span class="Comment"># update sandbox count</span>
+    sandbox-count:address:number<span class="Special"> &lt;- </span>get-address *env, <span class="Constant">number-of-sandboxes:offset</span>
+    *sandbox-count<span class="Special"> &lt;- </span>add *sandbox-count, <span class="Constant">1</span>
     <span class="Comment"># clear sandbox editor</span>
-    init:address:address:duplex-list:character<span class="Special"> &lt;- </span>get-address *current-sandbox, <span class="Constant">data:offset</span>
+    init:address:address:shared:duplex-list:character<span class="Special"> &lt;- </span>get-address *current-sandbox, <span class="Constant">data:offset</span>
     *init<span class="Special"> &lt;- </span>push <span class="Constant">167/§</span>, <span class="Constant">0/tail</span>
-    top-of-screen:address:address:duplex-list:character<span class="Special"> &lt;- </span>get-address *current-sandbox, <span class="Constant">top-of-screen:offset</span>
+    top-of-screen:address:address:shared:duplex-list:character<span class="Special"> &lt;- </span>get-address *current-sandbox, <span class="Constant">top-of-screen:offset</span>
     *top-of-screen<span class="Special"> &lt;- </span>copy *init
   <span class="Delimiter">}</span>
   <span class="Comment"># save all sandboxes before running, just in case we die when running</span>
   save-sandboxes env
   <span class="Comment"># run all sandboxes</span>
-  curr:address:sandbox-data<span class="Special"> &lt;- </span>get *env, <span class="Constant">sandbox:offset</span>
+  curr:address:shared:sandbox-data<span class="Special"> &lt;- </span>get *env, <span class="Constant">sandbox:offset</span>
+  idx:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
   <span class="Delimiter">{</span>
     <span class="muControl">break-unless</span> curr
-    curr<span class="Special"> &lt;- </span>update-sandbox curr
+    curr<span class="Special"> &lt;- </span>update-sandbox curr, env, idx
     curr<span class="Special"> &lt;- </span>get *curr, <span class="Constant">next-sandbox:offset</span>
+    idx<span class="Special"> &lt;- </span>add idx, <span class="Constant">1</span>
     <span class="muControl">loop</span>
   <span class="Delimiter">}</span>
-  errors-found?<span class="Special"> &lt;- </span>copy <span class="Constant">0/false</span>
+<span class="Constant">  &lt;run-sandboxes-end&gt;</span>
 ]
 
 <span class="Comment"># copy code from recipe editor, persist, load into mu</span>
 <span class="Comment"># replaced in a later layer (whereupon errors-found? will actually be set)</span>
-<span class="muRecipe">recipe</span> update-recipes env:address:programming-environment-data, screen:address:screen<span class="muRecipe"> -&gt; </span>errors-found?:boolean, env:address:programming-environment-data, screen:address:screen [
+<span class="muRecipe">recipe</span> update-recipes env:address:shared:programming-environment-data, screen:address:shared:screen<span class="muRecipe"> -&gt; </span>errors-found?:boolean, env:address:shared:programming-environment-data, screen:address:shared:screen [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
-  recipes:address:editor-data<span class="Special"> &lt;- </span>get *env, <span class="Constant">recipes:offset</span>
-  in:address:array:character<span class="Special"> &lt;- </span>editor-contents recipes
+  recipes:address:shared:editor-data<span class="Special"> &lt;- </span>get *env, <span class="Constant">recipes:offset</span>
+  in:address:shared:array:character<span class="Special"> &lt;- </span>editor-contents recipes
   save <span class="Constant">[recipes.mu]</span>, in  <span class="Comment"># newlayer: persistence</span>
   reload in
   errors-found?<span class="Special"> &lt;- </span>copy <span class="Constant">0/false</span>
 ]
 
 <span class="Comment"># replaced in a later layer</span>
-<span class="muRecipe">recipe</span> update-sandbox sandbox:address:sandbox-data<span class="muRecipe"> -&gt; </span>sandbox:address:sandbox-data [
+<span class="muRecipe">recipe!</span> update-sandbox sandbox:address:shared:sandbox-data, env:address:shared:programming-environment-data, idx:number<span class="muRecipe"> -&gt; </span>sandbox:address:shared:sandbox-data, env:address:shared:programming-environment-data [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
-  data:address:array:character<span class="Special"> &lt;- </span>get *sandbox, <span class="Constant">data:offset</span>
-  response:address:address:array:character<span class="Special"> &lt;- </span>get-address *sandbox, <span class="Constant">response:offset</span>
-  fake-screen:address:address:screen<span class="Special"> &lt;- </span>get-address *sandbox, <span class="Constant">screen:offset</span>
+  data:address:shared:array:character<span class="Special"> &lt;- </span>get *sandbox, <span class="Constant">data:offset</span>
+  response:address:address:shared:array:character<span class="Special"> &lt;- </span>get-address *sandbox, <span class="Constant">response:offset</span>
+  fake-screen:address:address:shared:screen<span class="Special"> &lt;- </span>get-address *sandbox, <span class="Constant">screen:offset</span>
   *response, _, *fake-screen<span class="Special"> &lt;- </span>run-interactive data
 ]
 
-<span class="muRecipe">recipe</span> update-status screen:address:screen, msg:address:array:character, color:number<span class="muRecipe"> -&gt; </span>screen:address:screen [
+<span class="muRecipe">recipe</span> update-status screen:address:shared:screen, msg:address:shared:array:character, color:number<span class="muRecipe"> -&gt; </span>screen:address:shared:screen [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   screen<span class="Special"> &lt;- </span>move-cursor screen, <span class="Constant">0</span>, <span class="Constant">2</span>
   screen<span class="Special"> &lt;- </span>print screen, msg, color, <span class="Constant">238/grey/background</span>
 ]
 
-<span class="muRecipe">recipe</span> save-sandboxes env:address:programming-environment-data [
+<span class="muRecipe">recipe</span> save-sandboxes env:address:shared:programming-environment-data [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
-  current-sandbox:address:editor-data<span class="Special"> &lt;- </span>get *env, <span class="Constant">current-sandbox:offset</span>
+  current-sandbox:address:shared:editor-data<span class="Special"> &lt;- </span>get *env, <span class="Constant">current-sandbox:offset</span>
   <span class="Comment"># first clear previous versions, in case we deleted some sandbox</span>
   $system <span class="Constant">[rm lesson/[0-9]</span>* &gt;/dev/null <span class="Constant">2</span>&gt;/dev/null]  <span class="Comment"># some shells can't handle '&gt;&amp;'</span>
-  curr:address:sandbox-data<span class="Special"> &lt;- </span>get *env, <span class="Constant">sandbox:offset</span>
-  suffix:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[.out]</span>
+  curr:address:shared:sandbox-data<span class="Special"> &lt;- </span>get *env, <span class="Constant">sandbox:offset</span>
+  suffix:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[.out]</span>
   idx:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
   <span class="Delimiter">{</span>
     <span class="muControl">break-unless</span> curr
-    data:address:array:character<span class="Special"> &lt;- </span>get *curr, <span class="Constant">data:offset</span>
-    filename:address:array:character<span class="Special"> &lt;- </span>to-text idx
+    data:address:shared:array:character<span class="Special"> &lt;- </span>get *curr, <span class="Constant">data:offset</span>
+    filename:address:shared:array:character<span class="Special"> &lt;- </span>to-text idx
     save filename, data
     <span class="Delimiter">{</span>
-      expected-response:address:array:character<span class="Special"> &lt;- </span>get *curr, <span class="Constant">expected-response:offset</span>
+      expected-response:address:shared:array:character<span class="Special"> &lt;- </span>get *curr, <span class="Constant">expected-response:offset</span>
       <span class="muControl">break-unless</span> expected-response
       filename<span class="Special"> &lt;- </span>append filename, suffix
       save filename, expected-response
@@ -260,24 +283,32 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   <span class="Delimiter">}</span>
 ]
 
-<span class="muRecipe">recipe!</span> render-sandbox-side screen:address:screen, env:address:programming-environment-data<span class="muRecipe"> -&gt; </span>screen:address:screen [
+<span class="muRecipe">recipe!</span> render-sandbox-side screen:address:shared:screen, env:address:shared:programming-environment-data<span class="muRecipe"> -&gt; </span>screen:address:shared:screen [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
 <span class="CommentedCode">#?   $log [render sandbox side]</span>
   trace <span class="Constant">11</span>, <span class="Constant">[app]</span>, <span class="Constant">[render sandbox side]</span>
-  current-sandbox:address:editor-data<span class="Special"> &lt;- </span>get *env, <span class="Constant">current-sandbox:offset</span>
+  current-sandbox:address:shared:editor-data<span class="Special"> &lt;- </span>get *env, <span class="Constant">current-sandbox:offset</span>
+  row:number, column:number<span class="Special"> &lt;- </span>copy <span class="Constant">1</span>, <span class="Constant">0</span>
   left:number<span class="Special"> &lt;- </span>get *current-sandbox, <span class="Constant">left:offset</span>
   right:number<span class="Special"> &lt;- </span>get *current-sandbox, <span class="Constant">right:offset</span>
-  row:number, column:number, screen, current-sandbox<span class="Special"> &lt;- </span>render screen, current-sandbox
-  clear-screen-from screen, row, column, left, right
-  row<span class="Special"> &lt;- </span>add row, <span class="Constant">1</span>
+  <span class="Comment"># render sandbox editor</span>
+  render-from:number<span class="Special"> &lt;- </span>get *env, <span class="Constant">render-from:offset</span>
+  <span class="Delimiter">{</span>
+    render-current-sandbox?:boolean<span class="Special"> &lt;- </span>equal render-from, <span class="Constant">-1</span>
+    <span class="muControl">break-unless</span> render-current-sandbox?
+    row, column, screen, current-sandbox<span class="Special"> &lt;- </span>render screen, current-sandbox
+    clear-screen-from screen, row, column, left, right
+    row<span class="Special"> &lt;- </span>add row, <span class="Constant">1</span>
+  <span class="Delimiter">}</span>
+  <span class="Comment"># render sandboxes</span>
   draw-horizontal screen, row, left, right, <span class="Constant">9473/horizontal-double</span>
-  sandbox:address:sandbox-data<span class="Special"> &lt;- </span>get *env, <span class="Constant">sandbox:offset</span>
-  row, screen<span class="Special"> &lt;- </span>render-sandboxes screen, sandbox, left, right, row
-  clear-rest-of-screen screen, row, left, left, right
+  sandbox:address:shared:sandbox-data<span class="Special"> &lt;- </span>get *env, <span class="Constant">sandbox:offset</span>
+  row, screen<span class="Special"> &lt;- </span>render-sandboxes screen, sandbox, left, right, row, render-from
+  clear-rest-of-screen screen, row, left, right
 ]
 
-<span class="muRecipe">recipe</span> render-sandboxes screen:address:screen, sandbox:address:sandbox-data, left:number, right:number, row:number<span class="muRecipe"> -&gt; </span>row:number, screen:address:screen, sandbox:address:sandbox-data [
+<span class="muRecipe">recipe</span> render-sandboxes screen:address:shared:screen, sandbox:address:shared:sandbox-data, left:number, right:number, row:number, render-from:number, idx:number<span class="muRecipe"> -&gt; </span>row:number, screen:address:shared:screen, sandbox:address:shared:sandbox-data [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
 <span class="CommentedCode">#?   $log [render sandbox]</span>
@@ -285,69 +316,86 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   screen-height:number<span class="Special"> &lt;- </span>screen-height screen
   at-bottom?:boolean<span class="Special"> &lt;- </span>greater-or-equal row, screen-height
   <span class="muControl">reply-if</span> at-bottom?:boolean
-  <span class="Comment"># render sandbox menu</span>
-  row<span class="Special"> &lt;- </span>add row, <span class="Constant">1</span>
-  screen<span class="Special"> &lt;- </span>move-cursor screen, row, left
-  clear-line-delimited screen, left, right
-  print screen, <span class="Constant">120/x</span>, <span class="Constant">245/grey</span>
-  <span class="Comment"># save menu row so we can detect clicks to it later</span>
-  starting-row:address:number<span class="Special"> &lt;- </span>get-address *sandbox, <span class="Constant">starting-row-on-screen:offset</span>
-  *starting-row<span class="Special"> &lt;- </span>copy row
-  <span class="Comment"># render sandbox contents</span>
-  row<span class="Special"> &lt;- </span>add row, <span class="Constant">1</span>
-  screen<span class="Special"> &lt;- </span>move-cursor screen, row, left
-  sandbox-data:address:array:character<span class="Special"> &lt;- </span>get *sandbox, <span class="Constant">data:offset</span>
-  row, screen<span class="Special"> &lt;- </span>render-code screen, sandbox-data, left, right, row
-  code-ending-row:address:number<span class="Special"> &lt;- </span>get-address *sandbox, <span class="Constant">code-ending-row-on-screen:offset</span>
-  *code-ending-row<span class="Special"> &lt;- </span>copy row
-  <span class="Comment"># render sandbox warnings, screen or response, in that order</span>
-  response-starting-row:address:number<span class="Special"> &lt;- </span>get-address *sandbox, <span class="Constant">response-starting-row-on-screen:offset</span>
-  sandbox-response:address:array:character<span class="Special"> &lt;- </span>get *sandbox, <span class="Constant">response:offset</span>
-<span class="Constant">  &lt;render-sandbox-results&gt;</span>
+  hidden?:boolean<span class="Special"> &lt;- </span>lesser-than idx, render-from
   <span class="Delimiter">{</span>
-    sandbox-screen:address:screen<span class="Special"> &lt;- </span>get *sandbox, <span class="Constant">screen:offset</span>
-    empty-screen?:boolean<span class="Special"> &lt;- </span>fake-screen-is-empty? sandbox-screen
-    <span class="muControl">break-if</span> empty-screen?
-    row, screen<span class="Special"> &lt;- </span>render-screen screen, sandbox-screen, left, right, row
+    <span class="muControl">break-if</span> hidden?
+    <span class="Comment"># render sandbox menu</span>
+    row<span class="Special"> &lt;- </span>add row, <span class="Constant">1</span>
+    screen<span class="Special"> &lt;- </span>move-cursor screen, row, left
+    print screen, idx, <span class="Constant">240/dark-grey</span>
+    clear-line-delimited screen, left, right
+    delete-icon:character<span class="Special"> &lt;- </span>copy <span class="Constant">120/x</span>
+    print screen, delete-icon, <span class="Constant">245/grey</span>
+    <span class="Comment"># save menu row so we can detect clicks to it later</span>
+    starting-row:address:number<span class="Special"> &lt;- </span>get-address *sandbox, <span class="Constant">starting-row-on-screen:offset</span>
+    *starting-row<span class="Special"> &lt;- </span>copy row
+    <span class="Comment"># render sandbox contents</span>
+    row<span class="Special"> &lt;- </span>add row, <span class="Constant">1</span>
+    screen<span class="Special"> &lt;- </span>move-cursor screen, row, left
+    sandbox-data:address:shared:array:character<span class="Special"> &lt;- </span>get *sandbox, <span class="Constant">data:offset</span>
+    row, screen<span class="Special"> &lt;- </span>render-code screen, sandbox-data, left, right, row
+    code-ending-row:address:number<span class="Special"> &lt;- </span>get-address *sandbox, <span class="Constant">code-ending-row-on-screen:offset</span>
+    *code-ending-row<span class="Special"> &lt;- </span>copy row
+    <span class="Comment"># render sandbox warnings, screen or response, in that order</span>
+    response-starting-row:address:number<span class="Special"> &lt;- </span>get-address *sandbox, <span class="Constant">response-starting-row-on-screen:offset</span>
+    sandbox-response:address:shared:array:character<span class="Special"> &lt;- </span>get *sandbox, <span class="Constant">response:offset</span>
+<span class="Constant">    &lt;render-sandbox-results&gt;</span>
+    <span class="Delimiter">{</span>
+      sandbox-screen:address:shared:screen<span class="Special"> &lt;- </span>get *sandbox, <span class="Constant">screen:offset</span>
+      empty-screen?:boolean<span class="Special"> &lt;- </span>fake-screen-is-empty? sandbox-screen
+      <span class="muControl">break-if</span> empty-screen?
+      row, screen<span class="Special"> &lt;- </span>render-screen screen, sandbox-screen, left, right, row
+    <span class="Delimiter">}</span>
+    <span class="Delimiter">{</span>
+      <span class="muControl">break-unless</span> empty-screen?
+      *response-starting-row<span class="Special"> &lt;- </span>copy row
+<span class="Constant">      &lt;render-sandbox-response&gt;</span>
+      row, screen<span class="Special"> &lt;- </span>render screen, sandbox-response, left, right, <span class="Constant">245/grey</span>, row
+    <span class="Delimiter">}</span>
+<span class="Constant">    +render-sandbox-end</span>
+    at-bottom?:boolean<span class="Special"> &lt;- </span>greater-or-equal row, screen-height
+    <span class="muControl">reply-if</span> at-bottom?
+    <span class="Comment"># draw solid line after sandbox</span>
+    draw-horizontal screen, row, left, right, <span class="Constant">9473/horizontal-double</span>
   <span class="Delimiter">}</span>
+  <span class="Comment"># if hidden, reset row attributes</span>
   <span class="Delimiter">{</span>
-    <span class="muControl">break-unless</span> empty-screen?
-    *response-starting-row<span class="Special"> &lt;- </span>copy row
-<span class="Constant">    &lt;render-sandbox-response&gt;</span>
-    row, screen<span class="Special"> &lt;- </span>render screen, sandbox-response, left, right, <span class="Constant">245/grey</span>, row
+    <span class="muControl">break-unless</span> hidden?
+    tmp:address:number<span class="Special"> &lt;- </span>get-address *sandbox, <span class="Constant">starting-row-on-screen:offset</span>
+    *tmp<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
+    tmp:address:number<span class="Special"> &lt;- </span>get-address *sandbox, <span class="Constant">code-ending-row-on-screen:offset</span>
+    *tmp<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
+    tmp:address:number<span class="Special"> &lt;- </span>get-address *sandbox, <span class="Constant">response-starting-row-on-screen:offset</span>
+    *tmp<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
   <span class="Delimiter">}</span>
-<span class="Constant">  +render-sandbox-end</span>
-  at-bottom?:boolean<span class="Special"> &lt;- </span>greater-or-equal row, screen-height
-  <span class="muControl">reply-if</span> at-bottom?
-  <span class="Comment"># draw solid line after sandbox</span>
-  draw-horizontal screen, row, left, right, <span class="Constant">9473/horizontal-double</span>
   <span class="Comment"># draw next sandbox</span>
-  next-sandbox:address:sandbox-data<span class="Special"> &lt;- </span>get *sandbox, <span class="Constant">next-sandbox:offset</span>
-  row, screen<span class="Special"> &lt;- </span>render-sandboxes screen, next-sandbox, left, right, row
+  next-sandbox:address:shared:sandbox-data<span class="Special"> &lt;- </span>get *sandbox, <span class="Constant">next-sandbox:offset</span>
+  next-idx:number<span class="Special"> &lt;- </span>add idx, <span class="Constant">1</span>
+  row, screen<span class="Special"> &lt;- </span>render-sandboxes screen, next-sandbox, left, right, row, render-from, next-idx
 ]
 
 <span class="Comment"># assumes programming environment has no sandboxes; restores them from previous session</span>
-<span class="muRecipe">recipe</span> restore-sandboxes env:address:programming-environment-data<span class="muRecipe"> -&gt; </span>env:address:programming-environment-data [
+<span class="muRecipe">recipe</span> restore-sandboxes env:address:shared:programming-environment-data<span class="muRecipe"> -&gt; </span>env:address:shared:programming-environment-data [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   <span class="Comment"># read all scenarios, pushing them to end of a list of scenarios</span>
-  suffix:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[.out]</span>
+  suffix:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[.out]</span>
   idx:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
-  curr:address:address:sandbox-data<span class="Special"> &lt;- </span>get-address *env, <span class="Constant">sandbox:offset</span>
+  curr:address:address:shared:sandbox-data<span class="Special"> &lt;- </span>get-address *env, <span class="Constant">sandbox:offset</span>
   <span class="Delimiter">{</span>
-    filename:address:array:character<span class="Special"> &lt;- </span>to-text idx
-    contents:address:array:character<span class="Special"> &lt;- </span>restore filename
+    filename:address:shared:array:character<span class="Special"> &lt;- </span>to-text idx
+    contents:address:shared:array:character<span class="Special"> &lt;- </span>restore filename
     <span class="muControl">break-unless</span> contents  <span class="Comment"># stop at first error; assuming file didn't exist</span>
     <span class="Comment"># create new sandbox for file</span>
     *curr<span class="Special"> &lt;- </span>new <span class="Constant">sandbox-data:type</span>
-    data:address:address:array:character<span class="Special"> &lt;- </span>get-address **curr, <span class="Constant">data:offset</span>
+    data:address:address:shared:array:character<span class="Special"> &lt;- </span>get-address **curr, <span class="Constant">data:offset</span>
     *data<span class="Special"> &lt;- </span>copy contents
     <span class="Comment"># restore expected output for sandbox if it exists</span>
     <span class="Delimiter">{</span>
       filename<span class="Special"> &lt;- </span>append filename, suffix
       contents<span class="Special"> &lt;- </span>restore filename
       <span class="muControl">break-unless</span> contents
-      expected-response:address:address:array:character<span class="Special"> &lt;- </span>get-address **curr, <span class="Constant">expected-response:offset</span>
+      expected-response:address:address:shared:array:character<span class="Special"> &lt;- </span>get-address **curr, <span class="Constant">expected-response:offset</span>
       *expected-response<span class="Special"> &lt;- </span>copy contents
     <span class="Delimiter">}</span>
 <span class="Constant">    +continue</span>
@@ -355,23 +403,26 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     curr<span class="Special"> &lt;- </span>get-address **curr, <span class="Constant">next-sandbox:offset</span>
     <span class="muControl">loop</span>
   <span class="Delimiter">}</span>
+  <span class="Comment"># update sandbox count</span>
+  number-of-sandboxes:address:number<span class="Special"> &lt;- </span>get-address *env, <span class="Constant">number-of-sandboxes:offset</span>
+  *number-of-sandboxes<span class="Special"> &lt;- </span>copy idx
 ]
 
 <span class="Comment"># print the fake sandbox screen to 'screen' with appropriate delimiters</span>
 <span class="Comment"># leave cursor at start of next line</span>
-<span class="muRecipe">recipe</span> render-screen screen:address:screen, sandbox-screen:address:screen, left:number, right:number, row:number<span class="muRecipe"> -&gt; </span>row:number, screen:address:screen [
+<span class="muRecipe">recipe</span> render-screen screen:address:shared:screen, sandbox-screen:address:shared:screen, left:number, right:number, row:number<span class="muRecipe"> -&gt; </span>row:number, screen:address:shared:screen [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   <span class="muControl">reply-unless</span> sandbox-screen
   <span class="Comment"># print 'screen:'</span>
-  header:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[screen:]</span>
+  header:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[screen:]</span>
   row<span class="Special"> &lt;- </span>render screen, header, left, right, <span class="Constant">245/grey</span>, row
   screen<span class="Special"> &lt;- </span>move-cursor screen, row, left
   <span class="Comment"># start printing sandbox-screen</span>
   column:number<span class="Special"> &lt;- </span>copy left
   s-width:number<span class="Special"> &lt;- </span>screen-width sandbox-screen
   s-height:number<span class="Special"> &lt;- </span>screen-height sandbox-screen
-  buf:address:array:screen-cell<span class="Special"> &lt;- </span>get *sandbox-screen, <span class="Constant">data:offset</span>
+  buf:address:shared:array:screen-cell<span class="Special"> &lt;- </span>get *sandbox-screen, <span class="Constant">data:offset</span>
   stop-printing:number<span class="Special"> &lt;- </span>add left, s-width, <span class="Constant">3</span>
   max-column:number<span class="Special"> &lt;- </span>min stop-printing, right
   i:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
@@ -385,9 +436,11 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     column<span class="Special"> &lt;- </span>copy left
     screen<span class="Special"> &lt;- </span>move-cursor screen, row, column
     <span class="Comment"># initial leader for each row: two spaces and a '.'</span>
-    print screen, <span class="Constant">32/space</span>, <span class="Constant">245/grey</span>
-    print screen, <span class="Constant">32/space</span>, <span class="Constant">245/grey</span>
-    print screen, <span class="Constant">46/full-stop</span>, <span class="Constant">245/grey</span>
+    space:character<span class="Special"> &lt;- </span>copy <span class="Constant">32/space</span>
+    print screen, space, <span class="Constant">245/grey</span>
+    print screen, space, <span class="Constant">245/grey</span>
+    full-stop:character<span class="Special"> &lt;- </span>copy <span class="Constant">46/period</span>
+    print screen, full-stop, <span class="Constant">245/grey</span>
     column<span class="Special"> &lt;- </span>add left, <span class="Constant">3</span>
     <span class="Delimiter">{</span>
       <span class="Comment"># print row</span>
@@ -408,13 +461,13 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
       <span class="muControl">loop</span>
     <span class="Delimiter">}</span>
     <span class="Comment"># print final '.'</span>
-    print screen, <span class="Constant">46/full-stop</span>, <span class="Constant">245/grey</span>
+    print screen, full-stop, <span class="Constant">245/grey</span>
     column<span class="Special"> &lt;- </span>add column, <span class="Constant">1</span>
     <span class="Delimiter">{</span>
       <span class="Comment"># clear rest of current line</span>
       line-done?:boolean<span class="Special"> &lt;- </span>greater-than column, right
       <span class="muControl">break-if</span> line-done?
-      print screen, <span class="Constant">32/space</span>
+      print screen, space
       column<span class="Special"> &lt;- </span>add column, <span class="Constant">1</span>
       <span class="muControl">loop</span>
     <span class="Delimiter">}</span>
@@ -427,24 +480,24 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
   assume-screen <span class="Constant">100/width</span>, <span class="Constant">12/height</span>
   <span class="Comment"># define a recipe (no indent for the 'add' line below so column numbers are more obvious)</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[ </span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[ </span>
 <span class="Constant">recipe foo [</span>
 <span class="Constant">z:number &lt;- add 2, 2</span>
 <span class="Constant">reply z</span>
 <span class="Constant">]</span>]
   <span class="Comment"># sandbox editor contains an instruction without storing outputs</span>
-  <span class="Constant">2</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[foo]</span>
-  <span class="Constant">3</span>:address:programming-environment-data<span class="Special"> &lt;- </span>new-programming-environment screen:address:screen, <span class="Constant">1</span>:address:array:character, <span class="Constant">2</span>:address:array:character
+  <span class="Constant">2</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[foo]</span>
+  <span class="Constant">3</span>:address:shared:programming-environment-data<span class="Special"> &lt;- </span>new-programming-environment screen:address:shared:screen, <span class="Constant">1</span>:address:shared:array:character, <span class="Constant">2</span>:address:shared:array:character
   <span class="Comment"># run the code in the editors</span>
   assume-console [
     press F4
   ]
-  event-loop screen:address:screen, console:address:console, <span class="Constant">3</span>:address:programming-environment-data
+  event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">3</span>:address:shared:programming-environment-data
   screen-should-contain [
    <span class="Constant"> .                                                                                 run (F4)           .</span>
    <span class="Constant"> .                                                  ┊                                                 .</span>
    <span class="Constant"> .recipe foo [                                      ┊━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━.</span>
-   <span class="Constant"> .z:number &lt;- add 2, 2                              ┊                                                x.</span>
+   <span class="Constant"> .z:number &lt;- add 2, 2                              ┊0                                               x.</span>
    <span class="Constant"> .reply z                                           ┊foo                                              .</span>
    <span class="Constant"> .]                                                 ┊4                                                .</span>
 <span class="Constant">    .┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┊━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━.</span>
@@ -458,14 +511,14 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     press F4
   ]
   run [
-    event-loop screen:address:screen, console:address:console, <span class="Constant">3</span>:address:programming-environment-data
+    event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">3</span>:address:shared:programming-environment-data
   ]
   <span class="Comment"># check that screen updates the result on the right</span>
   screen-should-contain [
    <span class="Constant"> .                                                                                 run (F4)           .</span>
    <span class="Constant"> .                                                  ┊                                                 .</span>
    <span class="Constant"> .recipe foo [                                      ┊━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━.</span>
-   <span class="Constant"> .z:number &lt;- add 2, 3                              ┊                                                x.</span>
+   <span class="Constant"> .z:number &lt;- add 2, 3                              ┊0                                               x.</span>
    <span class="Constant"> .reply z                                           ┊foo                                              .</span>
    <span class="Constant"> .]                                                 ┊5                                                .</span>
 <span class="Constant">    .┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┊━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━.</span>
@@ -477,23 +530,23 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
   assume-screen <span class="Constant">100/width</span>, <span class="Constant">20/height</span>
   <span class="Comment"># left editor is empty</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
   <span class="Comment"># right editor contains an instruction</span>
-  <span class="Constant">2</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[print-integer screen, 4]</span>
-  <span class="Constant">3</span>:address:programming-environment-data<span class="Special"> &lt;- </span>new-programming-environment screen:address:screen, <span class="Constant">1</span>:address:array:character, <span class="Constant">2</span>:address:array:character
+  <span class="Constant">2</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[print-integer screen, 4]</span>
+  <span class="Constant">3</span>:address:shared:programming-environment-data<span class="Special"> &lt;- </span>new-programming-environment screen:address:shared:screen, <span class="Constant">1</span>:address:shared:array:character, <span class="Constant">2</span>:address:shared:array:character
   <span class="Comment"># run the code in the editor</span>
   assume-console [
     press F4
   ]
   run [
-    event-loop screen:address:screen, console:address:console, <span class="Constant">3</span>:address:programming-environment-data
+    event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">3</span>:address:shared:programming-environment-data
   ]
   <span class="Comment"># check that it prints a little toy screen</span>
   screen-should-contain [
    <span class="Constant"> .                                                                                 run (F4)           .</span>
    <span class="Constant"> .                                                  ┊                                                 .</span>
 <span class="Constant">    .┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┊━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━.</span>
-   <span class="Constant"> .                                                  ┊                                                x.</span>
+   <span class="Constant"> .                                                  ┊0                                               x.</span>
    <span class="Constant"> .                                                  ┊print-integer screen, 4                          .</span>
    <span class="Constant"> .                                                  ┊screen:                                          .</span>
    <span class="Constant"> .                                                  ┊  .4                             .               .</span>
@@ -506,11 +559,11 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   ]
 ]
 
-<span class="muRecipe">recipe</span> editor-contents editor:address:editor-data<span class="muRecipe"> -&gt; </span>result:address:array:character [
+<span class="muRecipe">recipe</span> editor-contents editor:address:shared:editor-data<span class="muRecipe"> -&gt; </span>result:address:shared:array:character [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
-  buf:address:buffer<span class="Special"> &lt;- </span>new-buffer <span class="Constant">80</span>
-  curr:address:duplex-list:character<span class="Special"> &lt;- </span>get *editor, <span class="Constant">data:offset</span>
+  buf:address:shared:buffer<span class="Special"> &lt;- </span>new-buffer <span class="Constant">80</span>
+  curr:address:shared:duplex-list:character<span class="Special"> &lt;- </span>get *editor, <span class="Constant">data:offset</span>
   <span class="Comment"># skip § sentinel</span>
   assert curr, <span class="Constant">[editor without data is illegal; must have at least a sentinel]</span>
   curr<span class="Special"> &lt;- </span>next curr
@@ -527,21 +580,447 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muScenario">scenario</span> editor-provides-edited-contents [
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
   assume-console [
     left-click <span class="Constant">1</span>, <span class="Constant">2</span>
     type <span class="Constant">[def]</span>
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
-    <span class="Constant">3</span>:address:array:character<span class="Special"> &lt;- </span>editor-contents <span class="Constant">2</span>:address:editor-data
-    <span class="Constant">4</span>:array:character<span class="Special"> &lt;- </span>copy *<span class="Constant">3</span>:address:array:character
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
+    <span class="Constant">3</span>:address:shared:array:character<span class="Special"> &lt;- </span>editor-contents <span class="Constant">2</span>:address:shared:editor-data
+    <span class="Constant">4</span>:array:character<span class="Special"> &lt;- </span>copy *<span class="Constant">3</span>:address:shared:array:character
   ]
   memory-should-contain [
     <span class="Constant">4</span>:array:character<span class="Special"> &lt;- </span><span class="Constant">[abdefc]</span>
   ]
 ]
+
+<span class="Comment"># scrolling through sandboxes</span>
+
+<span class="muScenario">scenario</span> scrolling-down-past-bottom-of-sandbox-editor [
+  trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
+  assume-screen <span class="Constant">30/width</span>, <span class="Constant">10/height</span>
+  <span class="Comment"># initialize sandbox side</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
+  <span class="Constant">2</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[add 2, 2]</span>
+  <span class="Constant">3</span>:address:shared:programming-environment-data<span class="Special"> &lt;- </span>new-programming-environment screen:address:shared:screen, <span class="Constant">1</span>:address:shared:array:character, <span class="Constant">2</span>:address:shared:array:character
+  render-all screen, <span class="Constant">3</span>:address:shared:programming-environment-data
+  assume-console [
+    <span class="Comment"># create a sandbox</span>
+    press F4
+    <span class="Comment"># switch to sandbox editor and type in 2 lines</span>
+    press ctrl-n
+    type <span class="Constant">[abc</span>
+<span class="Constant">]</span>
+  ]
+  run [
+    event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">3</span>:address:shared:programming-environment-data
+    <span class="Constant">4</span>:character/cursor<span class="Special"> &lt;- </span>copy <span class="Constant">9251/␣</span>
+    print screen:address:shared:screen, <span class="Constant">4</span>:character/cursor
+  ]
+  screen-should-contain [
+   <span class="Constant"> .                              .  # minor: F4 clears menu tooltip in very narrow screens</span>
+   <span class="Constant"> .               ┊abc           .</span>
+   <span class="Constant"> .┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┊␣             .</span>
+   <span class="Constant"> .               ┊━━━━━━━━━━━━━━.</span>
+   <span class="Constant"> .               ┊0            x.</span>
+   <span class="Constant"> .               ┊add 2, 2      .</span>
+  ]
+  <span class="Comment"># hit 'down' at bottom of sandbox editor</span>
+  assume-console [
+    press down-arrow
+  ]
+  run [
+    event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">3</span>:address:shared:programming-environment-data
+    <span class="Constant">4</span>:character/cursor<span class="Special"> &lt;- </span>copy <span class="Constant">9251/␣</span>
+    print screen:address:shared:screen, <span class="Constant">4</span>:character/cursor
+  ]
+  <span class="Comment"># sandbox editor hidden; first sandbox displayed</span>
+  <span class="Comment"># cursor moves to first sandbox</span>
+  screen-should-contain [
+   <span class="Constant"> .                              .</span>
+   <span class="Constant"> .               ┊━━━━━━━━━━━━━━.</span>
+   <span class="Constant"> .┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┊␣            x.</span>
+   <span class="Constant"> .               ┊add 2, 2      .</span>
+   <span class="Constant"> .               ┊4             .</span>
+   <span class="Constant"> .               ┊━━━━━━━━━━━━━━.</span>
+   <span class="Constant"> .               ┊              .</span>
+  ]
+  <span class="Comment"># hit 'up'</span>
+  assume-console [
+    press up-arrow
+  ]
+  run [
+    event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">3</span>:address:shared:programming-environment-data
+    <span class="Constant">4</span>:character/cursor<span class="Special"> &lt;- </span>copy <span class="Constant">9251/␣</span>
+    print screen:address:shared:screen, <span class="Constant">4</span>:character/cursor
+  ]
+  <span class="Comment"># sandbox editor displays again</span>
+  screen-should-contain [
+   <span class="Constant"> .                              .  # minor: F4 clears menu tooltip in very narrow screens</span>
+   <span class="Constant"> .               ┊abc           .</span>
+   <span class="Constant"> .┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┊␣             .</span>
+   <span class="Constant"> .               ┊━━━━━━━━━━━━━━.</span>
+   <span class="Constant"> .               ┊0            x.</span>
+   <span class="Constant"> .               ┊add 2, 2      .</span>
+  ]
+]
+
+<span class="Comment"># down on sandbox side updates render-from when sandbox editor has cursor at bottom</span>
+<span class="muRecipe">after</span> <span class="Constant">&lt;global-keypress&gt;</span> [
+  <span class="Delimiter">{</span>
+    <span class="muControl">break-unless</span> *sandbox-in-focus?
+    down?:boolean<span class="Special"> &lt;- </span>equal *k, <span class="Constant">65516/down-arrow</span>
+    <span class="muControl">break-unless</span> down?
+    sandbox-bottom:number<span class="Special"> &lt;- </span>get *current-sandbox, <span class="Constant">bottom:offset</span>
+    sandbox-cursor:number<span class="Special"> &lt;- </span>get *current-sandbox, <span class="Constant">cursor-row:offset</span>
+    sandbox-cursor-on-last-line?:boolean<span class="Special"> &lt;- </span>equal sandbox-bottom, sandbox-cursor
+    <span class="muControl">break-unless</span> sandbox-cursor-on-last-line?
+    sandbox:address:shared:sandbox-data<span class="Special"> &lt;- </span>get *env, <span class="Constant">sandbox:offset</span>
+    <span class="muControl">break-unless</span> sandbox
+    <span class="Comment"># slide down if possible</span>
+    <span class="Delimiter">{</span>
+      render-from:address:number<span class="Special"> &lt;- </span>get-address *env, <span class="Constant">render-from:offset</span>
+      number-of-sandboxes:number<span class="Special"> &lt;- </span>get *env, <span class="Constant">number-of-sandboxes:offset</span>
+      max:number<span class="Special"> &lt;- </span>subtract number-of-sandboxes, <span class="Constant">1</span>
+      at-end?:boolean<span class="Special"> &lt;- </span>greater-or-equal *render-from, max
+      <span class="muControl">jump-if</span> at-end?, <span class="Constant">+finish-event:label</span>  <span class="Comment"># render nothing</span>
+      *render-from<span class="Special"> &lt;- </span>add *render-from, <span class="Constant">1</span>
+    <span class="Delimiter">}</span>
+    hide-screen screen
+    screen<span class="Special"> &lt;- </span>render-sandbox-side screen, env
+    show-screen screen
+    <span class="muControl">jump</span> <span class="Constant">+finish-event:label</span>
+  <span class="Delimiter">}</span>
+]
+
+<span class="Comment"># update-cursor takes render-from into account</span>
+<span class="muRecipe">after</span> <span class="Constant">&lt;update-cursor-special-cases&gt;</span> [
+  <span class="Delimiter">{</span>
+    <span class="muControl">break-unless</span> sandbox-in-focus?
+    render-from:number<span class="Special"> &lt;- </span>get *env, <span class="Constant">render-from:offset</span>
+    scrolling?:boolean<span class="Special"> &lt;- </span>greater-or-equal render-from, <span class="Constant">0</span>
+    <span class="muControl">break-unless</span> scrolling?
+    cursor-column:number<span class="Special"> &lt;- </span>get *current-sandbox, <span class="Constant">left:offset</span>
+    screen<span class="Special"> &lt;- </span>move-cursor screen, <span class="Constant">2/row</span>, cursor-column  <span class="Comment"># highlighted sandbox will always start at row 2</span>
+    <span class="muControl">reply</span>
+  <span class="Delimiter">}</span>
+]
+
+<span class="Comment"># 'up' on sandbox side is like 'down': updates render-from when necessary</span>
+<span class="muRecipe">after</span> <span class="Constant">&lt;global-keypress&gt;</span> [
+  <span class="Delimiter">{</span>
+    <span class="muControl">break-unless</span> *sandbox-in-focus?
+    up?:boolean<span class="Special"> &lt;- </span>equal *k, <span class="Constant">65517/up-arrow</span>
+    <span class="muControl">break-unless</span> up?
+    render-from:address:number<span class="Special"> &lt;- </span>get-address *env, <span class="Constant">render-from:offset</span>
+    at-beginning?:boolean<span class="Special"> &lt;- </span>equal *render-from, <span class="Constant">-1</span>
+    <span class="muControl">break-if</span> at-beginning?
+    *render-from<span class="Special"> &lt;- </span>subtract *render-from, <span class="Constant">1</span>
+    hide-screen screen
+    screen<span class="Special"> &lt;- </span>render-sandbox-side screen, env
+    show-screen screen
+    <span class="muControl">jump</span> <span class="Constant">+finish-event:label</span>
+  <span class="Delimiter">}</span>
+]
+
+<span class="Comment"># sandbox belonging to 'env' whose next-sandbox is 'in'</span>
+<span class="Comment"># return 0 if there's no such sandbox, either because 'in' doesn't exist in 'env', or because it's the first sandbox</span>
+<span class="muRecipe">recipe</span> previous-sandbox env:address:shared:programming-environment-data, in:address:shared:sandbox-data<span class="muRecipe"> -&gt; </span>out:address:shared:sandbox-data [
+  <span class="Constant">local-scope</span>
+  <span class="Constant">load-ingredients</span>
+  curr:address:shared:sandbox-data<span class="Special"> &lt;- </span>get *env, <span class="Constant">sandbox:offset</span>
+  <span class="muControl">reply-unless</span> curr, <span class="Constant">0/nil</span>
+  next:address:shared:sandbox-data<span class="Special"> &lt;- </span>get *curr, <span class="Constant">next-sandbox:offset</span>
+  <span class="Delimiter">{</span>
+    <span class="muControl">reply-unless</span> next, <span class="Constant">0/nil</span>
+    found?:boolean<span class="Special"> &lt;- </span>equal next, in
+    <span class="muControl">break-if</span> found?
+    curr<span class="Special"> &lt;- </span>copy next
+    next<span class="Special"> &lt;- </span>get *curr, <span class="Constant">next-sandbox:offset</span>
+    <span class="muControl">loop</span>
+  <span class="Delimiter">}</span>
+  <span class="muControl">reply</span> curr
+]
+
+<span class="muScenario">scenario</span> scrolling-down-on-recipe-side [
+  trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
+  assume-screen <span class="Constant">30/width</span>, <span class="Constant">10/height</span>
+  <span class="Comment"># initialize sandbox side and create a sandbox</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[ </span>
+<span class="Constant">]</span>
+  <span class="Comment"># create a sandbox</span>
+  <span class="Constant">2</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[add 2, 2]</span>
+  <span class="Constant">3</span>:address:shared:programming-environment-data<span class="Special"> &lt;- </span>new-programming-environment screen:address:shared:screen, <span class="Constant">1</span>:address:shared:array:character, <span class="Constant">2</span>:address:shared:array:character
+  render-all screen, <span class="Constant">3</span>:address:shared:programming-environment-data
+  assume-console [
+    press F4
+  ]
+  run [
+    event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">3</span>:address:shared:programming-environment-data
+  ]
+  <span class="Comment"># hit 'down' in recipe editor</span>
+  assume-console [
+    press down-arrow
+  ]
+  run [
+    event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">3</span>:address:shared:programming-environment-data
+    <span class="Constant">4</span>:character/cursor<span class="Special"> &lt;- </span>copy <span class="Constant">9251/␣</span>
+    print screen:address:shared:screen, <span class="Constant">4</span>:character/cursor
+  ]
+  <span class="Comment"># sandbox editor hidden; first sandbox displayed</span>
+  <span class="Comment"># cursor moves to first sandbox</span>
+  screen-should-contain [
+   <span class="Constant"> .                              .</span>
+   <span class="Constant"> .               ┊              .</span>
+   <span class="Constant"> .␣              ┊━━━━━━━━━━━━━━.</span>
+   <span class="Constant"> .┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┊0            x.</span>
+   <span class="Constant"> .               ┊add 2, 2      .</span>
+   <span class="Constant"> .               ┊4             .</span>
+   <span class="Constant"> .               ┊━━━━━━━━━━━━━━.</span>
+   <span class="Constant"> .               ┊              .</span>
+  ]
+]
+
+<span class="muScenario">scenario</span> scrolling-through-multiple-sandboxes [
+  trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
+  assume-screen <span class="Constant">30/width</span>, <span class="Constant">10/height</span>
+  <span class="Comment"># initialize environment</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
+  <span class="Constant">2</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
+  <span class="Constant">3</span>:address:shared:programming-environment-data<span class="Special"> &lt;- </span>new-programming-environment screen:address:shared:screen, <span class="Constant">1</span>:address:shared:array:character, <span class="Constant">2</span>:address:shared:array:character
+  render-all screen, <span class="Constant">3</span>:address:shared:programming-environment-data
+  <span class="Comment"># create 2 sandboxes</span>
+  assume-console [
+    press ctrl-n
+    type <span class="Constant">[add 2, 2]</span>
+    press F4
+    type <span class="Constant">[add 1, 1]</span>
+    press F4
+  ]
+  run [
+    event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">3</span>:address:shared:programming-environment-data
+    <span class="Constant">4</span>:character/cursor<span class="Special"> &lt;- </span>copy <span class="Constant">9251/␣</span>
+    print screen:address:shared:screen, <span class="Constant">4</span>:character/cursor
+  ]
+  screen-should-contain [
+   <span class="Constant"> .                              .</span>
+   <span class="Constant"> .               ┊␣             .</span>
+<span class="Constant">    .┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┊━━━━━━━━━━━━━━.</span>
+   <span class="Constant"> .               ┊0            x.</span>
+   <span class="Constant"> .               ┊add 1, 1      .</span>
+   <span class="Constant"> .               ┊2             .</span>
+   <span class="Constant"> .               ┊━━━━━━━━━━━━━━.</span>
+   <span class="Constant"> .               ┊1            x.</span>
+   <span class="Constant"> .               ┊add 2, 2      .</span>
+   <span class="Constant"> .               ┊4             .</span>
+  ]
+  <span class="Comment"># hit 'down'</span>
+  assume-console [
+    press down-arrow
+  ]
+  run [
+    event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">3</span>:address:shared:programming-environment-data
+    <span class="Constant">4</span>:character/cursor<span class="Special"> &lt;- </span>copy <span class="Constant">9251/␣</span>
+    print screen:address:shared:screen, <span class="Constant">4</span>:character/cursor
+  ]
+  <span class="Comment"># sandbox editor hidden; first sandbox displayed</span>
+  <span class="Comment"># cursor moves to first sandbox</span>
+  screen-should-contain [
+   <span class="Constant"> .                              .</span>
+   <span class="Constant"> .               ┊━━━━━━━━━━━━━━.</span>
+   <span class="Constant"> .┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┊␣            x.</span>
+   <span class="Constant"> .               ┊add 1, 1      .</span>
+   <span class="Constant"> .               ┊2             .</span>
+   <span class="Constant"> .               ┊━━━━━━━━━━━━━━.</span>
+   <span class="Constant"> .               ┊1            x.</span>
+   <span class="Constant"> .               ┊add 2, 2      .</span>
+   <span class="Constant"> .               ┊4             .</span>
+   <span class="Constant"> .               ┊━━━━━━━━━━━━━━.</span>
+  ]
+  <span class="Comment"># hit 'down' again</span>
+  assume-console [
+    press down-arrow
+  ]
+  run [
+    event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">3</span>:address:shared:programming-environment-data
+  ]
+  <span class="Comment"># just second sandbox displayed</span>
+  screen-should-contain [
+   <span class="Constant"> .                              .</span>
+   <span class="Constant"> .               ┊━━━━━━━━━━━━━━.</span>
+   <span class="Constant"> .┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┊1            x.</span>
+   <span class="Constant"> .               ┊add 2, 2      .</span>
+   <span class="Constant"> .               ┊4             .</span>
+   <span class="Constant"> .               ┊━━━━━━━━━━━━━━.</span>
+   <span class="Constant"> .               ┊              .</span>
+   <span class="Constant"> .               ┊              .</span>
+  ]
+  <span class="Comment"># hit 'down' again</span>
+  assume-console [
+    press down-arrow
+  ]
+  run [
+    event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">3</span>:address:shared:programming-environment-data
+  ]
+  <span class="Comment"># no change</span>
+  screen-should-contain [
+   <span class="Constant"> .                              .</span>
+   <span class="Constant"> .               ┊━━━━━━━━━━━━━━.</span>
+   <span class="Constant"> .┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┊1            x.</span>
+   <span class="Constant"> .               ┊add 2, 2      .</span>
+   <span class="Constant"> .               ┊4             .</span>
+   <span class="Constant"> .               ┊━━━━━━━━━━━━━━.</span>
+   <span class="Constant"> .               ┊              .</span>
+   <span class="Constant"> .               ┊              .</span>
+  ]
+  <span class="Comment"># hit 'up'</span>
+  assume-console [
+    press up-arrow
+  ]
+  run [
+    event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">3</span>:address:shared:programming-environment-data
+  ]
+  <span class="Comment"># back to displaying both sandboxes without editor</span>
+  screen-should-contain [
+   <span class="Constant"> .                              .</span>
+   <span class="Constant"> .               ┊━━━━━━━━━━━━━━.</span>
+   <span class="Constant"> .┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┊0            x.</span>
+   <span class="Constant"> .               ┊add 1, 1      .</span>
+   <span class="Constant"> .               ┊2             .</span>
+   <span class="Constant"> .               ┊━━━━━━━━━━━━━━.</span>
+   <span class="Constant"> .               ┊1            x.</span>
+   <span class="Constant"> .               ┊add 2, 2      .</span>
+   <span class="Constant"> .               ┊4             .</span>
+   <span class="Constant"> .               ┊━━━━━━━━━━━━━━.</span>
+  ]
+  <span class="Comment"># hit 'up' again</span>
+  assume-console [
+    press up-arrow
+  ]
+  run [
+    event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">3</span>:address:shared:programming-environment-data
+    <span class="Constant">4</span>:character/cursor<span class="Special"> &lt;- </span>copy <span class="Constant">9251/␣</span>
+    print screen:address:shared:screen, <span class="Constant">4</span>:character/cursor
+  ]
+  <span class="Comment"># back to displaying both sandboxes as well as editor</span>
+  screen-should-contain [
+   <span class="Constant"> .                              .</span>
+   <span class="Constant"> .               ┊␣             .</span>
+<span class="Constant">    .┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┊━━━━━━━━━━━━━━.</span>
+   <span class="Constant"> .               ┊0            x.</span>
+   <span class="Constant"> .               ┊add 1, 1      .</span>
+   <span class="Constant"> .               ┊2             .</span>
+   <span class="Constant"> .               ┊━━━━━━━━━━━━━━.</span>
+   <span class="Constant"> .               ┊1            x.</span>
+   <span class="Constant"> .               ┊add 2, 2      .</span>
+   <span class="Constant"> .               ┊4             .</span>
+  ]
+  <span class="Comment"># hit 'up' again</span>
+  assume-console [
+    press up-arrow
+  ]
+  run [
+    event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">3</span>:address:shared:programming-environment-data
+  ]
+  <span class="Comment"># no change</span>
+  screen-should-contain [
+   <span class="Constant"> .                              .</span>
+   <span class="Constant"> .               ┊␣             .</span>
+<span class="Constant">    .┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┊━━━━━━━━━━━━━━.</span>
+   <span class="Constant"> .               ┊0            x.</span>
+   <span class="Constant"> .               ┊add 1, 1      .</span>
+   <span class="Constant"> .               ┊2             .</span>
+   <span class="Constant"> .               ┊━━━━━━━━━━━━━━.</span>
+   <span class="Constant"> .               ┊1            x.</span>
+   <span class="Constant"> .               ┊add 2, 2      .</span>
+   <span class="Constant"> .               ┊4             .</span>
+  ]
+]
+
+<span class="muScenario">scenario</span> scrolling-manages-sandbox-index-correctly [
+  trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
+  assume-screen <span class="Constant">30/width</span>, <span class="Constant">10/height</span>
+  <span class="Comment"># initialize environment</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
+  <span class="Constant">2</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
+  <span class="Constant">3</span>:address:shared:programming-environment-data<span class="Special"> &lt;- </span>new-programming-environment screen:address:shared:screen, <span class="Constant">1</span>:address:shared:array:character, <span class="Constant">2</span>:address:shared:array:character
+  render-all screen, <span class="Constant">3</span>:address:shared:programming-environment-data
+  <span class="Comment"># create a sandbox</span>
+  assume-console [
+    press ctrl-n
+    type <span class="Constant">[add 1, 1]</span>
+    press F4
+  ]
+  run [
+    event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">3</span>:address:shared:programming-environment-data
+  ]
+  screen-should-contain [
+   <span class="Constant"> .                              .</span>
+   <span class="Constant"> .               ┊              .</span>
+<span class="Constant">    .┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┊━━━━━━━━━━━━━━.</span>
+   <span class="Constant"> .               ┊0            x.</span>
+   <span class="Constant"> .               ┊add 1, 1      .</span>
+   <span class="Constant"> .               ┊2             .</span>
+   <span class="Constant"> .               ┊━━━━━━━━━━━━━━.</span>
+   <span class="Constant"> .               ┊              .</span>
+  ]
+  <span class="Comment"># hit 'down' and 'up' a couple of times. sandbox index should be stable</span>
+  assume-console [
+    press down-arrow
+  ]
+  run [
+    event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">3</span>:address:shared:programming-environment-data
+  ]
+  <span class="Comment"># sandbox editor hidden; first sandbox displayed</span>
+  <span class="Comment"># cursor moves to first sandbox</span>
+  screen-should-contain [
+   <span class="Constant"> .                              .</span>
+   <span class="Constant"> .               ┊━━━━━━━━━━━━━━.</span>
+   <span class="Constant"> .┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┊0            x.</span>
+   <span class="Constant"> .               ┊add 1, 1      .</span>
+   <span class="Constant"> .               ┊2             .</span>
+   <span class="Constant"> .               ┊━━━━━━━━━━━━━━.</span>
+   <span class="Constant"> .               ┊              .</span>
+  ]
+  <span class="Comment"># hit 'up' again</span>
+  assume-console [
+    press up-arrow
+  ]
+  run [
+    event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">3</span>:address:shared:programming-environment-data
+  ]
+  <span class="Comment"># back to displaying both sandboxes as well as editor</span>
+  screen-should-contain [
+   <span class="Constant"> .                              .</span>
+   <span class="Constant"> .               ┊              .</span>
+<span class="Constant">    .┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┊━━━━━━━━━━━━━━.</span>
+   <span class="Constant"> .               ┊0            x.</span>
+   <span class="Constant"> .               ┊add 1, 1      .</span>
+   <span class="Constant"> .               ┊2             .</span>
+   <span class="Constant"> .               ┊━━━━━━━━━━━━━━.</span>
+   <span class="Constant"> .               ┊              .</span>
+  ]
+  <span class="Comment"># hit 'down'</span>
+  assume-console [
+    press down-arrow
+  ]
+  run [
+    event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">3</span>:address:shared:programming-environment-data
+  ]
+  <span class="Comment"># sandbox editor hidden; first sandbox displayed</span>
+  <span class="Comment"># cursor moves to first sandbox</span>
+  screen-should-contain [
+   <span class="Constant"> .                              .</span>
+   <span class="Constant"> .               ┊━━━━━━━━━━━━━━.</span>
+   <span class="Constant"> .┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┊0            x.  # no change</span>
+   <span class="Constant"> .               ┊add 1, 1      .</span>
+   <span class="Constant"> .               ┊2             .</span>
+   <span class="Constant"> .               ┊━━━━━━━━━━━━━━.</span>
+   <span class="Constant"> .               ┊              .</span>
+  ]
+]
 </pre>
 </body>
 </html>
diff --git a/html/edit/006-sandbox-edit.mu.html b/html/edit/006-sandbox-edit.mu.html
index d902c4b7..a4830985 100644
--- a/html/edit/006-sandbox-edit.mu.html
+++ b/html/edit/006-sandbox-edit.mu.html
@@ -38,22 +38,22 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
   assume-screen <span class="Constant">40/width</span>, <span class="Constant">10/height</span>
   <span class="Comment"># basic recipe</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[ </span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[ </span>
 <span class="Constant">recipe foo [</span>
 <span class="Constant">  reply 4</span>
 <span class="Constant">]</span>]
   <span class="Comment"># run it</span>
-  <span class="Constant">2</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[foo]</span>
+  <span class="Constant">2</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[foo]</span>
   assume-console [
     press F4
   ]
-  <span class="Constant">3</span>:address:programming-environment-data<span class="Special"> &lt;- </span>new-programming-environment screen:address:screen, <span class="Constant">1</span>:address:array:character, <span class="Constant">2</span>:address:array:character
-  event-loop screen:address:screen, console:address:console, <span class="Constant">3</span>:address:programming-environment-data
+  <span class="Constant">3</span>:address:shared:programming-environment-data<span class="Special"> &lt;- </span>new-programming-environment screen:address:shared:screen, <span class="Constant">1</span>:address:shared:array:character, <span class="Constant">2</span>:address:shared:array:character
+  event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">3</span>:address:shared:programming-environment-data
   screen-should-contain [
    <span class="Constant"> .                     run (F4)           .</span>
    <span class="Constant"> .                    ┊                   .</span>
    <span class="Constant"> .recipe foo [        ┊━━━━━━━━━━━━━━━━━━━.</span>
-   <span class="Constant"> .  reply 4           ┊                  x.</span>
+   <span class="Constant"> .  reply 4           ┊0                 x.</span>
    <span class="Constant"> .]                   ┊foo                .</span>
    <span class="Constant"> .┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┊4                  .</span>
    <span class="Constant"> .                    ┊━━━━━━━━━━━━━━━━━━━.</span>
@@ -64,7 +64,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     left-click <span class="Constant">3</span>, <span class="Constant">30</span>
   ]
   run [
-    event-loop screen:address:screen, console:address:console, <span class="Constant">3</span>:address:programming-environment-data
+    event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">3</span>:address:shared:programming-environment-data
   ]
   <span class="Comment"># it pops back into editor</span>
   screen-should-contain [
@@ -82,7 +82,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     type <span class="Constant">[0]</span>
   ]
   run [
-    event-loop screen:address:screen, console:address:console, <span class="Constant">3</span>:address:programming-environment-data
+    event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">3</span>:address:shared:programming-environment-data
   ]
   screen-should-contain [
    <span class="Constant"> .                     run (F4)           .</span>
@@ -103,7 +103,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     click-column:number<span class="Special"> &lt;- </span>get *t, <span class="Constant">column:offset</span>
     on-sandbox-side?:boolean<span class="Special"> &lt;- </span>greater-or-equal click-column, sandbox-left-margin
     <span class="muControl">break-unless</span> on-sandbox-side?
-    first-sandbox:address:sandbox-data<span class="Special"> &lt;- </span>get *env, <span class="Constant">sandbox:offset</span>
+    first-sandbox:address:shared:sandbox-data<span class="Special"> &lt;- </span>get *env, <span class="Constant">sandbox:offset</span>
     <span class="muControl">break-unless</span> first-sandbox
     first-sandbox-begins:number<span class="Special"> &lt;- </span>get *first-sandbox, <span class="Constant">starting-row-on-screen:offset</span>
     click-row:number<span class="Special"> &lt;- </span>get *t, <span class="Constant">row:offset</span>
@@ -112,35 +112,37 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     empty-sandbox-editor?:boolean<span class="Special"> &lt;- </span>empty-editor? current-sandbox
     <span class="muControl">break-unless</span> empty-sandbox-editor?  <span class="Comment"># don't clobber existing contents</span>
     <span class="Comment"># identify the sandbox to edit and remove it from the sandbox list</span>
-    sandbox:address:sandbox-data<span class="Special"> &lt;- </span>extract-sandbox env, click-row
-    text:address:array:character<span class="Special"> &lt;- </span>get *sandbox, <span class="Constant">data:offset</span>
+    sandbox:address:shared:sandbox-data<span class="Special"> &lt;- </span>extract-sandbox env, click-row
+    <span class="muControl">break-unless</span> sandbox
+    text:address:shared:array:character<span class="Special"> &lt;- </span>get *sandbox, <span class="Constant">data:offset</span>
     current-sandbox<span class="Special"> &lt;- </span>insert-text current-sandbox, text
+    render-from:address:number<span class="Special"> &lt;- </span>get-address *env, <span class="Constant">render-from:offset</span>
+    *render-from<span class="Special"> &lt;- </span>copy <span class="Constant">-1</span>
     hide-screen screen
     screen<span class="Special"> &lt;- </span>render-sandbox-side screen, env
-    screen<span class="Special"> &lt;- </span>update-cursor screen, recipes, current-sandbox, *sandbox-in-focus?
+    screen<span class="Special"> &lt;- </span>update-cursor screen, recipes, current-sandbox, *sandbox-in-focus?, env
     show-screen screen
     <span class="muControl">loop</span> <span class="Constant">+next-event:label</span>
   <span class="Delimiter">}</span>
 ]
 
-<span class="muRecipe">recipe</span> empty-editor? editor:address:editor-data<span class="muRecipe"> -&gt; </span>result:boolean [
+<span class="muRecipe">recipe</span> empty-editor? editor:address:shared:editor-data<span class="muRecipe"> -&gt; </span>result:boolean [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
-  head:address:duplex-list:character<span class="Special"> &lt;- </span>get *editor, <span class="Constant">data:offset</span>
-  first:address:duplex-list:character<span class="Special"> &lt;- </span>next head
+  head:address:shared:duplex-list:character<span class="Special"> &lt;- </span>get *editor, <span class="Constant">data:offset</span>
+  first:address:shared:duplex-list:character<span class="Special"> &lt;- </span>next head
   result<span class="Special"> &lt;- </span>not first
 ]
 
-<span class="muRecipe">recipe</span> extract-sandbox env:address:programming-environment-data, click-row:number<span class="muRecipe"> -&gt; </span>result:address:sandbox-data, env:address:programming-environment-data [
+<span class="muRecipe">recipe</span> extract-sandbox env:address:shared:programming-environment-data, click-row:number<span class="muRecipe"> -&gt; </span>result:address:shared:sandbox-data, env:address:shared:programming-environment-data [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
-  <span class="Comment"># assert click-row &gt;= sandbox.starting-row-on-screen</span>
-  sandbox:address:address:sandbox-data<span class="Special"> &lt;- </span>get-address *env, <span class="Constant">sandbox:offset</span>
+  sandbox:address:address:shared:sandbox-data<span class="Special"> &lt;- </span>get-address *env, <span class="Constant">sandbox:offset</span>
   start:number<span class="Special"> &lt;- </span>get **sandbox, <span class="Constant">starting-row-on-screen:offset</span>
-  clicked-on-sandboxes?:boolean<span class="Special"> &lt;- </span>greater-or-equal click-row, start
-  assert clicked-on-sandboxes?, <span class="Constant">[extract-sandbox called on click to sandbox editor]</span>
+  in-editor?:boolean<span class="Special"> &lt;- </span>lesser-than click-row, start
+  <span class="muControl">reply-if</span> in-editor?, <span class="Constant">0</span>
   <span class="Delimiter">{</span>
-    next-sandbox:address:sandbox-data<span class="Special"> &lt;- </span>get **sandbox, <span class="Constant">next-sandbox:offset</span>
+    next-sandbox:address:shared:sandbox-data<span class="Special"> &lt;- </span>get **sandbox, <span class="Constant">next-sandbox:offset</span>
     <span class="muControl">break-unless</span> next-sandbox
     <span class="Comment"># if click-row &lt; sandbox.next-sandbox.starting-row-on-screen, break</span>
     next-start:number<span class="Special"> &lt;- </span>get *next-sandbox, <span class="Constant">starting-row-on-screen:offset</span>
@@ -152,6 +154,9 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   <span class="Comment"># snip sandbox out of its list</span>
   result<span class="Special"> &lt;- </span>copy *sandbox
   *sandbox<span class="Special"> &lt;- </span>copy next-sandbox
+  <span class="Comment"># update sandbox count</span>
+  sandbox-count:address:number<span class="Special"> &lt;- </span>get-address *env, <span class="Constant">number-of-sandboxes:offset</span>
+  *sandbox-count<span class="Special"> &lt;- </span>subtract *sandbox-count, <span class="Constant">1</span>
   <span class="Comment"># position cursor in sandbox editor</span>
   sandbox-in-focus?:address:boolean<span class="Special"> &lt;- </span>get-address *env, <span class="Constant">sandbox-in-focus?:offset</span>
   *sandbox-in-focus?<span class="Special"> &lt;- </span>copy <span class="Constant">1/true</span>
@@ -161,20 +166,20 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
   assume-screen <span class="Constant">100/width</span>, <span class="Constant">20/height</span>
   <span class="Comment"># left editor is empty</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
   <span class="Comment"># right editor contains an instruction</span>
-  <span class="Constant">2</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[print-integer screen, 4]</span>
-  <span class="Constant">3</span>:address:programming-environment-data<span class="Special"> &lt;- </span>new-programming-environment screen:address:screen, <span class="Constant">1</span>:address:array:character, <span class="Constant">2</span>:address:array:character
+  <span class="Constant">2</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[print-integer screen, 4]</span>
+  <span class="Constant">3</span>:address:shared:programming-environment-data<span class="Special"> &lt;- </span>new-programming-environment screen:address:shared:screen, <span class="Constant">1</span>:address:shared:array:character, <span class="Constant">2</span>:address:shared:array:character
   <span class="Comment"># run the sandbox</span>
   assume-console [
     press F4
   ]
-  event-loop screen:address:screen, console:address:console, <span class="Constant">3</span>:address:programming-environment-data
+  event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">3</span>:address:shared:programming-environment-data
   screen-should-contain [
    <span class="Constant"> .                                                                                 run (F4)           .</span>
    <span class="Constant"> .                                                  ┊                                                 .</span>
 <span class="Constant">    .┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┊━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━.</span>
-   <span class="Constant"> .                                                  ┊                                                x.</span>
+   <span class="Constant"> .                                                  ┊0                                               x.</span>
    <span class="Constant"> .                                                  ┊print-integer screen, 4                          .</span>
    <span class="Constant"> .                                                  ┊screen:                                          .</span>
    <span class="Constant"> .                                                  ┊  .4                             .               .</span>
@@ -190,7 +195,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     left-click <span class="Constant">3</span>, <span class="Constant">70</span>
   ]
   run [
-    event-loop screen:address:screen, console:address:console, <span class="Constant">3</span>:address:programming-environment-data
+    event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">3</span>:address:shared:programming-environment-data
   ]
   screen-should-contain [
    <span class="Constant"> .                                                                                 run (F4)           .</span>
@@ -200,6 +205,125 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
    <span class="Constant"> .                                                  ┊                                                 .</span>
   ]
 ]
+
+<span class="muScenario">scenario</span> editing-sandbox-after-scrolling-resets-scroll [
+  trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
+  assume-screen <span class="Constant">30/width</span>, <span class="Constant">10/height</span>
+  <span class="Comment"># initialize environment</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
+  <span class="Constant">2</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
+  <span class="Constant">3</span>:address:shared:programming-environment-data<span class="Special"> &lt;- </span>new-programming-environment screen:address:shared:screen, <span class="Constant">1</span>:address:shared:array:character, <span class="Constant">2</span>:address:shared:array:character
+  render-all screen, <span class="Constant">3</span>:address:shared:programming-environment-data
+  <span class="Comment"># create 2 sandboxes and scroll to second</span>
+  assume-console [
+    press ctrl-n
+    type <span class="Constant">[add 2, 2]</span>
+    press F4
+    type <span class="Constant">[add 1, 1]</span>
+    press F4
+    press down-arrow
+    press down-arrow
+  ]
+  run [
+    event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">3</span>:address:shared:programming-environment-data
+  ]
+  screen-should-contain [
+   <span class="Constant"> .                              .</span>
+   <span class="Constant"> .               ┊━━━━━━━━━━━━━━.</span>
+   <span class="Constant"> .┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┊1            x.</span>
+   <span class="Constant"> .               ┊add 2, 2      .</span>
+   <span class="Constant"> .               ┊4             .</span>
+   <span class="Constant"> .               ┊━━━━━━━━━━━━━━.</span>
+   <span class="Constant"> .               ┊              .</span>
+  ]
+  <span class="Comment"># edit the second sandbox</span>
+  assume-console [
+    left-click <span class="Constant">2</span>, <span class="Constant">20</span>
+  ]
+  run [
+    event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">3</span>:address:shared:programming-environment-data
+  ]
+  <span class="Comment"># second sandbox shows in editor; scroll resets to display first sandbox</span>
+  screen-should-contain [
+   <span class="Constant"> .                              .</span>
+   <span class="Constant"> .               ┊add 2, 2      .</span>
+<span class="Constant">    .┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┊━━━━━━━━━━━━━━.</span>
+   <span class="Constant"> .               ┊0            x.</span>
+   <span class="Constant"> .               ┊add 1, 1      .</span>
+   <span class="Constant"> .               ┊2             .</span>
+   <span class="Constant"> .               ┊━━━━━━━━━━━━━━.</span>
+   <span class="Constant"> .               ┊              .</span>
+  ]
+]
+
+<span class="muScenario">scenario</span> editing-sandbox-updates-sandbox-count [
+  trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
+  assume-screen <span class="Constant">30/width</span>, <span class="Constant">10/height</span>
+  <span class="Comment"># initialize environment</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
+  <span class="Constant">2</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
+  <span class="Constant">3</span>:address:shared:programming-environment-data<span class="Special"> &lt;- </span>new-programming-environment screen:address:shared:screen, <span class="Constant">1</span>:address:shared:array:character, <span class="Constant">2</span>:address:shared:array:character
+  render-all screen, <span class="Constant">3</span>:address:shared:programming-environment-data
+  <span class="Comment"># create 2 sandboxes</span>
+  assume-console [
+    press ctrl-n
+    type <span class="Constant">[add 2, 2]</span>
+    press F4
+    type <span class="Constant">[add 1, 1]</span>
+    press F4
+  ]
+  run [
+    event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">3</span>:address:shared:programming-environment-data
+  ]
+  screen-should-contain [
+   <span class="Constant"> .                              .</span>
+   <span class="Constant"> .               ┊              .</span>
+<span class="Constant">    .┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┊━━━━━━━━━━━━━━.</span>
+   <span class="Constant"> .               ┊0            x.</span>
+   <span class="Constant"> .               ┊add 1, 1      .</span>
+   <span class="Constant"> .               ┊2             .</span>
+   <span class="Constant"> .               ┊━━━━━━━━━━━━━━.</span>
+   <span class="Constant"> .               ┊1            x.</span>
+  ]
+  <span class="Comment"># edit the second sandbox, then resave</span>
+  assume-console [
+    left-click <span class="Constant">3</span>, <span class="Constant">20</span>
+    press F4
+  ]
+  run [
+    event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">3</span>:address:shared:programming-environment-data
+  ]
+  <span class="Comment"># no change in contents</span>
+  screen-should-contain [
+   <span class="Constant"> .                              .</span>
+   <span class="Constant"> .               ┊              .</span>
+<span class="Constant">    .┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┊━━━━━━━━━━━━━━.</span>
+   <span class="Constant"> .               ┊0            x.</span>
+   <span class="Constant"> .               ┊add 1, 1      .</span>
+   <span class="Constant"> .               ┊2             .</span>
+   <span class="Constant"> .               ┊━━━━━━━━━━━━━━.</span>
+   <span class="Constant"> .               ┊1            x.</span>
+  ]
+  <span class="Comment"># now try to scroll past end</span>
+  assume-console [
+    press down-arrow
+    press down-arrow
+    press down-arrow
+  ]
+  run [
+    event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">3</span>:address:shared:programming-environment-data
+  ]
+  <span class="Comment"># screen should show just final sandbox</span>
+  screen-should-contain [
+   <span class="Constant"> .                              .</span>
+   <span class="Constant"> .               ┊━━━━━━━━━━━━━━.</span>
+   <span class="Constant"> .┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┊1            x.</span>
+   <span class="Constant"> .               ┊add 2, 2      .</span>
+   <span class="Constant"> .               ┊4             .</span>
+   <span class="Constant"> .               ┊━━━━━━━━━━━━━━.</span>
+   <span class="Constant"> .               ┊              .</span>
+  ]
+]
 </pre>
 </body>
 </html>
diff --git a/html/edit/007-sandbox-delete.mu.html b/html/edit/007-sandbox-delete.mu.html
index 6d289afa..b88de17f 100644
--- a/html/edit/007-sandbox-delete.mu.html
+++ b/html/edit/007-sandbox-delete.mu.html
@@ -37,9 +37,9 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="muScenario">scenario</span> deleting-sandboxes [
   trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
   assume-screen <span class="Constant">100/width</span>, <span class="Constant">15/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
-  <span class="Constant">2</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
-  <span class="Constant">3</span>:address:programming-environment-data<span class="Special"> &lt;- </span>new-programming-environment screen:address:screen, <span class="Constant">1</span>:address:array:character, <span class="Constant">2</span>:address:array:character
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
+  <span class="Constant">2</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
+  <span class="Constant">3</span>:address:shared:programming-environment-data<span class="Special"> &lt;- </span>new-programming-environment screen:address:shared:screen, <span class="Constant">1</span>:address:shared:array:character, <span class="Constant">2</span>:address:shared:array:character
   <span class="Comment"># run a few commands</span>
   assume-console [
     left-click <span class="Constant">1</span>, <span class="Constant">80</span>
@@ -48,16 +48,16 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     type <span class="Constant">[add 2, 2]</span>
     press F4
   ]
-  event-loop screen:address:screen, console:address:console, <span class="Constant">3</span>:address:programming-environment-data
+  event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">3</span>:address:shared:programming-environment-data
   screen-should-contain [
    <span class="Constant"> .                                                                                 run (F4)           .</span>
    <span class="Constant"> .                                                  ┊                                                 .</span>
 <span class="Constant">    .┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┊━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━.</span>
-   <span class="Constant"> .                                                  ┊                                                x.</span>
+   <span class="Constant"> .                                                  ┊0                                               x.</span>
    <span class="Constant"> .                                                  ┊add 2, 2                                         .</span>
    <span class="Constant"> .                                                  ┊4                                                .</span>
    <span class="Constant"> .                                                  ┊━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━.</span>
-   <span class="Constant"> .                                                  ┊                                                x.</span>
+   <span class="Constant"> .                                                  ┊1                                               x.</span>
    <span class="Constant"> .                                                  ┊divide-with-remainder 11, 3                      .</span>
    <span class="Constant"> .                                                  ┊3                                                .</span>
    <span class="Constant"> .                                                  ┊2                                                .</span>
@@ -69,13 +69,13 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     left-click <span class="Constant">7</span>, <span class="Constant">99</span>
   ]
   run [
-    event-loop screen:address:screen, console:address:console, <span class="Constant">3</span>:address:programming-environment-data
+    event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">3</span>:address:shared:programming-environment-data
   ]
   screen-should-contain [
    <span class="Constant"> .                                                                                 run (F4)           .</span>
    <span class="Constant"> .                                                  ┊                                                 .</span>
 <span class="Constant">    .┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┊━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━.</span>
-   <span class="Constant"> .                                                  ┊                                                x.</span>
+   <span class="Constant"> .                                                  ┊0                                               x.</span>
    <span class="Constant"> .                                                  ┊add 2, 2                                         .</span>
    <span class="Constant"> .                                                  ┊4                                                .</span>
    <span class="Constant"> .                                                  ┊━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━.</span>
@@ -87,7 +87,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     left-click <span class="Constant">3</span>, <span class="Constant">99</span>
   ]
   run [
-    event-loop screen:address:screen, console:address:console, <span class="Constant">3</span>:address:programming-environment-data
+    event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">3</span>:address:shared:programming-environment-data
   ]
   screen-should-contain [
    <span class="Constant"> .                                                                                 run (F4)           .</span>
@@ -105,23 +105,23 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     <span class="muControl">break-unless</span> was-delete?
     hide-screen screen
     screen<span class="Special"> &lt;- </span>render-sandbox-side screen, env
-    screen<span class="Special"> &lt;- </span>update-cursor screen, recipes, current-sandbox, *sandbox-in-focus?
+    screen<span class="Special"> &lt;- </span>update-cursor screen, recipes, current-sandbox, *sandbox-in-focus?, env
     show-screen screen
     <span class="muControl">loop</span> <span class="Constant">+next-event:label</span>
   <span class="Delimiter">}</span>
 ]
 
-<span class="muRecipe">recipe</span> delete-sandbox t:touch-event, env:address:programming-environment-data<span class="muRecipe"> -&gt; </span>was-delete?:boolean, env:address:programming-environment-data [
+<span class="muRecipe">recipe</span> delete-sandbox t:touch-event, env:address:shared:programming-environment-data<span class="muRecipe"> -&gt; </span>was-delete?:boolean, env:address:shared:programming-environment-data [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   click-column:number<span class="Special"> &lt;- </span>get t, <span class="Constant">column:offset</span>
-  current-sandbox:address:editor-data<span class="Special"> &lt;- </span>get *env, <span class="Constant">current-sandbox:offset</span>
+  current-sandbox:address:shared:editor-data<span class="Special"> &lt;- </span>get *env, <span class="Constant">current-sandbox:offset</span>
   right:number<span class="Special"> &lt;- </span>get *current-sandbox, <span class="Constant">right:offset</span>
   at-right?:boolean<span class="Special"> &lt;- </span>equal click-column, right
   <span class="muControl">reply-unless</span> at-right?, <span class="Constant">0/false</span>
   click-row:number<span class="Special"> &lt;- </span>get t, <span class="Constant">row:offset</span>
-  prev:address:address:sandbox-data<span class="Special"> &lt;- </span>get-address *env, <span class="Constant">sandbox:offset</span>
-  curr:address:sandbox-data<span class="Special"> &lt;- </span>get *env, <span class="Constant">sandbox:offset</span>
+  prev:address:address:shared:sandbox-data<span class="Special"> &lt;- </span>get-address *env, <span class="Constant">sandbox:offset</span>
+  curr:address:shared:sandbox-data<span class="Special"> &lt;- </span>get *env, <span class="Constant">sandbox:offset</span>
   <span class="Delimiter">{</span>
     <span class="muControl">break-unless</span> curr
     <span class="Comment"># more sandboxes to check</span>
@@ -129,9 +129,20 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
       target-row:number<span class="Special"> &lt;- </span>get *curr, <span class="Constant">starting-row-on-screen:offset</span>
       delete-curr?:boolean<span class="Special"> &lt;- </span>equal target-row, click-row
       <span class="muControl">break-unless</span> delete-curr?
-      <span class="Comment"># delete this sandbox, rerender and stop</span>
+      <span class="Comment"># delete this sandbox</span>
       *prev<span class="Special"> &lt;- </span>get *curr, <span class="Constant">next-sandbox:offset</span>
-      <span class="muControl">reply</span> <span class="Constant">1/true</span>
+      <span class="Comment"># update sandbox count</span>
+      sandbox-count:address:number<span class="Special"> &lt;- </span>get-address *env, <span class="Constant">number-of-sandboxes:offset</span>
+      *sandbox-count<span class="Special"> &lt;- </span>subtract *sandbox-count, <span class="Constant">1</span>
+      <span class="Comment"># if it's the last sandbox and if it was the only sandbox rendered, reset scroll</span>
+      <span class="Delimiter">{</span>
+        <span class="muControl">break-if</span> *prev
+        render-from:address:number<span class="Special"> &lt;- </span>get-address *env, <span class="Constant">render-from:offset</span>
+        reset-scroll?:boolean<span class="Special"> &lt;- </span>equal *render-from, *sandbox-count
+        <span class="muControl">break-unless</span> reset-scroll?
+        *render-from<span class="Special"> &lt;- </span>copy <span class="Constant">-1</span>
+      <span class="Delimiter">}</span>
+      <span class="muControl">reply</span> <span class="Constant">1/true</span>  <span class="Comment"># force rerender</span>
     <span class="Delimiter">}</span>
     prev<span class="Special"> &lt;- </span>get-address *curr, <span class="Constant">next-sandbox:offset</span>
     curr<span class="Special"> &lt;- </span>get *curr, <span class="Constant">next-sandbox:offset</span>
@@ -139,6 +150,204 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   <span class="Delimiter">}</span>
   <span class="muControl">reply</span> <span class="Constant">0/false</span>
 ]
+
+<span class="muScenario">scenario</span> deleting-sandbox-after-scroll [
+  trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
+  assume-screen <span class="Constant">30/width</span>, <span class="Constant">10/height</span>
+  <span class="Comment"># initialize environment</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
+  <span class="Constant">2</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
+  <span class="Constant">3</span>:address:shared:programming-environment-data<span class="Special"> &lt;- </span>new-programming-environment screen:address:shared:screen, <span class="Constant">1</span>:address:shared:array:character, <span class="Constant">2</span>:address:shared:array:character
+  render-all screen, <span class="Constant">3</span>:address:shared:programming-environment-data
+  <span class="Comment"># create 2 sandboxes and scroll to second</span>
+  assume-console [
+    press ctrl-n
+    type <span class="Constant">[add 2, 2]</span>
+    press F4
+    type <span class="Constant">[add 1, 1]</span>
+    press F4
+    press down-arrow
+  ]
+  run [
+    event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">3</span>:address:shared:programming-environment-data
+  ]
+  screen-should-contain [
+   <span class="Constant"> .                              .</span>
+   <span class="Constant"> .               ┊━━━━━━━━━━━━━━.</span>
+   <span class="Constant"> .┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┊0            x.</span>
+   <span class="Constant"> .               ┊add 1, 1      .</span>
+   <span class="Constant"> .               ┊2             .</span>
+   <span class="Constant"> .               ┊━━━━━━━━━━━━━━.</span>
+   <span class="Constant"> .               ┊1            x.</span>
+  ]
+  <span class="Comment"># delete the second sandbox</span>
+  assume-console [
+    left-click <span class="Constant">6</span>, <span class="Constant">29</span>
+  ]
+  run [
+    event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">3</span>:address:shared:programming-environment-data
+  ]
+  <span class="Comment"># second sandbox shows in editor; scroll resets to display first sandbox</span>
+  screen-should-contain [
+   <span class="Constant"> .                              .</span>
+   <span class="Constant"> .               ┊━━━━━━━━━━━━━━.</span>
+   <span class="Constant"> .┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┊0            x.</span>
+   <span class="Constant"> .               ┊add 1, 1      .</span>
+   <span class="Constant"> .               ┊2             .</span>
+   <span class="Constant"> .               ┊━━━━━━━━━━━━━━.</span>
+   <span class="Constant"> .               ┊              .</span>
+  ]
+]
+
+<span class="muScenario">scenario</span> deleting-top-sandbox-after-scroll [
+  trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
+  assume-screen <span class="Constant">30/width</span>, <span class="Constant">10/height</span>
+  <span class="Comment"># initialize environment</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
+  <span class="Constant">2</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
+  <span class="Constant">3</span>:address:shared:programming-environment-data<span class="Special"> &lt;- </span>new-programming-environment screen:address:shared:screen, <span class="Constant">1</span>:address:shared:array:character, <span class="Constant">2</span>:address:shared:array:character
+  render-all screen, <span class="Constant">3</span>:address:shared:programming-environment-data
+  <span class="Comment"># create 2 sandboxes and scroll to second</span>
+  assume-console [
+    press ctrl-n
+    type <span class="Constant">[add 2, 2]</span>
+    press F4
+    type <span class="Constant">[add 1, 1]</span>
+    press F4
+    press down-arrow
+  ]
+  run [
+    event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">3</span>:address:shared:programming-environment-data
+  ]
+  screen-should-contain [
+   <span class="Constant"> .                              .</span>
+   <span class="Constant"> .               ┊━━━━━━━━━━━━━━.</span>
+   <span class="Constant"> .┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┊0            x.</span>
+   <span class="Constant"> .               ┊add 1, 1      .</span>
+   <span class="Constant"> .               ┊2             .</span>
+   <span class="Constant"> .               ┊━━━━━━━━━━━━━━.</span>
+   <span class="Constant"> .               ┊1            x.</span>
+  ]
+  <span class="Comment"># delete the second sandbox</span>
+  assume-console [
+    left-click <span class="Constant">2</span>, <span class="Constant">29</span>
+  ]
+  run [
+    event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">3</span>:address:shared:programming-environment-data
+  ]
+  <span class="Comment"># second sandbox shows in editor; scroll resets to display first sandbox</span>
+  screen-should-contain [
+   <span class="Constant"> .                              .</span>
+   <span class="Constant"> .               ┊━━━━━━━━━━━━━━.</span>
+   <span class="Constant"> .┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┊0            x.</span>
+   <span class="Constant"> .               ┊add 2, 2      .</span>
+   <span class="Constant"> .               ┊4             .</span>
+   <span class="Constant"> .               ┊━━━━━━━━━━━━━━.</span>
+   <span class="Constant"> .               ┊              .</span>
+  ]
+]
+
+<span class="muScenario">scenario</span> deleting-final-sandbox-after-scroll [
+  trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
+  assume-screen <span class="Constant">30/width</span>, <span class="Constant">10/height</span>
+  <span class="Comment"># initialize environment</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
+  <span class="Constant">2</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
+  <span class="Constant">3</span>:address:shared:programming-environment-data<span class="Special"> &lt;- </span>new-programming-environment screen:address:shared:screen, <span class="Constant">1</span>:address:shared:array:character, <span class="Constant">2</span>:address:shared:array:character
+  render-all screen, <span class="Constant">3</span>:address:shared:programming-environment-data
+  <span class="Comment"># create 2 sandboxes and scroll to second</span>
+  assume-console [
+    press ctrl-n
+    type <span class="Constant">[add 2, 2]</span>
+    press F4
+    type <span class="Constant">[add 1, 1]</span>
+    press F4
+    press down-arrow
+    press down-arrow
+  ]
+  run [
+    event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">3</span>:address:shared:programming-environment-data
+  ]
+  screen-should-contain [
+   <span class="Constant"> .                              .</span>
+   <span class="Constant"> .               ┊━━━━━━━━━━━━━━.</span>
+   <span class="Constant"> .┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┊1            x.</span>
+   <span class="Constant"> .               ┊add 2, 2      .</span>
+   <span class="Constant"> .               ┊4             .</span>
+   <span class="Constant"> .               ┊━━━━━━━━━━━━━━.</span>
+   <span class="Constant"> .               ┊              .</span>
+  ]
+  <span class="Comment"># delete the second sandbox</span>
+  assume-console [
+    left-click <span class="Constant">2</span>, <span class="Constant">29</span>
+  ]
+  run [
+    event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">3</span>:address:shared:programming-environment-data
+  ]
+  <span class="Comment"># implicitly scroll up to first sandbox</span>
+  screen-should-contain [
+   <span class="Constant"> .                              .</span>
+   <span class="Constant"> .               ┊              .</span>
+<span class="Constant">    .┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┊━━━━━━━━━━━━━━.</span>
+   <span class="Constant"> .               ┊0            x.</span>
+   <span class="Constant"> .               ┊add 1, 1      .</span>
+   <span class="Constant"> .               ┊2             .</span>
+   <span class="Constant"> .               ┊━━━━━━━━━━━━━━.</span>
+   <span class="Constant"> .               ┊              .</span>
+  ]
+]
+
+<span class="muScenario">scenario</span> deleting-updates-sandbox-count [
+  trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
+  assume-screen <span class="Constant">30/width</span>, <span class="Constant">10/height</span>
+  <span class="Comment"># initialize environment</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
+  <span class="Constant">2</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
+  <span class="Constant">3</span>:address:shared:programming-environment-data<span class="Special"> &lt;- </span>new-programming-environment screen:address:shared:screen, <span class="Constant">1</span>:address:shared:array:character, <span class="Constant">2</span>:address:shared:array:character
+  render-all screen, <span class="Constant">3</span>:address:shared:programming-environment-data
+  <span class="Comment"># create 2 sandboxes</span>
+  assume-console [
+    press ctrl-n
+    type <span class="Constant">[add 2, 2]</span>
+    press F4
+    type <span class="Constant">[add 1, 1]</span>
+    press F4
+  ]
+  run [
+    event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">3</span>:address:shared:programming-environment-data
+  ]
+  screen-should-contain [
+   <span class="Constant"> .                              .</span>
+   <span class="Constant"> .               ┊              .</span>
+<span class="Constant">    .┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┊━━━━━━━━━━━━━━.</span>
+   <span class="Constant"> .               ┊0            x.</span>
+   <span class="Constant"> .               ┊add 1, 1      .</span>
+   <span class="Constant"> .               ┊2             .</span>
+   <span class="Constant"> .               ┊━━━━━━━━━━━━━━.</span>
+   <span class="Constant"> .               ┊1            x.</span>
+   <span class="Constant"> .               ┊add 2, 2      .</span>
+   <span class="Constant"> .               ┊4             .</span>
+  ]
+  <span class="Comment"># delete the second sandbox, then try to scroll down twice</span>
+  assume-console [
+    left-click <span class="Constant">3</span>, <span class="Constant">29</span>
+    press down-arrow
+    press down-arrow
+  ]
+  run [
+    event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">3</span>:address:shared:programming-environment-data
+  ]
+  <span class="Comment"># shouldn't go past last sandbox</span>
+  screen-should-contain [
+   <span class="Constant"> .                              .</span>
+   <span class="Constant"> .               ┊━━━━━━━━━━━━━━.</span>
+   <span class="Constant"> .┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┊0            x.</span>
+   <span class="Constant"> .               ┊add 2, 2      .</span>
+   <span class="Constant"> .               ┊4             .</span>
+   <span class="Constant"> .               ┊━━━━━━━━━━━━━━.</span>
+   <span class="Constant"> .               ┊              .</span>
+  ]
+]
 </pre>
 </body>
 </html>
diff --git a/html/edit/008-sandbox-test.mu.html b/html/edit/008-sandbox-test.mu.html
index bdf918e8..d5dbcfcb 100644
--- a/html/edit/008-sandbox-test.mu.html
+++ b/html/edit/008-sandbox-test.mu.html
@@ -38,22 +38,22 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
   assume-screen <span class="Constant">40/width</span>, <span class="Constant">10/height</span>
   <span class="Comment"># basic recipe</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[ </span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[ </span>
 <span class="Constant">recipe foo [</span>
 <span class="Constant">  reply 4</span>
 <span class="Constant">]</span>]
   <span class="Comment"># run it</span>
-  <span class="Constant">2</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[foo]</span>
+  <span class="Constant">2</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[foo]</span>
   assume-console [
     press F4
   ]
-  <span class="Constant">3</span>:address:programming-environment-data<span class="Special"> &lt;- </span>new-programming-environment screen:address:screen, <span class="Constant">1</span>:address:array:character, <span class="Constant">2</span>:address:array:character
-  event-loop screen:address:screen, console:address:console, <span class="Constant">3</span>:address:programming-environment-data
+  <span class="Constant">3</span>:address:shared:programming-environment-data<span class="Special"> &lt;- </span>new-programming-environment screen:address:shared:screen, <span class="Constant">1</span>:address:shared:array:character, <span class="Constant">2</span>:address:shared:array:character
+  event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">3</span>:address:shared:programming-environment-data
   screen-should-contain [
    <span class="Constant"> .                     run (F4)           .</span>
    <span class="Constant"> .                    ┊                   .</span>
    <span class="Constant"> .recipe foo [        ┊━━━━━━━━━━━━━━━━━━━.</span>
-   <span class="Constant"> .  reply 4           ┊                  x.</span>
+   <span class="Constant"> .  reply 4           ┊0                 x.</span>
    <span class="Constant"> .]                   ┊foo                .</span>
    <span class="Constant"> .┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┊4                  .</span>
    <span class="Constant"> .                    ┊━━━━━━━━━━━━━━━━━━━.</span>
@@ -64,7 +64,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     left-click <span class="Constant">5</span>, <span class="Constant">21</span>
   ]
   run [
-    event-loop screen:address:screen, console:address:console, <span class="Constant">3</span>:address:programming-environment-data
+    event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">3</span>:address:shared:programming-environment-data
   ]
   <span class="Comment"># color toggles to green</span>
   screen-should-contain-in-color <span class="Constant">2/green</span>, [
@@ -79,13 +79,14 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   ]
   <span class="Comment"># cursor should remain unmoved</span>
   run [
-    print screen:address:screen, <span class="Constant">9251/␣/cursor</span>
+    <span class="Constant">4</span>:character/cursor<span class="Special"> &lt;- </span>copy <span class="Constant">9251/␣</span>
+    print screen:address:shared:screen, <span class="Constant">4</span>:character/cursor
   ]
   screen-should-contain [
    <span class="Constant"> .                     run (F4)           .</span>
    <span class="Constant"> .␣                   ┊                   .</span>
    <span class="Constant"> .recipe foo [        ┊━━━━━━━━━━━━━━━━━━━.</span>
-   <span class="Constant"> .  reply 4           ┊                  x.</span>
+   <span class="Constant"> .  reply 4           ┊0                 x.</span>
    <span class="Constant"> .]                   ┊foo                .</span>
    <span class="Constant"> .┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┊4                  .</span>
    <span class="Constant"> .                    ┊━━━━━━━━━━━━━━━━━━━.</span>
@@ -100,7 +101,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     press F4
   ]
   run [
-    event-loop screen:address:screen, console:address:console, <span class="Constant">3</span>:address:programming-environment-data
+    event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">3</span>:address:shared:programming-environment-data
   ]
   <span class="Comment"># result turns red</span>
   screen-should-contain-in-color <span class="Constant">1/red</span>, [
@@ -123,38 +124,38 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     click-column:number<span class="Special"> &lt;- </span>get *t, <span class="Constant">column:offset</span>
     on-sandbox-side?:boolean<span class="Special"> &lt;- </span>greater-or-equal click-column, sandbox-left-margin
     <span class="muControl">break-unless</span> on-sandbox-side?
-    first-sandbox:address:sandbox-data<span class="Special"> &lt;- </span>get *env, <span class="Constant">sandbox:offset</span>
+    first-sandbox:address:shared:sandbox-data<span class="Special"> &lt;- </span>get *env, <span class="Constant">sandbox:offset</span>
     <span class="muControl">break-unless</span> first-sandbox
     first-sandbox-begins:number<span class="Special"> &lt;- </span>get *first-sandbox, <span class="Constant">starting-row-on-screen:offset</span>
     click-row:number<span class="Special"> &lt;- </span>get *t, <span class="Constant">row:offset</span>
     below-sandbox-editor?:boolean<span class="Special"> &lt;- </span>greater-or-equal click-row, first-sandbox-begins
     <span class="muControl">break-unless</span> below-sandbox-editor?
     <span class="Comment"># identify the sandbox whose output is being clicked on</span>
-    sandbox:address:sandbox-data<span class="Special"> &lt;- </span>find-click-in-sandbox-output env, click-row
+    sandbox:address:shared:sandbox-data<span class="Special"> &lt;- </span>find-click-in-sandbox-output env, click-row
     <span class="muControl">break-unless</span> sandbox
     <span class="Comment"># toggle its expected-response, and save session</span>
     sandbox<span class="Special"> &lt;- </span>toggle-expected-response sandbox
     save-sandboxes env
     hide-screen screen
     screen<span class="Special"> &lt;- </span>render-sandbox-side screen, env, <span class="Constant">1/clear</span>
-    screen<span class="Special"> &lt;- </span>update-cursor screen, recipes, current-sandbox, *sandbox-in-focus?
+    screen<span class="Special"> &lt;- </span>update-cursor screen, recipes, current-sandbox, *sandbox-in-focus?, env
     <span class="Comment"># no change in cursor</span>
     show-screen screen
     <span class="muControl">loop</span> <span class="Constant">+next-event:label</span>
   <span class="Delimiter">}</span>
 ]
 
-<span class="muRecipe">recipe</span> find-click-in-sandbox-output env:address:programming-environment-data, click-row:number<span class="muRecipe"> -&gt; </span>sandbox:address:sandbox-data [
+<span class="muRecipe">recipe</span> find-click-in-sandbox-output env:address:shared:programming-environment-data, click-row:number<span class="muRecipe"> -&gt; </span>sandbox:address:shared:sandbox-data [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   <span class="Comment"># assert click-row &gt;= sandbox.starting-row-on-screen</span>
-  sandbox:address:sandbox-data<span class="Special"> &lt;- </span>get *env, <span class="Constant">sandbox:offset</span>
+  sandbox:address:shared:sandbox-data<span class="Special"> &lt;- </span>get *env, <span class="Constant">sandbox:offset</span>
   start:number<span class="Special"> &lt;- </span>get *sandbox, <span class="Constant">starting-row-on-screen:offset</span>
   clicked-on-sandboxes?:boolean<span class="Special"> &lt;- </span>greater-or-equal click-row, start
   assert clicked-on-sandboxes?, <span class="Constant">[extract-sandbox called on click to sandbox editor]</span>
   <span class="Comment"># while click-row &lt; sandbox.next-sandbox.starting-row-on-screen</span>
   <span class="Delimiter">{</span>
-    next-sandbox:address:sandbox-data<span class="Special"> &lt;- </span>get *sandbox, <span class="Constant">next-sandbox:offset</span>
+    next-sandbox:address:shared:sandbox-data<span class="Special"> &lt;- </span>get *sandbox, <span class="Constant">next-sandbox:offset</span>
     <span class="muControl">break-unless</span> next-sandbox
     next-start:number<span class="Special"> &lt;- </span>get *next-sandbox, <span class="Constant">starting-row-on-screen:offset</span>
     found?:boolean<span class="Special"> &lt;- </span>lesser-than click-row, next-start
@@ -170,10 +171,10 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   <span class="muControl">reply</span> sandbox
 ]
 
-<span class="muRecipe">recipe</span> toggle-expected-response sandbox:address:sandbox-data<span class="muRecipe"> -&gt; </span>sandbox:address:sandbox-data [
+<span class="muRecipe">recipe</span> toggle-expected-response sandbox:address:shared:sandbox-data<span class="muRecipe"> -&gt; </span>sandbox:address:shared:sandbox-data [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
-  expected-response:address:address:array:character<span class="Special"> &lt;- </span>get-address *sandbox, <span class="Constant">expected-response:offset</span>
+  expected-response:address:address:shared:array:character<span class="Special"> &lt;- </span>get-address *sandbox, <span class="Constant">expected-response:offset</span>
   <span class="Delimiter">{</span>
     <span class="Comment"># if expected-response is set, reset</span>
     <span class="muControl">break-unless</span> *expected-response
@@ -181,7 +182,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     <span class="muControl">reply</span> sandbox/same-as-ingredient:<span class="Constant">0</span>
   <span class="Delimiter">}</span>
   <span class="Comment"># if not, current response is the expected response</span>
-  response:address:array:character<span class="Special"> &lt;- </span>get *sandbox, <span class="Constant">response:offset</span>
+  response:address:shared:array:character<span class="Special"> &lt;- </span>get *sandbox, <span class="Constant">response:offset</span>
   *expected-response<span class="Special"> &lt;- </span>copy response
 ]
 
@@ -189,7 +190,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="muRecipe">after</span> <span class="Constant">&lt;render-sandbox-response&gt;</span> [
   <span class="Delimiter">{</span>
     <span class="muControl">break-unless</span> sandbox-response
-    expected-response:address:array:character<span class="Special"> &lt;- </span>get *sandbox, <span class="Constant">expected-response:offset</span>
+    expected-response:address:shared:array:character<span class="Special"> &lt;- </span>get *sandbox, <span class="Constant">expected-response:offset</span>
     <span class="muControl">break-unless</span> expected-response  <span class="Comment"># fall-through to print in grey</span>
     response-is-expected?:boolean<span class="Special"> &lt;- </span>equal expected-response, sandbox-response
     <span class="Delimiter">{</span>
diff --git a/html/edit/009-sandbox-trace.mu.html b/html/edit/009-sandbox-trace.mu.html
index 6d5603bd..868d68fc 100644
--- a/html/edit/009-sandbox-trace.mu.html
+++ b/html/edit/009-sandbox-trace.mu.html
@@ -39,22 +39,22 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
   assume-screen <span class="Constant">40/width</span>, <span class="Constant">10/height</span>
   <span class="Comment"># basic recipe</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[ </span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[ </span>
 <span class="Constant">recipe foo [</span>
 <span class="Constant">  stash [abc]</span>
 ]]
   <span class="Comment"># run it</span>
-  <span class="Constant">2</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[foo]</span>
+  <span class="Constant">2</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[foo]</span>
   assume-console [
     press F4
   ]
-  <span class="Constant">3</span>:address:programming-environment-data<span class="Special"> &lt;- </span>new-programming-environment screen:address:screen, <span class="Constant">1</span>:address:array:character, <span class="Constant">2</span>:address:array:character
-  event-loop screen:address:screen, console:address:console, <span class="Constant">3</span>:address:programming-environment-data
+  <span class="Constant">3</span>:address:shared:programming-environment-data<span class="Special"> &lt;- </span>new-programming-environment screen:address:shared:screen, <span class="Constant">1</span>:address:shared:array:character, <span class="Constant">2</span>:address:shared:array:character
+  event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">3</span>:address:shared:programming-environment-data
   screen-should-contain [
    <span class="Constant"> .                     run (F4)           .</span>
    <span class="Constant"> .                    ┊                   .</span>
    <span class="Constant"> .recipe foo [        ┊━━━━━━━━━━━━━━━━━━━.</span>
-   <span class="Constant"> .  stash [abc]       ┊                  x.</span>
+   <span class="Constant"> .  stash [abc]       ┊0                 x.</span>
    <span class="Constant"> .]                   ┊foo                .</span>
 <span class="Constant">    .┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┊━━━━━━━━━━━━━━━━━━━.</span>
    <span class="Constant"> .                    ┊                   .</span>
@@ -64,15 +64,16 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     left-click <span class="Constant">4</span>, <span class="Constant">21</span>
   ]
   run [
-    event-loop screen:address:screen, console:address:console, <span class="Constant">3</span>:address:programming-environment-data
-    print screen:address:screen, <span class="Constant">9251/␣/cursor</span>
+    event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">3</span>:address:shared:programming-environment-data
+    <span class="Constant">4</span>:character/cursor-icon<span class="Special"> &lt;- </span>copy <span class="Constant">9251/␣</span>
+    print screen:address:shared:screen, <span class="Constant">4</span>:character/cursor-icon
   ]
   <span class="Comment"># trace now printed and cursor shouldn't have budged</span>
   screen-should-contain [
    <span class="Constant"> .                     run (F4)           .</span>
    <span class="Constant"> .␣                   ┊                   .</span>
    <span class="Constant"> .recipe foo [        ┊━━━━━━━━━━━━━━━━━━━.</span>
-   <span class="Constant"> .  stash [abc]       ┊                  x.</span>
+   <span class="Constant"> .  stash [abc]       ┊0                 x.</span>
    <span class="Constant"> .]                   ┊foo                .</span>
    <span class="Constant"> .┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┊abc                .</span>
    <span class="Constant"> .                    ┊━━━━━━━━━━━━━━━━━━━.</span>
@@ -93,15 +94,15 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     left-click <span class="Constant">4</span>, <span class="Constant">25</span>
   ]
   run [
-    event-loop screen:address:screen, console:address:console, <span class="Constant">3</span>:address:programming-environment-data
-    print screen:address:screen, <span class="Constant">9251/␣/cursor</span>
+    event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">3</span>:address:shared:programming-environment-data
+    print screen:address:shared:screen, <span class="Constant">4</span>:character/cursor-icon
   ]
   <span class="Comment"># trace hidden again</span>
   screen-should-contain [
    <span class="Constant"> .                     run (F4)           .</span>
    <span class="Constant"> .␣                   ┊                   .</span>
    <span class="Constant"> .recipe foo [        ┊━━━━━━━━━━━━━━━━━━━.</span>
-   <span class="Constant"> .  stash [abc]       ┊                  x.</span>
+   <span class="Constant"> .  stash [abc]       ┊0                 x.</span>
    <span class="Constant"> .]                   ┊foo                .</span>
 <span class="Constant">    .┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┊━━━━━━━━━━━━━━━━━━━.</span>
    <span class="Constant"> .                    ┊                   .</span>
@@ -112,23 +113,23 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
   assume-screen <span class="Constant">40/width</span>, <span class="Constant">10/height</span>
   <span class="Comment"># basic recipe</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[ </span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[ </span>
 <span class="Constant">recipe foo [</span>
 <span class="Constant">  stash [abc]</span>
   <span class="muControl">reply</span> <span class="Constant">4</span>
 ]]
   <span class="Comment"># run it</span>
-  <span class="Constant">2</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[foo]</span>
+  <span class="Constant">2</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[foo]</span>
   assume-console [
     press F4
   ]
-  <span class="Constant">3</span>:address:programming-environment-data<span class="Special"> &lt;- </span>new-programming-environment screen:address:screen, <span class="Constant">1</span>:address:array:character, <span class="Constant">2</span>:address:array:character
-  event-loop screen:address:screen, console:address:console, <span class="Constant">3</span>:address:programming-environment-data
+  <span class="Constant">3</span>:address:shared:programming-environment-data<span class="Special"> &lt;- </span>new-programming-environment screen:address:shared:screen, <span class="Constant">1</span>:address:shared:array:character, <span class="Constant">2</span>:address:shared:array:character
+  event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">3</span>:address:shared:programming-environment-data
   screen-should-contain [
    <span class="Constant"> .                     run (F4)           .</span>
    <span class="Constant"> .                    ┊                   .</span>
    <span class="Constant"> .recipe foo [        ┊━━━━━━━━━━━━━━━━━━━.</span>
-   <span class="Constant"> .  stash [abc]       ┊                  x.</span>
+   <span class="Constant"> .  stash [abc]       ┊0                 x.</span>
    <span class="Constant"> .  reply 4           ┊foo                .</span>
    <span class="Constant"> .]                   ┊4                  .</span>
 <span class="Constant">    .┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┊━━━━━━━━━━━━━━━━━━━.</span>
@@ -139,14 +140,14 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     left-click <span class="Constant">4</span>, <span class="Constant">21</span>
   ]
   run [
-    event-loop screen:address:screen, console:address:console, <span class="Constant">3</span>:address:programming-environment-data
+    event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">3</span>:address:shared:programming-environment-data
   ]
   <span class="Comment"># trace now printed above result</span>
   screen-should-contain [
    <span class="Constant"> .                     run (F4)           .</span>
    <span class="Constant"> .                    ┊                   .</span>
    <span class="Constant"> .recipe foo [        ┊━━━━━━━━━━━━━━━━━━━.</span>
-   <span class="Constant"> .  stash [abc]       ┊                  x.</span>
+   <span class="Constant"> .  stash [abc]       ┊0                 x.</span>
    <span class="Constant"> .  reply 4           ┊foo                .</span>
    <span class="Constant"> .]                   ┊abc                .</span>
    <span class="Constant"> .┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┊4                  .</span>
@@ -156,18 +157,18 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 ]
 
 <span class="muData">container</span> sandbox-data [
-  trace:address:array:character
+  trace:address:shared:array:character
   display-trace?:boolean
 ]
 
 <span class="Comment"># replaced in a later layer</span>
-<span class="muRecipe">recipe!</span> update-sandbox sandbox:address:sandbox-data<span class="muRecipe"> -&gt; </span>sandbox:address:sandbox-data [
+<span class="muRecipe">recipe!</span> update-sandbox sandbox:address:shared:sandbox-data, env:address:shared:programming-environment-data, idx:number<span class="muRecipe"> -&gt; </span>sandbox:address:shared:sandbox-data, env:address:shared:programming-environment-data [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
-  data:address:array:character<span class="Special"> &lt;- </span>get *sandbox, <span class="Constant">data:offset</span>
-  response:address:address:array:character<span class="Special"> &lt;- </span>get-address *sandbox, <span class="Constant">response:offset</span>
-  trace:address:address:array:character<span class="Special"> &lt;- </span>get-address *sandbox, <span class="Constant">trace:offset</span>
-  fake-screen:address:address:screen<span class="Special"> &lt;- </span>get-address *sandbox, <span class="Constant">screen:offset</span>
+  data:address:shared:array:character<span class="Special"> &lt;- </span>get *sandbox, <span class="Constant">data:offset</span>
+  response:address:address:shared:array:character<span class="Special"> &lt;- </span>get-address *sandbox, <span class="Constant">response:offset</span>
+  trace:address:address:shared:array:character<span class="Special"> &lt;- </span>get-address *sandbox, <span class="Constant">trace:offset</span>
+  fake-screen:address:address:shared:screen<span class="Special"> &lt;- </span>get-address *sandbox, <span class="Constant">screen:offset</span>
   *response, _, *fake-screen, *trace<span class="Special"> &lt;- </span>run-interactive data
 ]
 
@@ -179,28 +180,28 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     click-column:number<span class="Special"> &lt;- </span>get *t, <span class="Constant">column:offset</span>
     on-sandbox-side?:boolean<span class="Special"> &lt;- </span>greater-or-equal click-column, sandbox-left-margin
     <span class="muControl">break-unless</span> on-sandbox-side?
-    first-sandbox:address:sandbox-data<span class="Special"> &lt;- </span>get *env, <span class="Constant">sandbox:offset</span>
+    first-sandbox:address:shared:sandbox-data<span class="Special"> &lt;- </span>get *env, <span class="Constant">sandbox:offset</span>
     <span class="muControl">break-unless</span> first-sandbox
     first-sandbox-begins:number<span class="Special"> &lt;- </span>get *first-sandbox, <span class="Constant">starting-row-on-screen:offset</span>
     click-row:number<span class="Special"> &lt;- </span>get *t, <span class="Constant">row:offset</span>
     below-sandbox-editor?:boolean<span class="Special"> &lt;- </span>greater-or-equal click-row, first-sandbox-begins
     <span class="muControl">break-unless</span> below-sandbox-editor?
     <span class="Comment"># identify the sandbox whose code is being clicked on</span>
-    sandbox:address:sandbox-data<span class="Special"> &lt;- </span>find-click-in-sandbox-code env, click-row
+    sandbox:address:shared:sandbox-data<span class="Special"> &lt;- </span>find-click-in-sandbox-code env, click-row
     <span class="muControl">break-unless</span> sandbox
     <span class="Comment"># toggle its display-trace? property</span>
     x:address:boolean<span class="Special"> &lt;- </span>get-address *sandbox, <span class="Constant">display-trace?:offset</span>
     *x<span class="Special"> &lt;- </span>not *x
     hide-screen screen
     screen<span class="Special"> &lt;- </span>render-sandbox-side screen, env, <span class="Constant">1/clear</span>
-    screen<span class="Special"> &lt;- </span>update-cursor screen, recipes, current-sandbox, *sandbox-in-focus?
+    screen<span class="Special"> &lt;- </span>update-cursor screen, recipes, current-sandbox, *sandbox-in-focus?, env
     <span class="Comment"># no change in cursor</span>
     show-screen screen
     <span class="muControl">loop</span> <span class="Constant">+next-event:label</span>
   <span class="Delimiter">}</span>
 ]
 
-<span class="muRecipe">recipe</span> find-click-in-sandbox-code env:address:programming-environment-data, click-row:number<span class="muRecipe"> -&gt; </span>sandbox:address:sandbox-data [
+<span class="muRecipe">recipe</span> find-click-in-sandbox-code env:address:shared:programming-environment-data, click-row:number<span class="muRecipe"> -&gt; </span>sandbox:address:shared:sandbox-data [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   <span class="Comment"># assert click-row &gt;= sandbox.starting-row-on-screen</span>
@@ -210,7 +211,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   assert clicked-on-sandboxes?, <span class="Constant">[extract-sandbox called on click to sandbox editor]</span>
   <span class="Comment"># while click-row &lt; sandbox.next-sandbox.starting-row-on-screen</span>
   <span class="Delimiter">{</span>
-    next-sandbox:address:sandbox-data<span class="Special"> &lt;- </span>get *sandbox, <span class="Constant">next-sandbox:offset</span>
+    next-sandbox:address:shared:sandbox-data<span class="Special"> &lt;- </span>get *sandbox, <span class="Constant">next-sandbox:offset</span>
     <span class="muControl">break-unless</span> next-sandbox
     next-start:number<span class="Special"> &lt;- </span>get *next-sandbox, <span class="Constant">starting-row-on-screen:offset</span>
     found?:boolean<span class="Special"> &lt;- </span>lesser-than click-row, next-start
@@ -236,7 +237,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   <span class="Delimiter">{</span>
     display-trace?:boolean<span class="Special"> &lt;- </span>get *sandbox, <span class="Constant">display-trace?:offset</span>
     <span class="muControl">break-unless</span> display-trace?
-    sandbox-trace:address:array:character<span class="Special"> &lt;- </span>get *sandbox, <span class="Constant">trace:offset</span>
+    sandbox-trace:address:shared:array:character<span class="Special"> &lt;- </span>get *sandbox, <span class="Constant">trace:offset</span>
     <span class="muControl">break-unless</span> sandbox-trace  <span class="Comment"># nothing to print; move on</span>
     row, screen<span class="Special"> &lt;- </span>render screen, sandbox-trace, left, right, <span class="Constant">245/grey</span>, row
   <span class="Delimiter">}</span>
diff --git a/html/edit/010-warnings.mu.html b/html/edit/010-warnings.mu.html
index c675b386..a9b81c9e 100644
--- a/html/edit/010-warnings.mu.html
+++ b/html/edit/010-warnings.mu.html
@@ -37,23 +37,23 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="SalientComment">## handling malformed programs</span>
 
 <span class="muData">container</span> programming-environment-data [
-  recipe-warnings:address:array:character
+  recipe-warnings:address:shared:array:character
 ]
 
 <span class="Comment"># copy code from recipe editor, persist, load into mu, save any warnings</span>
-<span class="muRecipe">recipe!</span> update-recipes env:address:programming-environment-data, screen:address:screen<span class="muRecipe"> -&gt; </span>errors-found?:boolean, env:address:programming-environment-data, screen:address:screen [
+<span class="muRecipe">recipe!</span> update-recipes env:address:shared:programming-environment-data, screen:address:shared:screen<span class="muRecipe"> -&gt; </span>errors-found?:boolean, env:address:shared:programming-environment-data, screen:address:shared:screen [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
 <span class="CommentedCode">#?   $log [update recipes]</span>
-  recipes:address:editor-data<span class="Special"> &lt;- </span>get *env, <span class="Constant">recipes:offset</span>
-  in:address:array:character<span class="Special"> &lt;- </span>editor-contents recipes
+  recipes:address:shared:editor-data<span class="Special"> &lt;- </span>get *env, <span class="Constant">recipes:offset</span>
+  in:address:shared:array:character<span class="Special"> &lt;- </span>editor-contents recipes
   save <span class="Constant">[recipes.mu]</span>, in
-  recipe-warnings:address:address:array:character<span class="Special"> &lt;- </span>get-address *env, <span class="Constant">recipe-warnings:offset</span>
+  recipe-warnings:address:address:shared:array:character<span class="Special"> &lt;- </span>get-address *env, <span class="Constant">recipe-warnings:offset</span>
   *recipe-warnings<span class="Special"> &lt;- </span>reload in
   <span class="Comment"># if recipe editor has errors, stop</span>
   <span class="Delimiter">{</span>
     <span class="muControl">break-unless</span> *recipe-warnings
-    status:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[errors found]</span>
+    status:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[errors found     ]</span>
     update-status screen, status, <span class="Constant">1/red</span>
     errors-found?<span class="Special"> &lt;- </span>copy <span class="Constant">1/true</span>
     <span class="muControl">reply</span>
@@ -63,35 +63,72 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muRecipe">before</span> <span class="Constant">&lt;render-components-end&gt;</span> [
   trace <span class="Constant">11</span>, <span class="Constant">[app]</span>, <span class="Constant">[render status]</span>
-  recipe-warnings:address:array:character<span class="Special"> &lt;- </span>get *env, <span class="Constant">recipe-warnings:offset</span>
+  recipe-warnings:address:shared:array:character<span class="Special"> &lt;- </span>get *env, <span class="Constant">recipe-warnings:offset</span>
   <span class="Delimiter">{</span>
     <span class="muControl">break-unless</span> recipe-warnings
-    status:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[errors found]</span>
+    status:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[errors found     ]</span>
     update-status screen, status, <span class="Constant">1/red</span>
   <span class="Delimiter">}</span>
 ]
 
 <span class="muRecipe">before</span> <span class="Constant">&lt;render-recipe-components-end&gt;</span> [
   <span class="Delimiter">{</span>
-    recipe-warnings:address:array:character<span class="Special"> &lt;- </span>get *env, <span class="Constant">recipe-warnings:offset</span>
+    recipe-warnings:address:shared:array:character<span class="Special"> &lt;- </span>get *env, <span class="Constant">recipe-warnings:offset</span>
     <span class="muControl">break-unless</span> recipe-warnings
     row, screen<span class="Special"> &lt;- </span>render screen, recipe-warnings, left, right, <span class="Constant">1/red</span>, row
   <span class="Delimiter">}</span>
 ]
 
+<span class="muData">container</span> programming-environment-data [
+  warning-index:number  <span class="Comment"># index of first sandbox with an error (or -1 if none)</span>
+]
+
+<span class="muRecipe">after</span> <span class="Constant">&lt;programming-environment-initialization&gt;</span> [
+  warning-index:address:number<span class="Special"> &lt;- </span>get-address *result, <span class="Constant">warning-index:offset</span>
+  *warning-index<span class="Special"> &lt;- </span>copy <span class="Constant">-1</span>
+]
+
+<span class="muRecipe">after</span> <span class="Constant">&lt;run-sandboxes-begin&gt;</span> [
+  warning-index:address:number<span class="Special"> &lt;- </span>get-address *env, <span class="Constant">warning-index:offset</span>
+  *warning-index<span class="Special"> &lt;- </span>copy <span class="Constant">-1</span>
+]
+
+<span class="muRecipe">before</span> <span class="Constant">&lt;run-sandboxes-end&gt;</span> [
+  <span class="Delimiter">{</span>
+    sandboxes-completed-successfully?:boolean<span class="Special"> &lt;- </span>equal *warning-index, <span class="Constant">-1</span>
+    <span class="muControl">break-if</span> sandboxes-completed-successfully?
+    errors-found?<span class="Special"> &lt;- </span>copy <span class="Constant">1/true</span>
+  <span class="Delimiter">}</span>
+]
+
+<span class="muRecipe">before</span> <span class="Constant">&lt;render-components-end&gt;</span> [
+  <span class="Delimiter">{</span>
+    <span class="muControl">break-if</span> recipe-warnings
+    warning-index:number<span class="Special"> &lt;- </span>get *env, <span class="Constant">warning-index:offset</span>
+    sandboxes-completed-successfully?:boolean<span class="Special"> &lt;- </span>equal warning-index, <span class="Constant">-1</span>
+    <span class="muControl">break-if</span> sandboxes-completed-successfully?
+    status-template:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[errors found (_)    ]</span>
+    warning-index-text:address:shared:array:character<span class="Special"> &lt;- </span>to-text warning-index
+    status:address:shared:array:character<span class="Special"> &lt;- </span>interpolate status-template, warning-index-text
+<span class="CommentedCode">#?     $print [update-status: sandbox warning], 10/newline</span>
+    update-status screen, status, <span class="Constant">1/red</span>
+<span class="CommentedCode">#?     $print [run sandboxes end], 10/newline</span>
+  <span class="Delimiter">}</span>
+]
+
 <span class="muData">container</span> sandbox-data [
-  warnings:address:array:character
+  warnings:address:shared:array:character
 ]
 
-<span class="muRecipe">recipe!</span> update-sandbox sandbox:address:sandbox-data<span class="muRecipe"> -&gt; </span>sandbox:address:sandbox-data [
+<span class="muRecipe">recipe!</span> update-sandbox sandbox:address:shared:sandbox-data, env:address:shared:programming-environment-data, idx:number<span class="muRecipe"> -&gt; </span>sandbox:address:shared:sandbox-data, env:address:shared:programming-environment-data [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
 <span class="CommentedCode">#?   $log [update sandbox]</span>
-  data:address:array:character<span class="Special"> &lt;- </span>get *sandbox, <span class="Constant">data:offset</span>
-  response:address:address:array:character<span class="Special"> &lt;- </span>get-address *sandbox, <span class="Constant">response:offset</span>
-  warnings:address:address:array:character<span class="Special"> &lt;- </span>get-address *sandbox, <span class="Constant">warnings:offset</span>
-  trace:address:address:array:character<span class="Special"> &lt;- </span>get-address *sandbox, <span class="Constant">trace:offset</span>
-  fake-screen:address:address:screen<span class="Special"> &lt;- </span>get-address *sandbox, <span class="Constant">screen:offset</span>
+  data:address:shared:array:character<span class="Special"> &lt;- </span>get *sandbox, <span class="Constant">data:offset</span>
+  response:address:address:shared:array:character<span class="Special"> &lt;- </span>get-address *sandbox, <span class="Constant">response:offset</span>
+  warnings:address:address:shared:array:character<span class="Special"> &lt;- </span>get-address *sandbox, <span class="Constant">warnings:offset</span>
+  trace:address:address:shared:array:character<span class="Special"> &lt;- </span>get-address *sandbox, <span class="Constant">trace:offset</span>
+  fake-screen:address:address:shared:screen<span class="Special"> &lt;- </span>get-address *sandbox, <span class="Constant">screen:offset</span>
 <span class="CommentedCode">#?   $print [run-interactive], 10/newline</span>
   *response, *warnings, *fake-screen, *trace, completed?:boolean<span class="Special"> &lt;- </span>run-interactive data
   <span class="Delimiter">{</span>
@@ -100,13 +137,21 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     *warnings<span class="Special"> &lt;- </span>new <span class="Constant">[took too long!</span>
 <span class="Constant">]</span>
   <span class="Delimiter">}</span>
+  <span class="Delimiter">{</span>
+    <span class="muControl">break-unless</span> *warnings
+<span class="CommentedCode">#?     $print [setting warning-index to ], idx, 10/newline</span>
+    warning-index:address:number<span class="Special"> &lt;- </span>get-address *env, <span class="Constant">warning-index:offset</span>
+    warning-not-set?:boolean<span class="Special"> &lt;- </span>equal *warning-index, <span class="Constant">-1</span>
+    <span class="muControl">break-unless</span> warning-not-set?
+    *warning-index<span class="Special"> &lt;- </span>copy idx
+  <span class="Delimiter">}</span>
 <span class="CommentedCode">#?   $print [done with run-interactive], 10/newline</span>
 ]
 
 <span class="Comment"># make sure we render any trace</span>
 <span class="muRecipe">after</span> <span class="Constant">&lt;render-sandbox-trace-done&gt;</span> [
   <span class="Delimiter">{</span>
-    sandbox-warnings:address:array:character<span class="Special"> &lt;- </span>get *sandbox, <span class="Constant">warnings:offset</span>
+    sandbox-warnings:address:shared:array:character<span class="Special"> &lt;- </span>get *sandbox, <span class="Constant">warnings:offset</span>
     <span class="muControl">break-unless</span> sandbox-warnings
     *response-starting-row<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>  <span class="Comment"># no response</span>
     row, screen<span class="Special"> &lt;- </span>render screen, sandbox-warnings, left, right, <span class="Constant">1/red</span>, row
@@ -118,17 +163,17 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="muScenario">scenario</span> run-shows-warnings-in-get [
   trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
   assume-screen <span class="Constant">100/width</span>, <span class="Constant">15/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[ </span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[ </span>
 <span class="Constant">recipe foo [</span>
 <span class="Constant">  get 123:number, foo:offset</span>
 <span class="Constant">]</span>]
-  <span class="Constant">2</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[foo]</span>
-  <span class="Constant">3</span>:address:programming-environment-data<span class="Special"> &lt;- </span>new-programming-environment screen:address:screen, <span class="Constant">1</span>:address:array:character, <span class="Constant">2</span>:address:array:character
+  <span class="Constant">2</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[foo]</span>
+  <span class="Constant">3</span>:address:shared:programming-environment-data<span class="Special"> &lt;- </span>new-programming-environment screen:address:shared:screen, <span class="Constant">1</span>:address:shared:array:character, <span class="Constant">2</span>:address:shared:array:character
   assume-console [
     press F4
   ]
   run [
-    event-loop screen:address:screen, console:address:console, <span class="Constant">3</span>:address:programming-environment-data
+    event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">3</span>:address:shared:programming-environment-data
   ]
   screen-should-contain [
    <span class="Constant"> .  errors found                                                                   run (F4)           .</span>
@@ -155,32 +200,84 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   ]
 ]
 
+<span class="muScenario">scenario</span> run-updates-status-with-first-erroneous-sandbox [
+  trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
+  assume-screen <span class="Constant">100/width</span>, <span class="Constant">15/height</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
+  <span class="Constant">2</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
+  <span class="Constant">3</span>:address:shared:programming-environment-data<span class="Special"> &lt;- </span>new-programming-environment screen:address:shared:screen, <span class="Constant">1</span>:address:shared:array:character, <span class="Constant">2</span>:address:shared:array:character
+  assume-console [
+    left-click <span class="Constant">3</span>, <span class="Constant">80</span>
+    <span class="Comment"># create invalid sandbox 1</span>
+    type <span class="Constant">[get foo, x:offset]</span>
+    press F4
+    <span class="Comment"># create invalid sandbox 0</span>
+    type <span class="Constant">[get foo, x:offset]</span>
+    press F4
+  ]
+  run [
+    event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">3</span>:address:shared:programming-environment-data
+  ]
+  <span class="Comment"># status shows first sandbox with error</span>
+  screen-should-contain [
+   <span class="Constant"> .  errors found (0)                                                               run (F4)           .</span>
+  ]
+]
+
+<span class="muScenario">scenario</span> run-updates-status-with-first-erroneous-sandbox-2 [
+  trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
+  assume-screen <span class="Constant">100/width</span>, <span class="Constant">15/height</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
+  <span class="Constant">2</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
+  <span class="Constant">3</span>:address:shared:programming-environment-data<span class="Special"> &lt;- </span>new-programming-environment screen:address:shared:screen, <span class="Constant">1</span>:address:shared:array:character, <span class="Constant">2</span>:address:shared:array:character
+  assume-console [
+    left-click <span class="Constant">3</span>, <span class="Constant">80</span>
+    <span class="Comment"># create invalid sandbox 2</span>
+    type <span class="Constant">[get foo, x:offset]</span>
+    press F4
+    <span class="Comment"># create invalid sandbox 1</span>
+    type <span class="Constant">[get foo, x:offset]</span>
+    press F4
+    <span class="Comment"># create valid sandbox 0</span>
+    type <span class="Constant">[add 2, 2]</span>
+    press F4
+  ]
+  run [
+    event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">3</span>:address:shared:programming-environment-data
+  ]
+  <span class="Comment"># status shows first sandbox with error</span>
+  screen-should-contain [
+   <span class="Constant"> .  errors found (1)                                                               run (F4)           .</span>
+  ]
+]
+
 <span class="muScenario">scenario</span> run-hides-warnings-from-past-sandboxes [
   trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
   assume-screen <span class="Constant">100/width</span>, <span class="Constant">15/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
-  <span class="Constant">2</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[get foo, x:offset]</span>  <span class="Comment"># invalid</span>
-  <span class="Constant">3</span>:address:programming-environment-data<span class="Special"> &lt;- </span>new-programming-environment screen:address:screen, <span class="Constant">1</span>:address:array:character, <span class="Constant">2</span>:address:array:character
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
+  <span class="Constant">2</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[get foo, x:offset]</span>  <span class="Comment"># invalid</span>
+  <span class="Constant">3</span>:address:shared:programming-environment-data<span class="Special"> &lt;- </span>new-programming-environment screen:address:shared:screen, <span class="Constant">1</span>:address:shared:array:character, <span class="Constant">2</span>:address:shared:array:character
   assume-console [
     press F4  <span class="Comment"># generate error</span>
   ]
   run [
-    event-loop screen:address:screen, console:address:console, <span class="Constant">3</span>:address:programming-environment-data
+    event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">3</span>:address:shared:programming-environment-data
   ]
   assume-console [
     left-click <span class="Constant">3</span>, <span class="Constant">80</span>
     press ctrl-k
     type <span class="Constant">[add 2, 2]</span>  <span class="Comment"># valid code</span>
-    press F4  <span class="Comment"># error should disappear</span>
+    press F4  <span class="Comment"># update sandbox</span>
   ]
   run [
-    event-loop screen:address:screen, console:address:console, <span class="Constant">3</span>:address:programming-environment-data
+    event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">3</span>:address:shared:programming-environment-data
   ]
+  <span class="Comment"># error should disappear</span>
   screen-should-contain [
    <span class="Constant"> .                                                                                 run (F4)           .</span>
    <span class="Constant"> .                                                  ┊                                                 .</span>
 <span class="Constant">    .┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┊━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━.</span>
-   <span class="Constant"> .                                                  ┊                                                x.</span>
+   <span class="Constant"> .                                                  ┊0                                               x.</span>
    <span class="Constant"> .                                                  ┊add 2, 2                                         .</span>
    <span class="Constant"> .                                                  ┊4                                                .</span>
    <span class="Constant"> .                                                  ┊━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━.</span>
@@ -192,24 +289,24 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
   assume-screen <span class="Constant">100/width</span>, <span class="Constant">15/height</span>
   <span class="Comment"># define a shape-shifting recipe with an error</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[recipe foo x:_elem -&gt; z:_elem [</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[recipe foo x:_elem -&gt; z:_elem [</span>
 <span class="Constant">local-scope</span>
 <span class="Constant">load-ingredients</span>
 <span class="Constant">z &lt;- add x, [a]</span>
 ]]
-  <span class="Constant">2</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[foo 2]</span>
-  <span class="Constant">3</span>:address:programming-environment-data<span class="Special"> &lt;- </span>new-programming-environment screen:address:screen, <span class="Constant">1</span>:address:array:character, <span class="Constant">2</span>:address:array:character
+  <span class="Constant">2</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[foo 2]</span>
+  <span class="Constant">3</span>:address:shared:programming-environment-data<span class="Special"> &lt;- </span>new-programming-environment screen:address:shared:screen, <span class="Constant">1</span>:address:shared:array:character, <span class="Constant">2</span>:address:shared:array:character
   assume-console [
     press F4
   ]
   run [
-    event-loop screen:address:screen, console:address:console, <span class="Constant">3</span>:address:programming-environment-data
+    event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">3</span>:address:shared:programming-environment-data
   ]
   screen-should-contain [
-   <span class="Constant"> .                                                                                 run (F4)           .</span>
+   <span class="Constant"> .  errors found (0)                                                               run (F4)           .</span>
    <span class="Constant"> .recipe foo x:_elem -&gt; z:_elem [                   ┊                                                 .</span>
    <span class="Constant"> .local-scope                                       ┊━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━.</span>
-   <span class="Constant"> .load-ingredients                                  ┊                                                x.</span>
+   <span class="Constant"> .load-ingredients                                  ┊0                                               x.</span>
    <span class="Constant"> .z &lt;- add x, [a]                                   ┊foo 2                                            .</span>
    <span class="Constant"> .]                                                 ┊foo_2: 'add' requires number ingredients, but go↩.</span>
    <span class="Constant"> .┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┊t [a]                                            .</span>
@@ -221,14 +318,14 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     press F4
   ]
   run [
-    event-loop screen:address:screen, console:address:console, <span class="Constant">3</span>:address:programming-environment-data
+    event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">3</span>:address:shared:programming-environment-data
   ]
   <span class="Comment"># error should remain unchanged</span>
   screen-should-contain [
-   <span class="Constant"> .                                                                                 run (F4)           .</span>
+   <span class="Constant"> .  errors found (0)                                                               run (F4)           .</span>
    <span class="Constant"> .recipe foo x:_elem -&gt; z:_elem [                   ┊                                                 .</span>
    <span class="Constant"> .local-scope                                       ┊━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━.</span>
-   <span class="Constant"> .load-ingredients                                  ┊                                                x.</span>
+   <span class="Constant"> .load-ingredients                                  ┊0                                               x.</span>
    <span class="Constant"> .z &lt;- add x, [a]                                   ┊foo 2                                            .</span>
    <span class="Constant"> .]                                                 ┊foo_2: 'add' requires number ingredients, but go↩.</span>
    <span class="Constant"> .┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┊t [a]                                            .</span>
@@ -241,24 +338,24 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
   assume-screen <span class="Constant">100/width</span>, <span class="Constant">15/height</span>
   <span class="Comment"># overload a well-known shape-shifting recipe</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[recipe length l:address:list:_elem -&gt; n:number [</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[recipe length l:address:shared:list:_elem -&gt; n:number [</span>
 <span class="Constant">]</span>]
   <span class="Comment"># call code that uses other variants of it, but not it itself</span>
-  <span class="Constant">2</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[x:address:list:number &lt;- copy 0</span>
+  <span class="Constant">2</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[x:address:shared:list:number &lt;- copy 0</span>
 <span class="Constant">to-text x]</span>
-  <span class="Constant">3</span>:address:programming-environment-data<span class="Special"> &lt;- </span>new-programming-environment screen:address:screen, <span class="Constant">1</span>:address:array:character, <span class="Constant">2</span>:address:array:character
+  <span class="Constant">3</span>:address:shared:programming-environment-data<span class="Special"> &lt;- </span>new-programming-environment screen:address:shared:screen, <span class="Constant">1</span>:address:shared:array:character, <span class="Constant">2</span>:address:shared:array:character
   <span class="Comment"># run it once</span>
   assume-console [
     press F4
   ]
-  event-loop screen:address:screen, console:address:console, <span class="Constant">3</span>:address:programming-environment-data
+  event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">3</span>:address:shared:programming-environment-data
   <span class="Comment"># no errors anywhere on screen (can't check anything else, since to-text will return an address)</span>
   screen-should-contain-in-color <span class="Constant">1/red</span>, [
    <span class="Constant"> .                                                                                                    .</span>
    <span class="Constant"> .                                                                                                    .</span>
    <span class="Constant"> .                                                                                                    .</span>
    <span class="Constant"> .                                                                                                    .</span>
-   <span class="Constant"> .                                                                         &lt;-                         .</span>
+   <span class="Constant"> .                                                                                &lt;-                  .</span>
    <span class="Constant"> .                                                                                                    .</span>
    <span class="Constant"> .                                                                                                    .</span>
    <span class="Constant"> .                                                                                                    .</span>
@@ -275,7 +372,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     press F4
   ]
   run [
-    event-loop screen:address:screen, console:address:console, <span class="Constant">3</span>:address:programming-environment-data
+    event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">3</span>:address:shared:programming-environment-data
   ]
   <span class="Comment"># still no errors</span>
   screen-should-contain-in-color <span class="Constant">1/red</span>, [
@@ -283,7 +380,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
    <span class="Constant"> .                                                                                                    .</span>
    <span class="Constant"> .                                                                                                    .</span>
    <span class="Constant"> .                                                                                                    .</span>
-   <span class="Constant"> .                                                                         &lt;-                         .</span>
+   <span class="Constant"> .                                                                                &lt;-                  .</span>
    <span class="Constant"> .                                                                                                    .</span>
    <span class="Constant"> .                                                                                                    .</span>
    <span class="Constant"> .                                                                                                    .</span>
@@ -300,17 +397,17 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="muScenario">scenario</span> run-shows-missing-type-warnings [
   trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
   assume-screen <span class="Constant">100/width</span>, <span class="Constant">15/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[ </span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[ </span>
 <span class="Constant">recipe foo [</span>
 <span class="Constant">  x &lt;- copy 0</span>
 <span class="Constant">]</span>]
-  <span class="Constant">2</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[foo]</span>
-  <span class="Constant">3</span>:address:programming-environment-data<span class="Special"> &lt;- </span>new-programming-environment screen:address:screen, <span class="Constant">1</span>:address:array:character, <span class="Constant">2</span>:address:array:character
+  <span class="Constant">2</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[foo]</span>
+  <span class="Constant">3</span>:address:shared:programming-environment-data<span class="Special"> &lt;- </span>new-programming-environment screen:address:shared:screen, <span class="Constant">1</span>:address:shared:array:character, <span class="Constant">2</span>:address:shared:array:character
   assume-console [
     press F4
   ]
   run [
-    event-loop screen:address:screen, console:address:console, <span class="Constant">3</span>:address:programming-environment-data
+    event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">3</span>:address:shared:programming-environment-data
   ]
   screen-should-contain [
    <span class="Constant"> .  errors found                                                                   run (F4)           .</span>
@@ -326,18 +423,18 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
   assume-screen <span class="Constant">100/width</span>, <span class="Constant">15/height</span>
   <span class="Comment"># recipe is incomplete (unbalanced '[')</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[ </span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[ </span>
 <span class="Constant">recipe foo «</span>
 <span class="Constant">  x &lt;- copy 0</span>
 <span class="Constant">]</span>
-  replace <span class="Constant">1</span>:address:array:character, <span class="Constant">171/«</span>, <span class="Constant">91</span>  <span class="Comment"># '['</span>
-  <span class="Constant">2</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[foo]</span>
-  <span class="Constant">3</span>:address:programming-environment-data<span class="Special"> &lt;- </span>new-programming-environment screen:address:screen, <span class="Constant">1</span>:address:array:character, <span class="Constant">2</span>:address:array:character
+  replace <span class="Constant">1</span>:address:shared:array:character, <span class="Constant">171/«</span>, <span class="Constant">91</span>  <span class="Comment"># '['</span>
+  <span class="Constant">2</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[foo]</span>
+  <span class="Constant">3</span>:address:shared:programming-environment-data<span class="Special"> &lt;- </span>new-programming-environment screen:address:shared:screen, <span class="Constant">1</span>:address:shared:array:character, <span class="Constant">2</span>:address:shared:array:character
   assume-console [
     press F4
   ]
   run [
-    event-loop screen:address:screen, console:address:console, <span class="Constant">3</span>:address:programming-environment-data
+    event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">3</span>:address:shared:programming-environment-data
   ]
   screen-should-contain [
    <span class="Constant"> .  errors found                                                                   run (F4)           .</span>
@@ -354,28 +451,28 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="muScenario">scenario</span> run-shows-get-on-non-container-warnings [
   trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
   assume-screen <span class="Constant">100/width</span>, <span class="Constant">15/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[ </span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[ </span>
 <span class="Constant">recipe foo [</span>
-<span class="Constant">  x:address:point &lt;- new point:type</span>
-<span class="Constant">  get x:address:point, 1:offset</span>
+<span class="Constant">  x:address:shared:point &lt;- new point:type</span>
+<span class="Constant">  get x:address:shared:point, 1:offset</span>
 <span class="Constant">]</span>]
-  <span class="Constant">2</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[foo]</span>
-  <span class="Constant">3</span>:address:programming-environment-data<span class="Special"> &lt;- </span>new-programming-environment screen:address:screen, <span class="Constant">1</span>:address:array:character, <span class="Constant">2</span>:address:array:character
+  <span class="Constant">2</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[foo]</span>
+  <span class="Constant">3</span>:address:shared:programming-environment-data<span class="Special"> &lt;- </span>new-programming-environment screen:address:shared:screen, <span class="Constant">1</span>:address:shared:array:character, <span class="Constant">2</span>:address:shared:array:character
   assume-console [
     press F4
   ]
   run [
-    event-loop screen:address:screen, console:address:console, <span class="Constant">3</span>:address:programming-environment-data
+    event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">3</span>:address:shared:programming-environment-data
   ]
   screen-should-contain [
    <span class="Constant"> .  errors found                                                                   run (F4)           .</span>
    <span class="Constant"> .                                                  ┊foo                                              .</span>
    <span class="Constant"> .recipe foo [                                      ┊━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━.</span>
-   <span class="Constant"> .  x:address:point &lt;- new point:type               ┊                                                 .</span>
-   <span class="Constant"> .  get x:address:point, 1:offset                   ┊                                                 .</span>
+   <span class="Constant"> .  x:address:shared:point &lt;- new point:type        ┊                                                 .</span>
+   <span class="Constant"> .  get x:address:shared:point, 1:offset            ┊                                                 .</span>
    <span class="Constant"> .]                                                 ┊                                                 .</span>
    <span class="Constant"> .foo: first ingredient of 'get' should be a contai↩┊                                                 .</span>
-   <span class="Constant"> .ner, but got x:address:point                      ┊                                                 .</span>
+   <span class="Constant"> .ner, but got x:address:shared:point               ┊                                                 .</span>
    <span class="Constant"> .┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┊                                                 .</span>
    <span class="Constant"> .                                                  ┊                                                 .</span>
   ]
@@ -384,27 +481,27 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="muScenario">scenario</span> run-shows-non-literal-get-argument-warnings [
   trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
   assume-screen <span class="Constant">100/width</span>, <span class="Constant">15/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[ </span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[ </span>
 <span class="Constant">recipe foo [</span>
 <span class="Constant">  x:number &lt;- copy 0</span>
-<span class="Constant">  y:address:point &lt;- new point:type</span>
-<span class="Constant">  get *y:address:point, x:number</span>
+<span class="Constant">  y:address:shared:point &lt;- new point:type</span>
+<span class="Constant">  get *y:address:shared:point, x:number</span>
 <span class="Constant">]</span>]
-  <span class="Constant">2</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[foo]</span>
-  <span class="Constant">3</span>:address:programming-environment-data<span class="Special"> &lt;- </span>new-programming-environment screen:address:screen, <span class="Constant">1</span>:address:array:character, <span class="Constant">2</span>:address:array:character
+  <span class="Constant">2</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[foo]</span>
+  <span class="Constant">3</span>:address:shared:programming-environment-data<span class="Special"> &lt;- </span>new-programming-environment screen:address:shared:screen, <span class="Constant">1</span>:address:shared:array:character, <span class="Constant">2</span>:address:shared:array:character
   assume-console [
     press F4
   ]
   run [
-    event-loop screen:address:screen, console:address:console, <span class="Constant">3</span>:address:programming-environment-data
+    event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">3</span>:address:shared:programming-environment-data
   ]
   screen-should-contain [
    <span class="Constant"> .  errors found                                                                   run (F4)           .</span>
    <span class="Constant"> .                                                  ┊foo                                              .</span>
    <span class="Constant"> .recipe foo [                                      ┊━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━.</span>
    <span class="Constant"> .  x:number &lt;- copy 0                              ┊                                                 .</span>
-   <span class="Constant"> .  y:address:point &lt;- new point:type               ┊                                                 .</span>
-   <span class="Constant"> .  get *y:address:point, x:number                  ┊                                                 .</span>
+   <span class="Constant"> .  y:address:shared:point &lt;- new point:type        ┊                                                 .</span>
+   <span class="Constant"> .  get *y:address:shared:point, x:number           ┊                                                 .</span>
    <span class="Constant"> .]                                                 ┊                                                 .</span>
    <span class="Constant"> .foo: expected ingredient 1 of 'get' to have type ↩┊                                                 .</span>
    <span class="Constant"> .'offset'; got x:number                            ┊                                                 .</span>
@@ -419,17 +516,17 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
   <span class="Comment"># try to run a file with an error</span>
   assume-screen <span class="Constant">100/width</span>, <span class="Constant">15/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[ </span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[ </span>
 <span class="Constant">recipe foo [</span>
 <span class="Constant">  x:number &lt;- copy y:number</span>
 <span class="Constant">]</span>]
-  <span class="Constant">2</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[foo]</span>
-  <span class="Constant">3</span>:address:programming-environment-data<span class="Special"> &lt;- </span>new-programming-environment screen:address:screen, <span class="Constant">1</span>:address:array:character, <span class="Constant">2</span>:address:array:character
+  <span class="Constant">2</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[foo]</span>
+  <span class="Constant">3</span>:address:shared:programming-environment-data<span class="Special"> &lt;- </span>new-programming-environment screen:address:shared:screen, <span class="Constant">1</span>:address:shared:array:character, <span class="Constant">2</span>:address:shared:array:character
   assume-console [
     press F4
   ]
   run [
-    event-loop screen:address:screen, console:address:console, <span class="Constant">3</span>:address:programming-environment-data
+    event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">3</span>:address:shared:programming-environment-data
   ]
   screen-should-contain [
    <span class="Constant"> .  errors found                                                                   run (F4)           .</span>
@@ -446,7 +543,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     press F4
   ]
   run [
-    event-loop screen:address:screen, console:address:console, <span class="Constant">3</span>:address:programming-environment-data
+    event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">3</span>:address:shared:programming-environment-data
   ]
   screen-should-contain [
    <span class="Constant"> .  errors found                                                                   run (F4)           .</span>
@@ -464,23 +561,23 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
   assume-screen <span class="Constant">100/width</span>, <span class="Constant">10/height</span>
   <span class="Comment"># left editor is empty</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
   <span class="Comment"># right editor contains an illegal instruction</span>
-  <span class="Constant">2</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[get 1234:number, foo:offset]</span>
-  <span class="Constant">3</span>:address:programming-environment-data<span class="Special"> &lt;- </span>new-programming-environment screen:address:screen, <span class="Constant">1</span>:address:array:character, <span class="Constant">2</span>:address:array:character
+  <span class="Constant">2</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[get 1234:number, foo:offset]</span>
+  <span class="Constant">3</span>:address:shared:programming-environment-data<span class="Special"> &lt;- </span>new-programming-environment screen:address:shared:screen, <span class="Constant">1</span>:address:shared:array:character, <span class="Constant">2</span>:address:shared:array:character
   <span class="Comment"># run the code in the editors</span>
   assume-console [
     press F4
   ]
   run [
-    event-loop screen:address:screen, console:address:console, <span class="Constant">3</span>:address:programming-environment-data
+    event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">3</span>:address:shared:programming-environment-data
   ]
   <span class="Comment"># check that screen prints error message in red</span>
   screen-should-contain [
-   <span class="Constant"> .                                                                                 run (F4)           .</span>
+   <span class="Constant"> .  errors found (0)                                                               run (F4)           .</span>
    <span class="Constant"> .                                                  ┊                                                 .</span>
 <span class="Constant">    .┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┊━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━.</span>
-   <span class="Constant"> .                                                  ┊                                                x.</span>
+   <span class="Constant"> .                                                  ┊0                                               x.</span>
    <span class="Constant"> .                                                  ┊get 1234:number, foo:offset                      .</span>
    <span class="Constant"> .                                                  ┊unknown element foo in container number          .</span>
    <span class="Constant"> .                                                  ┊first ingredient of 'get' should be a container,↩.</span>
@@ -499,7 +596,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
    <span class="Constant"> .                                                                                                    .</span>
   ]
   screen-should-contain-in-color <span class="Constant">1/red</span>, [
-   <span class="Constant"> .                                                                                                    .</span>
+   <span class="Constant"> .  errors found (0)                                                                                  .</span>
    <span class="Constant"> .                                                                                                    .</span>
    <span class="Constant"> .                                                                                                    .</span>
    <span class="Constant"> .                                                                                                    .</span>
@@ -527,24 +624,24 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
   assume-screen <span class="Constant">100/width</span>, <span class="Constant">10/height</span>
   <span class="Comment"># left editor is empty</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
   <span class="Comment"># right editor contains an illegal instruction</span>
-  <span class="Constant">2</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[get 1234:number, foo:offset]</span>
-  <span class="Constant">3</span>:address:programming-environment-data<span class="Special"> &lt;- </span>new-programming-environment screen:address:screen, <span class="Constant">1</span>:address:array:character, <span class="Constant">2</span>:address:array:character
+  <span class="Constant">2</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[get 1234:number, foo:offset]</span>
+  <span class="Constant">3</span>:address:shared:programming-environment-data<span class="Special"> &lt;- </span>new-programming-environment screen:address:shared:screen, <span class="Constant">1</span>:address:shared:array:character, <span class="Constant">2</span>:address:shared:array:character
   <span class="Comment"># run the code in the editors multiple times</span>
   assume-console [
     press F4
     press F4
   ]
   run [
-    event-loop screen:address:screen, console:address:console, <span class="Constant">3</span>:address:programming-environment-data
+    event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">3</span>:address:shared:programming-environment-data
   ]
   <span class="Comment"># check that screen prints error message just once</span>
   screen-should-contain [
-   <span class="Constant"> .                                                                                 run (F4)           .</span>
+   <span class="Constant"> .  errors found (0)                                                               run (F4)           .</span>
    <span class="Constant"> .                                                  ┊                                                 .</span>
 <span class="Constant">    .┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┊━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━.</span>
-   <span class="Constant"> .                                                  ┊                                                x.</span>
+   <span class="Constant"> .                                                  ┊0                                               x.</span>
    <span class="Constant"> .                                                  ┊get 1234:number, foo:offset                      .</span>
    <span class="Constant"> .                                                  ┊unknown element foo in container number          .</span>
    <span class="Constant"> .                                                  ┊first ingredient of 'get' should be a container,↩.</span>
@@ -558,26 +655,26 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
   assume-screen <span class="Constant">100/width</span>, <span class="Constant">20/height</span>
   <span class="Comment"># left editor is empty</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[recipe foo [</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[recipe foo [</span>
 <span class="Constant">  {</span>
 <span class="Constant">    loop</span>
 <span class="Constant">  }</span>
 <span class="Constant">]</span>]
   <span class="Comment"># right editor contains an instruction</span>
-  <span class="Constant">2</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[foo]</span>
-  <span class="Constant">3</span>:address:programming-environment-data<span class="Special"> &lt;- </span>new-programming-environment screen:address:screen, <span class="Constant">1</span>:address:array:character, <span class="Constant">2</span>:address:array:character
+  <span class="Constant">2</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[foo]</span>
+  <span class="Constant">3</span>:address:shared:programming-environment-data<span class="Special"> &lt;- </span>new-programming-environment screen:address:shared:screen, <span class="Constant">1</span>:address:shared:array:character, <span class="Constant">2</span>:address:shared:array:character
   <span class="Comment"># run the sandbox</span>
   assume-console [
     press F4
   ]
   run [
-    event-loop screen:address:screen, console:address:console, <span class="Constant">3</span>:address:programming-environment-data
+    event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">3</span>:address:shared:programming-environment-data
   ]
   screen-should-contain [
-   <span class="Constant"> .                                                                                 run (F4)           .</span>
+   <span class="Constant"> .  errors found (0)                                                               run (F4)           .</span>
    <span class="Constant"> .recipe foo [                                      ┊                                                 .</span>
    <span class="Constant"> .  {                                               ┊━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━.</span>
-   <span class="Constant"> .    loop                                          ┊                                                x.</span>
+   <span class="Constant"> .    loop                                          ┊0                                               x.</span>
    <span class="Constant"> .  }                                               ┊foo                                              .</span>
    <span class="Constant"> .]                                                 ┊took too long!                                   .</span>
 <span class="Constant">    .┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┊━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━.</span>
@@ -589,7 +686,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
   assume-screen <span class="Constant">100/width</span>, <span class="Constant">10/height</span>
   <span class="Comment"># generate a stash and a warning</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[recipe foo [</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[recipe foo [</span>
 <span class="Constant">local-scope</span>
 <span class="Constant">a:number &lt;- next-ingredient</span>
 <span class="Constant">b:number &lt;- next-ingredient</span>
@@ -597,40 +694,43 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 _, c:number<span class="Special"> &lt;- </span>divide-with-remainder a, b
 <span class="muControl">reply</span> b
 ]]
-  <span class="Constant">2</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[foo 4, 0]</span>
-  <span class="Constant">3</span>:address:programming-environment-data<span class="Special"> &lt;- </span>new-programming-environment screen:address:screen, <span class="Constant">1</span>:address:array:character, <span class="Constant">2</span>:address:array:character
+  <span class="Constant">2</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[foo 4, 0]</span>
+  <span class="Constant">3</span>:address:shared:programming-environment-data<span class="Special"> &lt;- </span>new-programming-environment screen:address:shared:screen, <span class="Constant">1</span>:address:shared:array:character, <span class="Constant">2</span>:address:shared:array:character
   <span class="Comment"># run</span>
   assume-console [
     press F4
   ]
-  event-loop screen:address:screen, console:address:console, <span class="Constant">3</span>:address:programming-environment-data
+  event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">3</span>:address:shared:programming-environment-data
   <span class="Comment"># screen prints error message</span>
   screen-should-contain [
-   <span class="Constant"> .                                                                                 run (F4)           .</span>
-   <span class="Constant"> .recipe foo \\\[                                      ┊                                                 .</span>
+   <span class="Constant"> .  errors found (0)                                                               run (F4)           .</span>
+   <span class="Constant"> .recipe foo [                                      ┊                                                 .</span>
    <span class="Constant"> .local-scope                                       ┊━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━.</span>
-   <span class="Constant"> .a:number &lt;- next-ingredient                       ┊                                                x.</span>
+   <span class="Constant"> .a:number &lt;- next-ingredient                       ┊0                                               x.</span>
    <span class="Constant"> .b:number &lt;- next-ingredient                       ┊foo 4, 0                                         .</span>
    <span class="Constant"> .stash [dividing by], b                            ┊foo: divide by zero in '_, c:number &lt;- divide-wi↩.</span>
    <span class="Constant"> ._, c:number &lt;- divide-with-remainder a, b         ┊th-remainder a, b'                               .</span>
+   <span class="Constant"> .reply b                                           ┊━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━.</span>
+   <span class="Constant"> .]                                                 ┊                                                 .</span>
   ]
   <span class="Comment"># click on the call in the sandbox</span>
   assume-console [
     left-click <span class="Constant">4</span>, <span class="Constant">55</span>
   ]
   run [
-    event-loop screen:address:screen, console:address:console, <span class="Constant">3</span>:address:programming-environment-data
+    event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">3</span>:address:shared:programming-environment-data
   ]
   <span class="Comment"># screen should expand trace</span>
   screen-should-contain [
-   <span class="Constant"> .                                                                                 run (F4)           .</span>
-   <span class="Constant"> .recipe foo \\\[                                      ┊                                                 .</span>
+   <span class="Constant"> .  errors found (0)                                                               run (F4)           .</span>
+   <span class="Constant"> .recipe foo [                                      ┊                                                 .</span>
    <span class="Constant"> .local-scope                                       ┊━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━.</span>
-   <span class="Constant"> .a:number &lt;- next-ingredient                       ┊                                                x.</span>
+   <span class="Constant"> .a:number &lt;- next-ingredient                       ┊0                                               x.</span>
    <span class="Constant"> .b:number &lt;- next-ingredient                       ┊foo 4, 0                                         .</span>
    <span class="Constant"> .stash [dividing by], b                            ┊dividing by 0                                    .</span>
    <span class="Constant"> ._, c:number &lt;- divide-with-remainder a, b         ┊foo: divide by zero in '_, c:number &lt;- divide-wi↩.</span>
    <span class="Constant"> .reply b                                           ┊th-remainder a, b'                               .</span>
+   <span class="Constant"> .]                                                 ┊━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━.</span>
   ]
 ]
 </pre>
diff --git a/html/edit/011-editor-undo.mu.html b/html/edit/011-editor-undo.mu.html
index 801ca648..d5d66d09 100644
--- a/html/edit/011-editor-undo.mu.html
+++ b/html/edit/011-editor-undo.mu.html
@@ -46,13 +46,13 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="muData">container</span> insert-operation [
   before-row:number
   before-column:number
-  before-top-of-screen:address:duplex-list:character
+  before-top-of-screen:address:shared:duplex-list:character
   after-row:number
   after-column:number
-  after-top-of-screen:address:duplex-list:character
+  after-top-of-screen:address:shared:duplex-list:character
   <span class="Comment"># inserted text is from 'insert-from' until 'insert-until'; list doesn't have to terminate</span>
-  insert-from:address:duplex-list:character
-  insert-until:address:duplex-list:character
+  insert-from:address:shared:duplex-list:character
+  insert-until:address:shared:duplex-list:character
   tag:number  <span class="Comment"># event causing this operation; might be used to coalesce runs of similar events</span>
     <span class="Comment"># 0: no coalesce (enter+indent)</span>
     <span class="Comment"># 1: regular alphanumeric characters</span>
@@ -61,10 +61,10 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="muData">container</span> move-operation [
   before-row:number
   before-column:number
-  before-top-of-screen:address:duplex-list:character
+  before-top-of-screen:address:shared:duplex-list:character
   after-row:number
   after-column:number
-  after-top-of-screen:address:duplex-list:character
+  after-top-of-screen:address:shared:duplex-list:character
   tag:number  <span class="Comment"># event causing this operation; might be used to coalesce runs of similar events</span>
     <span class="Comment"># 0: no coalesce (touch events, etc)</span>
     <span class="Comment"># 1: left arrow</span>
@@ -76,13 +76,13 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="muData">container</span> delete-operation [
   before-row:number
   before-column:number
-  before-top-of-screen:address:duplex-list:character
+  before-top-of-screen:address:shared:duplex-list:character
   after-row:number
   after-column:number
-  after-top-of-screen:address:duplex-list:character
-  deleted-text:address:duplex-list:character
-  delete-from:address:duplex-list:character
-  delete-until:address:duplex-list:character
+  after-top-of-screen:address:shared:duplex-list:character
+  deleted-text:address:shared:duplex-list:character
+  delete-from:address:shared:duplex-list:character
+  delete-until:address:shared:duplex-list:character
   tag:number  <span class="Comment"># event causing this operation; might be used to coalesce runs of similar events</span>
     <span class="Comment"># 0: no coalesce (ctrl-k, ctrl-u)</span>
     <span class="Comment"># 1: backspace</span>
@@ -91,8 +91,8 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="Comment"># every editor accumulates a list of operations to undo/redo</span>
 <span class="muData">container</span> editor-data [
-  undo:address:list:address:operation
-  redo:address:list:address:operation
+  undo:address:shared:list:address:shared:operation
+  redo:address:shared:list:address:shared:operation
 ]
 
 <span class="Comment"># ctrl-z - undo operation</span>
@@ -100,11 +100,11 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   <span class="Delimiter">{</span>
     undo?:boolean<span class="Special"> &lt;- </span>equal *c, <span class="Constant">26/ctrl-z</span>
     <span class="muControl">break-unless</span> undo?
-    undo:address:address:list:address:operation<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">undo:offset</span>
+    undo:address:address:shared:list:address:shared:operation<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">undo:offset</span>
     <span class="muControl">break-unless</span> *undo
-    op:address:operation<span class="Special"> &lt;- </span>first *undo
+    op:address:shared:operation<span class="Special"> &lt;- </span>first *undo
     *undo<span class="Special"> &lt;- </span>rest *undo
-    redo:address:address:list:address:operation<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">redo:offset</span>
+    redo:address:address:shared:list:address:shared:operation<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">redo:offset</span>
     *redo<span class="Special"> &lt;- </span>push op, *redo
 <span class="Constant">    &lt;handle-undo&gt;</span>
     <span class="muControl">reply</span> screen/same-as-ingredient:<span class="Constant">0</span>, editor/same-as-ingredient:<span class="Constant">1</span>, <span class="Constant">1/go-render</span>
@@ -116,11 +116,11 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   <span class="Delimiter">{</span>
     redo?:boolean<span class="Special"> &lt;- </span>equal *c, <span class="Constant">25/ctrl-y</span>
     <span class="muControl">break-unless</span> redo?
-    redo:address:address:list:address:operation<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">redo:offset</span>
+    redo:address:address:shared:list:address:shared:operation<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">redo:offset</span>
     <span class="muControl">break-unless</span> *redo
-    op:address:operation<span class="Special"> &lt;- </span>first *redo
+    op:address:shared:operation<span class="Special"> &lt;- </span>first *redo
     *redo<span class="Special"> &lt;- </span>rest *redo
-    undo:address:address:list:address:operation<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">undo:offset</span>
+    undo:address:address:shared:list:address:shared:operation<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">undo:offset</span>
     *undo<span class="Special"> &lt;- </span>push op, *undo
 <span class="Constant">    &lt;handle-redo&gt;</span>
     <span class="muControl">reply</span> screen/same-as-ingredient:<span class="Constant">0</span>, editor/same-as-ingredient:<span class="Constant">1</span>, <span class="Constant">1/go-render</span>
@@ -132,19 +132,19 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="muScenario">scenario</span> editor-can-undo-typing [
   <span class="Comment"># create an editor and type a character</span>
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
-  editor-render screen, <span class="Constant">2</span>:address:editor-data
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+  editor-render screen, <span class="Constant">2</span>:address:shared:editor-data
   assume-console [
     type <span class="Constant">[0]</span>
   ]
-  editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+  editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   <span class="Comment"># undo</span>
   assume-console [
     press ctrl-z
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   <span class="Comment"># character should be gone</span>
   screen-should-contain [
@@ -158,7 +158,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     type <span class="Constant">[1]</span>
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   screen-should-contain [
    <span class="Constant"> .          .</span>
@@ -170,34 +170,34 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="Comment"># save operation to undo</span>
 <span class="muRecipe">after</span> <span class="Constant">&lt;insert-character-begin&gt;</span> [
-  top-before:address:duplex-list:character<span class="Special"> &lt;- </span>get *editor, <span class="Constant">top-of-screen:offset</span>
-  cursor-before:address:duplex-list:character<span class="Special"> &lt;- </span>copy *before-cursor
+  top-before:address:shared:duplex-list:character<span class="Special"> &lt;- </span>get *editor, <span class="Constant">top-of-screen:offset</span>
+  cursor-before:address:shared:duplex-list:character<span class="Special"> &lt;- </span>copy *before-cursor
 ]
 <span class="muRecipe">before</span> <span class="Constant">&lt;insert-character-end&gt;</span> [
-  top-after:address:duplex-list:character<span class="Special"> &lt;- </span>get *editor, <span class="Constant">top-of-screen:offset</span>
-  undo:address:address:list:address:operation<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">undo:offset</span>
+  top-after:address:shared:duplex-list:character<span class="Special"> &lt;- </span>get *editor, <span class="Constant">top-of-screen:offset</span>
+  undo:address:address:shared:list:address:shared:operation<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">undo:offset</span>
   <span class="Delimiter">{</span>
     <span class="Comment"># if previous operation was an insert, coalesce this operation with it</span>
     <span class="muControl">break-unless</span> *undo
-    op:address:operation<span class="Special"> &lt;- </span>first *undo
+    op:address:shared:operation<span class="Special"> &lt;- </span>first *undo
     typing:address:insert-operation<span class="Special"> &lt;- </span>maybe-convert *op, <span class="Constant">typing:variant</span>
     <span class="muControl">break-unless</span> typing
     previous-coalesce-tag:number<span class="Special"> &lt;- </span>get *typing, <span class="Constant">tag:offset</span>
     <span class="muControl">break-unless</span> previous-coalesce-tag
-    insert-until:address:address:duplex-list:character<span class="Special"> &lt;- </span>get-address *typing, <span class="Constant">insert-until:offset</span>
+    insert-until:address:address:shared:duplex-list:character<span class="Special"> &lt;- </span>get-address *typing, <span class="Constant">insert-until:offset</span>
     *insert-until<span class="Special"> &lt;- </span>next *before-cursor
     after-row:address:number<span class="Special"> &lt;- </span>get-address *typing, <span class="Constant">after-row:offset</span>
     *after-row<span class="Special"> &lt;- </span>copy *cursor-row
     after-column:address:number<span class="Special"> &lt;- </span>get-address *typing, <span class="Constant">after-column:offset</span>
     *after-column<span class="Special"> &lt;- </span>copy *cursor-column
-    after-top:address:address:duplex-list:character<span class="Special"> &lt;- </span>get-address *typing, <span class="Constant">after-top-of-screen:offset</span>
+    after-top:address:address:shared:duplex-list:character<span class="Special"> &lt;- </span>get-address *typing, <span class="Constant">after-top-of-screen:offset</span>
     *after-top<span class="Special"> &lt;- </span>get *editor, <span class="Constant">top-of-screen:offset</span>
     <span class="muControl">break</span> <span class="Constant">+done-adding-insert-operation:label</span>
   <span class="Delimiter">}</span>
   <span class="Comment"># if not, create a new operation</span>
-  insert-from:address:duplex-list:character<span class="Special"> &lt;- </span>next cursor-before
-  insert-to:address:duplex-list:character<span class="Special"> &lt;- </span>next insert-from
-  op:address:operation<span class="Special"> &lt;- </span>new <span class="Constant">operation:type</span>
+  insert-from:address:shared:duplex-list:character<span class="Special"> &lt;- </span>next cursor-before
+  insert-to:address:shared:duplex-list:character<span class="Special"> &lt;- </span>next insert-from
+  op:address:shared:operation<span class="Special"> &lt;- </span>new <span class="Constant">operation:type</span>
   *op<span class="Special"> &lt;- </span>merge <span class="Constant">0/insert-operation</span>, save-row/<span class="muRecipe">before</span>, save-column/<span class="muRecipe">before</span>, top-before, *cursor-row/<span class="muRecipe">after</span>, *cursor-column/<span class="muRecipe">after</span>, top-after, insert-from, insert-to, <span class="Constant">1/coalesce</span>
   editor<span class="Special"> &lt;- </span>add-operation editor, op
 <span class="Constant">  +done-adding-insert-operation</span>
@@ -207,15 +207,15 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="muRecipe">after</span> <span class="Constant">&lt;insert-enter-begin&gt;</span> [
   cursor-row-before:number<span class="Special"> &lt;- </span>copy *cursor-row
   cursor-column-before:number<span class="Special"> &lt;- </span>copy *cursor-column
-  top-before:address:duplex-list:character<span class="Special"> &lt;- </span>get *editor, <span class="Constant">top-of-screen:offset</span>
-  cursor-before:address:duplex-list:character<span class="Special"> &lt;- </span>copy *before-cursor
+  top-before:address:shared:duplex-list:character<span class="Special"> &lt;- </span>get *editor, <span class="Constant">top-of-screen:offset</span>
+  cursor-before:address:shared:duplex-list:character<span class="Special"> &lt;- </span>copy *before-cursor
 ]
 <span class="muRecipe">before</span> <span class="Constant">&lt;insert-enter-end&gt;</span> [
-  top-after:address:duplex-list:character<span class="Special"> &lt;- </span>get *editor, <span class="Constant">top-of-screen:offset</span>
+  top-after:address:shared:duplex-list:character<span class="Special"> &lt;- </span>get *editor, <span class="Constant">top-of-screen:offset</span>
   <span class="Comment"># never coalesce</span>
-  insert-from:address:duplex-list:character<span class="Special"> &lt;- </span>next cursor-before
-  insert-to:address:duplex-list:character<span class="Special"> &lt;- </span>next *before-cursor
-  op:address:operation<span class="Special"> &lt;- </span>new <span class="Constant">operation:type</span>
+  insert-from:address:shared:duplex-list:character<span class="Special"> &lt;- </span>next cursor-before
+  insert-to:address:shared:duplex-list:character<span class="Special"> &lt;- </span>next *before-cursor
+  op:address:shared:operation<span class="Special"> &lt;- </span>new <span class="Constant">operation:type</span>
   *op<span class="Special"> &lt;- </span>merge <span class="Constant">0/insert-operation</span>, cursor-row-before, cursor-column-before, top-before, *cursor-row/<span class="muRecipe">after</span>, *cursor-column/<span class="muRecipe">after</span>, top-after, insert-from, insert-to, <span class="Constant">0/never-coalesce</span>
   editor<span class="Special"> &lt;- </span>add-operation editor, op
 ]
@@ -224,12 +224,12 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="Comment"># redo stack, because it's now obsolete.</span>
 <span class="Comment"># Beware: since we're counting cursor moves as operations, this means just</span>
 <span class="Comment"># moving the cursor can lose work on the undo stack.</span>
-<span class="muRecipe">recipe</span> add-operation editor:address:editor-data, op:address:operation<span class="muRecipe"> -&gt; </span>editor:address:editor-data [
+<span class="muRecipe">recipe</span> add-operation editor:address:shared:editor-data, op:address:shared:operation<span class="muRecipe"> -&gt; </span>editor:address:shared:editor-data [
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
-  undo:address:address:list:address:operation<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">undo:offset</span>
+  undo:address:address:shared:list:address:shared:operation<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">undo:offset</span>
   *undo<span class="Special"> &lt;- </span>push op *undo
-  redo:address:address:list:address:operation<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">redo:offset</span>
+  redo:address:address:shared:list:address:shared:operation<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">redo:offset</span>
   *redo<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
   <span class="muControl">reply</span> editor/same-as-ingredient:<span class="Constant">0</span>
 ]
@@ -238,14 +238,14 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   <span class="Delimiter">{</span>
     typing:address:insert-operation<span class="Special"> &lt;- </span>maybe-convert *op, <span class="Constant">typing:variant</span>
     <span class="muControl">break-unless</span> typing
-    start:address:duplex-list:character<span class="Special"> &lt;- </span>get *typing, <span class="Constant">insert-from:offset</span>
-    end:address:duplex-list:character<span class="Special"> &lt;- </span>get *typing, <span class="Constant">insert-until:offset</span>
+    start:address:shared:duplex-list:character<span class="Special"> &lt;- </span>get *typing, <span class="Constant">insert-from:offset</span>
+    end:address:shared:duplex-list:character<span class="Special"> &lt;- </span>get *typing, <span class="Constant">insert-until:offset</span>
     <span class="Comment"># assert cursor-row/cursor-column/top-of-screen match after-row/after-column/after-top-of-screen</span>
     *before-cursor<span class="Special"> &lt;- </span>prev start
     remove-between *before-cursor, end
     *cursor-row<span class="Special"> &lt;- </span>get *typing, <span class="Constant">before-row:offset</span>
     *cursor-column<span class="Special"> &lt;- </span>get *typing, <span class="Constant">before-column:offset</span>
-    top:address:address:duplex-list:character<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">top-of-screen:offset</span>
+    top:address:address:shared:duplex-list:character<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">top-of-screen:offset</span>
     *top<span class="Special"> &lt;- </span>get *typing, <span class="Constant">before-top-of-screen:offset</span>
   <span class="Delimiter">}</span>
 ]
@@ -253,19 +253,19 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="muScenario">scenario</span> editor-can-undo-typing-multiple [
   <span class="Comment"># create an editor and type multiple characters</span>
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
-  editor-render screen, <span class="Constant">2</span>:address:editor-data
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+  editor-render screen, <span class="Constant">2</span>:address:shared:editor-data
   assume-console [
     type <span class="Constant">[012]</span>
   ]
-  editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+  editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   <span class="Comment"># undo</span>
   assume-console [
     press ctrl-z
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   <span class="Comment"># all characters must be gone</span>
   screen-should-contain [
@@ -279,14 +279,14 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="muScenario">scenario</span> editor-can-undo-typing-multiple-2 [
   <span class="Comment"># create an editor with some text</span>
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[a]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
-  editor-render screen, <span class="Constant">2</span>:address:editor-data
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[a]</span>
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+  editor-render screen, <span class="Constant">2</span>:address:shared:editor-data
   <span class="Comment"># type some characters</span>
   assume-console [
     type <span class="Constant">[012]</span>
   ]
-  editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+  editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   screen-should-contain [
    <span class="Constant"> .          .</span>
    <span class="Constant"> .012a      .</span>
@@ -298,7 +298,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     press ctrl-z
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   <span class="Comment"># back to original text</span>
   screen-should-contain [
@@ -312,7 +312,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     type <span class="Constant">[3]</span>
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   screen-should-contain [
    <span class="Constant"> .          .</span>
@@ -325,15 +325,15 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="muScenario">scenario</span> editor-can-undo-typing-enter [
   <span class="Comment"># create an editor with some text</span>
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[  abc]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
-  editor-render screen, <span class="Constant">2</span>:address:editor-data
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[  abc]</span>
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+  editor-render screen, <span class="Constant">2</span>:address:shared:editor-data
   <span class="Comment"># new line</span>
   assume-console [
     left-click <span class="Constant">1</span>, <span class="Constant">8</span>
     press enter
   ]
-  editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+  editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   screen-should-contain [
    <span class="Constant"> .          .</span>
    <span class="Constant"> .  abc     .</span>
@@ -342,8 +342,8 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
    <span class="Constant"> .          .</span>
   ]
   <span class="Comment"># line is indented</span>
-  <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-  <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+  <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+  <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   memory-should-contain [
     <span class="Constant">3</span><span class="Special"> &lt;- </span><span class="Constant">2</span>
     <span class="Constant">4</span><span class="Special"> &lt;- </span><span class="Constant">2</span>
@@ -353,10 +353,10 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     press ctrl-z
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
-  <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-  <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+  <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+  <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   memory-should-contain [
     <span class="Constant">3</span><span class="Special"> &lt;- </span><span class="Constant">1</span>
     <span class="Constant">4</span><span class="Special"> &lt;- </span><span class="Constant">5</span>
@@ -373,7 +373,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     type <span class="Constant">[1]</span>
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   screen-should-contain [
    <span class="Constant"> .          .</span>
@@ -388,14 +388,14 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="muScenario">scenario</span> editor-redo-typing [
   <span class="Comment"># create an editor, type something, undo</span>
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[a]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
-  editor-render screen, <span class="Constant">2</span>:address:editor-data
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[a]</span>
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+  editor-render screen, <span class="Constant">2</span>:address:shared:editor-data
   assume-console [
     type <span class="Constant">[012]</span>
     press ctrl-z
   ]
-  editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+  editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   screen-should-contain [
    <span class="Constant"> .          .</span>
    <span class="Constant"> .a         .</span>
@@ -407,7 +407,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     press ctrl-y
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   <span class="Comment"># all characters must be back</span>
   screen-should-contain [
@@ -421,7 +421,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     type <span class="Constant">[3]</span>
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   screen-should-contain [
    <span class="Constant"> .          .</span>
@@ -435,13 +435,13 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   <span class="Delimiter">{</span>
     typing:address:insert-operation<span class="Special"> &lt;- </span>maybe-convert *op, <span class="Constant">typing:variant</span>
     <span class="muControl">break-unless</span> typing
-    insert-from:address:duplex-list:character<span class="Special"> &lt;- </span>get *typing, <span class="Constant">insert-from:offset</span>  <span class="Comment"># ignore insert-to because it's already been spliced away</span>
+    insert-from:address:shared:duplex-list:character<span class="Special"> &lt;- </span>get *typing, <span class="Constant">insert-from:offset</span>  <span class="Comment"># ignore insert-to because it's already been spliced away</span>
     <span class="Comment"># assert insert-to matches next(*before-cursor)</span>
     insert-range *before-cursor, insert-from
     <span class="Comment"># assert cursor-row/cursor-column/top-of-screen match after-row/after-column/after-top-of-screen</span>
     *cursor-row<span class="Special"> &lt;- </span>get *typing, <span class="Constant">after-row:offset</span>
     *cursor-column<span class="Special"> &lt;- </span>get *typing, <span class="Constant">after-column:offset</span>
-    top:address:address:duplex-list:character<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">top-of-screen:offset</span>
+    top:address:address:shared:duplex-list:character<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">top-of-screen:offset</span>
     *top<span class="Special"> &lt;- </span>get *typing, <span class="Constant">after-top-of-screen:offset</span>
   <span class="Delimiter">}</span>
 ]
@@ -449,14 +449,14 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="muScenario">scenario</span> editor-redo-typing-empty [
   <span class="Comment"># create an editor, type something, undo</span>
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
-  editor-render screen, <span class="Constant">2</span>:address:editor-data
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+  editor-render screen, <span class="Constant">2</span>:address:shared:editor-data
   assume-console [
     type <span class="Constant">[012]</span>
     press ctrl-z
   ]
-  editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+  editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   screen-should-contain [
    <span class="Constant"> .          .</span>
    <span class="Constant"> .          .</span>
@@ -468,7 +468,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     press ctrl-y
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   <span class="Comment"># all characters must be back</span>
   screen-should-contain [
@@ -482,7 +482,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     type <span class="Constant">[3]</span>
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   screen-should-contain [
    <span class="Constant"> .          .</span>
@@ -495,21 +495,21 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="muScenario">scenario</span> editor-work-clears-redo-stack [
   <span class="Comment"># create an editor with some text, do some work, undo</span>
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
 <span class="Constant">def</span>
 <span class="Constant">ghi]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
-  editor-render screen, <span class="Constant">2</span>:address:editor-data
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+  editor-render screen, <span class="Constant">2</span>:address:shared:editor-data
   assume-console [
     type <span class="Constant">[1]</span>
     press ctrl-z
   ]
-  editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+  editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   <span class="Comment"># do some more work</span>
   assume-console [
     type <span class="Constant">[0]</span>
   ]
-  editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+  editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   screen-should-contain [
    <span class="Constant"> .          .</span>
    <span class="Constant"> .0abc      .</span>
@@ -522,7 +522,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     press ctrl-y
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   <span class="Comment"># nothing should happen</span>
   screen-should-contain [
@@ -537,9 +537,9 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="muScenario">scenario</span> editor-can-redo-typing-and-enter-and-tab [
   <span class="Comment"># create an editor</span>
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
-  editor-render screen, <span class="Constant">2</span>:address:editor-data
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+  editor-render screen, <span class="Constant">2</span>:address:shared:editor-data
   <span class="Comment"># insert some text and tabs, hit enter, some more text and tabs</span>
   assume-console [
     press tab
@@ -550,7 +550,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     press tab
     type <span class="Constant">[efg]</span>
   ]
-  editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+  editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   screen-should-contain [
    <span class="Constant"> .          .</span>
    <span class="Constant"> .  ab  cd  .</span>
@@ -558,8 +558,8 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="Constant">    .┈┈┈┈┈┈┈┈┈┈.</span>
    <span class="Constant"> .          .</span>
   ]
-  <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-  <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+  <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+  <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   memory-should-contain [
     <span class="Constant">3</span><span class="Special"> &lt;- </span><span class="Constant">2</span>
     <span class="Constant">4</span><span class="Special"> &lt;- </span><span class="Constant">7</span>
@@ -569,11 +569,11 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     press ctrl-z
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   <span class="Comment"># typing in second line deleted, but not indent</span>
-  <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-  <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+  <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+  <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   memory-should-contain [
     <span class="Constant">3</span><span class="Special"> &lt;- </span><span class="Constant">2</span>
     <span class="Constant">4</span><span class="Special"> &lt;- </span><span class="Constant">2</span>
@@ -590,11 +590,11 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     press ctrl-z
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   <span class="Comment"># indent and newline deleted</span>
-  <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-  <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+  <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+  <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   memory-should-contain [
     <span class="Constant">3</span><span class="Special"> &lt;- </span><span class="Constant">1</span>
     <span class="Constant">4</span><span class="Special"> &lt;- </span><span class="Constant">8</span>
@@ -610,11 +610,11 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     press ctrl-z
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   <span class="Comment"># empty screen</span>
-  <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-  <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+  <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+  <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   memory-should-contain [
     <span class="Constant">3</span><span class="Special"> &lt;- </span><span class="Constant">1</span>
     <span class="Constant">4</span><span class="Special"> &lt;- </span><span class="Constant">0</span>
@@ -630,11 +630,11 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     press ctrl-y
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   <span class="Comment"># first line inserted</span>
-  <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-  <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+  <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+  <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   memory-should-contain [
     <span class="Constant">3</span><span class="Special"> &lt;- </span><span class="Constant">1</span>
     <span class="Constant">4</span><span class="Special"> &lt;- </span><span class="Constant">8</span>
@@ -650,11 +650,11 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     press ctrl-y
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   <span class="Comment"># newline and indent inserted</span>
-  <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-  <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+  <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+  <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   memory-should-contain [
     <span class="Constant">3</span><span class="Special"> &lt;- </span><span class="Constant">2</span>
     <span class="Constant">4</span><span class="Special"> &lt;- </span><span class="Constant">2</span>
@@ -671,11 +671,11 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     press ctrl-y
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   <span class="Comment"># indent and newline deleted</span>
-  <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-  <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+  <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+  <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   memory-should-contain [
     <span class="Constant">3</span><span class="Special"> &lt;- </span><span class="Constant">2</span>
     <span class="Constant">4</span><span class="Special"> &lt;- </span><span class="Constant">7</span>
@@ -694,24 +694,24 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="muScenario">scenario</span> editor-can-undo-touch [
   <span class="Comment"># create an editor with some text</span>
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
 <span class="Constant">def</span>
 <span class="Constant">ghi]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
-  editor-render screen, <span class="Constant">2</span>:address:editor-data
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+  editor-render screen, <span class="Constant">2</span>:address:shared:editor-data
   <span class="Comment"># move the cursor</span>
   assume-console [
     left-click <span class="Constant">3</span>, <span class="Constant">1</span>
   ]
-  editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+  editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   <span class="Comment"># undo</span>
   assume-console [
     press ctrl-z
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
-    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
+    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   ]
   <span class="Comment"># click undone</span>
   memory-should-contain [
@@ -723,7 +723,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     type <span class="Constant">[1]</span>
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   screen-should-contain [
    <span class="Constant"> .          .</span>
@@ -737,19 +737,19 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="muRecipe">after</span> <span class="Constant">&lt;move-cursor-begin&gt;</span> [
   before-cursor-row:number<span class="Special"> &lt;- </span>get *editor, <span class="Constant">cursor-row:offset</span>
   before-cursor-column:number<span class="Special"> &lt;- </span>get *editor, <span class="Constant">cursor-column:offset</span>
-  before-top-of-screen:address:duplex-list:character<span class="Special"> &lt;- </span>get *editor, <span class="Constant">top-of-screen:offset</span>
+  before-top-of-screen:address:shared:duplex-list:character<span class="Special"> &lt;- </span>get *editor, <span class="Constant">top-of-screen:offset</span>
 ]
 <span class="muRecipe">before</span> <span class="Constant">&lt;move-cursor-end&gt;</span> [
   after-cursor-row:number<span class="Special"> &lt;- </span>get *editor, <span class="Constant">cursor-row:offset</span>
   after-cursor-column:number<span class="Special"> &lt;- </span>get *editor, <span class="Constant">cursor-column:offset</span>
-  after-top-of-screen:address:duplex-list:character<span class="Special"> &lt;- </span>get *editor, <span class="Constant">top-of-screen:offset</span>
+  after-top-of-screen:address:shared:duplex-list:character<span class="Special"> &lt;- </span>get *editor, <span class="Constant">top-of-screen:offset</span>
   <span class="Delimiter">{</span>
     <span class="muControl">break-unless</span> undo-coalesce-tag
     <span class="Comment"># if previous operation was also a move, and also had the same coalesce</span>
     <span class="Comment"># tag, coalesce with it</span>
-    undo:address:address:list:address:operation<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">undo:offset</span>
+    undo:address:address:shared:list:address:shared:operation<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">undo:offset</span>
     <span class="muControl">break-unless</span> *undo
-    op:address:operation<span class="Special"> &lt;- </span>first *undo
+    op:address:shared:operation<span class="Special"> &lt;- </span>first *undo
     move:address:move-operation<span class="Special"> &lt;- </span>maybe-convert *op, <span class="Constant">move:variant</span>
     <span class="muControl">break-unless</span> move
     previous-coalesce-tag:number<span class="Special"> &lt;- </span>get *move, <span class="Constant">tag:offset</span>
@@ -759,11 +759,11 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     *after-row<span class="Special"> &lt;- </span>copy after-cursor-row
     after-column:address:number<span class="Special"> &lt;- </span>get-address *move, <span class="Constant">after-column:offset</span>
     *after-column<span class="Special"> &lt;- </span>copy after-cursor-column
-    after-top:address:address:duplex-list:character<span class="Special"> &lt;- </span>get-address *move, <span class="Constant">after-top-of-screen:offset</span>
+    after-top:address:address:shared:duplex-list:character<span class="Special"> &lt;- </span>get-address *move, <span class="Constant">after-top-of-screen:offset</span>
     *after-top<span class="Special"> &lt;- </span>get *editor, <span class="Constant">top-of-screen:offset</span>
     <span class="muControl">break</span> <span class="Constant">+done-adding-move-operation:label</span>
   <span class="Delimiter">}</span>
-  op:address:operation<span class="Special"> &lt;- </span>new <span class="Constant">operation:type</span>
+  op:address:shared:operation<span class="Special"> &lt;- </span>new <span class="Constant">operation:type</span>
   *op<span class="Special"> &lt;- </span>merge <span class="Constant">1/move-operation</span>, before-cursor-row, before-cursor-column, before-top-of-screen, after-cursor-row, after-cursor-column, after-top-of-screen, undo-coalesce-tag
   editor<span class="Special"> &lt;- </span>add-operation editor, op
 <span class="Constant">  +done-adding-move-operation</span>
@@ -774,7 +774,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     move:address:move-operation<span class="Special"> &lt;- </span>maybe-convert *op, <span class="Constant">move:variant</span>
     <span class="muControl">break-unless</span> move
     <span class="Comment"># assert cursor-row/cursor-column/top-of-screen match after-row/after-column/after-top-of-screen</span>
-    top:address:address:duplex-list:character<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">top-of-screen:offset</span>
+    top:address:address:shared:duplex-list:character<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">top-of-screen:offset</span>
     *cursor-row<span class="Special"> &lt;- </span>get *move, <span class="Constant">before-row:offset</span>
     *cursor-column<span class="Special"> &lt;- </span>get *move, <span class="Constant">before-column:offset</span>
     *top<span class="Special"> &lt;- </span>get *move, <span class="Constant">before-top-of-screen:offset</span>
@@ -785,18 +785,18 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   <span class="Comment"># screen has 1 line for menu + 3 lines</span>
   assume-screen <span class="Constant">5/width</span>, <span class="Constant">4/height</span>
   <span class="Comment"># editor contains a wrapped line</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[a</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[a</span>
 <span class="Constant">b</span>
 <span class="Constant">cdefgh]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
   <span class="Comment"># position cursor at end of screen and try to move right</span>
   assume-console [
     left-click <span class="Constant">3</span>, <span class="Constant">3</span>
     press right-arrow
   ]
-  editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
-  <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-  <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+  editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
+  <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+  <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   <span class="Comment"># screen scrolls</span>
   screen-should-contain [
    <span class="Constant"> .     .</span>
@@ -813,9 +813,9 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     press ctrl-z
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
-    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
+    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   ]
   <span class="Comment"># cursor moved back</span>
   memory-should-contain [
@@ -834,7 +834,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     type <span class="Constant">[1]</span>
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   screen-should-contain [
    <span class="Constant"> .     .</span>
@@ -847,25 +847,25 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="muScenario">scenario</span> editor-can-undo-left-arrow [
   <span class="Comment"># create an editor with some text</span>
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
 <span class="Constant">def</span>
 <span class="Constant">ghi]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
-  editor-render screen, <span class="Constant">2</span>:address:editor-data
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+  editor-render screen, <span class="Constant">2</span>:address:shared:editor-data
   <span class="Comment"># move the cursor</span>
   assume-console [
     left-click <span class="Constant">3</span>, <span class="Constant">1</span>
     press left-arrow
   ]
-  editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+  editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   <span class="Comment"># undo</span>
   assume-console [
     press ctrl-z
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
-    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
+    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   ]
   <span class="Comment"># cursor moves back</span>
   memory-should-contain [
@@ -877,7 +877,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     type <span class="Constant">[1]</span>
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   screen-should-contain [
    <span class="Constant"> .          .</span>
@@ -891,19 +891,19 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="muScenario">scenario</span> editor-can-undo-up-arrow [
   <span class="Comment"># create an editor with some text</span>
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
 <span class="Constant">def</span>
 <span class="Constant">ghi]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
-  editor-render screen, <span class="Constant">2</span>:address:editor-data
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+  editor-render screen, <span class="Constant">2</span>:address:shared:editor-data
   <span class="Comment"># move the cursor</span>
   assume-console [
     left-click <span class="Constant">3</span>, <span class="Constant">1</span>
     press up-arrow
   ]
-  editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
-  <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-  <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+  editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
+  <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+  <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   memory-should-contain [
     <span class="Constant">3</span><span class="Special"> &lt;- </span><span class="Constant">2</span>
     <span class="Constant">4</span><span class="Special"> &lt;- </span><span class="Constant">1</span>
@@ -913,9 +913,9 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     press ctrl-z
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
-    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
+    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   ]
   <span class="Comment"># cursor moves back</span>
   memory-should-contain [
@@ -927,7 +927,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     type <span class="Constant">[1]</span>
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   screen-should-contain [
    <span class="Constant"> .          .</span>
@@ -941,25 +941,25 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="muScenario">scenario</span> editor-can-undo-down-arrow [
   <span class="Comment"># create an editor with some text</span>
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
 <span class="Constant">def</span>
 <span class="Constant">ghi]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
-  editor-render screen, <span class="Constant">2</span>:address:editor-data
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+  editor-render screen, <span class="Constant">2</span>:address:shared:editor-data
   <span class="Comment"># move the cursor</span>
   assume-console [
     left-click <span class="Constant">2</span>, <span class="Constant">1</span>
     press down-arrow
   ]
-  editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+  editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   <span class="Comment"># undo</span>
   assume-console [
     press ctrl-z
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
-    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
+    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   ]
   <span class="Comment"># cursor moves back</span>
   memory-should-contain [
@@ -971,7 +971,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     type <span class="Constant">[1]</span>
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   screen-should-contain [
    <span class="Constant"> .          .</span>
@@ -985,27 +985,27 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="muScenario">scenario</span> editor-can-undo-ctrl-f [
   <span class="Comment"># create an editor with multiple pages of text</span>
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[a</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[a</span>
 <span class="Constant">b</span>
 <span class="Constant">c</span>
 <span class="Constant">d</span>
 <span class="Constant">e</span>
 <span class="Constant">f]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
-  editor-render screen, <span class="Constant">2</span>:address:editor-data
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+  editor-render screen, <span class="Constant">2</span>:address:shared:editor-data
   <span class="Comment"># scroll the page</span>
   assume-console [
     press ctrl-f
   ]
-  editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+  editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   <span class="Comment"># undo</span>
   assume-console [
     press ctrl-z
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
-    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
+    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   ]
   <span class="Comment"># screen should again show page 1</span>
   screen-should-contain [
@@ -1020,27 +1020,27 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="muScenario">scenario</span> editor-can-undo-page-down [
   <span class="Comment"># create an editor with multiple pages of text</span>
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[a</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[a</span>
 <span class="Constant">b</span>
 <span class="Constant">c</span>
 <span class="Constant">d</span>
 <span class="Constant">e</span>
 <span class="Constant">f]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
-  editor-render screen, <span class="Constant">2</span>:address:editor-data
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+  editor-render screen, <span class="Constant">2</span>:address:shared:editor-data
   <span class="Comment"># scroll the page</span>
   assume-console [
     press page-down
   ]
-  editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+  editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   <span class="Comment"># undo</span>
   assume-console [
     press ctrl-z
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
-    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
+    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   ]
   <span class="Comment"># screen should again show page 1</span>
   screen-should-contain [
@@ -1055,28 +1055,28 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="muScenario">scenario</span> editor-can-undo-ctrl-b [
   <span class="Comment"># create an editor with multiple pages of text</span>
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[a</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[a</span>
 <span class="Constant">b</span>
 <span class="Constant">c</span>
 <span class="Constant">d</span>
 <span class="Constant">e</span>
 <span class="Constant">f]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
-  editor-render screen, <span class="Constant">2</span>:address:editor-data
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+  editor-render screen, <span class="Constant">2</span>:address:shared:editor-data
   <span class="Comment"># scroll the page down and up</span>
   assume-console [
     press page-down
     press ctrl-b
   ]
-  editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+  editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   <span class="Comment"># undo</span>
   assume-console [
     press ctrl-z
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
-    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
+    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   ]
   <span class="Comment"># screen should again show page 2</span>
   screen-should-contain [
@@ -1091,28 +1091,28 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="muScenario">scenario</span> editor-can-undo-page-up [
   <span class="Comment"># create an editor with multiple pages of text</span>
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[a</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[a</span>
 <span class="Constant">b</span>
 <span class="Constant">c</span>
 <span class="Constant">d</span>
 <span class="Constant">e</span>
 <span class="Constant">f]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
-  editor-render screen, <span class="Constant">2</span>:address:editor-data
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+  editor-render screen, <span class="Constant">2</span>:address:shared:editor-data
   <span class="Comment"># scroll the page down and up</span>
   assume-console [
     press page-down
     press page-up
   ]
-  editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+  editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   <span class="Comment"># undo</span>
   assume-console [
     press ctrl-z
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
-    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
+    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   ]
   <span class="Comment"># screen should again show page 2</span>
   screen-should-contain [
@@ -1127,25 +1127,25 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="muScenario">scenario</span> editor-can-undo-ctrl-a [
   <span class="Comment"># create an editor with some text</span>
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
 <span class="Constant">def</span>
 <span class="Constant">ghi]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
-  editor-render screen, <span class="Constant">2</span>:address:editor-data
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+  editor-render screen, <span class="Constant">2</span>:address:shared:editor-data
   <span class="Comment"># move the cursor, then to start of line</span>
   assume-console [
     left-click <span class="Constant">2</span>, <span class="Constant">1</span>
     press ctrl-a
   ]
-  editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+  editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   <span class="Comment"># undo</span>
   assume-console [
     press ctrl-z
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
-    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
+    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   ]
   <span class="Comment"># cursor moves back</span>
   memory-should-contain [
@@ -1157,7 +1157,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     type <span class="Constant">[1]</span>
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   screen-should-contain [
    <span class="Constant"> .          .</span>
@@ -1171,25 +1171,25 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="muScenario">scenario</span> editor-can-undo-home [
   <span class="Comment"># create an editor with some text</span>
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
 <span class="Constant">def</span>
 <span class="Constant">ghi]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
-  editor-render screen, <span class="Constant">2</span>:address:editor-data
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+  editor-render screen, <span class="Constant">2</span>:address:shared:editor-data
   <span class="Comment"># move the cursor, then to start of line</span>
   assume-console [
     left-click <span class="Constant">2</span>, <span class="Constant">1</span>
     press home
   ]
-  editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+  editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   <span class="Comment"># undo</span>
   assume-console [
     press ctrl-z
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
-    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
+    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   ]
   <span class="Comment"># cursor moves back</span>
   memory-should-contain [
@@ -1201,7 +1201,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     type <span class="Constant">[1]</span>
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   screen-should-contain [
    <span class="Constant"> .          .</span>
@@ -1215,25 +1215,25 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="muScenario">scenario</span> editor-can-undo-ctrl-e [
   <span class="Comment"># create an editor with some text</span>
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
 <span class="Constant">def</span>
 <span class="Constant">ghi]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
-  editor-render screen, <span class="Constant">2</span>:address:editor-data
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+  editor-render screen, <span class="Constant">2</span>:address:shared:editor-data
   <span class="Comment"># move the cursor, then to start of line</span>
   assume-console [
     left-click <span class="Constant">2</span>, <span class="Constant">1</span>
     press ctrl-e
   ]
-  editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+  editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   <span class="Comment"># undo</span>
   assume-console [
     press ctrl-z
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
-    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
+    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   ]
   <span class="Comment"># cursor moves back</span>
   memory-should-contain [
@@ -1245,7 +1245,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     type <span class="Constant">[1]</span>
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   screen-should-contain [
    <span class="Constant"> .          .</span>
@@ -1259,25 +1259,25 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="muScenario">scenario</span> editor-can-undo-end [
   <span class="Comment"># create an editor with some text</span>
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
 <span class="Constant">def</span>
 <span class="Constant">ghi]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
-  editor-render screen, <span class="Constant">2</span>:address:editor-data
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+  editor-render screen, <span class="Constant">2</span>:address:shared:editor-data
   <span class="Comment"># move the cursor, then to start of line</span>
   assume-console [
     left-click <span class="Constant">2</span>, <span class="Constant">1</span>
     press end
   ]
-  editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+  editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   <span class="Comment"># undo</span>
   assume-console [
     press ctrl-z
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
-    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
+    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   ]
   <span class="Comment"># cursor moves back</span>
   memory-should-contain [
@@ -1289,7 +1289,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     type <span class="Constant">[1]</span>
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   screen-should-contain [
    <span class="Constant"> .          .</span>
@@ -1303,17 +1303,17 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="muScenario">scenario</span> editor-separates-undo-insert-from-undo-cursor-move [
   <span class="Comment"># create an editor, type some text, move the cursor, type some more text</span>
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
-  editor-render screen, <span class="Constant">2</span>:address:editor-data
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+  editor-render screen, <span class="Constant">2</span>:address:shared:editor-data
   assume-console [
     type <span class="Constant">[abc]</span>
     left-click <span class="Constant">1</span>, <span class="Constant">1</span>
     type <span class="Constant">[d]</span>
   ]
-  editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
-  <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-  <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+  editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
+  <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+  <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   screen-should-contain [
    <span class="Constant"> .          .</span>
    <span class="Constant"> .adbc      .</span>
@@ -1329,9 +1329,9 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     press ctrl-z
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
-    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
+    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   ]
   <span class="Comment"># last letter typed is deleted</span>
   screen-should-contain [
@@ -1349,9 +1349,9 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     press ctrl-z
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
-    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
+    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   ]
   <span class="Comment"># no change to screen; cursor moves</span>
   screen-should-contain [
@@ -1369,9 +1369,9 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     press ctrl-z
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
-    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
+    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   ]
   <span class="Comment"># screen empty</span>
   screen-should-contain [
@@ -1389,9 +1389,9 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     press ctrl-y
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
-    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
+    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   ]
   <span class="Comment"># first insert</span>
   screen-should-contain [
@@ -1409,9 +1409,9 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     press ctrl-y
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
-    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
+    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   ]
   <span class="Comment"># cursor moves</span>
   screen-should-contain [
@@ -1429,9 +1429,9 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     press ctrl-y
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
-    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
+    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   ]
   <span class="Comment"># second insert</span>
   screen-should-contain [
@@ -1449,11 +1449,11 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="muScenario">scenario</span> editor-can-undo-multiple-arrows-in-the-same-direction [
   <span class="Comment"># create an editor with some text</span>
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
 <span class="Constant">def</span>
 <span class="Constant">ghi]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
-  editor-render screen, <span class="Constant">2</span>:address:editor-data
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+  editor-render screen, <span class="Constant">2</span>:address:shared:editor-data
   <span class="Comment"># move the cursor</span>
   assume-console [
     left-click <span class="Constant">2</span>, <span class="Constant">1</span>
@@ -1461,9 +1461,9 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     press right-arrow
     press up-arrow
   ]
-  editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
-  <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-  <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+  editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
+  <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+  <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   memory-should-contain [
     <span class="Constant">3</span><span class="Special"> &lt;- </span><span class="Constant">1</span>
     <span class="Constant">4</span><span class="Special"> &lt;- </span><span class="Constant">3</span>
@@ -1473,9 +1473,9 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     press ctrl-z
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
-    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
+    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   ]
   <span class="Comment"># up-arrow is undone</span>
   memory-should-contain [
@@ -1487,9 +1487,9 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     press ctrl-z
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
-    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
+    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   ]
   <span class="Comment"># both right-arrows are undone</span>
   memory-should-contain [
@@ -1503,24 +1503,24 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="muScenario">scenario</span> editor-redo-touch [
   <span class="Comment"># create an editor with some text, click on a character, undo</span>
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
 <span class="Constant">def</span>
 <span class="Constant">ghi]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
-  editor-render screen, <span class="Constant">2</span>:address:editor-data
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+  editor-render screen, <span class="Constant">2</span>:address:shared:editor-data
   assume-console [
     left-click <span class="Constant">3</span>, <span class="Constant">1</span>
     press ctrl-z
   ]
-  editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+  editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   <span class="Comment"># redo</span>
   assume-console [
     press ctrl-y
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
-    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
+    <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+    <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   ]
   <span class="Comment"># cursor moves to left-click</span>
   memory-should-contain [
@@ -1532,7 +1532,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     type <span class="Constant">[1]</span>
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   screen-should-contain [
    <span class="Constant"> .          .</span>
@@ -1550,7 +1550,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     <span class="Comment"># assert cursor-row/cursor-column/top-of-screen match after-row/after-column/after-top-of-screen</span>
     *cursor-row<span class="Special"> &lt;- </span>get *move, <span class="Constant">after-row:offset</span>
     *cursor-column<span class="Special"> &lt;- </span>get *move, <span class="Constant">after-column:offset</span>
-    top:address:address:duplex-list:character<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">top-of-screen:offset</span>
+    top:address:address:shared:duplex-list:character<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">top-of-screen:offset</span>
     *top<span class="Special"> &lt;- </span>get *move, <span class="Constant">after-top-of-screen:offset</span>
   <span class="Delimiter">}</span>
 ]
@@ -1560,24 +1560,24 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="muScenario">scenario</span> editor-can-undo-and-redo-backspace [
   <span class="Comment"># create an editor</span>
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
-  editor-render screen, <span class="Constant">2</span>:address:editor-data
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+  editor-render screen, <span class="Constant">2</span>:address:shared:editor-data
   <span class="Comment"># insert some text and hit backspace</span>
   assume-console [
     type <span class="Constant">[abc]</span>
     press backspace
     press backspace
   ]
-  editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+  editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   screen-should-contain [
    <span class="Constant"> .          .</span>
    <span class="Constant"> .a         .</span>
 <span class="Constant">    .┈┈┈┈┈┈┈┈┈┈.</span>
    <span class="Constant"> .          .</span>
   ]
-  <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-  <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+  <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+  <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   memory-should-contain [
     <span class="Constant">3</span><span class="Special"> &lt;- </span><span class="Constant">1</span>
     <span class="Constant">4</span><span class="Special"> &lt;- </span><span class="Constant">1</span>
@@ -1587,10 +1587,10 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     press ctrl-z
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
-  <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-  <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+  <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+  <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   memory-should-contain [
     <span class="Constant">3</span><span class="Special"> &lt;- </span><span class="Constant">1</span>
     <span class="Constant">4</span><span class="Special"> &lt;- </span><span class="Constant">3</span>
@@ -1606,10 +1606,10 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     press ctrl-y
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
-  <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-  <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+  <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+  <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   memory-should-contain [
     <span class="Constant">3</span><span class="Special"> &lt;- </span><span class="Constant">1</span>
     <span class="Constant">4</span><span class="Special"> &lt;- </span><span class="Constant">1</span>
@@ -1624,38 +1624,38 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="Comment"># save operation to undo</span>
 <span class="muRecipe">after</span> <span class="Constant">&lt;backspace-character-begin&gt;</span> [
-  top-before:address:duplex-list:character<span class="Special"> &lt;- </span>get *editor, <span class="Constant">top-of-screen:offset</span>
+  top-before:address:shared:duplex-list:character<span class="Special"> &lt;- </span>get *editor, <span class="Constant">top-of-screen:offset</span>
 ]
 <span class="muRecipe">before</span> <span class="Constant">&lt;backspace-character-end&gt;</span> [
   <span class="Delimiter">{</span>
     <span class="muControl">break-unless</span> backspaced-cell  <span class="Comment"># backspace failed; don't add an undo operation</span>
-    top-after:address:duplex-list:character<span class="Special"> &lt;- </span>get *editor, <span class="Constant">top-of-screen:offset</span>
-    undo:address:address:list:address:operation<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">undo:offset</span>
+    top-after:address:shared:duplex-list:character<span class="Special"> &lt;- </span>get *editor, <span class="Constant">top-of-screen:offset</span>
+    undo:address:address:shared:list:address:shared:operation<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">undo:offset</span>
     <span class="Delimiter">{</span>
       <span class="Comment"># if previous operation was an insert, coalesce this operation with it</span>
       <span class="muControl">break-unless</span> *undo
-      op:address:operation<span class="Special"> &lt;- </span>first *undo
+      op:address:shared:operation<span class="Special"> &lt;- </span>first *undo
       deletion:address:delete-operation<span class="Special"> &lt;- </span>maybe-convert *op, <span class="Constant">delete:variant</span>
       <span class="muControl">break-unless</span> deletion
       previous-coalesce-tag:number<span class="Special"> &lt;- </span>get *deletion, <span class="Constant">tag:offset</span>
       coalesce?:boolean<span class="Special"> &lt;- </span>equal previous-coalesce-tag, <span class="Constant">1/coalesce-backspace</span>
       <span class="muControl">break-unless</span> coalesce?
-      delete-from:address:address:duplex-list:character<span class="Special"> &lt;- </span>get-address *deletion, <span class="Constant">delete-from:offset</span>
+      delete-from:address:address:shared:duplex-list:character<span class="Special"> &lt;- </span>get-address *deletion, <span class="Constant">delete-from:offset</span>
       *delete-from<span class="Special"> &lt;- </span>copy *before-cursor
-      backspaced-so-far:address:address:duplex-list:character<span class="Special"> &lt;- </span>get-address *deletion, <span class="Constant">deleted-text:offset</span>
+      backspaced-so-far:address:address:shared:duplex-list:character<span class="Special"> &lt;- </span>get-address *deletion, <span class="Constant">deleted-text:offset</span>
       insert-range backspaced-cell, *backspaced-so-far
       *backspaced-so-far<span class="Special"> &lt;- </span>copy backspaced-cell
       after-row:address:number<span class="Special"> &lt;- </span>get-address *deletion, <span class="Constant">after-row:offset</span>
       *after-row<span class="Special"> &lt;- </span>copy *cursor-row
       after-column:address:number<span class="Special"> &lt;- </span>get-address *deletion, <span class="Constant">after-column:offset</span>
       *after-column<span class="Special"> &lt;- </span>copy *cursor-column
-      after-top:address:address:duplex-list:character<span class="Special"> &lt;- </span>get-address *deletion, <span class="Constant">after-top-of-screen:offset</span>
+      after-top:address:address:shared:duplex-list:character<span class="Special"> &lt;- </span>get-address *deletion, <span class="Constant">after-top-of-screen:offset</span>
       *after-top<span class="Special"> &lt;- </span>get *editor, <span class="Constant">top-of-screen:offset</span>
       <span class="muControl">break</span> <span class="Constant">+done-adding-backspace-operation:label</span>
     <span class="Delimiter">}</span>
     <span class="Comment"># if not, create a new operation</span>
-    op:address:operation<span class="Special"> &lt;- </span>new <span class="Constant">operation:type</span>
-    deleted-until:address:duplex-list:character<span class="Special"> &lt;- </span>next *before-cursor
+    op:address:shared:operation<span class="Special"> &lt;- </span>new <span class="Constant">operation:type</span>
+    deleted-until:address:shared:duplex-list:character<span class="Special"> &lt;- </span>next *before-cursor
     *op<span class="Special"> &lt;- </span>merge <span class="Constant">2/delete-operation</span>, save-row/<span class="muRecipe">before</span>, save-column/<span class="muRecipe">before</span>, top-before, *cursor-row/<span class="muRecipe">after</span>, *cursor-column/<span class="muRecipe">after</span>, top-after, backspaced-cell/deleted, *before-cursor/delete-from, deleted-until, <span class="Constant">1/coalesce-backspace</span>
     editor<span class="Special"> &lt;- </span>add-operation editor, op
 <span class="Constant">    +done-adding-backspace-operation</span>
@@ -1666,17 +1666,17 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   <span class="Delimiter">{</span>
     deletion:address:delete-operation<span class="Special"> &lt;- </span>maybe-convert *op, <span class="Constant">delete:variant</span>
     <span class="muControl">break-unless</span> deletion
-    start2:address:address:duplex-list:character<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">data:offset</span>
-    anchor:address:duplex-list:character<span class="Special"> &lt;- </span>get *deletion, <span class="Constant">delete-from:offset</span>
+    start2:address:address:shared:duplex-list:character<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">data:offset</span>
+    anchor:address:shared:duplex-list:character<span class="Special"> &lt;- </span>get *deletion, <span class="Constant">delete-from:offset</span>
     <span class="muControl">break-unless</span> anchor
-    deleted:address:duplex-list:character<span class="Special"> &lt;- </span>get *deletion, <span class="Constant">deleted-text:offset</span>
-    old-cursor:address:duplex-list:character<span class="Special"> &lt;- </span>last deleted
+    deleted:address:shared:duplex-list:character<span class="Special"> &lt;- </span>get *deletion, <span class="Constant">deleted-text:offset</span>
+    old-cursor:address:shared:duplex-list:character<span class="Special"> &lt;- </span>last deleted
     insert-range anchor, deleted
     <span class="Comment"># assert cursor-row/cursor-column/top-of-screen match after-row/after-column/after-top-of-screen</span>
     *before-cursor<span class="Special"> &lt;- </span>copy old-cursor
     *cursor-row<span class="Special"> &lt;- </span>get *deletion, <span class="Constant">before-row:offset</span>
     *cursor-column<span class="Special"> &lt;- </span>get *deletion, <span class="Constant">before-column:offset</span>
-    top:address:address:duplex-list:character<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">top-of-screen:offset</span>
+    top:address:address:shared:duplex-list:character<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">top-of-screen:offset</span>
     *top<span class="Special"> &lt;- </span>get *deletion, <span class="Constant">before-top-of-screen:offset</span>
   <span class="Delimiter">}</span>
 ]
@@ -1685,13 +1685,13 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
   <span class="Delimiter">{</span>
     deletion:address:delete-operation<span class="Special"> &lt;- </span>maybe-convert *op, <span class="Constant">delete:variant</span>
     <span class="muControl">break-unless</span> deletion
-    start:address:duplex-list:character<span class="Special"> &lt;- </span>get *deletion, <span class="Constant">delete-from:offset</span>
-    end:address:duplex-list:character<span class="Special"> &lt;- </span>get *deletion, <span class="Constant">delete-until:offset</span>
+    start:address:shared:duplex-list:character<span class="Special"> &lt;- </span>get *deletion, <span class="Constant">delete-from:offset</span>
+    end:address:shared:duplex-list:character<span class="Special"> &lt;- </span>get *deletion, <span class="Constant">delete-until:offset</span>
     remove-between start, end
     <span class="Comment"># assert cursor-row/cursor-column/top-of-screen match after-row/after-column/after-top-of-screen</span>
     *cursor-row<span class="Special"> &lt;- </span>get *deletion, <span class="Constant">after-row:offset</span>
     *cursor-column<span class="Special"> &lt;- </span>get *deletion, <span class="Constant">after-column:offset</span>
-    top:address:address:duplex-list:character<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">top-of-screen:offset</span>
+    top:address:address:shared:duplex-list:character<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">top-of-screen:offset</span>
     *top<span class="Special"> &lt;- </span>get *deletion, <span class="Constant">after-top-of-screen:offset</span>
   <span class="Delimiter">}</span>
 ]
@@ -1701,9 +1701,9 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="muScenario">scenario</span> editor-can-undo-and-redo-delete [
   <span class="Comment"># create an editor</span>
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
-  editor-render screen, <span class="Constant">2</span>:address:editor-data
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+  editor-render screen, <span class="Constant">2</span>:address:shared:editor-data
   <span class="Comment"># insert some text and hit delete and backspace a few times</span>
   assume-console [
     type <span class="Constant">[abcdef]</span>
@@ -1713,15 +1713,15 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     press delete
     press delete
   ]
-  editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+  editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   screen-should-contain [
    <span class="Constant"> .          .</span>
    <span class="Constant"> .af        .</span>
 <span class="Constant">    .┈┈┈┈┈┈┈┈┈┈.</span>
    <span class="Constant"> .          .</span>
   ]
-  <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-  <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+  <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+  <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   memory-should-contain [
     <span class="Constant">3</span><span class="Special"> &lt;- </span><span class="Constant">1</span>
     <span class="Constant">4</span><span class="Special"> &lt;- </span><span class="Constant">1</span>
@@ -1731,10 +1731,10 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     press ctrl-z
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
-  <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-  <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+  <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+  <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   memory-should-contain [
     <span class="Constant">3</span><span class="Special"> &lt;- </span><span class="Constant">1</span>
     <span class="Constant">4</span><span class="Special"> &lt;- </span><span class="Constant">1</span>
@@ -1750,10 +1750,10 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     press ctrl-z
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
-  <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-  <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+  <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+  <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   memory-should-contain [
     <span class="Constant">3</span><span class="Special"> &lt;- </span><span class="Constant">1</span>
     <span class="Constant">4</span><span class="Special"> &lt;- </span><span class="Constant">2</span>
@@ -1769,10 +1769,10 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     press ctrl-z
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
-  <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-  <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+  <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+  <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   memory-should-contain [
     <span class="Constant">3</span><span class="Special"> &lt;- </span><span class="Constant">1</span>
     <span class="Constant">4</span><span class="Special"> &lt;- </span><span class="Constant">2</span>
@@ -1788,11 +1788,11 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     press ctrl-y
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   <span class="Comment"># first line inserted</span>
-  <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-  <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+  <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+  <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   memory-should-contain [
     <span class="Constant">3</span><span class="Special"> &lt;- </span><span class="Constant">1</span>
     <span class="Constant">4</span><span class="Special"> &lt;- </span><span class="Constant">2</span>
@@ -1808,11 +1808,11 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     press ctrl-y
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   <span class="Comment"># first line inserted</span>
-  <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-  <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+  <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+  <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   memory-should-contain [
     <span class="Constant">3</span><span class="Special"> &lt;- </span><span class="Constant">1</span>
     <span class="Constant">4</span><span class="Special"> &lt;- </span><span class="Constant">1</span>
@@ -1828,11 +1828,11 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     press ctrl-y
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   <span class="Comment"># first line inserted</span>
-  <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-  <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+  <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+  <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   memory-should-contain [
     <span class="Constant">3</span><span class="Special"> &lt;- </span><span class="Constant">1</span>
     <span class="Constant">4</span><span class="Special"> &lt;- </span><span class="Constant">1</span>
@@ -1846,37 +1846,37 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 ]
 
 <span class="muRecipe">after</span> <span class="Constant">&lt;delete-character-begin&gt;</span> [
-  top-before:address:duplex-list:character<span class="Special"> &lt;- </span>get *editor, <span class="Constant">top-of-screen:offset</span>
+  top-before:address:shared:duplex-list:character<span class="Special"> &lt;- </span>get *editor, <span class="Constant">top-of-screen:offset</span>
 ]
 <span class="muRecipe">before</span> <span class="Constant">&lt;delete-character-end&gt;</span> [
   <span class="Delimiter">{</span>
     <span class="muControl">break-unless</span> deleted-cell  <span class="Comment"># delete failed; don't add an undo operation</span>
-    top-after:address:duplex-list:character<span class="Special"> &lt;- </span>get *editor, <span class="Constant">top-of-screen:offset</span>
-    undo:address:address:list:address:operation<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">undo:offset</span>
+    top-after:address:shared:duplex-list:character<span class="Special"> &lt;- </span>get *editor, <span class="Constant">top-of-screen:offset</span>
+    undo:address:address:shared:list:address:shared:operation<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">undo:offset</span>
     <span class="Delimiter">{</span>
       <span class="Comment"># if previous operation was an insert, coalesce this operation with it</span>
       <span class="muControl">break-unless</span> *undo
-      op:address:operation<span class="Special"> &lt;- </span>first *undo
+      op:address:shared:operation<span class="Special"> &lt;- </span>first *undo
       deletion:address:delete-operation<span class="Special"> &lt;- </span>maybe-convert *op, <span class="Constant">delete:variant</span>
       <span class="muControl">break-unless</span> deletion
       previous-coalesce-tag:number<span class="Special"> &lt;- </span>get *deletion, <span class="Constant">tag:offset</span>
       coalesce?:boolean<span class="Special"> &lt;- </span>equal previous-coalesce-tag, <span class="Constant">2/coalesce-delete</span>
       <span class="muControl">break-unless</span> coalesce?
-      delete-until:address:address:duplex-list:character<span class="Special"> &lt;- </span>get-address *deletion, <span class="Constant">delete-until:offset</span>
+      delete-until:address:address:shared:duplex-list:character<span class="Special"> &lt;- </span>get-address *deletion, <span class="Constant">delete-until:offset</span>
       *delete-until<span class="Special"> &lt;- </span>next *before-cursor
-      deleted-so-far:address:address:duplex-list:character<span class="Special"> &lt;- </span>get-address *deletion, <span class="Constant">deleted-text:offset</span>
+      deleted-so-far:address:address:shared:duplex-list:character<span class="Special"> &lt;- </span>get-address *deletion, <span class="Constant">deleted-text:offset</span>
       *deleted-so-far<span class="Special"> &lt;- </span>append *deleted-so-far, deleted-cell
       after-row:address:number<span class="Special"> &lt;- </span>get-address *deletion, <span class="Constant">after-row:offset</span>
       *after-row<span class="Special"> &lt;- </span>copy *cursor-row
       after-column:address:number<span class="Special"> &lt;- </span>get-address *deletion, <span class="Constant">after-column:offset</span>
       *after-column<span class="Special"> &lt;- </span>copy *cursor-column
-      after-top:address:address:duplex-list:character<span class="Special"> &lt;- </span>get-address *deletion, <span class="Constant">after-top-of-screen:offset</span>
+      after-top:address:address:shared:duplex-list:character<span class="Special"> &lt;- </span>get-address *deletion, <span class="Constant">after-top-of-screen:offset</span>
       *after-top<span class="Special"> &lt;- </span>get *editor, <span class="Constant">top-of-screen:offset</span>
       <span class="muControl">break</span> <span class="Constant">+done-adding-delete-operation:label</span>
     <span class="Delimiter">}</span>
     <span class="Comment"># if not, create a new operation</span>
-    op:address:operation<span class="Special"> &lt;- </span>new <span class="Constant">operation:type</span>
-    deleted-until:address:duplex-list:character<span class="Special"> &lt;- </span>next *before-cursor
+    op:address:shared:operation<span class="Special"> &lt;- </span>new <span class="Constant">operation:type</span>
+    deleted-until:address:shared:duplex-list:character<span class="Special"> &lt;- </span>next *before-cursor
     *op<span class="Special"> &lt;- </span>merge <span class="Constant">2/delete-operation</span>, save-row/<span class="muRecipe">before</span>, save-column/<span class="muRecipe">before</span>, top-before, *cursor-row/<span class="muRecipe">after</span>, *cursor-column/<span class="muRecipe">after</span>, top-after, deleted-cell/deleted, *before-cursor/delete-from, deleted-until, <span class="Constant">2/coalesce-delete</span>
     editor<span class="Special"> &lt;- </span>add-operation editor, op
 <span class="Constant">    +done-adding-delete-operation</span>
@@ -1888,16 +1888,16 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="muScenario">scenario</span> editor-can-undo-and-redo-ctrl-k [
   <span class="Comment"># create an editor</span>
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
 <span class="Constant">def]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
-  editor-render screen, <span class="Constant">2</span>:address:editor-data
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+  editor-render screen, <span class="Constant">2</span>:address:shared:editor-data
   <span class="Comment"># insert some text and hit delete and backspace a few times</span>
   assume-console [
     left-click <span class="Constant">1</span>, <span class="Constant">1</span>
     press ctrl-k
   ]
-  editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+  editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   screen-should-contain [
    <span class="Constant"> .          .</span>
    <span class="Constant"> .a         .</span>
@@ -1905,8 +1905,8 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="Constant">    .┈┈┈┈┈┈┈┈┈┈.</span>
    <span class="Constant"> .          .</span>
   ]
-  <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-  <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+  <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+  <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   memory-should-contain [
     <span class="Constant">3</span><span class="Special"> &lt;- </span><span class="Constant">1</span>
     <span class="Constant">4</span><span class="Special"> &lt;- </span><span class="Constant">1</span>
@@ -1916,7 +1916,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     press ctrl-z
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   screen-should-contain [
    <span class="Constant"> .          .</span>
@@ -1925,8 +1925,8 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="Constant">    .┈┈┈┈┈┈┈┈┈┈.</span>
    <span class="Constant"> .          .</span>
   ]
-  <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-  <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+  <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+  <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   memory-should-contain [
     <span class="Constant">3</span><span class="Special"> &lt;- </span><span class="Constant">1</span>
     <span class="Constant">4</span><span class="Special"> &lt;- </span><span class="Constant">1</span>
@@ -1936,7 +1936,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     press ctrl-y
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   <span class="Comment"># first line inserted</span>
   screen-should-contain [
@@ -1946,8 +1946,8 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="Constant">    .┈┈┈┈┈┈┈┈┈┈.</span>
    <span class="Constant"> .          .</span>
   ]
-  <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-  <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+  <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+  <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   memory-should-contain [
     <span class="Constant">3</span><span class="Special"> &lt;- </span><span class="Constant">1</span>
     <span class="Constant">4</span><span class="Special"> &lt;- </span><span class="Constant">1</span>
@@ -1957,7 +1957,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     type <span class="Constant">[1]</span>
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   screen-should-contain [
    <span class="Constant"> .          .</span>
@@ -1969,15 +1969,15 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 ]
 
 <span class="muRecipe">after</span> <span class="Constant">&lt;delete-to-end-of-line-begin&gt;</span> [
-  top-before:address:duplex-list:character<span class="Special"> &lt;- </span>get *editor, <span class="Constant">top-of-screen:offset</span>
+  top-before:address:shared:duplex-list:character<span class="Special"> &lt;- </span>get *editor, <span class="Constant">top-of-screen:offset</span>
 ]
 <span class="muRecipe">before</span> <span class="Constant">&lt;delete-to-end-of-line-end&gt;</span> [
   <span class="Delimiter">{</span>
     <span class="muControl">break-unless</span> deleted-cells  <span class="Comment"># delete failed; don't add an undo operation</span>
-    top-after:address:duplex-list:character<span class="Special"> &lt;- </span>get *editor, <span class="Constant">top-of-screen:offset</span>
-    undo:address:address:list:address:operation<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">undo:offset</span>
-    op:address:operation<span class="Special"> &lt;- </span>new <span class="Constant">operation:type</span>
-    deleted-until:address:duplex-list:character<span class="Special"> &lt;- </span>next *before-cursor
+    top-after:address:shared:duplex-list:character<span class="Special"> &lt;- </span>get *editor, <span class="Constant">top-of-screen:offset</span>
+    undo:address:address:shared:list:address:shared:operation<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">undo:offset</span>
+    op:address:shared:operation<span class="Special"> &lt;- </span>new <span class="Constant">operation:type</span>
+    deleted-until:address:shared:duplex-list:character<span class="Special"> &lt;- </span>next *before-cursor
     *op<span class="Special"> &lt;- </span>merge <span class="Constant">2/delete-operation</span>, save-row/<span class="muRecipe">before</span>, save-column/<span class="muRecipe">before</span>, top-before, *cursor-row/<span class="muRecipe">after</span>, *cursor-column/<span class="muRecipe">after</span>, top-after, deleted-cells/deleted, *before-cursor/delete-from, deleted-until, <span class="Constant">0/never-coalesce</span>
     editor<span class="Special"> &lt;- </span>add-operation editor, op
 <span class="Constant">    +done-adding-delete-operation</span>
@@ -1989,16 +1989,16 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="muScenario">scenario</span> editor-can-undo-and-redo-ctrl-u [
   <span class="Comment"># create an editor</span>
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
 <span class="Constant">def]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
-  editor-render screen, <span class="Constant">2</span>:address:editor-data
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+  editor-render screen, <span class="Constant">2</span>:address:shared:editor-data
   <span class="Comment"># insert some text and hit delete and backspace a few times</span>
   assume-console [
     left-click <span class="Constant">1</span>, <span class="Constant">2</span>
     press ctrl-u
   ]
-  editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+  editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   screen-should-contain [
    <span class="Constant"> .          .</span>
    <span class="Constant"> .c         .</span>
@@ -2006,8 +2006,8 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="Constant">    .┈┈┈┈┈┈┈┈┈┈.</span>
    <span class="Constant"> .          .</span>
   ]
-  <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-  <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+  <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+  <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   memory-should-contain [
     <span class="Constant">3</span><span class="Special"> &lt;- </span><span class="Constant">1</span>
     <span class="Constant">4</span><span class="Special"> &lt;- </span><span class="Constant">0</span>
@@ -2017,7 +2017,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     press ctrl-z
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   screen-should-contain [
    <span class="Constant"> .          .</span>
@@ -2026,8 +2026,8 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="Constant">    .┈┈┈┈┈┈┈┈┈┈.</span>
    <span class="Constant"> .          .</span>
   ]
-  <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-  <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+  <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+  <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   memory-should-contain [
     <span class="Constant">3</span><span class="Special"> &lt;- </span><span class="Constant">1</span>
     <span class="Constant">4</span><span class="Special"> &lt;- </span><span class="Constant">2</span>
@@ -2037,7 +2037,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     press ctrl-y
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   <span class="Comment"># first line inserted</span>
   screen-should-contain [
@@ -2047,8 +2047,8 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="Constant">    .┈┈┈┈┈┈┈┈┈┈.</span>
    <span class="Constant"> .          .</span>
   ]
-  <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-row:offset</span>
-  <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:editor-data, <span class="Constant">cursor-column:offset</span>
+  <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-row:offset</span>
+  <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>get *<span class="Constant">2</span>:address:shared:editor-data, <span class="Constant">cursor-column:offset</span>
   memory-should-contain [
     <span class="Constant">3</span><span class="Special"> &lt;- </span><span class="Constant">1</span>
     <span class="Constant">4</span><span class="Special"> &lt;- </span><span class="Constant">0</span>
@@ -2058,7 +2058,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
     type <span class="Constant">[1]</span>
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   ]
   screen-should-contain [
    <span class="Constant"> .          .</span>
@@ -2070,15 +2070,15 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 ]
 
 <span class="muRecipe">after</span> <span class="Constant">&lt;delete-to-start-of-line-begin&gt;</span> [
-  top-before:address:duplex-list:character<span class="Special"> &lt;- </span>get *editor, <span class="Constant">top-of-screen:offset</span>
+  top-before:address:shared:duplex-list:character<span class="Special"> &lt;- </span>get *editor, <span class="Constant">top-of-screen:offset</span>
 ]
 <span class="muRecipe">before</span> <span class="Constant">&lt;delete-to-start-of-line-end&gt;</span> [
   <span class="Delimiter">{</span>
     <span class="muControl">break-unless</span> deleted-cells  <span class="Comment"># delete failed; don't add an undo operation</span>
-    top-after:address:duplex-list:character<span class="Special"> &lt;- </span>get *editor, <span class="Constant">top-of-screen:offset</span>
-    undo:address:address:list:address:operation<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">undo:offset</span>
-    op:address:operation<span class="Special"> &lt;- </span>new <span class="Constant">operation:type</span>
-    deleted-until:address:duplex-list:character<span class="Special"> &lt;- </span>next *before-cursor
+    top-after:address:shared:duplex-list:character<span class="Special"> &lt;- </span>get *editor, <span class="Constant">top-of-screen:offset</span>
+    undo:address:address:shared:list:address:shared:operation<span class="Special"> &lt;- </span>get-address *editor, <span class="Constant">undo:offset</span>
+    op:address:shared:operation<span class="Special"> &lt;- </span>new <span class="Constant">operation:type</span>
+    deleted-until:address:shared:duplex-list:character<span class="Special"> &lt;- </span>next *before-cursor
     *op<span class="Special"> &lt;- </span>merge <span class="Constant">2/delete-operation</span>, save-row/<span class="muRecipe">before</span>, save-column/<span class="muRecipe">before</span>, top-before, *cursor-row/<span class="muRecipe">after</span>, *cursor-column/<span class="muRecipe">after</span>, top-after, deleted-cells/deleted, *before-cursor/delete-from, deleted-until, <span class="Constant">0/never-coalesce</span>
     editor<span class="Special"> &lt;- </span>add-operation editor, op
 <span class="Constant">    +done-adding-delete-operation</span>
@@ -2088,16 +2088,16 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="muScenario">scenario</span> editor-can-undo-and-redo-ctrl-u-2 [
   <span class="Comment"># create an editor</span>
   assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-  <span class="Constant">1</span>:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
-  <span class="Constant">2</span>:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:array:character, screen:address:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
-  editor-render screen, <span class="Constant">2</span>:address:editor-data
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
+  <span class="Constant">2</span>:address:shared:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">1</span>:address:shared:array:character, screen:address:shared:screen, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+  editor-render screen, <span class="Constant">2</span>:address:shared:editor-data
   <span class="Comment"># insert some text and hit delete and backspace a few times</span>
   assume-console [
     type <span class="Constant">[abc]</span>
     press ctrl-u
     press ctrl-z
   ]
-  editor-event-loop screen:address:screen, console:address:console, <span class="Constant">2</span>:address:editor-data
+  editor-event-loop screen:address:shared:screen, console:address:shared:console, <span class="Constant">2</span>:address:shared:editor-data
   screen-should-contain [
    <span class="Constant"> .          .</span>
    <span class="Constant"> .abc       .</span>
diff --git a/html/fork.mu.html b/html/fork.mu.html
index 69dc4e30..1a378255 100644
--- a/html/fork.mu.html
+++ b/html/fork.mu.html
@@ -16,8 +16,8 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 .muControl { color: #c0a020; }
 .muRecipe { color: #ff8700; }
 .Comment { color: #9090ff; }
-.Constant { color: #00a0a0; }
 .Delimiter { color: #a04060; }
+.Constant { color: #00a0a0; }
 -->
 </style>
 
@@ -32,7 +32,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="Comment"># example program: running multiple routines</span>
 
 <span class="muRecipe">recipe</span> main [
-  start-running <span class="Constant">thread2:recipe</span>
+  start-running thread2
   <span class="Delimiter">{</span>
     $print <span class="Constant">34</span>
     <span class="muControl">loop</span>
diff --git a/html/global.mu.html b/html/global.mu.html
index 6e2c0491..a95ef552 100644
--- a/html/global.mu.html
+++ b/html/global.mu.html
@@ -32,7 +32,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muRecipe">recipe</span> main [
   <span class="Comment"># allocate 5 locations for globals</span>
-  <span class="Constant">global-space</span>:address:array:location<span class="Special"> &lt;- </span>new <span class="Constant">location:type</span>, <span class="Constant">5</span>
+  <span class="Constant">global-space</span>:address:shared:array:location<span class="Special"> &lt;- </span>new <span class="Constant">location:type</span>, <span class="Constant">5</span>
   <span class="Comment"># read to globals by using /space:global</span>
   <span class="Special">1:number/space:global</span><span class="Special"> &lt;- </span>copy <span class="Constant">3</span>
   foo
@@ -40,7 +40,7 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muRecipe">recipe</span> foo [
   <span class="Comment"># ditto for writing to globals</span>
-  $print <span class="Special">1:number/space:global</span>
+  $print <span class="Special">1:number/space:global</span>, <span class="Constant">10/newline</span>
 ]
 </pre>
 </body>
diff --git a/html/screen.mu.html b/html/screen.mu.html
index ea2b0232..000304a5 100644
--- a/html/screen.mu.html
+++ b/html/screen.mu.html
@@ -35,12 +35,14 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 
 <span class="muRecipe">recipe</span> main [
   open-console
-  print <span class="Constant">0/screen</span>, <span class="Constant">97/a</span>, <span class="Constant">2/red</span>
+  <span class="Constant">10</span>:character<span class="Special"> &lt;- </span>copy <span class="Constant">97/a</span>
+  print <span class="Constant">0/screen</span>, <span class="Constant">10</span>:character/a, <span class="Constant">2/red</span>
   <span class="Constant">1</span>:number/<span class="Special">raw</span>, <span class="Constant">2</span>:number/<span class="Special">raw &lt;- </span>cursor-position <span class="Constant">0/screen</span>
   wait-for-event <span class="Constant">0/console</span>
   clear-screen <span class="Constant">0/screen</span>
   move-cursor <span class="Constant">0/screen</span>, <span class="Constant">0/row</span>, <span class="Constant">4/column</span>
-  print <span class="Constant">0/screen</span>, <span class="Constant">98/b</span>
+  <span class="Constant">10</span>:character<span class="Special"> &lt;- </span>copy <span class="Constant">98/b</span>
+  print <span class="Constant">0/screen</span>, <span class="Constant">10</span>:character
   wait-for-event <span class="Constant">0/console</span>
   move-cursor <span class="Constant">0/screen</span>, <span class="Constant">0/row</span>, <span class="Constant">0/column</span>
   clear-line <span class="Constant">0/screen</span>