2875

10 files changed, 212 insertions, 135 deletions

diff --git a/html/028call_reply.cc.html b/html/028call_reply.cc.html
index 39ecff7c..396e7332 100644
--- a/html/028call_reply.cc.html
+++ b/html/028call_reply.cc.html
@@ -34,7 +34,7 @@ body { font-size: 12pt; font-family: monospace; color: #eeeeee; background-color
 <pre id='vimCodeElement'>
 <span class="Comment">//: Calls can also generate products, using 'reply' or 'return'.</span>
 
-<span class="Delimiter">:(scenario reply)</span>
+<span class="Delimiter">:(scenario return)</span>
 def main [
   <span class="Constant">1</span>:number<span class="Delimiter">,</span> <span class="Constant">2</span>:number<span class="Special"> &lt;- </span>f <span class="Constant">34</span>
 ]
@@ -47,16 +47,16 @@ def f [
 <span class="traceContains">+mem: storing 35 in location 2</span>
 
 <span class="Delimiter">:(before &quot;End Primitive Recipe Declarations&quot;)</span>
-REPLY<span class="Delimiter">,</span>
+RETURN<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;reply&quot;</span><span class="Delimiter">,</span> REPLY<span class="Delimiter">);</span>
-put<span class="Delimiter">(</span>Recipe_ordinal<span class="Delimiter">,</span> <span class="Constant">&quot;return&quot;</span><span class="Delimiter">,</span> REPLY<span class="Delimiter">);</span>
+put<span class="Delimiter">(</span>Recipe_ordinal<span class="Delimiter">,</span> <span class="Constant">&quot;return&quot;</span><span class="Delimiter">,</span> RETURN<span class="Delimiter">);</span>
+put<span class="Delimiter">(</span>Recipe_ordinal<span class="Delimiter">,</span> <span class="Constant">&quot;reply&quot;</span><span class="Delimiter">,</span> RETURN<span class="Delimiter">);</span>  <span class="Comment">// synonym while teaching</span>
 <span class="Delimiter">:(before &quot;End Primitive Recipe Checks&quot;)</span>
-<span class="Normal">case</span> REPLY: <span class="Delimiter">{</span>
+<span class="Normal">case</span> RETURN: <span class="Delimiter">{</span>
   <span class="Identifier">break</span><span class="Delimiter">;</span>  <span class="Comment">// checks will be performed by a transform below</span>
 <span class="Delimiter">}</span>
 <span class="Delimiter">:(before &quot;End Primitive Recipe Implementations&quot;)</span>
-<span class="Normal">case</span> REPLY: <span class="Delimiter">{</span>
+<span class="Normal">case</span> RETURN: <span class="Delimiter">{</span>
   <span class="Comment">// Starting Reply</span>
   <span class="Normal">if</span> <span class="Delimiter">(</span>Trace_stream<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;trace&quot;</span><span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;reply: decrementing callstack depth from &quot;</span> &lt;&lt; Trace_stream<span class="Delimiter">-&gt;</span>callstack_depth &lt;&lt; end<span class="Delimiter">();</span>
@@ -95,7 +95,7 @@ Transform<span class="Delimiter">.</span>push_back<span class="Delimiter">(</spa
     <span class="Normal">const</span> recipe&amp; callee = get<span class="Delimiter">(</span>Recipe<span class="Delimiter">,</span> caller_instruction<span class="Delimiter">.</span>operation<span class="Delimiter">);</span>
     <span class="Normal">for</span> <span class="Delimiter">(</span><span class="Normal">int</span> i = <span class="Constant">0</span><span class="Delimiter">;</span> i &lt; SIZE<span class="Delimiter">(</span>callee<span class="Delimiter">.</span>steps<span class="Delimiter">);</span> ++i<span class="Delimiter">)</span> <span class="Delimiter">{</span>
       <span class="Normal">const</span> instruction&amp; reply_inst = callee<span class="Delimiter">.</span>steps<span class="Delimiter">.</span>at<span class="Delimiter">(</span>i<span class="Delimiter">);</span>
-      <span class="Normal">if</span> <span class="Delimiter">(</span>reply_inst<span class="Delimiter">.</span>operation != REPLY<span class="Delimiter">)</span> <span class="Identifier">continue</span><span class="Delimiter">;</span>
+      <span class="Normal">if</span> <span class="Delimiter">(</span>reply_inst<span class="Delimiter">.</span>operation != RETURN<span class="Delimiter">)</span> <span class="Identifier">continue</span><span class="Delimiter">;</span>
       <span class="Comment">// check types with the caller</span>
       <span class="Normal">if</span> <span class="Delimiter">(</span>SIZE<span class="Delimiter">(</span>caller_instruction<span class="Delimiter">.</span>products<span class="Delimiter">)</span> &gt; SIZE<span class="Delimiter">(</span>reply_inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">))</span> <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;too few values replied from &quot;</span> &lt;&lt; callee<span class="Delimiter">.</span>name &lt;&lt; <span class="cSpecial">'\n'</span> &lt;&lt; end<span class="Delimiter">();</span>
@@ -104,7 +104,7 @@ Transform<span class="Delimiter">.</span>push_back<span class="Delimiter">(</spa
       <span class="Normal">for</span> <span class="Delimiter">(</span><span class="Normal">int</span> i = <span class="Constant">0</span><span class="Delimiter">;</span> i &lt; SIZE<span class="Delimiter">(</span>caller_instruction<span class="Delimiter">.</span>products<span class="Delimiter">);</span> ++i<span class="Delimiter">)</span> <span class="Delimiter">{</span>
         reagent lhs = reply_inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span>i<span class="Delimiter">);</span>
         reagent rhs = caller_instruction<span class="Delimiter">.</span>products<span class="Delimiter">.</span>at<span class="Delimiter">(</span>i<span class="Delimiter">);</span>
-        <span class="Comment">// End Check REPLY Copy(lhs, rhs)</span>
+        <span class="Comment">// End Check RETURN Copy(lhs, rhs)</span>
         <span class="Normal">if</span> <span class="Delimiter">(</span>!types_coercible<span class="Delimiter">(</span>rhs<span class="Delimiter">,</span> lhs<span class="Delimiter">))</span> <span class="Delimiter">{</span>
           raise &lt;&lt; maybe<span class="Delimiter">(</span>callee<span class="Delimiter">.</span>name<span class="Delimiter">)</span> &lt;&lt; reply_inst<span class="Delimiter">.</span>name &lt;&lt; <span class="Constant">&quot; ingredient &quot;</span> &lt;&lt; lhs<span class="Delimiter">.</span>original_string &lt;&lt; <span class="Constant">&quot; can't be saved in &quot;</span> &lt;&lt; rhs<span class="Delimiter">.</span>original_string &lt;&lt; <span class="cSpecial">'\n'</span> &lt;&lt; end<span class="Delimiter">();</span>
           raise &lt;&lt; to_string<span class="Delimiter">(</span>lhs<span class="Delimiter">.</span>type<span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot; vs &quot;</span> &lt;&lt; to_string<span class="Delimiter">(</span>rhs<span class="Delimiter">.</span>type<span class="Delimiter">)</span> &lt;&lt; <span class="cSpecial">'\n'</span> &lt;&lt; end<span class="Delimiter">();</span>
@@ -135,7 +135,7 @@ Transform<span class="Delimiter">.</span>push_back<span class="Delimiter">(</spa
   <span class="Delimiter">}</span>
 <span class="Delimiter">}</span>
 
-<span class="Delimiter">:(scenario reply_type_mismatch)</span>
+<span class="Delimiter">:(scenario return_type_mismatch)</span>
 <span class="Special">% Hide_errors = true;</span>
 def main [
   <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>f <span class="Constant">2</span>
@@ -153,7 +153,7 @@ def f [
 <span class="Comment">//: the recipe's 'reply' will help catch accidental misuse of such</span>
 <span class="Comment">//: 'ingredient-products' (sometimes called in-out parameters in other languages).</span>
 
-<span class="Delimiter">:(scenario reply_same_as_ingredient)</span>
+<span class="Delimiter">:(scenario return_same_as_ingredient)</span>
 <span class="Special">% Hide_errors = true;</span>
 def main [
   <span class="Constant">1</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
@@ -165,7 +165,7 @@ def test1 [
 ]
 <span class="traceContains">+error: main: '2:number &lt;- test1 1:number' should write to 1:number rather than 2:number</span>
 
-<span class="Delimiter">:(scenario reply_same_as_ingredient_dummy)</span>
+<span class="Delimiter">:(scenario return_same_as_ingredient_dummy)</span>
 def main [
   <span class="Constant">1</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
   _<span class="Special"> &lt;- </span>test1 <span class="Constant">1</span>:number  <span class="Comment"># call with different ingredient and product</span>
@@ -192,76 +192,6 @@ string to_string<span class="Delimiter">(</span><span class="Normal">const</span
   out &lt;&lt; <span class="Constant">&quot;]&quot;</span><span class="Delimiter">;</span>
   <span class="Identifier">return</span> out<span class="Delimiter">.</span>str<span class="Delimiter">();</span>
 <span class="Delimiter">}</span>
-
-<span class="Comment">//: Conditional reply.</span>
-
-<span class="Delimiter">:(scenario reply_if)</span>
-def main [
-  <span class="Constant">1</span>:number<span class="Special"> &lt;- </span>test1
-]
-def test1 [
-  <span class="Identifier">return</span>-<span class="Normal">if</span> <span class="Constant">0</span><span class="Delimiter">,</span> <span class="Constant">34</span>
-  <span class="Identifier">return</span> <span class="Constant">35</span>
-]
-<span class="traceContains">+mem: storing 35 in location 1</span>
-
-<span class="Delimiter">:(scenario reply_if_2)</span>
-def main [
-  <span class="Constant">1</span>:number<span class="Special"> &lt;- </span>test1
-]
-def test1 [
-  <span class="Identifier">return</span>-<span class="Normal">if</span> <span class="Constant">1</span><span class="Delimiter">,</span> <span class="Constant">34</span>
-  <span class="Identifier">return</span> <span class="Constant">35</span>
-]
-<span class="traceContains">+mem: storing 34 in location 1</span>
-
-<span class="Delimiter">:(before &quot;End Rewrite Instruction(curr, recipe result)&quot;)</span>
-<span class="Comment">// rewrite `reply-if a, b, c, ...` to</span>
-<span class="Comment">//   ```</span>
-<span class="Comment">//   jump-unless a, 1:offset</span>
-<span class="Comment">//   reply b, c, ...</span>
-<span class="Comment">//   ```</span>
-<span class="Normal">if</span> <span class="Delimiter">(</span>curr<span class="Delimiter">.</span>name == <span class="Constant">&quot;reply-if&quot;</span> || curr<span class="Delimiter">.</span>name == <span class="Constant">&quot;return-if&quot;</span><span class="Delimiter">)</span> <span class="Delimiter">{</span>
-  <span class="Normal">if</span> <span class="Delimiter">(</span>curr<span class="Delimiter">.</span>products<span class="Delimiter">.</span>empty<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;jump-unless&quot;</span><span class="Delimiter">);</span>
-    curr<span class="Delimiter">.</span>name = <span class="Constant">&quot;jump-unless&quot;</span><span class="Delimiter">;</span>
-    vector&lt;reagent&gt; results<span class="Delimiter">;</span>
-    copy<span class="Delimiter">(</span>++curr<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>begin<span class="Delimiter">(),</span> curr<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>end<span class="Delimiter">(),</span> inserter<span class="Delimiter">(</span>results<span class="Delimiter">,</span> results<span class="Delimiter">.</span>end<span class="Delimiter">()));</span>
-    curr<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>resize<span class="Delimiter">(</span><span class="Constant">1</span><span class="Delimiter">);</span>
-    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;1:offset&quot;</span><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>
-    curr<span class="Delimiter">.</span>operation = get<span class="Delimiter">(</span>Recipe_ordinal<span class="Delimiter">,</span> <span class="Constant">&quot;reply&quot;</span><span class="Delimiter">);</span>
-    curr<span class="Delimiter">.</span>name = <span class="Constant">&quot;reply&quot;</span><span class="Delimiter">;</span>
-    curr<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>swap<span class="Delimiter">(</span>results<span class="Delimiter">);</span>
-  <span class="Delimiter">}</span>
-  <span class="Normal">else</span> <span class="Delimiter">{</span>
-    raise &lt;&lt; <span class="Constant">&quot;'&quot;</span> &lt;&lt; curr<span class="Delimiter">.</span>name &lt;&lt; <span class="Constant">&quot;' never yields any products</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="Comment">// rewrite `reply-unless a, b, c, ...` to</span>
-<span class="Comment">//   ```</span>
-<span class="Comment">//   jump-if a, 1:offset</span>
-<span class="Comment">//   reply b, c, ...</span>
-<span class="Comment">//   ```</span>
-<span class="Normal">if</span> <span class="Delimiter">(</span>curr<span class="Delimiter">.</span>name == <span class="Constant">&quot;reply-unless&quot;</span> || curr<span class="Delimiter">.</span>name == <span class="Constant">&quot;return-unless&quot;</span><span class="Delimiter">)</span> <span class="Delimiter">{</span>
-  <span class="Normal">if</span> <span class="Delimiter">(</span>curr<span class="Delimiter">.</span>products<span class="Delimiter">.</span>empty<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;jump-if&quot;</span><span class="Delimiter">);</span>
-    curr<span class="Delimiter">.</span>name = <span class="Constant">&quot;jump-if&quot;</span><span class="Delimiter">;</span>
-    vector&lt;reagent&gt; results<span class="Delimiter">;</span>
-    copy<span class="Delimiter">(</span>++curr<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>begin<span class="Delimiter">(),</span> curr<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>end<span class="Delimiter">(),</span> inserter<span class="Delimiter">(</span>results<span class="Delimiter">,</span> results<span class="Delimiter">.</span>end<span class="Delimiter">()));</span>
-    curr<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>resize<span class="Delimiter">(</span><span class="Constant">1</span><span class="Delimiter">);</span>
-    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;1:offset&quot;</span><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>
-    curr<span class="Delimiter">.</span>operation = get<span class="Delimiter">(</span>Recipe_ordinal<span class="Delimiter">,</span> <span class="Constant">&quot;reply&quot;</span><span class="Delimiter">);</span>
-    curr<span class="Delimiter">.</span>name = <span class="Constant">&quot;reply&quot;</span><span class="Delimiter">;</span>
-    curr<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>swap<span class="Delimiter">(</span>results<span class="Delimiter">);</span>
-  <span class="Delimiter">}</span>
-  <span class="Normal">else</span> <span class="Delimiter">{</span>
-    raise &lt;&lt; <span class="Constant">&quot;'&quot;</span> &lt;&lt; curr<span class="Delimiter">.</span>name &lt;&lt; <span class="Constant">&quot;' never yields any products</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>
 </pre>
 </body>
 </html>
diff --git a/html/030container.cc.html b/html/030container.cc.html
index 311631ea..716db06e 100644
--- a/html/030container.cc.html
+++ b/html/030container.cc.html
@@ -89,7 +89,7 @@ def main [
 <span class="traceContains">+mem: storing 36 in location 17</span>
 
 <span class="Comment">//: products of recipes can include containers</span>
-<span class="Delimiter">:(scenario reply_container)</span>
+<span class="Delimiter">:(scenario return_container)</span>
 def main [
   <span class="Constant">3</span>:point<span class="Special"> &lt;- </span>f <span class="Constant">2</span>
 ]
diff --git a/html/033address.cc.html b/html/033address.cc.html
index 04791321..f71ee22a 100644
--- a/html/033address.cc.html
+++ b/html/033address.cc.html
@@ -533,7 +533,7 @@ def main [
 canonize_type<span class="Delimiter">(</span>ingredient<span class="Delimiter">);</span>
 <span class="Delimiter">:(before &quot;End Preprocess NEXT_INGREDIENT product&quot;)</span>
 canonize_type<span class="Delimiter">(</span>product<span class="Delimiter">);</span>
-<span class="Delimiter">:(before &quot;End Check REPLY Copy(lhs, rhs)</span>
+<span class="Delimiter">:(before &quot;End Check RETURN Copy(lhs, rhs)</span>
 canonize_type<span class="Delimiter">(</span>lhs<span class="Delimiter">);</span>
 canonize_type<span class="Delimiter">(</span>rhs<span class="Delimiter">);</span>
 
diff --git a/html/040brace.cc.html b/html/040brace.cc.html
index 6077150d..b0912d1e 100644
--- a/html/040brace.cc.html
+++ b/html/040brace.cc.html
@@ -396,6 +396,91 @@ def main [
 ]
 <span class="traceContains">+error: break-if expects 1 or 2 ingredients, but got none</span>
 
+<span class="Comment">//: Using break we can now implement conditional returns.</span>
+
+<span class="Delimiter">:(scenario return_if)</span>
+def main [
+  <span class="Constant">1</span>:number<span class="Special"> &lt;- </span>test1
+]
+def test1 [
+  <span class="Identifier">return</span>-<span class="Normal">if</span> <span class="Constant">0</span><span class="Delimiter">,</span> <span class="Constant">34</span>
+  <span class="Identifier">return</span> <span class="Constant">35</span>
+]
+<span class="traceContains">+mem: storing 35 in location 1</span>
+
+<span class="Delimiter">:(scenario return_if_2)</span>
+def main [
+  <span class="Constant">1</span>:number<span class="Special"> &lt;- </span>test1
+]
+def test1 [
+  <span class="Identifier">return</span>-<span class="Normal">if</span> <span class="Constant">1</span><span class="Delimiter">,</span> <span class="Constant">34</span>
+  <span class="Identifier">return</span> <span class="Constant">35</span>
+]
+<span class="traceContains">+mem: storing 34 in location 1</span>
+
+<span class="Delimiter">:(before &quot;End Rewrite Instruction(curr, recipe result)&quot;)</span>
+<span class="Comment">// rewrite `return-if a, b, c, ...` to</span>
+<span class="Comment">//   ```</span>
+<span class="Comment">//   {</span>
+<span class="Comment">//     break-unless a</span>
+<span class="Comment">//     return b, c, ...</span>
+<span class="Comment">//   }</span>
+<span class="Comment">//   ```</span>
+<span class="Normal">if</span> <span class="Delimiter">(</span>curr<span class="Delimiter">.</span>name == <span class="Constant">&quot;return-if&quot;</span> || curr<span class="Delimiter">.</span>name == <span class="Constant">&quot;reply-if&quot;</span><span class="Delimiter">)</span> <span class="Delimiter">{</span>
+  <span class="Normal">if</span> <span class="Delimiter">(</span>curr<span class="Delimiter">.</span>products<span class="Delimiter">.</span>empty<span class="Delimiter">())</span> <span class="Delimiter">{</span>
+    emit_return_block<span class="Delimiter">(</span>result<span class="Delimiter">,</span> <span class="Constant">&quot;break-unless&quot;</span><span class="Delimiter">,</span> curr<span class="Delimiter">.</span>ingredients<span class="Delimiter">);</span>
+    curr<span class="Delimiter">.</span>clear<span class="Delimiter">();</span>
+  <span class="Delimiter">}</span>
+  <span class="Normal">else</span> <span class="Delimiter">{</span>
+    raise &lt;&lt; <span class="Constant">&quot;'&quot;</span> &lt;&lt; curr<span class="Delimiter">.</span>name &lt;&lt; <span class="Constant">&quot;' never yields any products</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="Comment">// rewrite `return-unless a, b, c, ...` to</span>
+<span class="Comment">//   ```</span>
+<span class="Comment">//   {</span>
+<span class="Comment">//     break-if a</span>
+<span class="Comment">//     return b, c, ...</span>
+<span class="Comment">//   }</span>
+<span class="Comment">//   ```</span>
+<span class="Normal">if</span> <span class="Delimiter">(</span>curr<span class="Delimiter">.</span>name == <span class="Constant">&quot;return-unless&quot;</span> || curr<span class="Delimiter">.</span>name == <span class="Constant">&quot;reply-unless&quot;</span><span class="Delimiter">)</span> <span class="Delimiter">{</span>
+  <span class="Normal">if</span> <span class="Delimiter">(</span>curr<span class="Delimiter">.</span>products<span class="Delimiter">.</span>empty<span class="Delimiter">())</span> <span class="Delimiter">{</span>
+    emit_return_block<span class="Delimiter">(</span>result<span class="Delimiter">,</span> <span class="Constant">&quot;break-if&quot;</span><span class="Delimiter">,</span> curr<span class="Delimiter">.</span>ingredients<span class="Delimiter">);</span>
+    curr<span class="Delimiter">.</span>clear<span class="Delimiter">();</span>
+  <span class="Delimiter">}</span>
+  <span class="Normal">else</span> <span class="Delimiter">{</span>
+    raise &lt;&lt; <span class="Constant">&quot;'&quot;</span> &lt;&lt; curr<span class="Delimiter">.</span>name &lt;&lt; <span class="Constant">&quot;' never yields any products</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">:(code)</span>
+<span class="Normal">void</span> emit_return_block<span class="Delimiter">(</span>recipe&amp; out<span class="Delimiter">,</span> <span class="Normal">const</span> string&amp; break_command<span class="Delimiter">,</span> <span class="Normal">const</span> vector&lt;reagent&gt;&amp; ingredients<span class="Delimiter">)</span> <span class="Delimiter">{</span>
+  reagent condition = ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">);</span>
+  vector&lt;reagent&gt; return_ingredients<span class="Delimiter">;</span>
+  copy<span class="Delimiter">(</span>++ingredients<span class="Delimiter">.</span>begin<span class="Delimiter">(),</span> ingredients<span class="Delimiter">.</span>end<span class="Delimiter">(),</span> inserter<span class="Delimiter">(</span>return_ingredients<span class="Delimiter">,</span> return_ingredients<span class="Delimiter">.</span>end<span class="Delimiter">()));</span>
+
+  <span class="Comment">// {</span>
+  instruction open_label<span class="Delimiter">;</span>  open_label<span class="Delimiter">.</span>is_label=<span class="Constant">true</span><span class="Delimiter">;</span>  open_label<span class="Delimiter">.</span>label = <span class="Constant">&quot;{&quot;</span><span class="Delimiter">;</span>
+  out<span class="Delimiter">.</span>steps<span class="Delimiter">.</span>push_back<span class="Delimiter">(</span>open_label<span class="Delimiter">);</span>
+
+  <span class="Comment">// &lt;break command&gt; &lt;condition&gt;</span>
+  instruction break_inst<span class="Delimiter">;</span>
+  break_inst<span class="Delimiter">.</span>operation = get<span class="Delimiter">(</span>Recipe_ordinal<span class="Delimiter">,</span> break_command<span class="Delimiter">);</span>
+  break_inst<span class="Delimiter">.</span>name = break_inst<span class="Delimiter">.</span>old_name = break_command<span class="Delimiter">;</span>
+  break_inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>push_back<span class="Delimiter">(</span>condition<span class="Delimiter">);</span>
+  out<span class="Delimiter">.</span>steps<span class="Delimiter">.</span>push_back<span class="Delimiter">(</span>break_inst<span class="Delimiter">);</span>
+
+  <span class="Comment">// return &lt;return ingredients&gt;</span>
+  instruction return_inst<span class="Delimiter">;</span>
+  return_inst<span class="Delimiter">.</span>operation = get<span class="Delimiter">(</span>Recipe_ordinal<span class="Delimiter">,</span> <span class="Constant">&quot;return&quot;</span><span class="Delimiter">);</span>
+  return_inst<span class="Delimiter">.</span>name = <span class="Constant">&quot;return&quot;</span><span class="Delimiter">;</span>
+  return_inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>swap<span class="Delimiter">(</span>return_ingredients<span class="Delimiter">);</span>
+  out<span class="Delimiter">.</span>steps<span class="Delimiter">.</span>push_back<span class="Delimiter">(</span>return_inst<span class="Delimiter">);</span>
+
+  <span class="Comment">// }</span>
+  instruction close_label<span class="Delimiter">;</span>  close_label<span class="Delimiter">.</span>is_label=<span class="Constant">true</span><span class="Delimiter">;</span>  close_label<span class="Delimiter">.</span>label = <span class="Constant">&quot;}&quot;</span><span class="Delimiter">;</span>
+  out<span class="Delimiter">.</span>steps<span class="Delimiter">.</span>push_back<span class="Delimiter">(</span>close_label<span class="Delimiter">);</span>
+<span class="Delimiter">}</span>
+
 <span class="Comment">//: Make sure these pseudo recipes get consistent numbers in all tests, even</span>
 <span class="Comment">//: though they aren't implemented. Allows greater flexibility in ordering</span>
 <span class="Comment">//: transforms.</span>
diff --git a/html/052tangle.cc.html b/html/052tangle.cc.html
index 4ffcaebf..6356cd68 100644
--- a/html/052tangle.cc.html
+++ b/html/052tangle.cc.html
@@ -168,14 +168,15 @@ tangle_done = <span class="Constant">false</span><span class="Delimiter">;</span
 <span class="Delimiter">}</span>
 
 <span class="Comment">//: complain about unapplied fragments</span>
-<span class="Delimiter">:(before &quot;End Globals&quot;)</span>
-<span class="Normal">bool</span> Transform_check_insert_fragments_Ran = <span class="Constant">false</span><span class="Delimiter">;</span>
-<span class="Delimiter">:(after &quot;Transform.push_back(insert_fragments)&quot;)</span>
-Transform<span class="Delimiter">.</span>push_back<span class="Delimiter">(</span>check_insert_fragments<span class="Delimiter">);</span>  <span class="Comment">// idempotent</span>
+<span class="Comment">//: This can't run during transform because later (shape-shifting recipes)</span>
+<span class="Comment">//: we'll encounter situations where fragments might get used long after</span>
+<span class="Comment">//: they're loaded, and we might run transform_all in between. To avoid</span>
+<span class="Comment">//: spurious errors, run this check right at the end, after all code is</span>
+<span class="Comment">//: loaded, right before we run main.</span>
+<span class="Delimiter">:(before &quot;End Commandline Parsing&quot;)</span>
+check_insert_fragments<span class="Delimiter">();</span>
 <span class="Delimiter">:(code)</span>
-<span class="Normal">void</span> check_insert_fragments<span class="Delimiter">(</span>unused recipe_ordinal<span class="Delimiter">)</span> <span class="Delimiter">{</span>
-  <span class="Normal">if</span> <span class="Delimiter">(</span>Transform_check_insert_fragments_Ran<span class="Delimiter">)</span> <span class="Identifier">return</span><span class="Delimiter">;</span>
-  Transform_check_insert_fragments_Ran = <span class="Constant">true</span><span class="Delimiter">;</span>
+<span class="Normal">void</span> check_insert_fragments<span class="Delimiter">()</span> <span class="Delimiter">{</span>
   <span class="Normal">for</span> <span class="Delimiter">(</span>map&lt;string<span class="Delimiter">,</span> recipe&gt;::iterator p = Before_fragments<span class="Delimiter">.</span>begin<span class="Delimiter">();</span> p != Before_fragments<span class="Delimiter">.</span>end<span class="Delimiter">();</span> ++p<span class="Delimiter">)</span> <span class="Delimiter">{</span>
     <span class="Normal">if</span> <span class="Delimiter">(</span>!contains_key<span class="Delimiter">(</span>Fragments_used<span class="Delimiter">,</span> p<span class="Delimiter">-&gt;</span>first<span class="Delimiter">))</span>
       raise &lt;&lt; <span class="Constant">&quot;could not locate insert before &quot;</span> &lt;&lt; p<span class="Delimiter">-&gt;</span>first &lt;&lt; <span class="cSpecial">'\n'</span> &lt;&lt; end<span class="Delimiter">();</span>
diff --git a/html/055recipe_header.cc.html b/html/055recipe_header.cc.html
index 93acb6c8..ccdee487 100644
--- a/html/055recipe_header.cc.html
+++ b/html/055recipe_header.cc.html
@@ -398,7 +398,7 @@ Transform<span class="Delimiter">.</span>push_back<span class="Delimiter">(</spa
 <span class="Comment">//: One final convenience: no need to say what to return if the information is</span>
 <span class="Comment">//: in the header.</span>
 
-<span class="Delimiter">:(scenario reply_based_on_header)</span>
+<span class="Delimiter">:(scenario return_based_on_header)</span>
 def main [
   <span class="Constant">1</span>:number/<span class="Special">raw &lt;- </span>add2 <span class="Constant">3</span><span class="Delimiter">,</span> <span class="Constant">5</span>
 ]
@@ -463,7 +463,7 @@ def add2 a:number<span class="Delimiter">,</span> b:number <span class="Delimite
 <span class="traceContains">+mem: storing 3 in location 1</span>
 <span class="traceContains">+mem: storing -2 in location 2</span>
 
-<span class="Delimiter">:(scenario reply_on_fallthrough_based_on_header)</span>
+<span class="Delimiter">:(scenario return_on_fallthrough_based_on_header)</span>
 def main [
   <span class="Constant">1</span>:number/<span class="Special">raw &lt;- </span>add2 <span class="Constant">3</span><span class="Delimiter">,</span> <span class="Constant">5</span>
 ]
@@ -475,7 +475,7 @@ def add2 x:number<span class="Delimiter">,</span> y:number <span class="Delimite
 <span class="traceContains">+transform: instruction: reply {z: &quot;number&quot;}</span>
 <span class="traceContains">+mem: storing 8 in location 1</span>
 
-<span class="Delimiter">:(scenario reply_on_fallthrough_already_exists)</span>
+<span class="Delimiter">:(scenario return_on_fallthrough_already_exists)</span>
 def main [
   <span class="Constant">1</span>:number/<span class="Special">raw &lt;- </span>add2 <span class="Constant">3</span><span class="Delimiter">,</span> <span class="Constant">5</span>
 ]
@@ -489,6 +489,18 @@ def add2 x:number<span class="Delimiter">,</span> y:number <span class="Delimite
 <span class="traceAbsent">-transform: instruction: reply z:number</span>
 <span class="traceContains">+mem: storing 8 in location 1</span>
 
+<span class="Delimiter">:(scenario return_after_conditional_reply_based_on_header)</span>
+def main [
+  <span class="Constant">1</span>:number/<span class="Special">raw &lt;- </span>add2 <span class="Constant">3</span><span class="Delimiter">,</span> <span class="Constant">5</span>
+]
+def add2 x:number<span class="Delimiter">,</span> y:number <span class="Delimiter">-&gt;</span> z:number [
+  local-scope
+  load-ingredients
+  z<span class="Special"> &lt;- </span>add x<span class="Delimiter">,</span> y  <span class="Comment"># no type for z</span>
+  <span class="Identifier">return</span>-<span class="Normal">if</span> <span class="Constant">0</span>/<span class="Constant">false</span><span class="Delimiter">,</span> <span class="Constant">34</span>
+]
+<span class="traceContains">+mem: storing 8 in location 1</span>
+
 <span class="Delimiter">:(scenario recipe_headers_perform_same_ingredient_check)</span>
 <span class="Special">% Hide_errors = true;</span>
 def main [
diff --git a/html/057shape_shifting_container.cc.html b/html/057shape_shifting_container.cc.html
index 7c8b2826..1dbf543b 100644
--- a/html/057shape_shifting_container.cc.html
+++ b/html/057shape_shifting_container.cc.html
@@ -120,7 +120,7 @@ map&lt;string<span class="Delimiter">,</span> type_ordinal&gt; type_ingredient_n
   <span class="Normal">while</span> <span class="Delimiter">(</span>has_data<span class="Delimiter">(</span>in<span class="Delimiter">))</span> <span class="Delimiter">{</span>
     string curr = slurp_until<span class="Delimiter">(</span>in<span class="Delimiter">,</span> <span class="Constant">':'</span><span class="Delimiter">);</span>
     <span class="Normal">if</span> <span class="Delimiter">(</span>info<span class="Delimiter">.</span>type_ingredient_names<span class="Delimiter">.</span>find<span class="Delimiter">(</span>curr<span class="Delimiter">)</span> != info<span class="Delimiter">.</span>type_ingredient_names<span class="Delimiter">.</span>end<span class="Delimiter">())</span> <span class="Delimiter">{</span>
-      raise &lt;&lt; <span class="Constant">&quot;can't repeat type ingredient names in a single container definition</span><span class="cSpecial">\n</span><span class="Constant">&quot;</span> &lt;&lt; end<span class="Delimiter">();</span>
+      raise &lt;&lt; <span class="Constant">&quot;can't repeat type ingredient names in a single container definition: &quot;</span> &lt;&lt; curr &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>
     put<span class="Delimiter">(</span>info<span class="Delimiter">.</span>type_ingredient_names<span class="Delimiter">,</span> curr<span class="Delimiter">,</span> next_type_ordinal++<span class="Delimiter">);</span>
diff --git a/html/072channel.mu.html b/html/072channel.mu.html
index afda2035..c710e692 100644
--- a/html/072channel.mu.html
+++ b/html/072channel.mu.html
@@ -96,6 +96,7 @@ body { font-size: 12pt; font-family: monospace; color: #eeeeee; background-color
   <span class="Constant">local-scope</span>
   <span class="Constant">load-ingredients</span>
   chan:address:channel:_elem<span class="Special"> &lt;- </span>get *out, <span class="Constant">chan:offset</span>
+<span class="Constant">  &lt;channel-write-initial&gt;</span>
   <span class="Delimiter">{</span>
     <span class="Comment"># block if chan is full</span>
     full:boolean<span class="Special"> &lt;- </span>channel-full? chan
@@ -129,6 +130,7 @@ body { font-size: 12pt; font-family: monospace; color: #eeeeee; background-color
     <span class="Comment"># block if chan is empty</span>
     empty?:boolean<span class="Special"> &lt;- </span>channel-empty? chan
     <span class="muControl">break-unless</span> empty?
+<span class="Constant">    &lt;channel-read-empty&gt;</span>
     free-address:location<span class="Special"> &lt;- </span>get-location *chan, <span class="Constant">first-free:offset</span>
     wait-for-location free-address
   <span class="Delimiter">}</span>
@@ -229,45 +231,6 @@ body { font-size: 12pt; font-family: monospace; color: #eeeeee; background-color
   ]
 ]
 
-<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">def</span> channel-empty? chan:address:channel:_elem<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>
-  full:number<span class="Special"> &lt;- </span>get *chan, <span class="Constant">first-full:offset</span>
-  free:number<span class="Special"> &lt;- </span>get *chan, <span class="Constant">first-free:offset</span>
-  result<span class="Special"> &lt;- </span>equal full, free
-]
-
-<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">def</span> channel-full? chan:address:channel:_elem<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>
-  tmp:number<span class="Special"> &lt;- </span>get *chan, <span class="Constant">first-free:offset</span>
-  tmp<span class="Special"> &lt;- </span>add tmp, <span class="Constant">1</span>
-  <span class="Delimiter">{</span>
-    <span class="Comment"># if tmp == chan.capacity, tmp = 0</span>
-    len:number<span class="Special"> &lt;- </span>capacity chan
-    at-end?:boolean<span class="Special"> &lt;- </span>greater-or-equal tmp, len
-    <span class="muControl">break-unless</span> at-end?
-    tmp<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
-  <span class="Delimiter">}</span>
-  <span class="Comment"># return chan.first-full == tmp</span>
-  full:number<span class="Special"> &lt;- </span>get *chan, <span class="Constant">first-full:offset</span>
-  result<span class="Special"> &lt;- </span>equal full, tmp
-]
-
-<span class="muRecipe">def</span> capacity chan:address:channel:_elem<span class="muRecipe"> -&gt; </span>result:number [
-  <span class="Constant">local-scope</span>
-  <span class="Constant">load-ingredients</span>
-  q:address:array:_elem<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:source:number, <span class="Constant">2</span>:address:sink:number<span class="Special"> &lt;- </span>new-channel <span class="Constant">3/capacity</span>
@@ -324,6 +287,85 @@ body { font-size: 12pt; font-family: monospace; color: #eeeeee; background-color
   ]
 ]
 
+<span class="SalientComment">## cancelling channels</span>
+
+<span class="Comment"># every channel comes with a boolean signifying if it's been closed</span>
+<span class="Comment"># initially this boolean is false</span>
+<span class="Comment"># todo: can't yet include type ingredients when extending containers</span>
+<span class="muData">container</span> channel [
+  closed?:boolean
+]
+
+<span class="Comment"># a channel can be closed from either the source or the sink</span>
+<span class="Comment"># both threads can modify it, but they can only set it, so this is a benign race</span>
+<span class="muRecipe">def</span> close x:address:source:_elem<span class="muRecipe"> -&gt; </span>x:address:source:_elem [
+  <span class="Constant">local-scope</span>
+  <span class="Constant">load-ingredients</span>
+  chan:address:channel:_elem<span class="Special"> &lt;- </span>get *x, <span class="Constant">chan:offset</span>
+  *chan<span class="Special"> &lt;- </span>put *chan, <span class="Constant">closed?:offset</span>, <span class="Constant">1/true</span>
+]
+<span class="muRecipe">def</span> close x:address:sink:_elem<span class="muRecipe"> -&gt; </span>x:address:sink:_elem [
+  <span class="Constant">local-scope</span>
+  <span class="Constant">load-ingredients</span>
+  chan:address:channel:_elem<span class="Special"> &lt;- </span>get *x, <span class="Constant">chan:offset</span>
+  *chan<span class="Special"> &lt;- </span>put *chan, <span class="Constant">closed?:offset</span>, <span class="Constant">1/true</span>
+]
+
+<span class="Comment"># once a channel is closed from one side, no further operations are expected from that side</span>
+<span class="Comment"># if a channel is closed for reading,</span>
+<span class="Comment">#   no further writes will be let through</span>
+<span class="Comment"># if a channel is closed for writing,</span>
+<span class="Comment">#   future reads continue until the channel empties,</span>
+<span class="Comment">#   then the channel is also closed for reading</span>
+<span class="muRecipe">after</span> <span class="Constant">&lt;channel-write-initial&gt;</span> [
+  closed?:boolean<span class="Special"> &lt;- </span>get *chan, <span class="Constant">closed?:offset</span>
+  <span class="muControl">return-if</span> closed?
+]
+
+<span class="muRecipe">after</span> <span class="Constant">&lt;channel-read-empty&gt;</span> [
+  closed?:boolean<span class="Special"> &lt;- </span>get *chan, <span class="Constant">closed?:offset</span>
+  <span class="muControl">return-if</span> closed?, <span class="Constant">0/hack</span>  <span class="Comment"># only scalar _elems supported in channels; need to support construction of arbitrary empty containers</span>
+]
+
+<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">def</span> channel-empty? chan:address:channel:_elem<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>
+  full:number<span class="Special"> &lt;- </span>get *chan, <span class="Constant">first-full:offset</span>
+  free:number<span class="Special"> &lt;- </span>get *chan, <span class="Constant">first-free:offset</span>
+  result<span class="Special"> &lt;- </span>equal full, free
+]
+
+<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">def</span> channel-full? chan:address:channel:_elem<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>
+  tmp:number<span class="Special"> &lt;- </span>get *chan, <span class="Constant">first-free:offset</span>
+  tmp<span class="Special"> &lt;- </span>add tmp, <span class="Constant">1</span>
+  <span class="Delimiter">{</span>
+    <span class="Comment"># if tmp == chan.capacity, tmp = 0</span>
+    len:number<span class="Special"> &lt;- </span>capacity chan
+    at-end?:boolean<span class="Special"> &lt;- </span>greater-or-equal tmp, len
+    <span class="muControl">break-unless</span> at-end?
+    tmp<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
+  <span class="Delimiter">}</span>
+  <span class="Comment"># return chan.first-full == tmp</span>
+  full:number<span class="Special"> &lt;- </span>get *chan, <span class="Constant">first-full:offset</span>
+  result<span class="Special"> &lt;- </span>equal full, tmp
+]
+
+<span class="muRecipe">def</span> capacity chan:address:channel:_elem<span class="muRecipe"> -&gt; </span>result:number [
+  <span class="Constant">local-scope</span>
+  <span class="Constant">load-ingredients</span>
+  q:address:array:_elem<span class="Special"> &lt;- </span>get *chan, <span class="Constant">data:offset</span>
+  result<span class="Special"> &lt;- </span>length *q
+]
+
 <span class="Comment"># helper for channels of characters in particular</span>
 <span class="muRecipe">def</span> buffer-lines in:address:source:character, buffered-out:address:sink:character<span class="muRecipe"> -&gt; </span>buffered-out:address:sink:character, in:address:source:character [
   <span class="Constant">local-scope</span>
@@ -372,6 +414,11 @@ body { font-size: 12pt; font-family: monospace; color: #eeeeee; background-color
       i<span class="Special"> &lt;- </span>add i, <span class="Constant">1</span>
       <span class="muControl">loop</span>
     <span class="Delimiter">}</span>
+    <span class="Delimiter">{</span>
+      <span class="muControl">break-unless</span> eof?
+      buffered-out<span class="Special"> &lt;- </span>close buffered-out
+      <span class="muControl">return</span>
+    <span class="Delimiter">}</span>
     <span class="muControl">loop</span>
   <span class="Delimiter">}</span>
 ]
diff --git a/html/084console.mu.html b/html/084console.mu.html
index 157e7504..fb6df826 100644
--- a/html/084console.mu.html
+++ b/html/084console.mu.html
@@ -115,6 +115,7 @@ body { font-size: 12pt; font-family: monospace; color: #eeeeee; background-color
     chan<span class="Special"> &lt;- </span>write chan, c
     <span class="muControl">loop</span>
   <span class="Delimiter">}</span>
+  chan<span class="Special"> &lt;- </span>close chan
 ]
 
 <span class="muRecipe">def</span> wait-for-event console:address:console<span class="muRecipe"> -&gt; </span>console:address:console [
diff --git a/html/chessboard.mu.html b/html/chessboard.mu.html
index 357c33ff..d4241248 100644
--- a/html/chessboard.mu.html
+++ b/html/chessboard.mu.html
@@ -71,7 +71,8 @@ body { font-size: 12pt; font-family: monospace; color: #eeeeee; background-color
   run [
     screen:address:screen, console:address:console<span class="Special"> &lt;- </span>chessboard screen:address:screen, console:address:console
     <span class="Comment"># icon for the cursor</span>
-    screen<span class="Special"> &lt;- </span>print screen, <span class="Constant">9251/␣</span>
+    <span class="Constant">1</span>:character/cursor-icon<span class="Special"> &lt;- </span>copy <span class="Constant">9251/␣</span>
+    screen<span class="Special"> &lt;- </span>print screen, <span class="Constant">1</span>:character/cursor-icon
   ]
   screen-should-contain [
   <span class="Comment">#            1         2         3         4         5         6         7         8         9         10        11</span>
@@ -291,7 +292,7 @@ body { font-size: 12pt; font-family: monospace; color: #eeeeee; background-color
   to-rank:number, quit?, error?<span class="Special"> &lt;- </span>read-rank stdin, screen
   <span class="muControl">return-if</span> quit?, <span class="Constant">0/dummy</span>
   <span class="muControl">return-if</span> error?, <span class="Constant">0/dummy</span>
-  *result<span class="Special"> &lt;- </span>put *result, <span class="Constant">to-rank:offset</span>, to-file
+  *result<span class="Special"> &lt;- </span>put *result, <span class="Constant">to-rank:offset</span>, to-rank
   error?<span class="Special"> &lt;- </span>expect-from-channel stdin, <span class="Constant">10/newline</span>, screen
   <span class="muControl">return-if</span> error?, <span class="Constant">0/dummy</span>, <span class="Constant">0/quit</span>
 ]