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Diffstat (limited to 'html/065duplex_list.mu.html')
-rw-r--r--html/065duplex_list.mu.html926
1 files changed, 469 insertions, 457 deletions
diff --git a/html/065duplex_list.mu.html b/html/065duplex_list.mu.html
index 6b0ecab7..fedcd670 100644
--- a/html/065duplex_list.mu.html
+++ b/html/065duplex_list.mu.html
@@ -145,468 +145,480 @@ if ('onhashchange' in window) {
 <span id="L83" class="LineNr"> 83 </span>  ]
 <span id="L84" class="LineNr"> 84 </span>]
 <span id="L85" class="LineNr"> 85 </span>
-<span id="L86" class="LineNr"> 86 </span><span class="Comment"># insert 'x' after 'in'</span>
-<span id="L87" class="LineNr"> 87 </span><span class="muRecipe">def</span> insert x:_elem, in:&amp;:duplex-list:_elem<span class="muRecipe"> -&gt; </span>in:&amp;:duplex-list:_elem [
-<span id="L88" class="LineNr"> 88 </span>  <span class="Constant">local-scope</span>
-<span id="L89" class="LineNr"> 89 </span>  <span class="Constant">load-ingredients</span>
-<span id="L90" class="LineNr"> 90 </span>  new-node:&amp;:duplex-list:_elem <span class="Special">&lt;-</span> new <span class="Delimiter">{</span>(duplex-list _elem): type<span class="Delimiter">}</span>
-<span id="L91" class="LineNr"> 91 </span>  *new-node <span class="Special">&lt;-</span> put *new-node, <span class="Constant">value:offset</span>, x
-<span id="L92" class="LineNr"> 92 </span>  <span class="Comment"># save old next before changing it</span>
-<span id="L93" class="LineNr"> 93 </span>  next-node:&amp;:duplex-list:_elem <span class="Special">&lt;-</span> get *in, <span class="Constant"><a href='065duplex_list.mu.html#L29'>next</a>:offset</span>
-<span id="L94" class="LineNr"> 94 </span>  *in <span class="Special">&lt;-</span> put *in, <span class="Constant"><a href='065duplex_list.mu.html#L29'>next</a>:offset</span>, new-node
-<span id="L95" class="LineNr"> 95 </span>  *new-node <span class="Special">&lt;-</span> put *new-node, <span class="Constant"><a href='065duplex_list.mu.html#L36'>prev</a>:offset</span>, in
-<span id="L96" class="LineNr"> 96 </span>  *new-node <span class="Special">&lt;-</span> put *new-node, <span class="Constant"><a href='065duplex_list.mu.html#L29'>next</a>:offset</span>, next-node
-<span id="L97" class="LineNr"> 97 </span>  <span class="muControl">return-unless</span> next-node
-<span id="L98" class="LineNr"> 98 </span>  *next-node <span class="Special">&lt;-</span> put *next-node, <span class="Constant"><a href='065duplex_list.mu.html#L36'>prev</a>:offset</span>, new-node
-<span id="L99" class="LineNr"> 99 </span>]
-<span id="L100" class="LineNr">100 </span>
-<span id="L101" class="LineNr">101 </span><span class="muScenario">scenario</span> inserting-into-duplex-list [
-<span id="L102" class="LineNr">102 </span>  <span class="Constant">local-scope</span>
-<span id="L103" class="LineNr">103 </span>  list:&amp;:duplex-list:char <span class="Special">&lt;-</span> push<span class="Constant"> 3</span>,<span class="Constant"> 0</span>
-<span id="L104" class="LineNr">104 </span>  list <span class="Special">&lt;-</span> push<span class="Constant"> 4</span>, list
-<span id="L105" class="LineNr">105 </span>  list <span class="Special">&lt;-</span> push<span class="Constant"> 5</span>, list
-<span id="L106" class="LineNr">106 </span>  run [
-<span id="L107" class="LineNr">107 </span>  <span class="Conceal">¦</span> list2:&amp;:duplex-list:char <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> list  <span class="Comment"># inside list</span>
-<span id="L108" class="LineNr">108 </span>  <span class="Conceal">¦</span> list2 <span class="Special">&lt;-</span> insert<span class="Constant"> 6</span>, list2
-<span id="L109" class="LineNr">109 </span>  <span class="Conceal">¦</span> <span class="Comment"># check structure like before</span>
-<span id="L110" class="LineNr">110 </span>  <span class="Conceal">¦</span> list2 <span class="Special">&lt;-</span> copy list
-<span id="L111" class="LineNr">111 </span>  <span class="Conceal">¦</span> 10:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> first list2
-<span id="L112" class="LineNr">112 </span>  <span class="Conceal">¦</span> list2 <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> list2
-<span id="L113" class="LineNr">113 </span>  <span class="Conceal">¦</span> 11:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> first list2
-<span id="L114" class="LineNr">114 </span>  <span class="Conceal">¦</span> list2 <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> list2
-<span id="L115" class="LineNr">115 </span>  <span class="Conceal">¦</span> 12:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> first list2
-<span id="L116" class="LineNr">116 </span>  <span class="Conceal">¦</span> list2 <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> list2
-<span id="L117" class="LineNr">117 </span>  <span class="Conceal">¦</span> 13:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> first list2
-<span id="L118" class="LineNr">118 </span>  <span class="Conceal">¦</span> list2 <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L36'>prev</a> list2
-<span id="L119" class="LineNr">119 </span>  <span class="Conceal">¦</span> 20:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> first list2
-<span id="L120" class="LineNr">120 </span>  <span class="Conceal">¦</span> list2 <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L36'>prev</a> list2
-<span id="L121" class="LineNr">121 </span>  <span class="Conceal">¦</span> 21:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> first list2
-<span id="L122" class="LineNr">122 </span>  <span class="Conceal">¦</span> list2 <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L36'>prev</a> list2
-<span id="L123" class="LineNr">123 </span>  <span class="Conceal">¦</span> 22:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> first list2
-<span id="L124" class="LineNr">124 </span>  <span class="Conceal">¦</span> 30:bool/<span class="Special">raw</span> <span class="Special">&lt;-</span> equal list, list2
-<span id="L125" class="LineNr">125 </span>  ]
-<span id="L126" class="LineNr">126 </span>  memory-should-contain [
-<span id="L127" class="LineNr">127 </span>  <span class="Conceal">¦</span><span class="Constant"> 10</span> <span class="Special">&lt;-</span><span class="Constant"> 5</span>  <span class="Comment"># scanning next</span>
-<span id="L128" class="LineNr">128 </span>  <span class="Conceal">¦</span><span class="Constant"> 11</span> <span class="Special">&lt;-</span><span class="Constant"> 4</span>
-<span id="L129" class="LineNr">129 </span>  <span class="Conceal">¦</span><span class="Constant"> 12</span> <span class="Special">&lt;-</span><span class="Constant"> 6</span>  <span class="Comment"># inserted element</span>
-<span id="L130" class="LineNr">130 </span>  <span class="Conceal">¦</span><span class="Constant"> 13</span> <span class="Special">&lt;-</span><span class="Constant"> 3</span>
-<span id="L131" class="LineNr">131 </span>  <span class="Conceal">¦</span><span class="Constant"> 20</span> <span class="Special">&lt;-</span><span class="Constant"> 6</span>  <span class="Comment"># then prev</span>
-<span id="L132" class="LineNr">132 </span>  <span class="Conceal">¦</span><span class="Constant"> 21</span> <span class="Special">&lt;-</span><span class="Constant"> 4</span>
-<span id="L133" class="LineNr">133 </span>  <span class="Conceal">¦</span><span class="Constant"> 22</span> <span class="Special">&lt;-</span><span class="Constant"> 5</span>
-<span id="L134" class="LineNr">134 </span>  <span class="Conceal">¦</span><span class="Constant"> 30</span> <span class="Special">&lt;-</span><span class="Constant"> 1</span>  <span class="Comment"># list back at start</span>
-<span id="L135" class="LineNr">135 </span>  ]
-<span id="L136" class="LineNr">136 </span>]
-<span id="L137" class="LineNr">137 </span>
-<span id="L138" class="LineNr">138 </span><span class="muScenario">scenario</span> inserting-at-end-of-duplex-list [
-<span id="L139" class="LineNr">139 </span>  <span class="Constant">local-scope</span>
-<span id="L140" class="LineNr">140 </span>  list:&amp;:duplex-list:char <span class="Special">&lt;-</span> push<span class="Constant"> 3</span>,<span class="Constant"> 0</span>
-<span id="L141" class="LineNr">141 </span>  list <span class="Special">&lt;-</span> push<span class="Constant"> 4</span>, list
-<span id="L142" class="LineNr">142 </span>  list <span class="Special">&lt;-</span> push<span class="Constant"> 5</span>, list
-<span id="L143" class="LineNr">143 </span>  run [
-<span id="L144" class="LineNr">144 </span>  <span class="Conceal">¦</span> list2:&amp;:duplex-list:char <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> list  <span class="Comment"># inside list</span>
-<span id="L145" class="LineNr">145 </span>  <span class="Conceal">¦</span> list2 <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> list2  <span class="Comment"># now at end of list</span>
-<span id="L146" class="LineNr">146 </span>  <span class="Conceal">¦</span> list2 <span class="Special">&lt;-</span> insert<span class="Constant"> 6</span>, list2
-<span id="L147" class="LineNr">147 </span>  <span class="Conceal">¦</span> <span class="Comment"># check structure like before</span>
-<span id="L148" class="LineNr">148 </span>  <span class="Conceal">¦</span> list2 <span class="Special">&lt;-</span> copy list
-<span id="L149" class="LineNr">149 </span>  <span class="Conceal">¦</span> 10:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> first list2
-<span id="L150" class="LineNr">150 </span>  <span class="Conceal">¦</span> list2 <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> list2
-<span id="L151" class="LineNr">151 </span>  <span class="Conceal">¦</span> 11:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> first list2
-<span id="L152" class="LineNr">152 </span>  <span class="Conceal">¦</span> list2 <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> list2
-<span id="L153" class="LineNr">153 </span>  <span class="Conceal">¦</span> 12:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> first list2
-<span id="L154" class="LineNr">154 </span>  <span class="Conceal">¦</span> list2 <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> list2
-<span id="L155" class="LineNr">155 </span>  <span class="Conceal">¦</span> 13:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> first list2
-<span id="L156" class="LineNr">156 </span>  <span class="Conceal">¦</span> list2 <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L36'>prev</a> list2
-<span id="L157" class="LineNr">157 </span>  <span class="Conceal">¦</span> 20:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> first list2
-<span id="L158" class="LineNr">158 </span>  <span class="Conceal">¦</span> list2 <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L36'>prev</a> list2
-<span id="L159" class="LineNr">159 </span>  <span class="Conceal">¦</span> 21:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> first list2
-<span id="L160" class="LineNr">160 </span>  <span class="Conceal">¦</span> list2 <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L36'>prev</a> list2
-<span id="L161" class="LineNr">161 </span>  <span class="Conceal">¦</span> 22:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> first list2
-<span id="L162" class="LineNr">162 </span>  <span class="Conceal">¦</span> 30:bool/<span class="Special">raw</span> <span class="Special">&lt;-</span> equal list, list2
-<span id="L163" class="LineNr">163 </span>  ]
-<span id="L164" class="LineNr">164 </span>  memory-should-contain [
-<span id="L165" class="LineNr">165 </span>  <span class="Conceal">¦</span><span class="Constant"> 10</span> <span class="Special">&lt;-</span><span class="Constant"> 5</span>  <span class="Comment"># scanning next</span>
-<span id="L166" class="LineNr">166 </span>  <span class="Conceal">¦</span><span class="Constant"> 11</span> <span class="Special">&lt;-</span><span class="Constant"> 4</span>
-<span id="L167" class="LineNr">167 </span>  <span class="Conceal">¦</span><span class="Constant"> 12</span> <span class="Special">&lt;-</span><span class="Constant"> 3</span>
-<span id="L168" class="LineNr">168 </span>  <span class="Conceal">¦</span><span class="Constant"> 13</span> <span class="Special">&lt;-</span><span class="Constant"> 6</span>  <span class="Comment"># inserted element</span>
-<span id="L169" class="LineNr">169 </span>  <span class="Conceal">¦</span><span class="Constant"> 20</span> <span class="Special">&lt;-</span><span class="Constant"> 3</span>  <span class="Comment"># then prev</span>
-<span id="L170" class="LineNr">170 </span>  <span class="Conceal">¦</span><span class="Constant"> 21</span> <span class="Special">&lt;-</span><span class="Constant"> 4</span>
-<span id="L171" class="LineNr">171 </span>  <span class="Conceal">¦</span><span class="Constant"> 22</span> <span class="Special">&lt;-</span><span class="Constant"> 5</span>
-<span id="L172" class="LineNr">172 </span>  <span class="Conceal">¦</span><span class="Constant"> 30</span> <span class="Special">&lt;-</span><span class="Constant"> 1</span>  <span class="Comment"># list back at start</span>
-<span id="L173" class="LineNr">173 </span>  ]
-<span id="L174" class="LineNr">174 </span>]
-<span id="L175" class="LineNr">175 </span>
-<span id="L176" class="LineNr">176 </span><span class="muScenario">scenario</span> inserting-after-start-of-duplex-list [
-<span id="L177" class="LineNr">177 </span>  <span class="Constant">local-scope</span>
-<span id="L178" class="LineNr">178 </span>  list:&amp;:duplex-list:char <span class="Special">&lt;-</span> push<span class="Constant"> 3</span>,<span class="Constant"> 0</span>
-<span id="L179" class="LineNr">179 </span>  list <span class="Special">&lt;-</span> push<span class="Constant"> 4</span>, list
-<span id="L180" class="LineNr">180 </span>  list <span class="Special">&lt;-</span> push<span class="Constant"> 5</span>, list
-<span id="L181" class="LineNr">181 </span>  run [
-<span id="L182" class="LineNr">182 </span>  <span class="Conceal">¦</span> list <span class="Special">&lt;-</span> insert<span class="Constant"> 6</span>, list
-<span id="L183" class="LineNr">183 </span>  <span class="Conceal">¦</span> <span class="Comment"># check structure like before</span>
-<span id="L184" class="LineNr">184 </span>  <span class="Conceal">¦</span> list2:&amp;:duplex-list:char <span class="Special">&lt;-</span> copy list
-<span id="L185" class="LineNr">185 </span>  <span class="Conceal">¦</span> 10:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> first list2
-<span id="L186" class="LineNr">186 </span>  <span class="Conceal">¦</span> list2 <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> list2
-<span id="L187" class="LineNr">187 </span>  <span class="Conceal">¦</span> 11:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> first list2
-<span id="L188" class="LineNr">188 </span>  <span class="Conceal">¦</span> list2 <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> list2
-<span id="L189" class="LineNr">189 </span>  <span class="Conceal">¦</span> 12:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> first list2
-<span id="L190" class="LineNr">190 </span>  <span class="Conceal">¦</span> list2 <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> list2
-<span id="L191" class="LineNr">191 </span>  <span class="Conceal">¦</span> 13:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> first list2
-<span id="L192" class="LineNr">192 </span>  <span class="Conceal">¦</span> list2 <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L36'>prev</a> list2
-<span id="L193" class="LineNr">193 </span>  <span class="Conceal">¦</span> 20:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> first list2
-<span id="L194" class="LineNr">194 </span>  <span class="Conceal">¦</span> list2 <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L36'>prev</a> list2
-<span id="L195" class="LineNr">195 </span>  <span class="Conceal">¦</span> 21:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> first list2
-<span id="L196" class="LineNr">196 </span>  <span class="Conceal">¦</span> list2 <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L36'>prev</a> list2
-<span id="L197" class="LineNr">197 </span>  <span class="Conceal">¦</span> 22:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> first list2
-<span id="L198" class="LineNr">198 </span>  <span class="Conceal">¦</span> 30:bool/<span class="Special">raw</span> <span class="Special">&lt;-</span> equal list, list2
-<span id="L199" class="LineNr">199 </span>  ]
-<span id="L200" class="LineNr">200 </span>  memory-should-contain [
-<span id="L201" class="LineNr">201 </span>  <span class="Conceal">¦</span><span class="Constant"> 10</span> <span class="Special">&lt;-</span><span class="Constant"> 5</span>  <span class="Comment"># scanning next</span>
-<span id="L202" class="LineNr">202 </span>  <span class="Conceal">¦</span><span class="Constant"> 11</span> <span class="Special">&lt;-</span><span class="Constant"> 6</span>  <span class="Comment"># inserted element</span>
-<span id="L203" class="LineNr">203 </span>  <span class="Conceal">¦</span><span class="Constant"> 12</span> <span class="Special">&lt;-</span><span class="Constant"> 4</span>
-<span id="L204" class="LineNr">204 </span>  <span class="Conceal">¦</span><span class="Constant"> 13</span> <span class="Special">&lt;-</span><span class="Constant"> 3</span>
-<span id="L205" class="LineNr">205 </span>  <span class="Conceal">¦</span><span class="Constant"> 20</span> <span class="Special">&lt;-</span><span class="Constant"> 4</span>  <span class="Comment"># then prev</span>
-<span id="L206" class="LineNr">206 </span>  <span class="Conceal">¦</span><span class="Constant"> 21</span> <span class="Special">&lt;-</span><span class="Constant"> 6</span>
-<span id="L207" class="LineNr">207 </span>  <span class="Conceal">¦</span><span class="Constant"> 22</span> <span class="Special">&lt;-</span><span class="Constant"> 5</span>
-<span id="L208" class="LineNr">208 </span>  <span class="Conceal">¦</span><span class="Constant"> 30</span> <span class="Special">&lt;-</span><span class="Constant"> 1</span>  <span class="Comment"># list back at start</span>
-<span id="L209" class="LineNr">209 </span>  ]
-<span id="L210" class="LineNr">210 </span>]
-<span id="L211" class="LineNr">211 </span>
-<span id="L212" class="LineNr">212 </span><span class="Comment"># remove 'x' from its surrounding list 'in'</span>
-<span id="L213" class="LineNr">213 </span><span class="Comment">#</span>
-<span id="L214" class="LineNr">214 </span><span class="Comment"># Returns null if and only if list is empty. Beware: in that case any other</span>
-<span id="L215" class="LineNr">215 </span><span class="Comment"># pointers to the head are now invalid.</span>
-<span id="L216" class="LineNr">216 </span><span class="muRecipe">def</span> remove x:&amp;:duplex-list:_elem/contained-in:in, in:&amp;:duplex-list:_elem<span class="muRecipe"> -&gt; </span>in:&amp;:duplex-list:_elem [
-<span id="L217" class="LineNr">217 </span>  <span class="Constant">local-scope</span>
-<span id="L218" class="LineNr">218 </span>  <span class="Constant">load-ingredients</span>
-<span id="L219" class="LineNr">219 </span>  <span class="Comment"># if 'x' is null, return</span>
-<span id="L220" class="LineNr">220 </span>  <span class="muControl">return-unless</span> x
-<span id="L221" class="LineNr">221 </span>  next-node:&amp;:duplex-list:_elem <span class="Special">&lt;-</span> get *x, <span class="Constant"><a href='065duplex_list.mu.html#L29'>next</a>:offset</span>
-<span id="L222" class="LineNr">222 </span>  prev-node:&amp;:duplex-list:_elem <span class="Special">&lt;-</span> get *x, <span class="Constant"><a href='065duplex_list.mu.html#L36'>prev</a>:offset</span>
-<span id="L223" class="LineNr">223 </span>  <span class="Comment"># null x's pointers</span>
-<span id="L224" class="LineNr">224 </span>  *x <span class="Special">&lt;-</span> put *x, <span class="Constant"><a href='065duplex_list.mu.html#L29'>next</a>:offset</span>,<span class="Constant"> 0</span>
-<span id="L225" class="LineNr">225 </span>  *x <span class="Special">&lt;-</span> put *x, <span class="Constant"><a href='065duplex_list.mu.html#L36'>prev</a>:offset</span>,<span class="Constant"> 0</span>
-<span id="L226" class="LineNr">226 </span>  <span class="Comment"># if next-node is not null, set its prev pointer</span>
-<span id="L227" class="LineNr">227 </span>  <span class="Delimiter">{</span>
-<span id="L228" class="LineNr">228 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> next-node
-<span id="L229" class="LineNr">229 </span>  <span class="Conceal">¦</span> *next-node <span class="Special">&lt;-</span> put *next-node, <span class="Constant"><a href='065duplex_list.mu.html#L36'>prev</a>:offset</span>, prev-node
-<span id="L230" class="LineNr">230 </span>  <span class="Delimiter">}</span>
-<span id="L231" class="LineNr">231 </span>  <span class="Comment"># if prev-node is not null, set its next pointer and return</span>
-<span id="L232" class="LineNr">232 </span>  <span class="Delimiter">{</span>
-<span id="L233" class="LineNr">233 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> prev-node
-<span id="L234" class="LineNr">234 </span>  <span class="Conceal">¦</span> *prev-node <span class="Special">&lt;-</span> put *prev-node, <span class="Constant"><a href='065duplex_list.mu.html#L29'>next</a>:offset</span>, next-node
-<span id="L235" class="LineNr">235 </span>  <span class="Conceal">¦</span> <span class="muControl">return</span>
-<span id="L236" class="LineNr">236 </span>  <span class="Delimiter">}</span>
-<span id="L237" class="LineNr">237 </span>  <span class="Comment"># if prev-node is null, then we removed the head node at 'in'</span>
-<span id="L238" class="LineNr">238 </span>  <span class="Comment"># return the new head rather than the old 'in'</span>
-<span id="L239" class="LineNr">239 </span>  <span class="muControl">return</span> next-node
-<span id="L240" class="LineNr">240 </span>]
-<span id="L241" class="LineNr">241 </span>
-<span id="L242" class="LineNr">242 </span><span class="muScenario">scenario</span> removing-from-duplex-list [
-<span id="L243" class="LineNr">243 </span>  <span class="Constant">local-scope</span>
-<span id="L244" class="LineNr">244 </span>  list:&amp;:duplex-list:char <span class="Special">&lt;-</span> push<span class="Constant"> 3</span>,<span class="Constant"> 0</span>
-<span id="L245" class="LineNr">245 </span>  list <span class="Special">&lt;-</span> push<span class="Constant"> 4</span>, list
-<span id="L246" class="LineNr">246 </span>  list <span class="Special">&lt;-</span> push<span class="Constant"> 5</span>, list
-<span id="L247" class="LineNr">247 </span>  run [
-<span id="L248" class="LineNr">248 </span>  <span class="Conceal">¦</span> list2:&amp;:duplex-list:char <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> list  <span class="Comment"># second element</span>
-<span id="L249" class="LineNr">249 </span>  <span class="Conceal">¦</span> list <span class="Special">&lt;-</span> remove list2, list
-<span id="L250" class="LineNr">250 </span>  <span class="Conceal">¦</span> 10:bool/<span class="Special">raw</span> <span class="Special">&lt;-</span> equal list2,<span class="Constant"> 0</span>
-<span id="L251" class="LineNr">251 </span>  <span class="Conceal">¦</span> <span class="Comment"># check structure like before</span>
-<span id="L252" class="LineNr">252 </span>  <span class="Conceal">¦</span> list2 <span class="Special">&lt;-</span> copy list
-<span id="L253" class="LineNr">253 </span>  <span class="Conceal">¦</span> 11:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> first list2
-<span id="L254" class="LineNr">254 </span>  <span class="Conceal">¦</span> list2 <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> list2
-<span id="L255" class="LineNr">255 </span>  <span class="Conceal">¦</span> 12:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> first list2
-<span id="L256" class="LineNr">256 </span>  <span class="Conceal">¦</span> 20:&amp;:duplex-list:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> list2
-<span id="L257" class="LineNr">257 </span>  <span class="Conceal">¦</span> list2 <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L36'>prev</a> list2
-<span id="L258" class="LineNr">258 </span>  <span class="Conceal">¦</span> 30:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> first list2
-<span id="L259" class="LineNr">259 </span>  <span class="Conceal">¦</span> 40:bool/<span class="Special">raw</span> <span class="Special">&lt;-</span> equal list, list2
-<span id="L260" class="LineNr">260 </span>  ]
-<span id="L261" class="LineNr">261 </span>  memory-should-contain [
-<span id="L262" class="LineNr">262 </span>  <span class="Conceal">¦</span><span class="Constant"> 10</span> <span class="Special">&lt;-</span><span class="Constant"> 0</span>  <span class="Comment"># remove returned non-null</span>
-<span id="L263" class="LineNr">263 </span>  <span class="Conceal">¦</span><span class="Constant"> 11</span> <span class="Special">&lt;-</span><span class="Constant"> 5</span>  <span class="Comment"># scanning next, skipping deleted element</span>
-<span id="L264" class="LineNr">264 </span>  <span class="Conceal">¦</span><span class="Constant"> 12</span> <span class="Special">&lt;-</span><span class="Constant"> 3</span>
-<span id="L265" class="LineNr">265 </span>  <span class="Conceal">¦</span><span class="Constant"> 20</span> <span class="Special">&lt;-</span><span class="Constant"> 0</span>  <span class="Comment"># no more elements</span>
-<span id="L266" class="LineNr">266 </span>  <span class="Conceal">¦</span><span class="Constant"> 30</span> <span class="Special">&lt;-</span><span class="Constant"> 5</span>  <span class="Comment"># prev of final element</span>
-<span id="L267" class="LineNr">267 </span>  <span class="Conceal">¦</span><span class="Constant"> 40</span> <span class="Special">&lt;-</span><span class="Constant"> 1</span>  <span class="Comment"># list back at start</span>
-<span id="L268" class="LineNr">268 </span>  ]
-<span id="L269" class="LineNr">269 </span>]
-<span id="L270" class="LineNr">270 </span>
-<span id="L271" class="LineNr">271 </span><span class="muScenario">scenario</span> removing-from-start-of-duplex-list [
-<span id="L272" class="LineNr">272 </span>  <span class="Constant">local-scope</span>
-<span id="L273" class="LineNr">273 </span>  list:&amp;:duplex-list:char <span class="Special">&lt;-</span> push<span class="Constant"> 3</span>,<span class="Constant"> 0</span>
-<span id="L274" class="LineNr">274 </span>  list <span class="Special">&lt;-</span> push<span class="Constant"> 4</span>, list
-<span id="L275" class="LineNr">275 </span>  list <span class="Special">&lt;-</span> push<span class="Constant"> 5</span>, list
-<span id="L276" class="LineNr">276 </span>  run [
-<span id="L277" class="LineNr">277 </span>  <span class="Conceal">¦</span> list <span class="Special">&lt;-</span> remove list, list
-<span id="L278" class="LineNr">278 </span>  <span class="Conceal">¦</span> <span class="Comment"># check structure like before</span>
-<span id="L279" class="LineNr">279 </span>  <span class="Conceal">¦</span> list2:&amp;:duplex-list:char <span class="Special">&lt;-</span> copy list
-<span id="L280" class="LineNr">280 </span>  <span class="Conceal">¦</span> 10:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> first list2
-<span id="L281" class="LineNr">281 </span>  <span class="Conceal">¦</span> list2 <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> list2
-<span id="L282" class="LineNr">282 </span>  <span class="Conceal">¦</span> 11:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> first list2
-<span id="L283" class="LineNr">283 </span>  <span class="Conceal">¦</span> 20:&amp;:duplex-list:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> list2
-<span id="L284" class="LineNr">284 </span>  <span class="Conceal">¦</span> list2 <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L36'>prev</a> list2
-<span id="L285" class="LineNr">285 </span>  <span class="Conceal">¦</span> 30:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> first list2
-<span id="L286" class="LineNr">286 </span>  <span class="Conceal">¦</span> 40:bool/<span class="Special">raw</span> <span class="Special">&lt;-</span> equal list, list2
-<span id="L287" class="LineNr">287 </span>  ]
-<span id="L288" class="LineNr">288 </span>  memory-should-contain [
-<span id="L289" class="LineNr">289 </span>  <span class="Conceal">¦</span><span class="Constant"> 10</span> <span class="Special">&lt;-</span><span class="Constant"> 4</span>  <span class="Comment"># scanning next, skipping deleted element</span>
-<span id="L290" class="LineNr">290 </span>  <span class="Conceal">¦</span><span class="Constant"> 11</span> <span class="Special">&lt;-</span><span class="Constant"> 3</span>
-<span id="L291" class="LineNr">291 </span>  <span class="Conceal">¦</span><span class="Constant"> 20</span> <span class="Special">&lt;-</span><span class="Constant"> 0</span>  <span class="Comment"># no more elements</span>
-<span id="L292" class="LineNr">292 </span>  <span class="Conceal">¦</span><span class="Constant"> 30</span> <span class="Special">&lt;-</span><span class="Constant"> 4</span>  <span class="Comment"># prev of final element</span>
-<span id="L293" class="LineNr">293 </span>  <span class="Conceal">¦</span><span class="Constant"> 40</span> <span class="Special">&lt;-</span><span class="Constant"> 1</span>  <span class="Comment"># list back at start</span>
-<span id="L294" class="LineNr">294 </span>  ]
-<span id="L295" class="LineNr">295 </span>]
-<span id="L296" class="LineNr">296 </span>
-<span id="L297" class="LineNr">297 </span><span class="muScenario">scenario</span> removing-from-end-of-duplex-list [
-<span id="L298" class="LineNr">298 </span>  <span class="Constant">local-scope</span>
-<span id="L299" class="LineNr">299 </span>  list:&amp;:duplex-list:char <span class="Special">&lt;-</span> push<span class="Constant"> 3</span>,<span class="Constant"> 0</span>
-<span id="L300" class="LineNr">300 </span>  list <span class="Special">&lt;-</span> push<span class="Constant"> 4</span>, list
-<span id="L301" class="LineNr">301 </span>  list <span class="Special">&lt;-</span> push<span class="Constant"> 5</span>, list
-<span id="L302" class="LineNr">302 </span>  run [
-<span id="L303" class="LineNr">303 </span>  <span class="Conceal">¦</span> <span class="Comment"># delete last element</span>
-<span id="L304" class="LineNr">304 </span>  <span class="Conceal">¦</span> list2:&amp;:duplex-list:char <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> list
-<span id="L305" class="LineNr">305 </span>  <span class="Conceal">¦</span> list2 <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> list2
-<span id="L306" class="LineNr">306 </span>  <span class="Conceal">¦</span> list <span class="Special">&lt;-</span> remove list2, list
-<span id="L307" class="LineNr">307 </span>  <span class="Conceal">¦</span> 10:bool/<span class="Special">raw</span> <span class="Special">&lt;-</span> equal list2,<span class="Constant"> 0</span>
-<span id="L308" class="LineNr">308 </span>  <span class="Conceal">¦</span> <span class="Comment"># check structure like before</span>
-<span id="L309" class="LineNr">309 </span>  <span class="Conceal">¦</span> list2 <span class="Special">&lt;-</span> copy list
-<span id="L310" class="LineNr">310 </span>  <span class="Conceal">¦</span> 11:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> first list2
-<span id="L311" class="LineNr">311 </span>  <span class="Conceal">¦</span> list2 <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> list2
-<span id="L312" class="LineNr">312 </span>  <span class="Conceal">¦</span> 12:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> first list2
-<span id="L313" class="LineNr">313 </span>  <span class="Conceal">¦</span> 20:&amp;:duplex-list:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> list2
-<span id="L314" class="LineNr">314 </span>  <span class="Conceal">¦</span> list2 <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L36'>prev</a> list2
-<span id="L315" class="LineNr">315 </span>  <span class="Conceal">¦</span> 30:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> first list2
-<span id="L316" class="LineNr">316 </span>  <span class="Conceal">¦</span> 40:bool/<span class="Special">raw</span> <span class="Special">&lt;-</span> equal list, list2
-<span id="L317" class="LineNr">317 </span>  ]
-<span id="L318" class="LineNr">318 </span>  memory-should-contain [
-<span id="L319" class="LineNr">319 </span>  <span class="Conceal">¦</span><span class="Constant"> 10</span> <span class="Special">&lt;-</span><span class="Constant"> 0</span>  <span class="Comment"># remove returned non-null</span>
-<span id="L320" class="LineNr">320 </span>  <span class="Conceal">¦</span><span class="Constant"> 11</span> <span class="Special">&lt;-</span><span class="Constant"> 5</span>  <span class="Comment"># scanning next, skipping deleted element</span>
-<span id="L321" class="LineNr">321 </span>  <span class="Conceal">¦</span><span class="Constant"> 12</span> <span class="Special">&lt;-</span><span class="Constant"> 4</span>
-<span id="L322" class="LineNr">322 </span>  <span class="Conceal">¦</span><span class="Constant"> 20</span> <span class="Special">&lt;-</span><span class="Constant"> 0</span>  <span class="Comment"># no more elements</span>
-<span id="L323" class="LineNr">323 </span>  <span class="Conceal">¦</span><span class="Constant"> 30</span> <span class="Special">&lt;-</span><span class="Constant"> 5</span>  <span class="Comment"># prev of final element</span>
-<span id="L324" class="LineNr">324 </span>  <span class="Conceal">¦</span><span class="Constant"> 40</span> <span class="Special">&lt;-</span><span class="Constant"> 1</span>  <span class="Comment"># list back at start</span>
-<span id="L325" class="LineNr">325 </span>  ]
-<span id="L326" class="LineNr">326 </span>]
-<span id="L327" class="LineNr">327 </span>
-<span id="L328" class="LineNr">328 </span><span class="muScenario">scenario</span> removing-from-singleton-duplex-list [
-<span id="L329" class="LineNr">329 </span>  <span class="Constant">local-scope</span>
-<span id="L330" class="LineNr">330 </span>  list:&amp;:duplex-list:char <span class="Special">&lt;-</span> push<span class="Constant"> 3</span>,<span class="Constant"> 0</span>
-<span id="L331" class="LineNr">331 </span>  run [
-<span id="L332" class="LineNr">332 </span>  <span class="Conceal">¦</span> list <span class="Special">&lt;-</span> remove list, list
-<span id="L333" class="LineNr">333 </span>  <span class="Conceal">¦</span> 1:num/<span class="Special">raw</span> <span class="Special">&lt;-</span> copy list
-<span id="L334" class="LineNr">334 </span>  ]
-<span id="L335" class="LineNr">335 </span>  memory-should-contain [
-<span id="L336" class="LineNr">336 </span>  <span class="Conceal">¦</span><span class="Constant"> 1</span> <span class="Special">&lt;-</span><span class="Constant"> 0</span>  <span class="Comment"># back to an empty list</span>
+<span id="L86" class="LineNr"> 86 </span><span class="muRecipe">def</span> length l:&amp;:duplex-list:_elem<span class="muRecipe"> -&gt; </span>result:num [
+<span id="L87" class="LineNr"> 87 </span>  <span class="Constant">local-scope</span>
+<span id="L88" class="LineNr"> 88 </span>  <span class="Constant">load-ingredients</span>
+<span id="L89" class="LineNr"> 89 </span>  result <span class="Special">&lt;-</span> copy<span class="Constant"> 0</span>
+<span id="L90" class="LineNr"> 90 </span>  <span class="Delimiter">{</span>
+<span id="L91" class="LineNr"> 91 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> l
+<span id="L92" class="LineNr"> 92 </span>  <span class="Conceal">¦</span> result <span class="Special">&lt;-</span> add result,<span class="Constant"> 1</span>
+<span id="L93" class="LineNr"> 93 </span>  <span class="Conceal">¦</span> l <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> l
+<span id="L94" class="LineNr"> 94 </span>  <span class="Conceal">¦</span> <span class="muControl">loop</span>
+<span id="L95" class="LineNr"> 95 </span>  <span class="Delimiter">}</span>
+<span id="L96" class="LineNr"> 96 </span>]
+<span id="L97" class="LineNr"> 97 </span>
+<span id="L98" class="LineNr"> 98 </span><span class="Comment"># insert 'x' after 'in'</span>
+<span id="L99" class="LineNr"> 99 </span><span class="muRecipe">def</span> insert x:_elem, in:&amp;:duplex-list:_elem<span class="muRecipe"> -&gt; </span>in:&amp;:duplex-list:_elem [
+<span id="L100" class="LineNr">100 </span>  <span class="Constant">local-scope</span>
+<span id="L101" class="LineNr">101 </span>  <span class="Constant">load-ingredients</span>
+<span id="L102" class="LineNr">102 </span>  new-node:&amp;:duplex-list:_elem <span class="Special">&lt;-</span> new <span class="Delimiter">{</span>(duplex-list _elem): type<span class="Delimiter">}</span>
+<span id="L103" class="LineNr">103 </span>  *new-node <span class="Special">&lt;-</span> put *new-node, <span class="Constant">value:offset</span>, x
+<span id="L104" class="LineNr">104 </span>  <span class="Comment"># save old next before changing it</span>
+<span id="L105" class="LineNr">105 </span>  next-node:&amp;:duplex-list:_elem <span class="Special">&lt;-</span> get *in, <span class="Constant"><a href='065duplex_list.mu.html#L29'>next</a>:offset</span>
+<span id="L106" class="LineNr">106 </span>  *in <span class="Special">&lt;-</span> put *in, <span class="Constant"><a href='065duplex_list.mu.html#L29'>next</a>:offset</span>, new-node
+<span id="L107" class="LineNr">107 </span>  *new-node <span class="Special">&lt;-</span> put *new-node, <span class="Constant"><a href='065duplex_list.mu.html#L36'>prev</a>:offset</span>, in
+<span id="L108" class="LineNr">108 </span>  *new-node <span class="Special">&lt;-</span> put *new-node, <span class="Constant"><a href='065duplex_list.mu.html#L29'>next</a>:offset</span>, next-node
+<span id="L109" class="LineNr">109 </span>  <span class="muControl">return-unless</span> next-node
+<span id="L110" class="LineNr">110 </span>  *next-node <span class="Special">&lt;-</span> put *next-node, <span class="Constant"><a href='065duplex_list.mu.html#L36'>prev</a>:offset</span>, new-node
+<span id="L111" class="LineNr">111 </span>]
+<span id="L112" class="LineNr">112 </span>
+<span id="L113" class="LineNr">113 </span><span class="muScenario">scenario</span> inserting-into-duplex-list [
+<span id="L114" class="LineNr">114 </span>  <span class="Constant">local-scope</span>
+<span id="L115" class="LineNr">115 </span>  list:&amp;:duplex-list:char <span class="Special">&lt;-</span> push<span class="Constant"> 3</span>,<span class="Constant"> 0</span>
+<span id="L116" class="LineNr">116 </span>  list <span class="Special">&lt;-</span> push<span class="Constant"> 4</span>, list
+<span id="L117" class="LineNr">117 </span>  list <span class="Special">&lt;-</span> push<span class="Constant"> 5</span>, list
+<span id="L118" class="LineNr">118 </span>  run [
+<span id="L119" class="LineNr">119 </span>  <span class="Conceal">¦</span> list2:&amp;:duplex-list:char <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> list  <span class="Comment"># inside list</span>
+<span id="L120" class="LineNr">120 </span>  <span class="Conceal">¦</span> list2 <span class="Special">&lt;-</span> insert<span class="Constant"> 6</span>, list2
+<span id="L121" class="LineNr">121 </span>  <span class="Conceal">¦</span> <span class="Comment"># check structure like before</span>
+<span id="L122" class="LineNr">122 </span>  <span class="Conceal">¦</span> list2 <span class="Special">&lt;-</span> copy list
+<span id="L123" class="LineNr">123 </span>  <span class="Conceal">¦</span> 10:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> first list2
+<span id="L124" class="LineNr">124 </span>  <span class="Conceal">¦</span> list2 <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> list2
+<span id="L125" class="LineNr">125 </span>  <span class="Conceal">¦</span> 11:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> first list2
+<span id="L126" class="LineNr">126 </span>  <span class="Conceal">¦</span> list2 <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> list2
+<span id="L127" class="LineNr">127 </span>  <span class="Conceal">¦</span> 12:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> first list2
+<span id="L128" class="LineNr">128 </span>  <span class="Conceal">¦</span> list2 <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> list2
+<span id="L129" class="LineNr">129 </span>  <span class="Conceal">¦</span> 13:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> first list2
+<span id="L130" class="LineNr">130 </span>  <span class="Conceal">¦</span> list2 <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L36'>prev</a> list2
+<span id="L131" class="LineNr">131 </span>  <span class="Conceal">¦</span> 20:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> first list2
+<span id="L132" class="LineNr">132 </span>  <span class="Conceal">¦</span> list2 <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L36'>prev</a> list2
+<span id="L133" class="LineNr">133 </span>  <span class="Conceal">¦</span> 21:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> first list2
+<span id="L134" class="LineNr">134 </span>  <span class="Conceal">¦</span> list2 <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L36'>prev</a> list2
+<span id="L135" class="LineNr">135 </span>  <span class="Conceal">¦</span> 22:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> first list2
+<span id="L136" class="LineNr">136 </span>  <span class="Conceal">¦</span> 30:bool/<span class="Special">raw</span> <span class="Special">&lt;-</span> equal list, list2
+<span id="L137" class="LineNr">137 </span>  ]
+<span id="L138" class="LineNr">138 </span>  memory-should-contain [
+<span id="L139" class="LineNr">139 </span>  <span class="Conceal">¦</span><span class="Constant"> 10</span> <span class="Special">&lt;-</span><span class="Constant"> 5</span>  <span class="Comment"># scanning next</span>
+<span id="L140" class="LineNr">140 </span>  <span class="Conceal">¦</span><span class="Constant"> 11</span> <span class="Special">&lt;-</span><span class="Constant"> 4</span>
+<span id="L141" class="LineNr">141 </span>  <span class="Conceal">¦</span><span class="Constant"> 12</span> <span class="Special">&lt;-</span><span class="Constant"> 6</span>  <span class="Comment"># inserted element</span>
+<span id="L142" class="LineNr">142 </span>  <span class="Conceal">¦</span><span class="Constant"> 13</span> <span class="Special">&lt;-</span><span class="Constant"> 3</span>
+<span id="L143" class="LineNr">143 </span>  <span class="Conceal">¦</span><span class="Constant"> 20</span> <span class="Special">&lt;-</span><span class="Constant"> 6</span>  <span class="Comment"># then prev</span>
+<span id="L144" class="LineNr">144 </span>  <span class="Conceal">¦</span><span class="Constant"> 21</span> <span class="Special">&lt;-</span><span class="Constant"> 4</span>
+<span id="L145" class="LineNr">145 </span>  <span class="Conceal">¦</span><span class="Constant"> 22</span> <span class="Special">&lt;-</span><span class="Constant"> 5</span>
+<span id="L146" class="LineNr">146 </span>  <span class="Conceal">¦</span><span class="Constant"> 30</span> <span class="Special">&lt;-</span><span class="Constant"> 1</span>  <span class="Comment"># list back at start</span>
+<span id="L147" class="LineNr">147 </span>  ]
+<span id="L148" class="LineNr">148 </span>]
+<span id="L149" class="LineNr">149 </span>
+<span id="L150" class="LineNr">150 </span><span class="muScenario">scenario</span> inserting-at-end-of-duplex-list [
+<span id="L151" class="LineNr">151 </span>  <span class="Constant">local-scope</span>
+<span id="L152" class="LineNr">152 </span>  list:&amp;:duplex-list:char <span class="Special">&lt;-</span> push<span class="Constant"> 3</span>,<span class="Constant"> 0</span>
+<span id="L153" class="LineNr">153 </span>  list <span class="Special">&lt;-</span> push<span class="Constant"> 4</span>, list
+<span id="L154" class="LineNr">154 </span>  list <span class="Special">&lt;-</span> push<span class="Constant"> 5</span>, list
+<span id="L155" class="LineNr">155 </span>  run [
+<span id="L156" class="LineNr">156 </span>  <span class="Conceal">¦</span> list2:&amp;:duplex-list:char <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> list  <span class="Comment"># inside list</span>
+<span id="L157" class="LineNr">157 </span>  <span class="Conceal">¦</span> list2 <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> list2  <span class="Comment"># now at end of list</span>
+<span id="L158" class="LineNr">158 </span>  <span class="Conceal">¦</span> list2 <span class="Special">&lt;-</span> insert<span class="Constant"> 6</span>, list2
+<span id="L159" class="LineNr">159 </span>  <span class="Conceal">¦</span> <span class="Comment"># check structure like before</span>
+<span id="L160" class="LineNr">160 </span>  <span class="Conceal">¦</span> list2 <span class="Special">&lt;-</span> copy list
+<span id="L161" class="LineNr">161 </span>  <span class="Conceal">¦</span> 10:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> first list2
+<span id="L162" class="LineNr">162 </span>  <span class="Conceal">¦</span> list2 <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> list2
+<span id="L163" class="LineNr">163 </span>  <span class="Conceal">¦</span> 11:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> first list2
+<span id="L164" class="LineNr">164 </span>  <span class="Conceal">¦</span> list2 <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> list2
+<span id="L165" class="LineNr">165 </span>  <span class="Conceal">¦</span> 12:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> first list2
+<span id="L166" class="LineNr">166 </span>  <span class="Conceal">¦</span> list2 <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> list2
+<span id="L167" class="LineNr">167 </span>  <span class="Conceal">¦</span> 13:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> first list2
+<span id="L168" class="LineNr">168 </span>  <span class="Conceal">¦</span> list2 <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L36'>prev</a> list2
+<span id="L169" class="LineNr">169 </span>  <span class="Conceal">¦</span> 20:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> first list2
+<span id="L170" class="LineNr">170 </span>  <span class="Conceal">¦</span> list2 <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L36'>prev</a> list2
+<span id="L171" class="LineNr">171 </span>  <span class="Conceal">¦</span> 21:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> first list2
+<span id="L172" class="LineNr">172 </span>  <span class="Conceal">¦</span> list2 <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L36'>prev</a> list2
+<span id="L173" class="LineNr">173 </span>  <span class="Conceal">¦</span> 22:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> first list2
+<span id="L174" class="LineNr">174 </span>  <span class="Conceal">¦</span> 30:bool/<span class="Special">raw</span> <span class="Special">&lt;-</span> equal list, list2
+<span id="L175" class="LineNr">175 </span>  ]
+<span id="L176" class="LineNr">176 </span>  memory-should-contain [
+<span id="L177" class="LineNr">177 </span>  <span class="Conceal">¦</span><span class="Constant"> 10</span> <span class="Special">&lt;-</span><span class="Constant"> 5</span>  <span class="Comment"># scanning next</span>
+<span id="L178" class="LineNr">178 </span>  <span class="Conceal">¦</span><span class="Constant"> 11</span> <span class="Special">&lt;-</span><span class="Constant"> 4</span>
+<span id="L179" class="LineNr">179 </span>  <span class="Conceal">¦</span><span class="Constant"> 12</span> <span class="Special">&lt;-</span><span class="Constant"> 3</span>
+<span id="L180" class="LineNr">180 </span>  <span class="Conceal">¦</span><span class="Constant"> 13</span> <span class="Special">&lt;-</span><span class="Constant"> 6</span>  <span class="Comment"># inserted element</span>
+<span id="L181" class="LineNr">181 </span>  <span class="Conceal">¦</span><span class="Constant"> 20</span> <span class="Special">&lt;-</span><span class="Constant"> 3</span>  <span class="Comment"># then prev</span>
+<span id="L182" class="LineNr">182 </span>  <span class="Conceal">¦</span><span class="Constant"> 21</span> <span class="Special">&lt;-</span><span class="Constant"> 4</span>
+<span id="L183" class="LineNr">183 </span>  <span class="Conceal">¦</span><span class="Constant"> 22</span> <span class="Special">&lt;-</span><span class="Constant"> 5</span>
+<span id="L184" class="LineNr">184 </span>  <span class="Conceal">¦</span><span class="Constant"> 30</span> <span class="Special">&lt;-</span><span class="Constant"> 1</span>  <span class="Comment"># list back at start</span>
+<span id="L185" class="LineNr">185 </span>  ]
+<span id="L186" class="LineNr">186 </span>]
+<span id="L187" class="LineNr">187 </span>
+<span id="L188" class="LineNr">188 </span><span class="muScenario">scenario</span> inserting-after-start-of-duplex-list [
+<span id="L189" class="LineNr">189 </span>  <span class="Constant">local-scope</span>
+<span id="L190" class="LineNr">190 </span>  list:&amp;:duplex-list:char <span class="Special">&lt;-</span> push<span class="Constant"> 3</span>,<span class="Constant"> 0</span>
+<span id="L191" class="LineNr">191 </span>  list <span class="Special">&lt;-</span> push<span class="Constant"> 4</span>, list
+<span id="L192" class="LineNr">192 </span>  list <span class="Special">&lt;-</span> push<span class="Constant"> 5</span>, list
+<span id="L193" class="LineNr">193 </span>  run [
+<span id="L194" class="LineNr">194 </span>  <span class="Conceal">¦</span> list <span class="Special">&lt;-</span> insert<span class="Constant"> 6</span>, list
+<span id="L195" class="LineNr">195 </span>  <span class="Conceal">¦</span> <span class="Comment"># check structure like before</span>
+<span id="L196" class="LineNr">196 </span>  <span class="Conceal">¦</span> list2:&amp;:duplex-list:char <span class="Special">&lt;-</span> copy list
+<span id="L197" class="LineNr">197 </span>  <span class="Conceal">¦</span> 10:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> first list2
+<span id="L198" class="LineNr">198 </span>  <span class="Conceal">¦</span> list2 <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> list2
+<span id="L199" class="LineNr">199 </span>  <span class="Conceal">¦</span> 11:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> first list2
+<span id="L200" class="LineNr">200 </span>  <span class="Conceal">¦</span> list2 <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> list2
+<span id="L201" class="LineNr">201 </span>  <span class="Conceal">¦</span> 12:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> first list2
+<span id="L202" class="LineNr">202 </span>  <span class="Conceal">¦</span> list2 <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> list2
+<span id="L203" class="LineNr">203 </span>  <span class="Conceal">¦</span> 13:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> first list2
+<span id="L204" class="LineNr">204 </span>  <span class="Conceal">¦</span> list2 <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L36'>prev</a> list2
+<span id="L205" class="LineNr">205 </span>  <span class="Conceal">¦</span> 20:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> first list2
+<span id="L206" class="LineNr">206 </span>  <span class="Conceal">¦</span> list2 <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L36'>prev</a> list2
+<span id="L207" class="LineNr">207 </span>  <span class="Conceal">¦</span> 21:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> first list2
+<span id="L208" class="LineNr">208 </span>  <span class="Conceal">¦</span> list2 <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L36'>prev</a> list2
+<span id="L209" class="LineNr">209 </span>  <span class="Conceal">¦</span> 22:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> first list2
+<span id="L210" class="LineNr">210 </span>  <span class="Conceal">¦</span> 30:bool/<span class="Special">raw</span> <span class="Special">&lt;-</span> equal list, list2
+<span id="L211" class="LineNr">211 </span>  ]
+<span id="L212" class="LineNr">212 </span>  memory-should-contain [
+<span id="L213" class="LineNr">213 </span>  <span class="Conceal">¦</span><span class="Constant"> 10</span> <span class="Special">&lt;-</span><span class="Constant"> 5</span>  <span class="Comment"># scanning next</span>
+<span id="L214" class="LineNr">214 </span>  <span class="Conceal">¦</span><span class="Constant"> 11</span> <span class="Special">&lt;-</span><span class="Constant"> 6</span>  <span class="Comment"># inserted element</span>
+<span id="L215" class="LineNr">215 </span>  <span class="Conceal">¦</span><span class="Constant"> 12</span> <span class="Special">&lt;-</span><span class="Constant"> 4</span>
+<span id="L216" class="LineNr">216 </span>  <span class="Conceal">¦</span><span class="Constant"> 13</span> <span class="Special">&lt;-</span><span class="Constant"> 3</span>
+<span id="L217" class="LineNr">217 </span>  <span class="Conceal">¦</span><span class="Constant"> 20</span> <span class="Special">&lt;-</span><span class="Constant"> 4</span>  <span class="Comment"># then prev</span>
+<span id="L218" class="LineNr">218 </span>  <span class="Conceal">¦</span><span class="Constant"> 21</span> <span class="Special">&lt;-</span><span class="Constant"> 6</span>
+<span id="L219" class="LineNr">219 </span>  <span class="Conceal">¦</span><span class="Constant"> 22</span> <span class="Special">&lt;-</span><span class="Constant"> 5</span>
+<span id="L220" class="LineNr">220 </span>  <span class="Conceal">¦</span><span class="Constant"> 30</span> <span class="Special">&lt;-</span><span class="Constant"> 1</span>  <span class="Comment"># list back at start</span>
+<span id="L221" class="LineNr">221 </span>  ]
+<span id="L222" class="LineNr">222 </span>]
+<span id="L223" class="LineNr">223 </span>
+<span id="L224" class="LineNr">224 </span><span class="Comment"># remove 'x' from its surrounding list 'in'</span>
+<span id="L225" class="LineNr">225 </span><span class="Comment">#</span>
+<span id="L226" class="LineNr">226 </span><span class="Comment"># Returns null if and only if list is empty. Beware: in that case any other</span>
+<span id="L227" class="LineNr">227 </span><span class="Comment"># pointers to the head are now invalid.</span>
+<span id="L228" class="LineNr">228 </span><span class="muRecipe">def</span> remove x:&amp;:duplex-list:_elem/contained-in:in, in:&amp;:duplex-list:_elem<span class="muRecipe"> -&gt; </span>in:&amp;:duplex-list:_elem [
+<span id="L229" class="LineNr">229 </span>  <span class="Constant">local-scope</span>
+<span id="L230" class="LineNr">230 </span>  <span class="Constant">load-ingredients</span>
+<span id="L231" class="LineNr">231 </span>  <span class="Comment"># if 'x' is null, return</span>
+<span id="L232" class="LineNr">232 </span>  <span class="muControl">return-unless</span> x
+<span id="L233" class="LineNr">233 </span>  next-node:&amp;:duplex-list:_elem <span class="Special">&lt;-</span> get *x, <span class="Constant"><a href='065duplex_list.mu.html#L29'>next</a>:offset</span>
+<span id="L234" class="LineNr">234 </span>  prev-node:&amp;:duplex-list:_elem <span class="Special">&lt;-</span> get *x, <span class="Constant"><a href='065duplex_list.mu.html#L36'>prev</a>:offset</span>
+<span id="L235" class="LineNr">235 </span>  <span class="Comment"># null x's pointers</span>
+<span id="L236" class="LineNr">236 </span>  *x <span class="Special">&lt;-</span> put *x, <span class="Constant"><a href='065duplex_list.mu.html#L29'>next</a>:offset</span>,<span class="Constant"> 0</span>
+<span id="L237" class="LineNr">237 </span>  *x <span class="Special">&lt;-</span> put *x, <span class="Constant"><a href='065duplex_list.mu.html#L36'>prev</a>:offset</span>,<span class="Constant"> 0</span>
+<span id="L238" class="LineNr">238 </span>  <span class="Comment"># if next-node is not null, set its prev pointer</span>
+<span id="L239" class="LineNr">239 </span>  <span class="Delimiter">{</span>
+<span id="L240" class="LineNr">240 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> next-node
+<span id="L241" class="LineNr">241 </span>  <span class="Conceal">¦</span> *next-node <span class="Special">&lt;-</span> put *next-node, <span class="Constant"><a href='065duplex_list.mu.html#L36'>prev</a>:offset</span>, prev-node
+<span id="L242" class="LineNr">242 </span>  <span class="Delimiter">}</span>
+<span id="L243" class="LineNr">243 </span>  <span class="Comment"># if prev-node is not null, set its next pointer and return</span>
+<span id="L244" class="LineNr">244 </span>  <span class="Delimiter">{</span>
+<span id="L245" class="LineNr">245 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> prev-node
+<span id="L246" class="LineNr">246 </span>  <span class="Conceal">¦</span> *prev-node <span class="Special">&lt;-</span> put *prev-node, <span class="Constant"><a href='065duplex_list.mu.html#L29'>next</a>:offset</span>, next-node
+<span id="L247" class="LineNr">247 </span>  <span class="Conceal">¦</span> <span class="muControl">return</span>
+<span id="L248" class="LineNr">248 </span>  <span class="Delimiter">}</span>
+<span id="L249" class="LineNr">249 </span>  <span class="Comment"># if prev-node is null, then we removed the head node at 'in'</span>
+<span id="L250" class="LineNr">250 </span>  <span class="Comment"># return the new head rather than the old 'in'</span>
+<span id="L251" class="LineNr">251 </span>  <span class="muControl">return</span> next-node
+<span id="L252" class="LineNr">252 </span>]
+<span id="L253" class="LineNr">253 </span>
+<span id="L254" class="LineNr">254 </span><span class="muScenario">scenario</span> removing-from-duplex-list [
+<span id="L255" class="LineNr">255 </span>  <span class="Constant">local-scope</span>
+<span id="L256" class="LineNr">256 </span>  list:&amp;:duplex-list:char <span class="Special">&lt;-</span> push<span class="Constant"> 3</span>,<span class="Constant"> 0</span>
+<span id="L257" class="LineNr">257 </span>  list <span class="Special">&lt;-</span> push<span class="Constant"> 4</span>, list
+<span id="L258" class="LineNr">258 </span>  list <span class="Special">&lt;-</span> push<span class="Constant"> 5</span>, list
+<span id="L259" class="LineNr">259 </span>  run [
+<span id="L260" class="LineNr">260 </span>  <span class="Conceal">¦</span> list2:&amp;:duplex-list:char <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> list  <span class="Comment"># second element</span>
+<span id="L261" class="LineNr">261 </span>  <span class="Conceal">¦</span> list <span class="Special">&lt;-</span> remove list2, list
+<span id="L262" class="LineNr">262 </span>  <span class="Conceal">¦</span> 10:bool/<span class="Special">raw</span> <span class="Special">&lt;-</span> equal list2,<span class="Constant"> 0</span>
+<span id="L263" class="LineNr">263 </span>  <span class="Conceal">¦</span> <span class="Comment"># check structure like before</span>
+<span id="L264" class="LineNr">264 </span>  <span class="Conceal">¦</span> list2 <span class="Special">&lt;-</span> copy list
+<span id="L265" class="LineNr">265 </span>  <span class="Conceal">¦</span> 11:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> first list2
+<span id="L266" class="LineNr">266 </span>  <span class="Conceal">¦</span> list2 <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> list2
+<span id="L267" class="LineNr">267 </span>  <span class="Conceal">¦</span> 12:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> first list2
+<span id="L268" class="LineNr">268 </span>  <span class="Conceal">¦</span> 20:&amp;:duplex-list:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> list2
+<span id="L269" class="LineNr">269 </span>  <span class="Conceal">¦</span> list2 <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L36'>prev</a> list2
+<span id="L270" class="LineNr">270 </span>  <span class="Conceal">¦</span> 30:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> first list2
+<span id="L271" class="LineNr">271 </span>  <span class="Conceal">¦</span> 40:bool/<span class="Special">raw</span> <span class="Special">&lt;-</span> equal list, list2
+<span id="L272" class="LineNr">272 </span>  ]
+<span id="L273" class="LineNr">273 </span>  memory-should-contain [
+<span id="L274" class="LineNr">274 </span>  <span class="Conceal">¦</span><span class="Constant"> 10</span> <span class="Special">&lt;-</span><span class="Constant"> 0</span>  <span class="Comment"># remove returned non-null</span>
+<span id="L275" class="LineNr">275 </span>  <span class="Conceal">¦</span><span class="Constant"> 11</span> <span class="Special">&lt;-</span><span class="Constant"> 5</span>  <span class="Comment"># scanning next, skipping deleted element</span>
+<span id="L276" class="LineNr">276 </span>  <span class="Conceal">¦</span><span class="Constant"> 12</span> <span class="Special">&lt;-</span><span class="Constant"> 3</span>
+<span id="L277" class="LineNr">277 </span>  <span class="Conceal">¦</span><span class="Constant"> 20</span> <span class="Special">&lt;-</span><span class="Constant"> 0</span>  <span class="Comment"># no more elements</span>
+<span id="L278" class="LineNr">278 </span>  <span class="Conceal">¦</span><span class="Constant"> 30</span> <span class="Special">&lt;-</span><span class="Constant"> 5</span>  <span class="Comment"># prev of final element</span>
+<span id="L279" class="LineNr">279 </span>  <span class="Conceal">¦</span><span class="Constant"> 40</span> <span class="Special">&lt;-</span><span class="Constant"> 1</span>  <span class="Comment"># list back at start</span>
+<span id="L280" class="LineNr">280 </span>  ]
+<span id="L281" class="LineNr">281 </span>]
+<span id="L282" class="LineNr">282 </span>
+<span id="L283" class="LineNr">283 </span><span class="muScenario">scenario</span> removing-from-start-of-duplex-list [
+<span id="L284" class="LineNr">284 </span>  <span class="Constant">local-scope</span>
+<span id="L285" class="LineNr">285 </span>  list:&amp;:duplex-list:char <span class="Special">&lt;-</span> push<span class="Constant"> 3</span>,<span class="Constant"> 0</span>
+<span id="L286" class="LineNr">286 </span>  list <span class="Special">&lt;-</span> push<span class="Constant"> 4</span>, list
+<span id="L287" class="LineNr">287 </span>  list <span class="Special">&lt;-</span> push<span class="Constant"> 5</span>, list
+<span id="L288" class="LineNr">288 </span>  run [
+<span id="L289" class="LineNr">289 </span>  <span class="Conceal">¦</span> list <span class="Special">&lt;-</span> remove list, list
+<span id="L290" class="LineNr">290 </span>  <span class="Conceal">¦</span> <span class="Comment"># check structure like before</span>
+<span id="L291" class="LineNr">291 </span>  <span class="Conceal">¦</span> list2:&amp;:duplex-list:char <span class="Special">&lt;-</span> copy list
+<span id="L292" class="LineNr">292 </span>  <span class="Conceal">¦</span> 10:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> first list2
+<span id="L293" class="LineNr">293 </span>  <span class="Conceal">¦</span> list2 <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> list2
+<span id="L294" class="LineNr">294 </span>  <span class="Conceal">¦</span> 11:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> first list2
+<span id="L295" class="LineNr">295 </span>  <span class="Conceal">¦</span> 20:&amp;:duplex-list:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> list2
+<span id="L296" class="LineNr">296 </span>  <span class="Conceal">¦</span> list2 <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L36'>prev</a> list2
+<span id="L297" class="LineNr">297 </span>  <span class="Conceal">¦</span> 30:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> first list2
+<span id="L298" class="LineNr">298 </span>  <span class="Conceal">¦</span> 40:bool/<span class="Special">raw</span> <span class="Special">&lt;-</span> equal list, list2
+<span id="L299" class="LineNr">299 </span>  ]
+<span id="L300" class="LineNr">300 </span>  memory-should-contain [
+<span id="L301" class="LineNr">301 </span>  <span class="Conceal">¦</span><span class="Constant"> 10</span> <span class="Special">&lt;-</span><span class="Constant"> 4</span>  <span class="Comment"># scanning next, skipping deleted element</span>
+<span id="L302" class="LineNr">302 </span>  <span class="Conceal">¦</span><span class="Constant"> 11</span> <span class="Special">&lt;-</span><span class="Constant"> 3</span>
+<span id="L303" class="LineNr">303 </span>  <span class="Conceal">¦</span><span class="Constant"> 20</span> <span class="Special">&lt;-</span><span class="Constant"> 0</span>  <span class="Comment"># no more elements</span>
+<span id="L304" class="LineNr">304 </span>  <span class="Conceal">¦</span><span class="Constant"> 30</span> <span class="Special">&lt;-</span><span class="Constant"> 4</span>  <span class="Comment"># prev of final element</span>
+<span id="L305" class="LineNr">305 </span>  <span class="Conceal">¦</span><span class="Constant"> 40</span> <span class="Special">&lt;-</span><span class="Constant"> 1</span>  <span class="Comment"># list back at start</span>
+<span id="L306" class="LineNr">306 </span>  ]
+<span id="L307" class="LineNr">307 </span>]
+<span id="L308" class="LineNr">308 </span>
+<span id="L309" class="LineNr">309 </span><span class="muScenario">scenario</span> removing-from-end-of-duplex-list [
+<span id="L310" class="LineNr">310 </span>  <span class="Constant">local-scope</span>
+<span id="L311" class="LineNr">311 </span>  list:&amp;:duplex-list:char <span class="Special">&lt;-</span> push<span class="Constant"> 3</span>,<span class="Constant"> 0</span>
+<span id="L312" class="LineNr">312 </span>  list <span class="Special">&lt;-</span> push<span class="Constant"> 4</span>, list
+<span id="L313" class="LineNr">313 </span>  list <span class="Special">&lt;-</span> push<span class="Constant"> 5</span>, list
+<span id="L314" class="LineNr">314 </span>  run [
+<span id="L315" class="LineNr">315 </span>  <span class="Conceal">¦</span> <span class="Comment"># delete last element</span>
+<span id="L316" class="LineNr">316 </span>  <span class="Conceal">¦</span> list2:&amp;:duplex-list:char <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> list
+<span id="L317" class="LineNr">317 </span>  <span class="Conceal">¦</span> list2 <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> list2
+<span id="L318" class="LineNr">318 </span>  <span class="Conceal">¦</span> list <span class="Special">&lt;-</span> remove list2, list
+<span id="L319" class="LineNr">319 </span>  <span class="Conceal">¦</span> 10:bool/<span class="Special">raw</span> <span class="Special">&lt;-</span> equal list2,<span class="Constant"> 0</span>
+<span id="L320" class="LineNr">320 </span>  <span class="Conceal">¦</span> <span class="Comment"># check structure like before</span>
+<span id="L321" class="LineNr">321 </span>  <span class="Conceal">¦</span> list2 <span class="Special">&lt;-</span> copy list
+<span id="L322" class="LineNr">322 </span>  <span class="Conceal">¦</span> 11:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> first list2
+<span id="L323" class="LineNr">323 </span>  <span class="Conceal">¦</span> list2 <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> list2
+<span id="L324" class="LineNr">324 </span>  <span class="Conceal">¦</span> 12:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> first list2
+<span id="L325" class="LineNr">325 </span>  <span class="Conceal">¦</span> 20:&amp;:duplex-list:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> list2
+<span id="L326" class="LineNr">326 </span>  <span class="Conceal">¦</span> list2 <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L36'>prev</a> list2
+<span id="L327" class="LineNr">327 </span>  <span class="Conceal">¦</span> 30:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> first list2
+<span id="L328" class="LineNr">328 </span>  <span class="Conceal">¦</span> 40:bool/<span class="Special">raw</span> <span class="Special">&lt;-</span> equal list, list2
+<span id="L329" class="LineNr">329 </span>  ]
+<span id="L330" class="LineNr">330 </span>  memory-should-contain [
+<span id="L331" class="LineNr">331 </span>  <span class="Conceal">¦</span><span class="Constant"> 10</span> <span class="Special">&lt;-</span><span class="Constant"> 0</span>  <span class="Comment"># remove returned non-null</span>
+<span id="L332" class="LineNr">332 </span>  <span class="Conceal">¦</span><span class="Constant"> 11</span> <span class="Special">&lt;-</span><span class="Constant"> 5</span>  <span class="Comment"># scanning next, skipping deleted element</span>
+<span id="L333" class="LineNr">333 </span>  <span class="Conceal">¦</span><span class="Constant"> 12</span> <span class="Special">&lt;-</span><span class="Constant"> 4</span>
+<span id="L334" class="LineNr">334 </span>  <span class="Conceal">¦</span><span class="Constant"> 20</span> <span class="Special">&lt;-</span><span class="Constant"> 0</span>  <span class="Comment"># no more elements</span>
+<span id="L335" class="LineNr">335 </span>  <span class="Conceal">¦</span><span class="Constant"> 30</span> <span class="Special">&lt;-</span><span class="Constant"> 5</span>  <span class="Comment"># prev of final element</span>
+<span id="L336" class="LineNr">336 </span>  <span class="Conceal">¦</span><span class="Constant"> 40</span> <span class="Special">&lt;-</span><span class="Constant"> 1</span>  <span class="Comment"># list back at start</span>
 <span id="L337" class="LineNr">337 </span>  ]
 <span id="L338" class="LineNr">338 </span>]
 <span id="L339" class="LineNr">339 </span>
-<span id="L340" class="LineNr">340 </span><span class="Comment"># remove values between 'start' and 'end' (both exclusive).</span>
-<span id="L341" class="LineNr">341 </span><span class="Comment"># also clear pointers back out from start/end for hygiene.</span>
-<span id="L342" class="LineNr">342 </span><span class="Comment"># set end to 0 to delete everything past start.</span>
-<span id="L343" class="LineNr">343 </span><span class="Comment"># can't set start to 0 to delete everything before end, because there's no</span>
-<span id="L344" class="LineNr">344 </span><span class="Comment"># clean way to return the new head pointer.</span>
-<span id="L345" class="LineNr">345 </span><span class="muRecipe">def</span> <a href='065duplex_list.mu.html#L345'>remove-between</a> start:&amp;:duplex-list:_elem, end:&amp;:duplex-list:_elem/contained-in:start<span class="muRecipe"> -&gt; </span>start:&amp;:duplex-list:_elem [
-<span id="L346" class="LineNr">346 </span>  <span class="Constant">local-scope</span>
-<span id="L347" class="LineNr">347 </span>  <span class="Constant">load-ingredients</span>
-<span id="L348" class="LineNr">348 </span>  <a href='065duplex_list.mu.html#L29'>next</a>:&amp;:duplex-list:_elem <span class="Special">&lt;-</span> get *start, <span class="Constant"><a href='065duplex_list.mu.html#L29'>next</a>:offset</span>
-<span id="L349" class="LineNr">349 </span>  nothing-to-delete?:bool <span class="Special">&lt;-</span> equal <a href='065duplex_list.mu.html#L29'>next</a>, end
-<span id="L350" class="LineNr">350 </span>  <span class="muControl">return-if</span> nothing-to-delete?
-<span id="L351" class="LineNr">351 </span>  assert <a href='065duplex_list.mu.html#L29'>next</a>, <span class="Constant">[malformed duplex list]</span>
-<span id="L352" class="LineNr">352 </span>  <span class="Comment"># start-&gt;next-&gt;prev = 0</span>
-<span id="L353" class="LineNr">353 </span>  <span class="Comment"># start-&gt;next = end</span>
-<span id="L354" class="LineNr">354 </span>  *next <span class="Special">&lt;-</span> put *next, <span class="Constant"><a href='065duplex_list.mu.html#L36'>prev</a>:offset</span>,<span class="Constant"> 0</span>
-<span id="L355" class="LineNr">355 </span>  *start <span class="Special">&lt;-</span> put *start, <span class="Constant"><a href='065duplex_list.mu.html#L29'>next</a>:offset</span>, end
-<span id="L356" class="LineNr">356 </span>  <span class="muControl">return-unless</span> end
-<span id="L357" class="LineNr">357 </span>  <span class="Comment"># end-&gt;prev-&gt;next = 0</span>
-<span id="L358" class="LineNr">358 </span>  <span class="Comment"># end-&gt;prev = start</span>
-<span id="L359" class="LineNr">359 </span>  <a href='065duplex_list.mu.html#L36'>prev</a>:&amp;:duplex-list:_elem <span class="Special">&lt;-</span> get *end, <span class="Constant"><a href='065duplex_list.mu.html#L36'>prev</a>:offset</span>
-<span id="L360" class="LineNr">360 </span>  assert <a href='065duplex_list.mu.html#L36'>prev</a>, <span class="Constant">[malformed duplex list - 2]</span>
-<span id="L361" class="LineNr">361 </span>  *prev <span class="Special">&lt;-</span> put *prev, <span class="Constant"><a href='065duplex_list.mu.html#L29'>next</a>:offset</span>,<span class="Constant"> 0</span>
-<span id="L362" class="LineNr">362 </span>  *end <span class="Special">&lt;-</span> put *end, <span class="Constant"><a href='065duplex_list.mu.html#L36'>prev</a>:offset</span>, start
-<span id="L363" class="LineNr">363 </span>]
-<span id="L364" class="LineNr">364 </span>
-<span id="L365" class="LineNr">365 </span><span class="muScenario">scenario</span> remove-range [
-<span id="L366" class="LineNr">366 </span>  <span class="Comment"># construct a duplex list with six elements [13, 14, 15, 16, 17, 18]</span>
-<span id="L367" class="LineNr">367 </span>  <span class="Constant">local-scope</span>
-<span id="L368" class="LineNr">368 </span>  list:&amp;:duplex-list:char <span class="Special">&lt;-</span> push<span class="Constant"> 18</span>,<span class="Constant"> 0</span>
-<span id="L369" class="LineNr">369 </span>  list <span class="Special">&lt;-</span> push<span class="Constant"> 17</span>, list
-<span id="L370" class="LineNr">370 </span>  list <span class="Special">&lt;-</span> push<span class="Constant"> 16</span>, list
-<span id="L371" class="LineNr">371 </span>  list <span class="Special">&lt;-</span> push<span class="Constant"> 15</span>, list
-<span id="L372" class="LineNr">372 </span>  list <span class="Special">&lt;-</span> push<span class="Constant"> 14</span>, list
-<span id="L373" class="LineNr">373 </span>  list <span class="Special">&lt;-</span> push<span class="Constant"> 13</span>, list
-<span id="L374" class="LineNr">374 </span>  run [
-<span id="L375" class="LineNr">375 </span>  <span class="Conceal">¦</span> <span class="Comment"># delete 16 onwards</span>
-<span id="L376" class="LineNr">376 </span>  <span class="Conceal">¦</span> <span class="Comment"># first pointer: to the third element</span>
-<span id="L377" class="LineNr">377 </span>  <span class="Conceal">¦</span> list2:&amp;:duplex-list:char <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> list
-<span id="L378" class="LineNr">378 </span>  <span class="Conceal">¦</span> list2 <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> list2
-<span id="L379" class="LineNr">379 </span>  <span class="Conceal">¦</span> list2 <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L345'>remove-between</a> list2,<span class="Constant"> 0</span>
-<span id="L380" class="LineNr">380 </span>  <span class="Conceal">¦</span> <span class="Comment"># now check the list</span>
-<span id="L381" class="LineNr">381 </span>  <span class="Conceal">¦</span> 10:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> get *list, <span class="Constant">value:offset</span>
-<span id="L382" class="LineNr">382 </span>  <span class="Conceal">¦</span> list <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> list
-<span id="L383" class="LineNr">383 </span>  <span class="Conceal">¦</span> 11:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> get *list, <span class="Constant">value:offset</span>
-<span id="L384" class="LineNr">384 </span>  <span class="Conceal">¦</span> list <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> list
-<span id="L385" class="LineNr">385 </span>  <span class="Conceal">¦</span> 12:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> get *list, <span class="Constant">value:offset</span>
-<span id="L386" class="LineNr">386 </span>  <span class="Conceal">¦</span> 20:&amp;:duplex-list:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> list
-<span id="L387" class="LineNr">387 </span>  ]
-<span id="L388" class="LineNr">388 </span>  memory-should-contain [
-<span id="L389" class="LineNr">389 </span>  <span class="Conceal">¦</span><span class="Constant"> 10</span> <span class="Special">&lt;-</span><span class="Constant"> 13</span>
-<span id="L390" class="LineNr">390 </span>  <span class="Conceal">¦</span><span class="Constant"> 11</span> <span class="Special">&lt;-</span><span class="Constant"> 14</span>
-<span id="L391" class="LineNr">391 </span>  <span class="Conceal">¦</span><span class="Constant"> 12</span> <span class="Special">&lt;-</span><span class="Constant"> 15</span>
-<span id="L392" class="LineNr">392 </span>  <span class="Conceal">¦</span><span class="Constant"> 20</span> <span class="Special">&lt;-</span><span class="Constant"> 0</span>
-<span id="L393" class="LineNr">393 </span>  ]
-<span id="L394" class="LineNr">394 </span>]
-<span id="L395" class="LineNr">395 </span>
-<span id="L396" class="LineNr">396 </span><span class="muScenario">scenario</span> remove-range-to-final [
-<span id="L397" class="LineNr">397 </span>  <span class="Constant">local-scope</span>
-<span id="L398" class="LineNr">398 </span>  <span class="Comment"># construct a duplex list with six elements [13, 14, 15, 16, 17, 18]</span>
-<span id="L399" class="LineNr">399 </span>  list:&amp;:duplex-list:char <span class="Special">&lt;-</span> push<span class="Constant"> 18</span>,<span class="Constant"> 0</span>
-<span id="L400" class="LineNr">400 </span>  list <span class="Special">&lt;-</span> push<span class="Constant"> 17</span>, list
-<span id="L401" class="LineNr">401 </span>  list <span class="Special">&lt;-</span> push<span class="Constant"> 16</span>, list
-<span id="L402" class="LineNr">402 </span>  list <span class="Special">&lt;-</span> push<span class="Constant"> 15</span>, list
-<span id="L403" class="LineNr">403 </span>  list <span class="Special">&lt;-</span> push<span class="Constant"> 14</span>, list
-<span id="L404" class="LineNr">404 </span>  list <span class="Special">&lt;-</span> push<span class="Constant"> 13</span>, list
-<span id="L405" class="LineNr">405 </span>  run [
-<span id="L406" class="LineNr">406 </span>  <span class="Conceal">¦</span> <span class="Comment"># delete 15, 16 and 17</span>
-<span id="L407" class="LineNr">407 </span>  <span class="Conceal">¦</span> <span class="Comment"># start pointer: to the second element</span>
-<span id="L408" class="LineNr">408 </span>  <span class="Conceal">¦</span> list2:&amp;:duplex-list:char <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> list
-<span id="L409" class="LineNr">409 </span>  <span class="Conceal">¦</span> <span class="Comment"># end pointer: to the last (sixth) element</span>
-<span id="L410" class="LineNr">410 </span>  <span class="Conceal">¦</span> end:&amp;:duplex-list:char <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> list2
-<span id="L411" class="LineNr">411 </span>  <span class="Conceal">¦</span> end <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> end
-<span id="L412" class="LineNr">412 </span>  <span class="Conceal">¦</span> end <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> end
-<span id="L413" class="LineNr">413 </span>  <span class="Conceal">¦</span> end <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> end
-<span id="L414" class="LineNr">414 </span>  <span class="Conceal">¦</span> <a href='065duplex_list.mu.html#L345'>remove-between</a> list2, end
-<span id="L415" class="LineNr">415 </span>  <span class="Conceal">¦</span> <span class="Comment"># now check the list</span>
-<span id="L416" class="LineNr">416 </span>  <span class="Conceal">¦</span> 10:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> get *list, <span class="Constant">value:offset</span>
-<span id="L417" class="LineNr">417 </span>  <span class="Conceal">¦</span> list <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> list
-<span id="L418" class="LineNr">418 </span>  <span class="Conceal">¦</span> 11:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> get *list, <span class="Constant">value:offset</span>
-<span id="L419" class="LineNr">419 </span>  <span class="Conceal">¦</span> list <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> list
-<span id="L420" class="LineNr">420 </span>  <span class="Conceal">¦</span> 12:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> get *list, <span class="Constant">value:offset</span>
-<span id="L421" class="LineNr">421 </span>  <span class="Conceal">¦</span> 20:&amp;:duplex-list:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> list
-<span id="L422" class="LineNr">422 </span>  ]
-<span id="L423" class="LineNr">423 </span>  memory-should-contain [
-<span id="L424" class="LineNr">424 </span>  <span class="Conceal">¦</span><span class="Constant"> 10</span> <span class="Special">&lt;-</span><span class="Constant"> 13</span>
-<span id="L425" class="LineNr">425 </span>  <span class="Conceal">¦</span><span class="Constant"> 11</span> <span class="Special">&lt;-</span><span class="Constant"> 14</span>
-<span id="L426" class="LineNr">426 </span>  <span class="Conceal">¦</span><span class="Constant"> 12</span> <span class="Special">&lt;-</span><span class="Constant"> 18</span>
-<span id="L427" class="LineNr">427 </span>  <span class="Conceal">¦</span><span class="Constant"> 20</span> <span class="Special">&lt;-</span><span class="Constant"> 0</span>  <span class="Comment"># no more elements</span>
-<span id="L428" class="LineNr">428 </span>  ]
-<span id="L429" class="LineNr">429 </span>]
-<span id="L430" class="LineNr">430 </span>
-<span id="L431" class="LineNr">431 </span><span class="muScenario">scenario</span> remove-range-empty [
-<span id="L432" class="LineNr">432 </span>  <span class="Constant">local-scope</span>
-<span id="L433" class="LineNr">433 </span>  <span class="Comment"># construct a duplex list with three elements [13, 14, 15]</span>
-<span id="L434" class="LineNr">434 </span>  list:&amp;:duplex-list:char <span class="Special">&lt;-</span> push<span class="Constant"> 15</span>,<span class="Constant"> 0</span>
-<span id="L435" class="LineNr">435 </span>  list <span class="Special">&lt;-</span> push<span class="Constant"> 14</span>, list
-<span id="L436" class="LineNr">436 </span>  list <span class="Special">&lt;-</span> push<span class="Constant"> 13</span>, list
-<span id="L437" class="LineNr">437 </span>  run [
-<span id="L438" class="LineNr">438 </span>  <span class="Conceal">¦</span> <span class="Comment"># delete between first and second element (i.e. nothing)</span>
-<span id="L439" class="LineNr">439 </span>  <span class="Conceal">¦</span> list2:&amp;:duplex-list:char <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> list
-<span id="L440" class="LineNr">440 </span>  <span class="Conceal">¦</span> <a href='065duplex_list.mu.html#L345'>remove-between</a> list, list2
-<span id="L441" class="LineNr">441 </span>  <span class="Conceal">¦</span> <span class="Comment"># now check the list</span>
-<span id="L442" class="LineNr">442 </span>  <span class="Conceal">¦</span> 10:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> get *list, <span class="Constant">value:offset</span>
-<span id="L443" class="LineNr">443 </span>  <span class="Conceal">¦</span> list <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> list
-<span id="L444" class="LineNr">444 </span>  <span class="Conceal">¦</span> 11:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> get *list, <span class="Constant">value:offset</span>
-<span id="L445" class="LineNr">445 </span>  <span class="Conceal">¦</span> list <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> list
-<span id="L446" class="LineNr">446 </span>  <span class="Conceal">¦</span> 12:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> get *list, <span class="Constant">value:offset</span>
-<span id="L447" class="LineNr">447 </span>  <span class="Conceal">¦</span> 20:&amp;:duplex-list:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> list
-<span id="L448" class="LineNr">448 </span>  ]
-<span id="L449" class="LineNr">449 </span>  <span class="Comment"># no change</span>
-<span id="L450" class="LineNr">450 </span>  memory-should-contain [
-<span id="L451" class="LineNr">451 </span>  <span class="Conceal">¦</span><span class="Constant"> 10</span> <span class="Special">&lt;-</span><span class="Constant"> 13</span>
-<span id="L452" class="LineNr">452 </span>  <span class="Conceal">¦</span><span class="Constant"> 11</span> <span class="Special">&lt;-</span><span class="Constant"> 14</span>
-<span id="L453" class="LineNr">453 </span>  <span class="Conceal">¦</span><span class="Constant"> 12</span> <span class="Special">&lt;-</span><span class="Constant"> 15</span>
-<span id="L454" class="LineNr">454 </span>  <span class="Conceal">¦</span><span class="Constant"> 20</span> <span class="Special">&lt;-</span><span class="Constant"> 0</span>
-<span id="L455" class="LineNr">455 </span>  ]
-<span id="L456" class="LineNr">456 </span>]
-<span id="L457" class="LineNr">457 </span>
-<span id="L458" class="LineNr">458 </span><span class="muScenario">scenario</span> remove-range-to-end [
-<span id="L459" class="LineNr">459 </span>  <span class="Constant">local-scope</span>
-<span id="L460" class="LineNr">460 </span>  <span class="Comment"># construct a duplex list with six elements [13, 14, 15, 16, 17, 18]</span>
-<span id="L461" class="LineNr">461 </span>  list:&amp;:duplex-list:char <span class="Special">&lt;-</span> push<span class="Constant"> 18</span>,<span class="Constant"> 0</span>
-<span id="L462" class="LineNr">462 </span>  list <span class="Special">&lt;-</span> push<span class="Constant"> 17</span>, list
-<span id="L463" class="LineNr">463 </span>  list <span class="Special">&lt;-</span> push<span class="Constant"> 16</span>, list
-<span id="L464" class="LineNr">464 </span>  list <span class="Special">&lt;-</span> push<span class="Constant"> 15</span>, list
-<span id="L465" class="LineNr">465 </span>  list <span class="Special">&lt;-</span> push<span class="Constant"> 14</span>, list
-<span id="L466" class="LineNr">466 </span>  list <span class="Special">&lt;-</span> push<span class="Constant"> 13</span>, list
-<span id="L467" class="LineNr">467 </span>  run [
-<span id="L468" class="LineNr">468 </span>  <span class="Conceal">¦</span> <span class="Comment"># remove the third element and beyond</span>
-<span id="L469" class="LineNr">469 </span>  <span class="Conceal">¦</span> list2:&amp;:duplex-list:char <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> list
-<span id="L470" class="LineNr">470 </span>  <span class="Conceal">¦</span> <a href='065duplex_list.mu.html#L345'>remove-between</a> list2,<span class="Constant"> 0</span>
-<span id="L471" class="LineNr">471 </span>  <span class="Conceal">¦</span> <span class="Comment"># now check the list</span>
-<span id="L472" class="LineNr">472 </span>  <span class="Conceal">¦</span> 10:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> get *list, <span class="Constant">value:offset</span>
-<span id="L473" class="LineNr">473 </span>  <span class="Conceal">¦</span> list <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> list
-<span id="L474" class="LineNr">474 </span>  <span class="Conceal">¦</span> 11:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> get *list, <span class="Constant">value:offset</span>
-<span id="L475" class="LineNr">475 </span>  <span class="Conceal">¦</span> 20:&amp;:duplex-list:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> list
-<span id="L476" class="LineNr">476 </span>  ]
-<span id="L477" class="LineNr">477 </span>  memory-should-contain [
-<span id="L478" class="LineNr">478 </span>  <span class="Conceal">¦</span><span class="Constant"> 10</span> <span class="Special">&lt;-</span><span class="Constant"> 13</span>
-<span id="L479" class="LineNr">479 </span>  <span class="Conceal">¦</span><span class="Constant"> 11</span> <span class="Special">&lt;-</span><span class="Constant"> 14</span>
-<span id="L480" class="LineNr">480 </span>  <span class="Conceal">¦</span><span class="Constant"> 20</span> <span class="Special">&lt;-</span><span class="Constant"> 0</span>
-<span id="L481" class="LineNr">481 </span>  ]
-<span id="L482" class="LineNr">482 </span>]
-<span id="L483" class="LineNr">483 </span>
-<span id="L484" class="LineNr">484 </span><span class="Comment"># insert list beginning at 'new' after 'in'</span>
-<span id="L485" class="LineNr">485 </span><span class="muRecipe">def</span> <a href='065duplex_list.mu.html#L485'>insert-range</a> in:&amp;:duplex-list:_elem, start:&amp;:duplex-list:_elem/contained-in:in<span class="muRecipe"> -&gt; </span>in:&amp;:duplex-list:_elem [
-<span id="L486" class="LineNr">486 </span>  <span class="Constant">local-scope</span>
-<span id="L487" class="LineNr">487 </span>  <span class="Constant">load-ingredients</span>
-<span id="L488" class="LineNr">488 </span>  <span class="muControl">return-unless</span> in
-<span id="L489" class="LineNr">489 </span>  <span class="muControl">return-unless</span> start
-<span id="L490" class="LineNr">490 </span>  end:&amp;:duplex-list:_elem <span class="Special">&lt;-</span> copy start
-<span id="L491" class="LineNr">491 </span>  <span class="Delimiter">{</span>
-<span id="L492" class="LineNr">492 </span>  <span class="Conceal">¦</span> <a href='065duplex_list.mu.html#L29'>next</a>:&amp;:duplex-list:_elem <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> end/insert-range
-<span id="L493" class="LineNr">493 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> <a href='065duplex_list.mu.html#L29'>next</a>
-<span id="L494" class="LineNr">494 </span>  <span class="Conceal">¦</span> end <span class="Special">&lt;-</span> copy <a href='065duplex_list.mu.html#L29'>next</a>
-<span id="L495" class="LineNr">495 </span>  <span class="Conceal">¦</span> <span class="muControl">loop</span>
-<span id="L496" class="LineNr">496 </span>  <span class="Delimiter">}</span>
-<span id="L497" class="LineNr">497 </span>  <a href='065duplex_list.mu.html#L29'>next</a>:&amp;:duplex-list:_elem <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> in
-<span id="L498" class="LineNr">498 </span>  *end <span class="Special">&lt;-</span> put *end, <span class="Constant"><a href='065duplex_list.mu.html#L29'>next</a>:offset</span>, <a href='065duplex_list.mu.html#L29'>next</a>
-<span id="L499" class="LineNr">499 </span>  <span class="Delimiter">{</span>
-<span id="L500" class="LineNr">500 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> <a href='065duplex_list.mu.html#L29'>next</a>
-<span id="L501" class="LineNr">501 </span>  <span class="Conceal">¦</span> *next <span class="Special">&lt;-</span> put *next, <span class="Constant"><a href='065duplex_list.mu.html#L36'>prev</a>:offset</span>, end
-<span id="L502" class="LineNr">502 </span>  <span class="Delimiter">}</span>
-<span id="L503" class="LineNr">503 </span>  *in <span class="Special">&lt;-</span> put *in, <span class="Constant"><a href='065duplex_list.mu.html#L29'>next</a>:offset</span>, start
-<span id="L504" class="LineNr">504 </span>  *start <span class="Special">&lt;-</span> put *start, <span class="Constant"><a href='065duplex_list.mu.html#L36'>prev</a>:offset</span>, in
-<span id="L505" class="LineNr">505 </span>]
-<span id="L506" class="LineNr">506 </span>
-<span id="L507" class="LineNr">507 </span><span class="muRecipe">def</span> append in:&amp;:duplex-list:_elem, new:&amp;:duplex-list:_elem/contained-in:in<span class="muRecipe"> -&gt; </span>in:&amp;:duplex-list:_elem [
-<span id="L508" class="LineNr">508 </span>  <span class="Constant">local-scope</span>
-<span id="L509" class="LineNr">509 </span>  <span class="Constant">load-ingredients</span>
-<span id="L510" class="LineNr">510 </span>  <a href='065duplex_list.mu.html#L516'>last</a>:&amp;:duplex-list:_elem <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L516'>last</a> in
-<span id="L511" class="LineNr">511 </span>  *last <span class="Special">&lt;-</span> put *last, <span class="Constant"><a href='065duplex_list.mu.html#L29'>next</a>:offset</span>, new
-<span id="L512" class="LineNr">512 </span>  <span class="muControl">return-unless</span> new
-<span id="L513" class="LineNr">513 </span>  *new <span class="Special">&lt;-</span> put *new, <span class="Constant"><a href='065duplex_list.mu.html#L36'>prev</a>:offset</span>, <a href='065duplex_list.mu.html#L516'>last</a>
-<span id="L514" class="LineNr">514 </span>]
-<span id="L515" class="LineNr">515 </span>
-<span id="L516" class="LineNr">516 </span><span class="muRecipe">def</span> <a href='065duplex_list.mu.html#L516'>last</a> in:&amp;:duplex-list:_elem<span class="muRecipe"> -&gt; </span>result:&amp;:duplex-list:_elem [
-<span id="L517" class="LineNr">517 </span>  <span class="Constant">local-scope</span>
-<span id="L518" class="LineNr">518 </span>  <span class="Constant">load-ingredients</span>
-<span id="L519" class="LineNr">519 </span>  result <span class="Special">&lt;-</span> copy in
-<span id="L520" class="LineNr">520 </span>  <span class="Delimiter">{</span>
-<span id="L521" class="LineNr">521 </span>  <span class="Conceal">¦</span> <a href='065duplex_list.mu.html#L29'>next</a>:&amp;:duplex-list:_elem <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> result
-<span id="L522" class="LineNr">522 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> <a href='065duplex_list.mu.html#L29'>next</a>
-<span id="L523" class="LineNr">523 </span>  <span class="Conceal">¦</span> result <span class="Special">&lt;-</span> copy <a href='065duplex_list.mu.html#L29'>next</a>
-<span id="L524" class="LineNr">524 </span>  <span class="Conceal">¦</span> <span class="muControl">loop</span>
-<span id="L525" class="LineNr">525 </span>  <span class="Delimiter">}</span>
+<span id="L340" class="LineNr">340 </span><span class="muScenario">scenario</span> removing-from-singleton-duplex-list [
+<span id="L341" class="LineNr">341 </span>  <span class="Constant">local-scope</span>
+<span id="L342" class="LineNr">342 </span>  list:&amp;:duplex-list:char <span class="Special">&lt;-</span> push<span class="Constant"> 3</span>,<span class="Constant"> 0</span>
+<span id="L343" class="LineNr">343 </span>  run [
+<span id="L344" class="LineNr">344 </span>  <span class="Conceal">¦</span> list <span class="Special">&lt;-</span> remove list, list
+<span id="L345" class="LineNr">345 </span>  <span class="Conceal">¦</span> 1:num/<span class="Special">raw</span> <span class="Special">&lt;-</span> copy list
+<span id="L346" class="LineNr">346 </span>  ]
+<span id="L347" class="LineNr">347 </span>  memory-should-contain [
+<span id="L348" class="LineNr">348 </span>  <span class="Conceal">¦</span><span class="Constant"> 1</span> <span class="Special">&lt;-</span><span class="Constant"> 0</span>  <span class="Comment"># back to an empty list</span>
+<span id="L349" class="LineNr">349 </span>  ]
+<span id="L350" class="LineNr">350 </span>]
+<span id="L351" class="LineNr">351 </span>
+<span id="L352" class="LineNr">352 </span><span class="Comment"># remove values between 'start' and 'end' (both exclusive).</span>
+<span id="L353" class="LineNr">353 </span><span class="Comment"># also clear pointers back out from start/end for hygiene.</span>
+<span id="L354" class="LineNr">354 </span><span class="Comment"># set end to 0 to delete everything past start.</span>
+<span id="L355" class="LineNr">355 </span><span class="Comment"># can't set start to 0 to delete everything before end, because there's no</span>
+<span id="L356" class="LineNr">356 </span><span class="Comment"># clean way to return the new head pointer.</span>
+<span id="L357" class="LineNr">357 </span><span class="muRecipe">def</span> <a href='065duplex_list.mu.html#L357'>remove-between</a> start:&amp;:duplex-list:_elem, end:&amp;:duplex-list:_elem/contained-in:start<span class="muRecipe"> -&gt; </span>start:&amp;:duplex-list:_elem [
+<span id="L358" class="LineNr">358 </span>  <span class="Constant">local-scope</span>
+<span id="L359" class="LineNr">359 </span>  <span class="Constant">load-ingredients</span>
+<span id="L360" class="LineNr">360 </span>  <a href='065duplex_list.mu.html#L29'>next</a>:&amp;:duplex-list:_elem <span class="Special">&lt;-</span> get *start, <span class="Constant"><a href='065duplex_list.mu.html#L29'>next</a>:offset</span>
+<span id="L361" class="LineNr">361 </span>  nothing-to-delete?:bool <span class="Special">&lt;-</span> equal <a href='065duplex_list.mu.html#L29'>next</a>, end
+<span id="L362" class="LineNr">362 </span>  <span class="muControl">return-if</span> nothing-to-delete?
+<span id="L363" class="LineNr">363 </span>  assert <a href='065duplex_list.mu.html#L29'>next</a>, <span class="Constant">[malformed duplex list]</span>
+<span id="L364" class="LineNr">364 </span>  <span class="Comment"># start-&gt;next-&gt;prev = 0</span>
+<span id="L365" class="LineNr">365 </span>  <span class="Comment"># start-&gt;next = end</span>
+<span id="L366" class="LineNr">366 </span>  *next <span class="Special">&lt;-</span> put *next, <span class="Constant"><a href='065duplex_list.mu.html#L36'>prev</a>:offset</span>,<span class="Constant"> 0</span>
+<span id="L367" class="LineNr">367 </span>  *start <span class="Special">&lt;-</span> put *start, <span class="Constant"><a href='065duplex_list.mu.html#L29'>next</a>:offset</span>, end
+<span id="L368" class="LineNr">368 </span>  <span class="muControl">return-unless</span> end
+<span id="L369" class="LineNr">369 </span>  <span class="Comment"># end-&gt;prev-&gt;next = 0</span>
+<span id="L370" class="LineNr">370 </span>  <span class="Comment"># end-&gt;prev = start</span>
+<span id="L371" class="LineNr">371 </span>  <a href='065duplex_list.mu.html#L36'>prev</a>:&amp;:duplex-list:_elem <span class="Special">&lt;-</span> get *end, <span class="Constant"><a href='065duplex_list.mu.html#L36'>prev</a>:offset</span>
+<span id="L372" class="LineNr">372 </span>  assert <a href='065duplex_list.mu.html#L36'>prev</a>, <span class="Constant">[malformed duplex list - 2]</span>
+<span id="L373" class="LineNr">373 </span>  *prev <span class="Special">&lt;-</span> put *prev, <span class="Constant"><a href='065duplex_list.mu.html#L29'>next</a>:offset</span>,<span class="Constant"> 0</span>
+<span id="L374" class="LineNr">374 </span>  *end <span class="Special">&lt;-</span> put *end, <span class="Constant"><a href='065duplex_list.mu.html#L36'>prev</a>:offset</span>, start
+<span id="L375" class="LineNr">375 </span>]
+<span id="L376" class="LineNr">376 </span>
+<span id="L377" class="LineNr">377 </span><span class="muScenario">scenario</span> remove-range [
+<span id="L378" class="LineNr">378 </span>  <span class="Comment"># construct a duplex list with six elements [13, 14, 15, 16, 17, 18]</span>
+<span id="L379" class="LineNr">379 </span>  <span class="Constant">local-scope</span>
+<span id="L380" class="LineNr">380 </span>  list:&amp;:duplex-list:char <span class="Special">&lt;-</span> push<span class="Constant"> 18</span>,<span class="Constant"> 0</span>
+<span id="L381" class="LineNr">381 </span>  list <span class="Special">&lt;-</span> push<span class="Constant"> 17</span>, list
+<span id="L382" class="LineNr">382 </span>  list <span class="Special">&lt;-</span> push<span class="Constant"> 16</span>, list
+<span id="L383" class="LineNr">383 </span>  list <span class="Special">&lt;-</span> push<span class="Constant"> 15</span>, list
+<span id="L384" class="LineNr">384 </span>  list <span class="Special">&lt;-</span> push<span class="Constant"> 14</span>, list
+<span id="L385" class="LineNr">385 </span>  list <span class="Special">&lt;-</span> push<span class="Constant"> 13</span>, list
+<span id="L386" class="LineNr">386 </span>  run [
+<span id="L387" class="LineNr">387 </span>  <span class="Conceal">¦</span> <span class="Comment"># delete 16 onwards</span>
+<span id="L388" class="LineNr">388 </span>  <span class="Conceal">¦</span> <span class="Comment"># first pointer: to the third element</span>
+<span id="L389" class="LineNr">389 </span>  <span class="Conceal">¦</span> list2:&amp;:duplex-list:char <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> list
+<span id="L390" class="LineNr">390 </span>  <span class="Conceal">¦</span> list2 <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> list2
+<span id="L391" class="LineNr">391 </span>  <span class="Conceal">¦</span> list2 <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L357'>remove-between</a> list2,<span class="Constant"> 0</span>
+<span id="L392" class="LineNr">392 </span>  <span class="Conceal">¦</span> <span class="Comment"># now check the list</span>
+<span id="L393" class="LineNr">393 </span>  <span class="Conceal">¦</span> 10:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> get *list, <span class="Constant">value:offset</span>
+<span id="L394" class="LineNr">394 </span>  <span class="Conceal">¦</span> list <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> list
+<span id="L395" class="LineNr">395 </span>  <span class="Conceal">¦</span> 11:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> get *list, <span class="Constant">value:offset</span>
+<span id="L396" class="LineNr">396 </span>  <span class="Conceal">¦</span> list <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> list
+<span id="L397" class="LineNr">397 </span>  <span class="Conceal">¦</span> 12:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> get *list, <span class="Constant">value:offset</span>
+<span id="L398" class="LineNr">398 </span>  <span class="Conceal">¦</span> 20:&amp;:duplex-list:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> list
+<span id="L399" class="LineNr">399 </span>  ]
+<span id="L400" class="LineNr">400 </span>  memory-should-contain [
+<span id="L401" class="LineNr">401 </span>  <span class="Conceal">¦</span><span class="Constant"> 10</span> <span class="Special">&lt;-</span><span class="Constant"> 13</span>
+<span id="L402" class="LineNr">402 </span>  <span class="Conceal">¦</span><span class="Constant"> 11</span> <span class="Special">&lt;-</span><span class="Constant"> 14</span>
+<span id="L403" class="LineNr">403 </span>  <span class="Conceal">¦</span><span class="Constant"> 12</span> <span class="Special">&lt;-</span><span class="Constant"> 15</span>
+<span id="L404" class="LineNr">404 </span>  <span class="Conceal">¦</span><span class="Constant"> 20</span> <span class="Special">&lt;-</span><span class="Constant"> 0</span>
+<span id="L405" class="LineNr">405 </span>  ]
+<span id="L406" class="LineNr">406 </span>]
+<span id="L407" class="LineNr">407 </span>
+<span id="L408" class="LineNr">408 </span><span class="muScenario">scenario</span> remove-range-to-final [
+<span id="L409" class="LineNr">409 </span>  <span class="Constant">local-scope</span>
+<span id="L410" class="LineNr">410 </span>  <span class="Comment"># construct a duplex list with six elements [13, 14, 15, 16, 17, 18]</span>
+<span id="L411" class="LineNr">411 </span>  list:&amp;:duplex-list:char <span class="Special">&lt;-</span> push<span class="Constant"> 18</span>,<span class="Constant"> 0</span>
+<span id="L412" class="LineNr">412 </span>  list <span class="Special">&lt;-</span> push<span class="Constant"> 17</span>, list
+<span id="L413" class="LineNr">413 </span>  list <span class="Special">&lt;-</span> push<span class="Constant"> 16</span>, list
+<span id="L414" class="LineNr">414 </span>  list <span class="Special">&lt;-</span> push<span class="Constant"> 15</span>, list
+<span id="L415" class="LineNr">415 </span>  list <span class="Special">&lt;-</span> push<span class="Constant"> 14</span>, list
+<span id="L416" class="LineNr">416 </span>  list <span class="Special">&lt;-</span> push<span class="Constant"> 13</span>, list
+<span id="L417" class="LineNr">417 </span>  run [
+<span id="L418" class="LineNr">418 </span>  <span class="Conceal">¦</span> <span class="Comment"># delete 15, 16 and 17</span>
+<span id="L419" class="LineNr">419 </span>  <span class="Conceal">¦</span> <span class="Comment"># start pointer: to the second element</span>
+<span id="L420" class="LineNr">420 </span>  <span class="Conceal">¦</span> list2:&amp;:duplex-list:char <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> list
+<span id="L421" class="LineNr">421 </span>  <span class="Conceal">¦</span> <span class="Comment"># end pointer: to the last (sixth) element</span>
+<span id="L422" class="LineNr">422 </span>  <span class="Conceal">¦</span> end:&amp;:duplex-list:char <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> list2
+<span id="L423" class="LineNr">423 </span>  <span class="Conceal">¦</span> end <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> end
+<span id="L424" class="LineNr">424 </span>  <span class="Conceal">¦</span> end <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> end
+<span id="L425" class="LineNr">425 </span>  <span class="Conceal">¦</span> end <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> end
+<span id="L426" class="LineNr">426 </span>  <span class="Conceal">¦</span> <a href='065duplex_list.mu.html#L357'>remove-between</a> list2, end
+<span id="L427" class="LineNr">427 </span>  <span class="Conceal">¦</span> <span class="Comment"># now check the list</span>
+<span id="L428" class="LineNr">428 </span>  <span class="Conceal">¦</span> 10:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> get *list, <span class="Constant">value:offset</span>
+<span id="L429" class="LineNr">429 </span>  <span class="Conceal">¦</span> list <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> list
+<span id="L430" class="LineNr">430 </span>  <span class="Conceal">¦</span> 11:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> get *list, <span class="Constant">value:offset</span>
+<span id="L431" class="LineNr">431 </span>  <span class="Conceal">¦</span> list <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> list
+<span id="L432" class="LineNr">432 </span>  <span class="Conceal">¦</span> 12:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> get *list, <span class="Constant">value:offset</span>
+<span id="L433" class="LineNr">433 </span>  <span class="Conceal">¦</span> 20:&amp;:duplex-list:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> list
+<span id="L434" class="LineNr">434 </span>  ]
+<span id="L435" class="LineNr">435 </span>  memory-should-contain [
+<span id="L436" class="LineNr">436 </span>  <span class="Conceal">¦</span><span class="Constant"> 10</span> <span class="Special">&lt;-</span><span class="Constant"> 13</span>
+<span id="L437" class="LineNr">437 </span>  <span class="Conceal">¦</span><span class="Constant"> 11</span> <span class="Special">&lt;-</span><span class="Constant"> 14</span>
+<span id="L438" class="LineNr">438 </span>  <span class="Conceal">¦</span><span class="Constant"> 12</span> <span class="Special">&lt;-</span><span class="Constant"> 18</span>
+<span id="L439" class="LineNr">439 </span>  <span class="Conceal">¦</span><span class="Constant"> 20</span> <span class="Special">&lt;-</span><span class="Constant"> 0</span>  <span class="Comment"># no more elements</span>
+<span id="L440" class="LineNr">440 </span>  ]
+<span id="L441" class="LineNr">441 </span>]
+<span id="L442" class="LineNr">442 </span>
+<span id="L443" class="LineNr">443 </span><span class="muScenario">scenario</span> remove-range-empty [
+<span id="L444" class="LineNr">444 </span>  <span class="Constant">local-scope</span>
+<span id="L445" class="LineNr">445 </span>  <span class="Comment"># construct a duplex list with three elements [13, 14, 15]</span>
+<span id="L446" class="LineNr">446 </span>  list:&amp;:duplex-list:char <span class="Special">&lt;-</span> push<span class="Constant"> 15</span>,<span class="Constant"> 0</span>
+<span id="L447" class="LineNr">447 </span>  list <span class="Special">&lt;-</span> push<span class="Constant"> 14</span>, list
+<span id="L448" class="LineNr">448 </span>  list <span class="Special">&lt;-</span> push<span class="Constant"> 13</span>, list
+<span id="L449" class="LineNr">449 </span>  run [
+<span id="L450" class="LineNr">450 </span>  <span class="Conceal">¦</span> <span class="Comment"># delete between first and second element (i.e. nothing)</span>
+<span id="L451" class="LineNr">451 </span>  <span class="Conceal">¦</span> list2:&amp;:duplex-list:char <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> list
+<span id="L452" class="LineNr">452 </span>  <span class="Conceal">¦</span> <a href='065duplex_list.mu.html#L357'>remove-between</a> list, list2
+<span id="L453" class="LineNr">453 </span>  <span class="Conceal">¦</span> <span class="Comment"># now check the list</span>
+<span id="L454" class="LineNr">454 </span>  <span class="Conceal">¦</span> 10:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> get *list, <span class="Constant">value:offset</span>
+<span id="L455" class="LineNr">455 </span>  <span class="Conceal">¦</span> list <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> list
+<span id="L456" class="LineNr">456 </span>  <span class="Conceal">¦</span> 11:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> get *list, <span class="Constant">value:offset</span>
+<span id="L457" class="LineNr">457 </span>  <span class="Conceal">¦</span> list <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> list
+<span id="L458" class="LineNr">458 </span>  <span class="Conceal">¦</span> 12:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> get *list, <span class="Constant">value:offset</span>
+<span id="L459" class="LineNr">459 </span>  <span class="Conceal">¦</span> 20:&amp;:duplex-list:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> list
+<span id="L460" class="LineNr">460 </span>  ]
+<span id="L461" class="LineNr">461 </span>  <span class="Comment"># no change</span>
+<span id="L462" class="LineNr">462 </span>  memory-should-contain [
+<span id="L463" class="LineNr">463 </span>  <span class="Conceal">¦</span><span class="Constant"> 10</span> <span class="Special">&lt;-</span><span class="Constant"> 13</span>
+<span id="L464" class="LineNr">464 </span>  <span class="Conceal">¦</span><span class="Constant"> 11</span> <span class="Special">&lt;-</span><span class="Constant"> 14</span>
+<span id="L465" class="LineNr">465 </span>  <span class="Conceal">¦</span><span class="Constant"> 12</span> <span class="Special">&lt;-</span><span class="Constant"> 15</span>
+<span id="L466" class="LineNr">466 </span>  <span class="Conceal">¦</span><span class="Constant"> 20</span> <span class="Special">&lt;-</span><span class="Constant"> 0</span>
+<span id="L467" class="LineNr">467 </span>  ]
+<span id="L468" class="LineNr">468 </span>]
+<span id="L469" class="LineNr">469 </span>
+<span id="L470" class="LineNr">470 </span><span class="muScenario">scenario</span> remove-range-to-end [
+<span id="L471" class="LineNr">471 </span>  <span class="Constant">local-scope</span>
+<span id="L472" class="LineNr">472 </span>  <span class="Comment"># construct a duplex list with six elements [13, 14, 15, 16, 17, 18]</span>
+<span id="L473" class="LineNr">473 </span>  list:&amp;:duplex-list:char <span class="Special">&lt;-</span> push<span class="Constant"> 18</span>,<span class="Constant"> 0</span>
+<span id="L474" class="LineNr">474 </span>  list <span class="Special">&lt;-</span> push<span class="Constant"> 17</span>, list
+<span id="L475" class="LineNr">475 </span>  list <span class="Special">&lt;-</span> push<span class="Constant"> 16</span>, list
+<span id="L476" class="LineNr">476 </span>  list <span class="Special">&lt;-</span> push<span class="Constant"> 15</span>, list
+<span id="L477" class="LineNr">477 </span>  list <span class="Special">&lt;-</span> push<span class="Constant"> 14</span>, list
+<span id="L478" class="LineNr">478 </span>  list <span class="Special">&lt;-</span> push<span class="Constant"> 13</span>, list
+<span id="L479" class="LineNr">479 </span>  run [
+<span id="L480" class="LineNr">480 </span>  <span class="Conceal">¦</span> <span class="Comment"># remove the third element and beyond</span>
+<span id="L481" class="LineNr">481 </span>  <span class="Conceal">¦</span> list2:&amp;:duplex-list:char <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> list
+<span id="L482" class="LineNr">482 </span>  <span class="Conceal">¦</span> <a href='065duplex_list.mu.html#L357'>remove-between</a> list2,<span class="Constant"> 0</span>
+<span id="L483" class="LineNr">483 </span>  <span class="Conceal">¦</span> <span class="Comment"># now check the list</span>
+<span id="L484" class="LineNr">484 </span>  <span class="Conceal">¦</span> 10:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> get *list, <span class="Constant">value:offset</span>
+<span id="L485" class="LineNr">485 </span>  <span class="Conceal">¦</span> list <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> list
+<span id="L486" class="LineNr">486 </span>  <span class="Conceal">¦</span> 11:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> get *list, <span class="Constant">value:offset</span>
+<span id="L487" class="LineNr">487 </span>  <span class="Conceal">¦</span> 20:&amp;:duplex-list:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> list
+<span id="L488" class="LineNr">488 </span>  ]
+<span id="L489" class="LineNr">489 </span>  memory-should-contain [
+<span id="L490" class="LineNr">490 </span>  <span class="Conceal">¦</span><span class="Constant"> 10</span> <span class="Special">&lt;-</span><span class="Constant"> 13</span>
+<span id="L491" class="LineNr">491 </span>  <span class="Conceal">¦</span><span class="Constant"> 11</span> <span class="Special">&lt;-</span><span class="Constant"> 14</span>
+<span id="L492" class="LineNr">492 </span>  <span class="Conceal">¦</span><span class="Constant"> 20</span> <span class="Special">&lt;-</span><span class="Constant"> 0</span>
+<span id="L493" class="LineNr">493 </span>  ]
+<span id="L494" class="LineNr">494 </span>]
+<span id="L495" class="LineNr">495 </span>
+<span id="L496" class="LineNr">496 </span><span class="Comment"># insert list beginning at 'new' after 'in'</span>
+<span id="L497" class="LineNr">497 </span><span class="muRecipe">def</span> <a href='065duplex_list.mu.html#L497'>insert-range</a> in:&amp;:duplex-list:_elem, start:&amp;:duplex-list:_elem/contained-in:in<span class="muRecipe"> -&gt; </span>in:&amp;:duplex-list:_elem [
+<span id="L498" class="LineNr">498 </span>  <span class="Constant">local-scope</span>
+<span id="L499" class="LineNr">499 </span>  <span class="Constant">load-ingredients</span>
+<span id="L500" class="LineNr">500 </span>  <span class="muControl">return-unless</span> in
+<span id="L501" class="LineNr">501 </span>  <span class="muControl">return-unless</span> start
+<span id="L502" class="LineNr">502 </span>  end:&amp;:duplex-list:_elem <span class="Special">&lt;-</span> copy start
+<span id="L503" class="LineNr">503 </span>  <span class="Delimiter">{</span>
+<span id="L504" class="LineNr">504 </span>  <span class="Conceal">¦</span> <a href='065duplex_list.mu.html#L29'>next</a>:&amp;:duplex-list:_elem <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> end/insert-range
+<span id="L505" class="LineNr">505 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> <a href='065duplex_list.mu.html#L29'>next</a>
+<span id="L506" class="LineNr">506 </span>  <span class="Conceal">¦</span> end <span class="Special">&lt;-</span> copy <a href='065duplex_list.mu.html#L29'>next</a>
+<span id="L507" class="LineNr">507 </span>  <span class="Conceal">¦</span> <span class="muControl">loop</span>
+<span id="L508" class="LineNr">508 </span>  <span class="Delimiter">}</span>
+<span id="L509" class="LineNr">509 </span>  <a href='065duplex_list.mu.html#L29'>next</a>:&amp;:duplex-list:_elem <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> in
+<span id="L510" class="LineNr">510 </span>  *end <span class="Special">&lt;-</span> put *end, <span class="Constant"><a href='065duplex_list.mu.html#L29'>next</a>:offset</span>, <a href='065duplex_list.mu.html#L29'>next</a>
+<span id="L511" class="LineNr">511 </span>  <span class="Delimiter">{</span>
+<span id="L512" class="LineNr">512 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> <a href='065duplex_list.mu.html#L29'>next</a>
+<span id="L513" class="LineNr">513 </span>  <span class="Conceal">¦</span> *next <span class="Special">&lt;-</span> put *next, <span class="Constant"><a href='065duplex_list.mu.html#L36'>prev</a>:offset</span>, end
+<span id="L514" class="LineNr">514 </span>  <span class="Delimiter">}</span>
+<span id="L515" class="LineNr">515 </span>  *in <span class="Special">&lt;-</span> put *in, <span class="Constant"><a href='065duplex_list.mu.html#L29'>next</a>:offset</span>, start
+<span id="L516" class="LineNr">516 </span>  *start <span class="Special">&lt;-</span> put *start, <span class="Constant"><a href='065duplex_list.mu.html#L36'>prev</a>:offset</span>, in
+<span id="L517" class="LineNr">517 </span>]
+<span id="L518" class="LineNr">518 </span>
+<span id="L519" class="LineNr">519 </span><span class="muRecipe">def</span> append in:&amp;:duplex-list:_elem, new:&amp;:duplex-list:_elem/contained-in:in<span class="muRecipe"> -&gt; </span>in:&amp;:duplex-list:_elem [
+<span id="L520" class="LineNr">520 </span>  <span class="Constant">local-scope</span>
+<span id="L521" class="LineNr">521 </span>  <span class="Constant">load-ingredients</span>
+<span id="L522" class="LineNr">522 </span>  <a href='065duplex_list.mu.html#L528'>last</a>:&amp;:duplex-list:_elem <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L528'>last</a> in
+<span id="L523" class="LineNr">523 </span>  *last <span class="Special">&lt;-</span> put *last, <span class="Constant"><a href='065duplex_list.mu.html#L29'>next</a>:offset</span>, new
+<span id="L524" class="LineNr">524 </span>  <span class="muControl">return-unless</span> new
+<span id="L525" class="LineNr">525 </span>  *new <span class="Special">&lt;-</span> put *new, <span class="Constant"><a href='065duplex_list.mu.html#L36'>prev</a>:offset</span>, <a href='065duplex_list.mu.html#L528'>last</a>
 <span id="L526" class="LineNr">526 </span>]
 <span id="L527" class="LineNr">527 </span>
-<span id="L528" class="LineNr">528 </span><span class="Comment"># helper for debugging</span>
-<span id="L529" class="LineNr">529 </span><span class="muRecipe">def</span> <a href='065duplex_list.mu.html#L529'>dump-from</a> x:&amp;:duplex-list:_elem [
-<span id="L530" class="LineNr">530 </span>  <span class="Constant">local-scope</span>
-<span id="L531" class="LineNr">531 </span>  <span class="Constant">load-ingredients</span>
-<span id="L532" class="LineNr">532 </span>  $print x, <span class="Constant">[: ]</span>
-<span id="L533" class="LineNr">533 </span>  <span class="Delimiter">{</span>
-<span id="L534" class="LineNr">534 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> x
-<span id="L535" class="LineNr">535 </span>  <span class="Conceal">¦</span> c:_elem <span class="Special">&lt;-</span> get *x, <span class="Constant">value:offset</span>
-<span id="L536" class="LineNr">536 </span>  <span class="Conceal">¦</span> $print c, <span class="Constant">[ ]</span>
-<span id="L537" class="LineNr">537 </span>  <span class="Conceal">¦</span> x <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> x
-<span id="L538" class="LineNr">538 </span>  <span class="Conceal">¦</span> <span class="Delimiter">{</span>
-<span id="L539" class="LineNr">539 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> is-newline?:bool <span class="Special">&lt;-</span> equal c, <span class="Constant">10/newline</span>
-<span id="L540" class="LineNr">540 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">break-unless</span> is-newline?
-<span id="L541" class="LineNr">541 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> $print <span class="Constant">10/newline</span>
-<span id="L542" class="LineNr">542 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> $print x, <span class="Constant">[: ]</span>
-<span id="L543" class="LineNr">543 </span>  <span class="Conceal">¦</span> <span class="Delimiter">}</span>
-<span id="L544" class="LineNr">544 </span>  <span class="Conceal">¦</span> <span class="muControl">loop</span>
-<span id="L545" class="LineNr">545 </span>  <span class="Delimiter">}</span>
-<span id="L546" class="LineNr">546 </span>  $print <span class="Constant">10/newline</span>, <span class="Constant">[---]</span>, <span class="Constant">10/newline</span>
-<span id="L547" class="LineNr">547 </span>]
+<span id="L528" class="LineNr">528 </span><span class="muRecipe">def</span> <a href='065duplex_list.mu.html#L528'>last</a> in:&amp;:duplex-list:_elem<span class="muRecipe"> -&gt; </span>result:&amp;:duplex-list:_elem [
+<span id="L529" class="LineNr">529 </span>  <span class="Constant">local-scope</span>
+<span id="L530" class="LineNr">530 </span>  <span class="Constant">load-ingredients</span>
+<span id="L531" class="LineNr">531 </span>  result <span class="Special">&lt;-</span> copy in
+<span id="L532" class="LineNr">532 </span>  <span class="Delimiter">{</span>
+<span id="L533" class="LineNr">533 </span>  <span class="Conceal">¦</span> <a href='065duplex_list.mu.html#L29'>next</a>:&amp;:duplex-list:_elem <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> result
+<span id="L534" class="LineNr">534 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> <a href='065duplex_list.mu.html#L29'>next</a>
+<span id="L535" class="LineNr">535 </span>  <span class="Conceal">¦</span> result <span class="Special">&lt;-</span> copy <a href='065duplex_list.mu.html#L29'>next</a>
+<span id="L536" class="LineNr">536 </span>  <span class="Conceal">¦</span> <span class="muControl">loop</span>
+<span id="L537" class="LineNr">537 </span>  <span class="Delimiter">}</span>
+<span id="L538" class="LineNr">538 </span>]
+<span id="L539" class="LineNr">539 </span>
+<span id="L540" class="LineNr">540 </span><span class="Comment"># helper for debugging</span>
+<span id="L541" class="LineNr">541 </span><span class="muRecipe">def</span> <a href='065duplex_list.mu.html#L541'>dump-from</a> x:&amp;:duplex-list:_elem [
+<span id="L542" class="LineNr">542 </span>  <span class="Constant">local-scope</span>
+<span id="L543" class="LineNr">543 </span>  <span class="Constant">load-ingredients</span>
+<span id="L544" class="LineNr">544 </span>  $print x, <span class="Constant">[: ]</span>
+<span id="L545" class="LineNr">545 </span>  <span class="Delimiter">{</span>
+<span id="L546" class="LineNr">546 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> x
+<span id="L547" class="LineNr">547 </span>  <span class="Conceal">¦</span> c:_elem <span class="Special">&lt;-</span> get *x, <span class="Constant">value:offset</span>
+<span id="L548" class="LineNr">548 </span>  <span class="Conceal">¦</span> $print c, <span class="Constant">[ ]</span>
+<span id="L549" class="LineNr">549 </span>  <span class="Conceal">¦</span> x <span class="Special">&lt;-</span> <a href='065duplex_list.mu.html#L29'>next</a> x
+<span id="L550" class="LineNr">550 </span>  <span class="Conceal">¦</span> <span class="Delimiter">{</span>
+<span id="L551" class="LineNr">551 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> is-newline?:bool <span class="Special">&lt;-</span> equal c, <span class="Constant">10/newline</span>
+<span id="L552" class="LineNr">552 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">break-unless</span> is-newline?
+<span id="L553" class="LineNr">553 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> $print <span class="Constant">10/newline</span>
+<span id="L554" class="LineNr">554 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> $print x, <span class="Constant">[: ]</span>
+<span id="L555" class="LineNr">555 </span>  <span class="Conceal">¦</span> <span class="Delimiter">}</span>
+<span id="L556" class="LineNr">556 </span>  <span class="Conceal">¦</span> <span class="muControl">loop</span>
+<span id="L557" class="LineNr">557 </span>  <span class="Delimiter">}</span>
+<span id="L558" class="LineNr">558 </span>  $print <span class="Constant">10/newline</span>, <span class="Constant">[---]</span>, <span class="Constant">10/newline</span>
+<span id="L559" class="LineNr">559 </span>]
 </pre>
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