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+<!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 - 075duplex_list.mu</title>
+<meta name="Generator" content="Vim/7.4">
+<meta name="plugin-version" content="vim7.4_v1">
+<meta name="syntax" content="none">
+<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; }
+.muControl { color: #c0a020; }
+.muRecipe { color: #ff8700; }
+.muScenario { color: #00af00; }
+.muData { color: #ffff00; }
+.Comment { color: #9090ff; }
+.Constant { color: #00a0a0; }
+.Special { color: #ff6060; }
+.Delimiter { color: #a04060; }
+-->
+</style>
+
+<script type='text/javascript'>
+<!--
+
+-->
+</script>
+</head>
+<body>
+<pre id='vimCodeElement'>
+<span class="Comment"># A doubly linked list permits bidirectional traversal.</span>
+
+<span class="muData">container</span> duplex-list:_elem [
+  value:_elem
+  next:address:duplex-list:_elem
+  prev:address:duplex-list:_elem
+]
+
+<span class="muRecipe">recipe</span> push-duplex x:_elem, in:address:duplex-list:_elem<span class="muRecipe"> -&gt; </span>result:address:duplex-list:_elem [
+  <span class="Constant">local-scope</span>
+  <span class="Constant">load-ingredients</span>
+  result<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<span class="Special"> &lt;- </span>copy in
+  <span class="muControl">reply-unless</span> in
+  prev:address:address: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="muRecipe">recipe</span> first-duplex in:address: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-duplex in:address:duplex-list:_elem<span class="muRecipe"> -&gt; </span>result:address:duplex-list:_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">next:offset</span>
+]
+
+<span class="muRecipe">recipe</span> prev-duplex in:address:duplex-list:_elem<span class="muRecipe"> -&gt; </span>result:address:duplex-list:_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">prev:offset</span>
+  <span class="muControl">reply</span> result
+]
+
+<span class="muScenario">scenario</span> duplex-list-handling [
+  run [
+    <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>copy <span class="Constant">0</span>
+    <span class="Constant">3</span>:address:duplex-list:character<span class="Special"> &lt;- </span>push-duplex <span class="Constant">3</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-duplex <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-duplex <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-duplex <span class="Constant">4</span>:address:duplex-list:character
+    <span class="Constant">4</span>:address:duplex-list:character<span class="Special"> &lt;- </span>next-duplex <span class="Constant">4</span>:address:duplex-list:character
+    <span class="Constant">6</span>:character<span class="Special"> &lt;- </span>first-duplex <span class="Constant">4</span>:address:duplex-list:character
+    <span class="Constant">4</span>:address:duplex-list:character<span class="Special"> &lt;- </span>next-duplex <span class="Constant">4</span>:address:duplex-list:character
+    <span class="Constant">7</span>:character<span class="Special"> &lt;- </span>first-duplex <span class="Constant">4</span>:address:duplex-list:character
+    <span class="Constant">8</span>:address:duplex-list:character<span class="Special"> &lt;- </span>next-duplex <span class="Constant">4</span>:address:duplex-list:character
+    <span class="Constant">9</span>:character<span class="Special"> &lt;- </span>first-duplex <span class="Constant">8</span>:address:duplex-list:character
+    <span class="Constant">10</span>:address:duplex-list:character<span class="Special"> &lt;- </span>next-duplex <span class="Constant">8</span>:address:duplex-list:character
+    <span class="Constant">11</span>:address:duplex-list:character<span class="Special"> &lt;- </span>prev-duplex <span class="Constant">8</span>:address:duplex-list:character
+    <span class="Constant">4</span>:address:duplex-list:character<span class="Special"> &lt;- </span>prev-duplex <span class="Constant">4</span>:address:duplex-list:character
+    <span class="Constant">12</span>:character<span class="Special"> &lt;- </span>first-duplex <span class="Constant">4</span>:address:duplex-list:character
+    <span class="Constant">4</span>:address:duplex-list:character<span class="Special"> &lt;- </span>prev-duplex <span class="Constant">4</span>:address:duplex-list:character
+    <span class="Constant">13</span>:character<span class="Special"> &lt;- </span>first-duplex <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
+  ]
+  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>
+    <span class="Constant">1</span><span class="Special"> &lt;- </span><span class="Constant">34</span>
+    <span class="Constant">2</span><span class="Special"> &lt;- </span><span class="Constant">35</span>
+    <span class="Constant">5</span><span class="Special"> &lt;- </span><span class="Constant">5</span>  <span class="Comment"># scanning next</span>
+    <span class="Constant">6</span><span class="Special"> &lt;- </span><span class="Constant">4</span>
+    <span class="Constant">7</span><span class="Special"> &lt;- </span><span class="Constant">3</span>
+    <span class="Constant">8</span><span class="Special"> &lt;- </span><span class="Constant">0</span>  <span class="Comment"># null</span>
+    <span class="Constant">9</span><span class="Special"> &lt;- </span><span class="Constant">0</span>  <span class="Comment"># first of null</span>
+    <span class="Constant">10</span><span class="Special"> &lt;- </span><span class="Constant">0</span>  <span class="Comment"># next of null</span>
+    <span class="Constant">11</span><span class="Special"> &lt;- </span><span class="Constant">0</span>  <span class="Comment"># prev of null</span>
+    <span class="Constant">12</span><span class="Special"> &lt;- </span><span class="Constant">4</span>  <span class="Comment"># then start scanning prev</span>
+    <span class="Constant">13</span><span class="Special"> &lt;- </span><span class="Constant">5</span>
+    <span class="Constant">14</span><span class="Special"> &lt;- </span><span class="Constant">1</span>  <span class="Comment"># list back at start</span>
+  ]
+]
+
+<span class="Comment"># Inserts 'x' after 'in'. Returns some pointer into the list.</span>
+<span class="muRecipe">recipe</span> insert-duplex x:_elem, in:address:duplex-list:_elem<span class="muRecipe"> -&gt; </span>new-node:address:duplex-list:_elem [
+  <span class="Constant">local-scope</span>
+  <span class="Constant">load-ingredients</span>
+  new-node<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>
+  <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<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>
+  *y<span class="Special"> &lt;- </span>copy in
+  <span class="Comment"># new-node.next = next-node</span>
+  y<span class="Special"> &lt;- </span>get-address *new-node, <span class="Constant">next:offset</span>
+  *y<span class="Special"> &lt;- </span>copy next-node
+  <span class="Comment"># if next-node is not null</span>
+  <span class="muControl">reply-unless</span> next-node, new-node
+  <span class="Comment"># next-node.prev = new-node</span>
+  y<span class="Special"> &lt;- </span>get-address *next-node, <span class="Constant">prev:offset</span>
+  *y<span class="Special"> &lt;- </span>copy new-node
+  <span class="muControl">reply</span> new-node  <span class="Comment"># just signalling something changed; don't rely on the result</span>
+]
+
+<span class="muScenario">scenario</span> inserting-into-duplex-list [
+  run [
+    <span class="Constant">1</span>:address:duplex-list:character<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>  <span class="Comment"># 1 points to head of list</span>
+    <span class="Constant">1</span>:address:duplex-list:character<span class="Special"> &lt;- </span>push-duplex <span class="Constant">3</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-duplex <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-duplex <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-duplex <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-duplex <span class="Constant">6</span>, <span class="Constant">2</span>:address: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-duplex <span class="Constant">2</span>:address:duplex-list:character
+    <span class="Constant">2</span>:address:duplex-list:character<span class="Special"> &lt;- </span>next-duplex <span class="Constant">2</span>:address:duplex-list:character
+    <span class="Constant">4</span>:character<span class="Special"> &lt;- </span>first-duplex <span class="Constant">2</span>:address:duplex-list:character
+    <span class="Constant">2</span>:address:duplex-list:character<span class="Special"> &lt;- </span>next-duplex <span class="Constant">2</span>:address:duplex-list:character
+    <span class="Constant">5</span>:character<span class="Special"> &lt;- </span>first-duplex <span class="Constant">2</span>:address:duplex-list:character
+    <span class="Constant">2</span>:address:duplex-list:character<span class="Special"> &lt;- </span>next-duplex <span class="Constant">2</span>:address:duplex-list:character
+    <span class="Constant">6</span>:character<span class="Special"> &lt;- </span>first-duplex <span class="Constant">2</span>:address:duplex-list:character
+    <span class="Constant">2</span>:address:duplex-list:character<span class="Special"> &lt;- </span>prev-duplex <span class="Constant">2</span>:address:duplex-list:character
+    <span class="Constant">7</span>:character<span class="Special"> &lt;- </span>first-duplex <span class="Constant">2</span>:address:duplex-list:character
+    <span class="Constant">2</span>:address:duplex-list:character<span class="Special"> &lt;- </span>prev-duplex <span class="Constant">2</span>:address:duplex-list:character
+    <span class="Constant">8</span>:character<span class="Special"> &lt;- </span>first-duplex <span class="Constant">2</span>:address:duplex-list:character
+    <span class="Constant">2</span>:address:duplex-list:character<span class="Special"> &lt;- </span>prev-duplex <span class="Constant">2</span>:address:duplex-list:character
+    <span class="Constant">9</span>:character<span class="Special"> &lt;- </span>first-duplex <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
+  ]
+  memory-should-contain [
+    <span class="Constant">3</span><span class="Special"> &lt;- </span><span class="Constant">5</span>  <span class="Comment"># scanning next</span>
+    <span class="Constant">4</span><span class="Special"> &lt;- </span><span class="Constant">4</span>
+    <span class="Constant">5</span><span class="Special"> &lt;- </span><span class="Constant">6</span>  <span class="Comment"># inserted element</span>
+    <span class="Constant">6</span><span class="Special"> &lt;- </span><span class="Constant">3</span>
+    <span class="Constant">7</span><span class="Special"> &lt;- </span><span class="Constant">6</span>  <span class="Comment"># then prev</span>
+    <span class="Constant">8</span><span class="Special"> &lt;- </span><span class="Constant">4</span>
+    <span class="Constant">9</span><span class="Special"> &lt;- </span><span class="Constant">5</span>
+    <span class="Constant">10</span><span class="Special"> &lt;- </span><span class="Constant">1</span>  <span class="Comment"># list back at start</span>
+  ]
+]
+
+<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>copy <span class="Constant">0</span>  <span class="Comment"># 1 points to head of list</span>
+    <span class="Constant">1</span>:address:duplex-list:character<span class="Special"> &lt;- </span>push-duplex <span class="Constant">3</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-duplex <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-duplex <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-duplex <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-duplex <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-duplex <span class="Constant">6</span>, <span class="Constant">2</span>:address: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-duplex <span class="Constant">2</span>:address:duplex-list:character
+    <span class="Constant">2</span>:address:duplex-list:character<span class="Special"> &lt;- </span>next-duplex <span class="Constant">2</span>:address:duplex-list:character
+    <span class="Constant">4</span>:character<span class="Special"> &lt;- </span>first-duplex <span class="Constant">2</span>:address:duplex-list:character
+    <span class="Constant">2</span>:address:duplex-list:character<span class="Special"> &lt;- </span>next-duplex <span class="Constant">2</span>:address:duplex-list:character
+    <span class="Constant">5</span>:character<span class="Special"> &lt;- </span>first-duplex <span class="Constant">2</span>:address:duplex-list:character
+    <span class="Constant">2</span>:address:duplex-list:character<span class="Special"> &lt;- </span>next-duplex <span class="Constant">2</span>:address:duplex-list:character
+    <span class="Constant">6</span>:character<span class="Special"> &lt;- </span>first-duplex <span class="Constant">2</span>:address:duplex-list:character
+    <span class="Constant">2</span>:address:duplex-list:character<span class="Special"> &lt;- </span>prev-duplex <span class="Constant">2</span>:address:duplex-list:character
+    <span class="Constant">7</span>:character<span class="Special"> &lt;- </span>first-duplex <span class="Constant">2</span>:address:duplex-list:character
+    <span class="Constant">2</span>:address:duplex-list:character<span class="Special"> &lt;- </span>prev-duplex <span class="Constant">2</span>:address:duplex-list:character
+    <span class="Constant">8</span>:character<span class="Special"> &lt;- </span>first-duplex <span class="Constant">2</span>:address:duplex-list:character
+    <span class="Constant">2</span>:address:duplex-list:character<span class="Special"> &lt;- </span>prev-duplex <span class="Constant">2</span>:address:duplex-list:character
+    <span class="Constant">9</span>:character<span class="Special"> &lt;- </span>first-duplex <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
+  ]
+  memory-should-contain [
+    <span class="Constant">3</span><span class="Special"> &lt;- </span><span class="Constant">5</span>  <span class="Comment"># scanning next</span>
+    <span class="Constant">4</span><span class="Special"> &lt;- </span><span class="Constant">4</span>
+    <span class="Constant">5</span><span class="Special"> &lt;- </span><span class="Constant">3</span>
+    <span class="Constant">6</span><span class="Special"> &lt;- </span><span class="Constant">6</span>  <span class="Comment"># inserted element</span>
+    <span class="Constant">7</span><span class="Special"> &lt;- </span><span class="Constant">3</span>  <span class="Comment"># then prev</span>
+    <span class="Constant">8</span><span class="Special"> &lt;- </span><span class="Constant">4</span>
+    <span class="Constant">9</span><span class="Special"> &lt;- </span><span class="Constant">5</span>
+    <span class="Constant">10</span><span class="Special"> &lt;- </span><span class="Constant">1</span>  <span class="Comment"># list back at start</span>
+  ]
+]
+
+<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>copy <span class="Constant">0</span>  <span class="Comment"># 1 points to head of list</span>
+    <span class="Constant">1</span>:address:duplex-list:character<span class="Special"> &lt;- </span>push-duplex <span class="Constant">3</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-duplex <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-duplex <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>insert-duplex <span class="Constant">6</span>, <span class="Constant">1</span>:address: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-duplex <span class="Constant">2</span>:address:duplex-list:character
+    <span class="Constant">2</span>:address:duplex-list:character<span class="Special"> &lt;- </span>next-duplex <span class="Constant">2</span>:address:duplex-list:character
+    <span class="Constant">4</span>:character<span class="Special"> &lt;- </span>first-duplex <span class="Constant">2</span>:address:duplex-list:character
+    <span class="Constant">2</span>:address:duplex-list:character<span class="Special"> &lt;- </span>next-duplex <span class="Constant">2</span>:address:duplex-list:character
+    <span class="Constant">5</span>:character<span class="Special"> &lt;- </span>first-duplex <span class="Constant">2</span>:address:duplex-list:character
+    <span class="Constant">2</span>:address:duplex-list:character<span class="Special"> &lt;- </span>next-duplex <span class="Constant">2</span>:address:duplex-list:character
+    <span class="Constant">6</span>:character<span class="Special"> &lt;- </span>first-duplex <span class="Constant">2</span>:address:duplex-list:character
+    <span class="Constant">2</span>:address:duplex-list:character<span class="Special"> &lt;- </span>prev-duplex <span class="Constant">2</span>:address:duplex-list:character
+    <span class="Constant">7</span>:character<span class="Special"> &lt;- </span>first-duplex <span class="Constant">2</span>:address:duplex-list:character
+    <span class="Constant">2</span>:address:duplex-list:character<span class="Special"> &lt;- </span>prev-duplex <span class="Constant">2</span>:address:duplex-list:character
+    <span class="Constant">8</span>:character<span class="Special"> &lt;- </span>first-duplex <span class="Constant">2</span>:address:duplex-list:character
+    <span class="Constant">2</span>:address:duplex-list:character<span class="Special"> &lt;- </span>prev-duplex <span class="Constant">2</span>:address:duplex-list:character
+    <span class="Constant">9</span>:character<span class="Special"> &lt;- </span>first-duplex <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
+  ]
+  memory-should-contain [
+    <span class="Constant">3</span><span class="Special"> &lt;- </span><span class="Constant">5</span>  <span class="Comment"># scanning next</span>
+    <span class="Constant">4</span><span class="Special"> &lt;- </span><span class="Constant">6</span>  <span class="Comment"># inserted element</span>
+    <span class="Constant">5</span><span class="Special"> &lt;- </span><span class="Constant">4</span>
+    <span class="Constant">6</span><span class="Special"> &lt;- </span><span class="Constant">3</span>
+    <span class="Constant">7</span><span class="Special"> &lt;- </span><span class="Constant">4</span>  <span class="Comment"># then prev</span>
+    <span class="Constant">8</span><span class="Special"> &lt;- </span><span class="Constant">6</span>
+    <span class="Constant">9</span><span class="Special"> &lt;- </span><span class="Constant">5</span>
+    <span class="Constant">10</span><span class="Special"> &lt;- </span><span class="Constant">1</span>  <span class="Comment"># list back at start</span>
+  ]
+]
+
+<span class="Comment"># Removes 'in' from its surrounding list. Returns some valid pointer into the</span>
+<span class="Comment"># rest of the list.</span>
+<span class="Comment">#</span>
+<span class="Comment"># Returns null if and only if list is empty. Beware: in that case any pointers</span>
+<span class="Comment"># to the head are now invalid.</span>
+<span class="muRecipe">recipe</span> remove-duplex in:address:duplex-list:_elem<span class="muRecipe"> -&gt; </span>next-node:address:duplex-list:_elem [
+  <span class="Constant">local-scope</span>
+  <span class="Constant">load-ingredients</span>
+  <span class="Comment"># if 'in' is null, return</span>
+  <span class="muControl">reply-unless</span> in, in
+  next-node:address:duplex-list:_elem<span class="Special"> &lt;- </span>get *in, <span class="Constant">next:offset</span>
+  prev-node:address:duplex-list:_elem<span class="Special"> &lt;- </span>get *in, <span class="Constant">prev:offset</span>
+  <span class="Comment"># null in's pointers</span>
+  x:address:address:duplex-list:_elem<span class="Special"> &lt;- </span>get-address *in, <span class="Constant">next:offset</span>
+  *x<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
+  x<span class="Special"> &lt;- </span>get-address *in, <span class="Constant">prev:offset</span>
+  *x<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
+  <span class="Delimiter">{</span>
+    <span class="Comment"># if next-node is not null</span>
+    <span class="muControl">break-unless</span> next-node
+    <span class="Comment"># next-node.prev = prev-node</span>
+    x<span class="Special"> &lt;- </span>get-address *next-node, <span class="Constant">prev:offset</span>
+    *x<span class="Special"> &lt;- </span>copy prev-node
+  <span class="Delimiter">}</span>
+  <span class="Delimiter">{</span>
+    <span class="Comment"># if prev-node is not null</span>
+    <span class="muControl">break-unless</span> prev-node
+    <span class="Comment"># prev-node.next = next-node</span>
+    x<span class="Special"> &lt;- </span>get-address *prev-node, <span class="Constant">next:offset</span>
+    *x<span class="Special"> &lt;- </span>copy next-node
+    <span class="muControl">reply</span> prev-node
+  <span class="Delimiter">}</span>
+  <span class="muControl">reply</span> next-node
+]
+
+<span class="muScenario">scenario</span> removing-from-duplex-list [
+  run [
+    <span class="Constant">1</span>:address:duplex-list:character<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>  <span class="Comment"># 1 points to head of list</span>
+    <span class="Constant">1</span>:address:duplex-list:character<span class="Special"> &lt;- </span>push-duplex <span class="Constant">3</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-duplex <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-duplex <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-duplex <span class="Constant">1</span>:address:duplex-list:character  <span class="Comment"># 2 points at second element</span>
+    <span class="Constant">2</span>:address:duplex-list:character<span class="Special"> &lt;- </span>remove-duplex <span class="Constant">2</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="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-duplex <span class="Constant">2</span>:address:duplex-list:character
+    <span class="Constant">2</span>:address:duplex-list:character<span class="Special"> &lt;- </span>next-duplex <span class="Constant">2</span>:address:duplex-list:character
+    <span class="Constant">5</span>:character<span class="Special"> &lt;- </span>first-duplex <span class="Constant">2</span>:address:duplex-list:character
+    <span class="Constant">6</span>:address:duplex-list:character<span class="Special"> &lt;- </span>next-duplex <span class="Constant">2</span>:address:duplex-list:character
+    <span class="Constant">2</span>:address:duplex-list:character<span class="Special"> &lt;- </span>prev-duplex <span class="Constant">2</span>:address:duplex-list:character
+    <span class="Constant">7</span>:character<span class="Special"> &lt;- </span>first-duplex <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
+  ]
+  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>
+    <span class="Constant">4</span><span class="Special"> &lt;- </span><span class="Constant">5</span>  <span class="Comment"># scanning next, skipping deleted element</span>
+    <span class="Constant">5</span><span class="Special"> &lt;- </span><span class="Constant">3</span>
+    <span class="Constant">6</span><span class="Special"> &lt;- </span><span class="Constant">0</span>  <span class="Comment"># no more elements</span>
+    <span class="Constant">7</span><span class="Special"> &lt;- </span><span class="Constant">5</span>  <span class="Comment"># prev of final element</span>
+    <span class="Constant">8</span><span class="Special"> &lt;- </span><span class="Constant">1</span>  <span class="Comment"># list back at start</span>
+  ]
+]
+
+<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>copy <span class="Constant">0</span>  <span class="Comment"># 1 points to head of list</span>
+    <span class="Constant">1</span>:address:duplex-list:character<span class="Special"> &lt;- </span>push-duplex <span class="Constant">3</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-duplex <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-duplex <span class="Constant">5</span>, <span class="Constant">1</span>:address:duplex-list:character
+    <span class="Comment"># removing from head? return value matters.</span>
+    <span class="Constant">1</span>:address:duplex-list:character<span class="Special"> &lt;- </span>remove-duplex <span class="Constant">1</span>:address: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-duplex <span class="Constant">2</span>:address:duplex-list:character
+    <span class="Constant">2</span>:address:duplex-list:character<span class="Special"> &lt;- </span>next-duplex <span class="Constant">2</span>:address:duplex-list:character
+    <span class="Constant">4</span>:character<span class="Special"> &lt;- </span>first-duplex <span class="Constant">2</span>:address:duplex-list:character
+    <span class="Constant">5</span>:address:duplex-list:character<span class="Special"> &lt;- </span>next-duplex <span class="Constant">2</span>:address:duplex-list:character
+    <span class="Constant">2</span>:address:duplex-list:character<span class="Special"> &lt;- </span>prev-duplex <span class="Constant">2</span>:address:duplex-list:character
+    <span class="Constant">6</span>:character<span class="Special"> &lt;- </span>first-duplex <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
+  ]
+  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>
+    <span class="Constant">4</span><span class="Special"> &lt;- </span><span class="Constant">3</span>
+    <span class="Constant">5</span><span class="Special"> &lt;- </span><span class="Constant">0</span>  <span class="Comment"># no more elements</span>
+    <span class="Constant">6</span><span class="Special"> &lt;- </span><span class="Constant">4</span>  <span class="Comment"># prev of final element</span>
+    <span class="Constant">7</span><span class="Special"> &lt;- </span><span class="Constant">1</span>  <span class="Comment"># list back at start</span>
+  ]
+]
+
+<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>copy <span class="Constant">0</span>  <span class="Comment"># 1 points to head of list</span>
+    <span class="Constant">1</span>:address:duplex-list:character<span class="Special"> &lt;- </span>push-duplex <span class="Constant">3</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-duplex <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-duplex <span class="Constant">5</span>, <span class="Constant">1</span>:address: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-duplex <span class="Constant">1</span>:address:duplex-list:character
+    <span class="Constant">2</span>:address:duplex-list:character<span class="Special"> &lt;- </span>next-duplex <span class="Constant">2</span>:address:duplex-list:character
+    <span class="Constant">2</span>:address:duplex-list:character<span class="Special"> &lt;- </span>remove-duplex <span class="Constant">2</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="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-duplex <span class="Constant">2</span>:address:duplex-list:character
+    <span class="Constant">2</span>:address:duplex-list:character<span class="Special"> &lt;- </span>next-duplex <span class="Constant">2</span>:address:duplex-list:character
+    <span class="Constant">5</span>:character<span class="Special"> &lt;- </span>first-duplex <span class="Constant">2</span>:address:duplex-list:character
+    <span class="Constant">6</span>:address:duplex-list:character<span class="Special"> &lt;- </span>next-duplex <span class="Constant">2</span>:address:duplex-list:character
+    <span class="Constant">2</span>:address:duplex-list:character<span class="Special"> &lt;- </span>prev-duplex <span class="Constant">2</span>:address:duplex-list:character
+    <span class="Constant">7</span>:character<span class="Special"> &lt;- </span>first-duplex <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
+  ]
+  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>
+    <span class="Constant">4</span><span class="Special"> &lt;- </span><span class="Constant">5</span>  <span class="Comment"># scanning next, skipping deleted element</span>
+    <span class="Constant">5</span><span class="Special"> &lt;- </span><span class="Constant">4</span>
+    <span class="Constant">6</span><span class="Special"> &lt;- </span><span class="Constant">0</span>  <span class="Comment"># no more elements</span>
+    <span class="Constant">7</span><span class="Special"> &lt;- </span><span class="Constant">5</span>  <span class="Comment"># prev of final element</span>
+    <span class="Constant">8</span><span class="Special"> &lt;- </span><span class="Constant">1</span>  <span class="Comment"># list back at start</span>
+  ]
+]
+
+<span class="muScenario">scenario</span> removing-from-singleton-list [
+  run [
+    <span class="Constant">1</span>:address:duplex-list:character<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>  <span class="Comment"># 1 points to singleton list</span>
+    <span class="Constant">1</span>:address:duplex-list:character<span class="Special"> &lt;- </span>push-duplex <span class="Constant">3</span>, <span class="Constant">1</span>:address:duplex-list:character
+    <span class="Constant">2</span>:address:duplex-list:character<span class="Special"> &lt;- </span>remove-duplex <span class="Constant">1</span>:address:duplex-list:character
+    <span class="Constant">3</span>:address:duplex-list:character<span class="Special"> &lt;- </span>get *<span class="Constant">1</span>:address:duplex-list:character, <span class="Constant">next:offset</span>
+    <span class="Constant">4</span>:address:duplex-list:character<span class="Special"> &lt;- </span>get *<span class="Constant">1</span>:address:duplex-list:character, <span class="Constant">prev:offset</span>
+  ]
+  memory-should-contain [
+    <span class="Constant">2</span><span class="Special"> &lt;- </span><span class="Constant">0</span>  <span class="Comment"># remove returned null</span>
+    <span class="Constant">3</span><span class="Special"> &lt;- </span><span class="Constant">0</span>  <span class="Comment"># removed node is also detached</span>
+    <span class="Constant">4</span><span class="Special"> &lt;- </span><span class="Constant">0</span>
+  ]
+]
+
+<span class="Comment"># l:address:duplex-list &lt;- remove-duplex-between start:address:duplex-list, end:address:duplex-list</span>
+<span class="Comment"># Remove values between 'start' and 'end' (both exclusive). Returns some valid</span>
+<span class="Comment"># pointer into the rest of the list.</span>
+<span class="Comment"># Also clear pointers back out from start/end for hygiene.</span>
+<span class="muRecipe">recipe</span> remove-duplex-between start:address:duplex-list:_elem, end:address:duplex-list:_elem<span class="muRecipe"> -&gt; </span>start:address: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>
+  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<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
+  <span class="Comment"># end-&gt;prev-&gt;next = 0</span>
+  <span class="Comment"># end-&gt;prev = start</span>
+  prev<span class="Special"> &lt;- </span>get-address *end, <span class="Constant">prev:offset</span>
+  next<span class="Special"> &lt;- </span>get-address **prev, <span class="Constant">next:offset</span>
+  *next<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
+  *prev<span class="Special"> &lt;- </span>copy start
+]
+
+<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>copy <span class="Constant">0</span>  <span class="Comment"># 1 points to singleton list</span>
+  <span class="Constant">1</span>:address:duplex-list:character<span class="Special"> &lt;- </span>push-duplex <span class="Constant">18</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-duplex <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-duplex <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-duplex <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-duplex <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-duplex <span class="Constant">13</span>, <span class="Constant">1</span>:address: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-duplex <span class="Constant">1</span>:address:duplex-list:character
+    <span class="Constant">2</span>:address:duplex-list:character<span class="Special"> &lt;- </span>next-duplex <span class="Constant">2</span>:address:duplex-list:character
+    <span class="Constant">2</span>:address:duplex-list:character<span class="Special"> &lt;- </span>remove-duplex-between <span class="Constant">2</span>:address: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-duplex <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-duplex <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-duplex <span class="Constant">7</span>:address:duplex-list:character
+  ]
+  memory-should-contain [
+    <span class="Constant">4</span><span class="Special"> &lt;- </span><span class="Constant">13</span>
+    <span class="Constant">6</span><span class="Special"> &lt;- </span><span class="Constant">14</span>
+    <span class="Constant">8</span><span class="Special"> &lt;- </span><span class="Constant">15</span>
+    <span class="Constant">9</span><span class="Special"> &lt;- </span><span class="Constant">0</span>
+  ]
+]
+
+<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>copy <span class="Constant">0</span>  <span class="Comment"># 1 points to singleton list</span>
+  <span class="Constant">1</span>:address:duplex-list:character<span class="Special"> &lt;- </span>push-duplex <span class="Constant">18</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-duplex <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-duplex <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-duplex <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-duplex <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-duplex <span class="Constant">13</span>, <span class="Constant">1</span>:address: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-duplex <span class="Constant">1</span>:address: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-duplex <span class="Constant">2</span>:address:duplex-list:character
+    <span class="Constant">3</span>:address:duplex-list:character<span class="Special"> &lt;- </span>next-duplex <span class="Constant">3</span>:address:duplex-list:character
+    <span class="Constant">3</span>:address:duplex-list:character<span class="Special"> &lt;- </span>next-duplex <span class="Constant">3</span>:address:duplex-list:character
+    <span class="Constant">3</span>:address:duplex-list:character<span class="Special"> &lt;- </span>next-duplex <span class="Constant">3</span>:address:duplex-list:character
+    remove-duplex-between <span class="Constant">2</span>:address:duplex-list:character, <span class="Constant">3</span>:address: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-duplex <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-duplex <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-duplex <span class="Constant">7</span>:address:duplex-list:character
+  ]
+  memory-should-contain [
+    <span class="Constant">4</span><span class="Special"> &lt;- </span><span class="Constant">13</span>
+    <span class="Constant">6</span><span class="Special"> &lt;- </span><span class="Constant">14</span>
+    <span class="Constant">8</span><span class="Special"> &lt;- </span><span class="Constant">18</span>
+    <span class="Constant">9</span><span class="Special"> &lt;- </span><span class="Constant">0</span>
+  ]
+]
+
+<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>copy <span class="Constant">0</span>  <span class="Comment"># 1 points to singleton list</span>
+  <span class="Constant">1</span>:address:duplex-list:character<span class="Special"> &lt;- </span>push-duplex <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-duplex <span class="Constant">13</span>, <span class="Constant">1</span>:address: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-duplex <span class="Constant">1</span>:address:duplex-list:character
+    remove-duplex-between <span class="Constant">1</span>:address:duplex-list:character, <span class="Constant">2</span>:address: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-duplex <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-duplex <span class="Constant">5</span>:address:duplex-list:character
+  ]
+  memory-should-contain [
+    <span class="Constant">4</span><span class="Special"> &lt;- </span><span class="Constant">13</span>
+    <span class="Constant">6</span><span class="Special"> &lt;- </span><span class="Constant">14</span>
+    <span class="Constant">7</span><span class="Special"> &lt;- </span><span class="Constant">0</span>
+  ]
+]
+
+<span class="Comment"># Inserts list beginning at 'new' after 'in'. Returns some pointer into the list.</span>
+<span class="muRecipe">recipe</span> insert-duplex-range in:address:duplex-list:_elem, start:address:duplex-list:_elem<span class="muRecipe"> -&gt; </span>in:address: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
+  <span class="Delimiter">{</span>
+    next:address:duplex-list:_elem<span class="Special"> &lt;- </span>next-duplex 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-duplex in
+  dest:address:address: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
+    dest<span class="Special"> &lt;- </span>get-address *next, <span class="Constant">prev:offset</span>
+    *dest<span class="Special"> &lt;- </span>copy end
+  <span class="Delimiter">}</span>
+  dest<span class="Special"> &lt;- </span>get-address *in, <span class="Constant">next:offset</span>
+  *dest<span class="Special"> &lt;- </span>copy start
+  dest<span class="Special"> &lt;- </span>get-address *start, <span class="Constant">prev:offset</span>
+  *dest<span class="Special"> &lt;- </span>copy in
+]
+
+<span class="muRecipe">recipe</span> append-duplex in:address:duplex-list:_elem, new:address:duplex-list:_elem<span class="muRecipe"> -&gt; </span>in:address: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-duplex in
+  dest:address:address: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-duplex in:address:duplex-list:_elem<span class="muRecipe"> -&gt; </span>result:address: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-duplex result
+    <span class="muControl">break-unless</span> next
+    result<span class="Special"> &lt;- </span>copy next
+    <span class="muControl">loop</span>
+  <span class="Delimiter">}</span>
+]
+
+<span class="Comment"># helper for debugging</span>
+<span class="muRecipe">recipe</span> dump-duplex-from x:address:duplex-list:_elem [
+  <span class="Constant">local-scope</span>
+  <span class="Constant">load-ingredients</span>
+  $print x, <span class="Constant">[: ]</span>
+  <span class="Delimiter">{</span>
+    <span class="muControl">break-unless</span> x
+    c:_elem<span class="Special"> &lt;- </span>get *x, <span class="Constant">value:offset</span>
+    $print c, <span class="Constant">[ ]</span>
+    x<span class="Special"> &lt;- </span>next-duplex x
+    <span class="Delimiter">{</span>
+      is-newline?:boolean<span class="Special"> &lt;- </span>equal c, <span class="Constant">10/newline</span>
+      <span class="muControl">break-unless</span> is-newline?
+      $print <span class="Constant">10/newline</span>
+      $print x, <span class="Constant">[: ]</span>
+    <span class="Delimiter">}</span>
+    <span class="muControl">loop</span>
+  <span class="Delimiter">}</span>
+  $print <span class="Constant">10/newline</span>, <span class="Constant">[---]</span>, <span class="Constant">10/newline</span>
+]
+
+<span class="muRecipe">recipe</span> force-specialization-duplex-list-character [
+  <span class="Constant">1</span>:address:duplex-list:character<span class="Special"> &lt;- </span>push-duplex <span class="Constant">2</span>:character, <span class="Constant">1</span>:address:duplex-list:character
+  <span class="Constant">2</span>:character<span class="Special"> &lt;- </span>first-duplex <span class="Constant">1</span>:address:duplex-list:character
+  <span class="Constant">1</span>:address:duplex-list:character<span class="Special"> &lt;- </span>next-duplex <span class="Constant">1</span>:address:duplex-list:character
+  <span class="Constant">1</span>:address:duplex-list:character<span class="Special"> &lt;- </span>prev-duplex <span class="Constant">1</span>:address:duplex-list:character
+  <span class="Constant">1</span>:address:duplex-list:character<span class="Special"> &lt;- </span>insert-duplex <span class="Constant">2</span>:character, <span class="Constant">1</span>:address:duplex-list:character
+  <span class="Constant">1</span>:address:duplex-list:character<span class="Special"> &lt;- </span>remove-duplex <span class="Constant">1</span>:address:duplex-list:character
+  <span class="Constant">1</span>:address:duplex-list:character<span class="Special"> &lt;- </span>remove-duplex-between <span class="Constant">1</span>:address:duplex-list:character, <span class="Constant">1</span>:address:duplex-list:character
+  <span class="Constant">1</span>:address:duplex-list:character<span class="Special"> &lt;- </span>insert-duplex-range <span class="Constant">1</span>:address:duplex-list:character, <span class="Constant">1</span>:address:duplex-list:character
+  <span class="Constant">1</span>:address:duplex-list:character<span class="Special"> &lt;- </span>append-duplex <span class="Constant">1</span>:address:duplex-list:character, <span class="Constant">1</span>:address:duplex-list:character
+  <span class="Constant">1</span>:address:duplex-list:character<span class="Special"> &lt;- </span>last-duplex <span class="Constant">1</span>:address:duplex-list:character
+]
+</pre>
+</body>
+</html>
+<!-- vim: set foldmethod=manual : -->