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<title>Mu - 064list.mu</title>
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.muScenario { color: #00af00; }
.Delimiter { color: #800080; }
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<pre id='vimCodeElement'>
<span class="Comment"># A list links up multiple objects together to make them easier to manage.</span>
<span class="Comment">#</span>
<span class="Comment"># The objects must be of the same type. If you want to store multiple types in</span>
<span class="Comment"># a single list, use an exclusive-container.</span>

<span class="muData">container</span> list:_elem [
  value:_elem
  next:&amp;:list:_elem
]

<span class="muRecipe">def</span> push x:_elem, in:&amp;:list:_elem<span class="muRecipe"> -&gt; </span>result:&amp;:list:_elem [
  <span class="Constant">local-scope</span>
  <span class="Constant">load-ingredients</span>
  result<span class="Special"> &lt;- </span>new <span class="Delimiter">{</span>(list _elem): <span class="muData">type</span><span class="Delimiter">}</span>
  *result<span class="Special"> &lt;- </span>merge x, in
]

<span class="muRecipe">def</span> first in:&amp;:list:_elem<span class="muRecipe"> -&gt; </span>result:_elem [
  <span class="Constant">local-scope</span>
  <span class="Constant">load-ingredients</span>
  result<span class="Special"> &lt;- </span>get *in, <span class="Constant">value:offset</span>
]

<span class="muRecipe">def</span> rest in:&amp;:list:_elem<span class="muRecipe"> -&gt; </span>result:&amp;:list:_elem/contained-in:in [
  <span class="Constant">local-scope</span>
  <span class="Constant">load-ingredients</span>
  result<span class="Special"> &lt;- </span>get *in, <span class="Constant">next:offset</span>
]

<span class="muScenario">scenario</span> list-handling [
  run [
    <span class="Constant">local-scope</span>
    x:&amp;:list:num<span class="Special"> &lt;- </span>push <span class="Constant">3</span>, <span class="Constant">0</span>
    x<span class="Special"> &lt;- </span>push <span class="Constant">4</span>, x
    x<span class="Special"> &lt;- </span>push <span class="Constant">5</span>, x
    <span class="Constant">10</span>:num/<span class="Special">raw &lt;- </span>first x
    x<span class="Special"> &lt;- </span>rest x
    <span class="Constant">11</span>:num/<span class="Special">raw &lt;- </span>first x
    x<span class="Special"> &lt;- </span>rest x
    <span class="Constant">12</span>:num/<span class="Special">raw &lt;- </span>first x
    <span class="Constant">20</span>:&amp;:list:num/<span class="Special">raw &lt;- </span>rest x
  ]
  memory-should-contain [
    <span class="Constant">10</span><span class="Special"> &lt;- </span><span class="Constant">5</span>
    <span class="Constant">11</span><span class="Special"> &lt;- </span><span class="Constant">4</span>
    <span class="Constant">12</span><span class="Special"> &lt;- </span><span class="Constant">3</span>
    <span class="Constant">20</span><span class="Special"> &lt;- </span><span class="Constant">0</span>  <span class="Comment"># nothing left</span>
  ]
]

<span class="muRecipe">def</span> length l:&amp;:list:_elem<span class="muRecipe"> -&gt; </span>result:num [
  <span class="Constant">local-scope</span>
  <span class="Constant">load-ingredients</span>
  <span class="muControl">return-unless</span> l, <span class="Constant">0</span>
  rest:&amp;:list:_elem<span class="Special"> &lt;- </span>rest l
  length-of-rest:num<span class="Special"> &lt;- </span>length rest
  result<span class="Special"> &lt;- </span>add length-of-rest, <span class="Constant">1</span>
]

<span class="Comment"># insert 'x' after 'in'</span>
<span class="muRecipe">def</span> insert x:_elem, in:&amp;:list:_elem<span class="muRecipe"> -&gt; </span>in:&amp;:list:_elem [
  <span class="Constant">local-scope</span>
  <span class="Constant">load-ingredients</span>
  new-node:&amp;:list:_elem<span class="Special"> &lt;- </span>new <span class="Delimiter">{</span>(list _elem): <span class="muData">type</span><span class="Delimiter">}</span>
  *new-node<span class="Special"> &lt;- </span>put *new-node, <span class="Constant">value:offset</span>, x
  next-node:&amp;:list:_elem<span class="Special"> &lt;- </span>get *in, <span class="Constant">next:offset</span>
  *in<span class="Special"> &lt;- </span>put *in, <span class="Constant">next:offset</span>, new-node
  *new-node<span class="Special"> &lt;- </span>put *new-node, <span class="Constant">next:offset</span>, next-node
]

<span class="muScenario">scenario</span> inserting-into-list [
  <span class="Constant">local-scope</span>
  list:&amp;:list:char<span class="Special"> &lt;- </span>push <span class="Constant">3</span>, <span class="Constant">0</span>
  list<span class="Special"> &lt;- </span>push <span class="Constant">4</span>, list
  list<span class="Special"> &lt;- </span>push <span class="Constant">5</span>, list
  run [
    list2:&amp;:list:char<span class="Special"> &lt;- </span>rest list  <span class="Comment"># inside list</span>
    list2<span class="Special"> &lt;- </span>insert <span class="Constant">6</span>, list2
    <span class="Comment"># check structure</span>
    list2<span class="Special"> &lt;- </span>copy list
    <span class="Constant">10</span>:char/<span class="Special">raw &lt;- </span>first list2
    list2<span class="Special"> &lt;- </span>rest list2
    <span class="Constant">11</span>:char/<span class="Special">raw &lt;- </span>first list2
    list2<span class="Special"> &lt;- </span>rest list2
    <span class="Constant">12</span>:char/<span class="Special">raw &lt;- </span>first list2
    list2<span class="Special"> &lt;- </span>rest list2
    <span class="Constant">13</span>:char/<span class="Special">raw &lt;- </span>first list2
  ]
  memory-should-contain [
    <span class="Constant">10</span><span class="Special"> &lt;- </span><span class="Constant">5</span>  <span class="Comment"># scanning next</span>
    <span class="Constant">11</span><span class="Special"> &lt;- </span><span class="Constant">4</span>
    <span class="Constant">12</span><span class="Special"> &lt;- </span><span class="Constant">6</span>  <span class="Comment"># inserted element</span>
    <span class="Constant">13</span><span class="Special"> &lt;- </span><span class="Constant">3</span>
  ]
]

<span class="muScenario">scenario</span> inserting-at-end-of-list [
  <span class="Constant">local-scope</span>
  list:&amp;:list:char<span class="Special"> &lt;- </span>push <span class="Constant">3</span>, <span class="Constant">0</span>
  list<span class="Special"> &lt;- </span>push <span class="Constant">4</span>, list
  list<span class="Special"> &lt;- </span>push <span class="Constant">5</span>, list
  run [
    list2:&amp;:list:char<span class="Special"> &lt;- </span>rest list  <span class="Comment"># inside list</span>
    list2<span class="Special"> &lt;- </span>rest list2  <span class="Comment"># now at end of list</span>
    list2<span class="Special"> &lt;- </span>insert <span class="Constant">6</span>, list2
    <span class="Comment"># check structure like before</span>
    list2<span class="Special"> &lt;- </span>copy list
    <span class="Constant">10</span>:char/<span class="Special">raw &lt;- </span>first list2
    list2<span class="Special"> &lt;- </span>rest list2
    <span class="Constant">11</span>:char/<span class="Special">raw &lt;- </span>first list2
    list2<span class="Special"> &lt;- </span>rest list2
    <span class="Constant">12</span>:char/<span class="Special">raw &lt;- </span>first list2
    list2<span class="Special"> &lt;- </span>rest list2
    <span class="Constant">13</span>:char/<span class="Special">raw &lt;- </span>first list2
  ]
  memory-should-contain [
    <span class="Constant">10</span><span class="Special"> &lt;- </span><span class="Constant">5</span>  <span class="Comment"># scanning next</span>
    <span class="Constant">11</span><span class="Special"> &lt;- </span><span class="Constant">4</span>
    <span class="Constant">12</span><span class="Special"> &lt;- </span><span class="Constant">3</span>
    <span class="Constant">13</span><span class="Special"> &lt;- </span><span class="Constant">6</span>  <span class="Comment"># inserted element</span>
  ]
]

<span class="muScenario">scenario</span> inserting-after-start-of-list [
  <span class="Constant">local-scope</span>
  list:&amp;:list:char<span class="Special"> &lt;- </span>push <span class="Constant">3</span>, <span class="Constant">0</span>
  list<span class="Special"> &lt;- </span>push <span class="Constant">4</span>, list
  list<span class="Special"> &lt;- </span>push <span class="Constant">5</span>, list
  run [
    list<span class="Special"> &lt;- </span>insert <span class="Constant">6</span>, list
    <span class="Comment"># check structure like before</span>
    list2:&amp;:list:char<span class="Special"> &lt;- </span>copy list
    <span class="Constant">10</span>:char/<span class="Special">raw &lt;- </span>first list2
    list2<span class="Special"> &lt;- </span>rest list2
    <span class="Constant">11</span>:char/<span class="Special">raw &lt;- </span>first list2
    list2<span class="Special"> &lt;- </span>rest list2
    <span class="Constant">12</span>:char/<span class="Special">raw &lt;- </span>first list2
    list2<span class="Special"> &lt;- </span>rest list2
    <span class="Constant">13</span>:char/<span class="Special">raw &lt;- </span>first list2
  ]
  memory-should-contain [
    <span class="Constant">10</span><span class="Special"> &lt;- </span><span class="Constant">5</span>  <span class="Comment"># scanning next</span>
    <span class="Constant">11</span><span class="Special"> &lt;- </span><span class="Constant">6</span>  <span class="Comment"># inserted element</span>
    <span class="Constant">12</span><span class="Special"> &lt;- </span><span class="Constant">4</span>
    <span class="Constant">13</span><span class="Special"> &lt;- </span><span class="Constant">3</span>
  ]
]

<span class="Comment"># remove 'x' from its surrounding list 'in'</span>
<span class="Comment">#</span>
<span class="Comment"># Returns null if and only if list is empty. Beware: in that case any other</span>
<span class="Comment"># pointers to the head are now invalid.</span>
<span class="muRecipe">def</span> remove x:&amp;:list:_elem/contained-in:in, in:&amp;:list:_elem<span class="muRecipe"> -&gt; </span>in:&amp;:list:_elem [
  <span class="Constant">local-scope</span>
  <span class="Constant">load-ingredients</span>
  <span class="Comment"># if 'x' is null, return</span>
  <span class="muControl">return-unless</span> x
  next-node:&amp;:list:_elem<span class="Special"> &lt;- </span>rest x
  <span class="Comment"># clear next pointer of 'x'</span>
  *x<span class="Special"> &lt;- </span>put *x, <span class="Constant">next:offset</span>, <span class="Constant">0</span>
  <span class="Comment"># if 'x' is at the head of 'in', return the new head</span>
  at-head?:bool<span class="Special"> &lt;- </span>equal x, in
  <span class="muControl">return-if</span> at-head?, next-node
  <span class="Comment"># compute prev-node</span>
  prev-node:&amp;:list:_elem<span class="Special"> &lt;- </span>copy in
  curr:&amp;:list:_elem<span class="Special"> &lt;- </span>rest prev-node
  <span class="Delimiter">{</span>
    <span class="muControl">return-unless</span> curr
    found?:bool<span class="Special"> &lt;- </span>equal curr, x
    <span class="muControl">break-if</span> found?
    prev-node<span class="Special"> &lt;- </span>copy curr
    curr<span class="Special"> &lt;- </span>rest curr
  <span class="Delimiter">}</span>
  <span class="Comment"># set its next pointer to skip 'x'</span>
  *prev-node<span class="Special"> &lt;- </span>put *prev-node, <span class="Constant">next:offset</span>, next-node
]

<span class="muScenario">scenario</span> removing-from-list [
  <span class="Constant">local-scope</span>
  list:&amp;:list:char<span class="Special"> &lt;- </span>push <span class="Constant">3</span>, <span class="Constant">0</span>
  list<span class="Special"> &lt;- </span>push <span class="Constant">4</span>, list
  list<span class="Special"> &lt;- </span>push <span class="Constant">5</span>, list
  run [
    list2:&amp;:list:char<span class="Special"> &lt;- </span>rest list  <span class="Comment"># second element</span>
    list<span class="Special"> &lt;- </span>remove list2, list
    <span class="Constant">10</span>:bool/<span class="Special">raw &lt;- </span>equal list2, <span class="Constant">0</span>
    <span class="Comment"># check structure like before</span>
    list2<span class="Special"> &lt;- </span>copy list
    <span class="Constant">11</span>:char/<span class="Special">raw &lt;- </span>first list2
    list2<span class="Special"> &lt;- </span>rest list2
    <span class="Constant">12</span>:char/<span class="Special">raw &lt;- </span>first list2
    <span class="Constant">20</span>:&amp;:list:char/<span class="Special">raw &lt;- </span>rest list2
  ]
  memory-should-contain [
    <span class="Constant">10</span><span class="Special"> &lt;- </span><span class="Constant">0</span>  <span class="Comment"># remove returned non-null</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 class="Constant">12</span><span class="Special"> &lt;- </span><span class="Constant">3</span>
    <span class="Constant">20</span><span class="Special"> &lt;- </span><span class="Constant">0</span>  <span class="Comment"># no more elements</span>
  ]
]

<span class="muScenario">scenario</span> removing-from-start-of-list [
  <span class="Constant">local-scope</span>
  list:&amp;:list:char<span class="Special"> &lt;- </span>push <span class="Constant">3</span>, <span class="Constant">0</span>
  list<span class="Special"> &lt;- </span>push <span class="Constant">4</span>, list
  list<span class="Special"> &lt;- </span>push <span class="Constant">5</span>, list
  run [
    list<span class="Special"> &lt;- </span>remove list, list
    <span class="Comment"># check structure like before</span>
    list2:&amp;:list:char<span class="Special"> &lt;- </span>copy list
    <span class="Constant">10</span>:char/<span class="Special">raw &lt;- </span>first list2
    list2<span class="Special"> &lt;- </span>rest list2
    <span class="Constant">11</span>:char/<span class="Special">raw &lt;- </span>first list2
    <span class="Constant">20</span>:&amp;:list:char/<span class="Special">raw &lt;- </span>rest list2
  ]
  memory-should-contain [
    <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 class="Constant">11</span><span class="Special"> &lt;- </span><span class="Constant">3</span>
    <span class="Constant">20</span><span class="Special"> &lt;- </span><span class="Constant">0</span>  <span class="Comment"># no more elements</span>
  ]
]

<span class="muScenario">scenario</span> removing-from-end-of-list [
  <span class="Constant">local-scope</span>
  list:&amp;:list:char<span class="Special"> &lt;- </span>push <span class="Constant">3</span>, <span class="Constant">0</span>
  list<span class="Special"> &lt;- </span>push <span class="Constant">4</span>, list
  list<span class="Special"> &lt;- </span>push <span class="Constant">5</span>, list
  run [
    <span class="Comment"># delete last element</span>
    list2:&amp;:list:char<span class="Special"> &lt;- </span>rest list
    list2<span class="Special"> &lt;- </span>rest list2
    list<span class="Special"> &lt;- </span>remove list2, list
    <span class="Constant">10</span>:bool/<span class="Special">raw &lt;- </span>equal list2, <span class="Constant">0</span>
    <span class="Comment"># check structure like before</span>
    list2<span class="Special"> &lt;- </span>copy list
    <span class="Constant">11</span>:char/<span class="Special">raw &lt;- </span>first list2
    list2<span class="Special"> &lt;- </span>rest list2
    <span class="Constant">12</span>:char/<span class="Special">raw &lt;- </span>first list2
    <span class="Constant">20</span>:&amp;:list:char/<span class="Special">raw &lt;- </span>rest list2
  ]
  memory-should-contain [
    <span class="Constant">10</span><span class="Special"> &lt;- </span><span class="Constant">0</span>  <span class="Comment"># remove returned non-null</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 class="Constant">12</span><span class="Special"> &lt;- </span><span class="Constant">4</span>
    <span class="Constant">20</span><span class="Special"> &lt;- </span><span class="Constant">0</span>  <span class="Comment"># no more elements</span>
  ]
]

<span class="muScenario">scenario</span> removing-from-singleton-list [
  <span class="Constant">local-scope</span>
  list:&amp;:list:char<span class="Special"> &lt;- </span>push <span class="Constant">3</span>, <span class="Constant">0</span>
  run [
    list<span class="Special"> &lt;- </span>remove list, list
    <span class="Constant">1</span>:num/<span class="Special">raw &lt;- </span>copy list
  ]
  memory-should-contain [
    <span class="Constant">1</span><span class="Special"> &lt;- </span><span class="Constant">0</span>  <span class="Comment"># back to an empty list</span>
  ]
]

<span class="Comment"># reverse the elements of a list</span>
<span class="Comment"># (contributed by Caleb Couch)</span>
<span class="muRecipe">def</span> reverse list:&amp;:list:_elem temp:&amp;:list:_elem<span class="muRecipe"> -&gt; </span>result:&amp;:list:_elem [
  <span class="Constant">local-scope</span>
  <span class="Constant">load-ingredients</span>
  <span class="muControl">reply-unless</span> list, temp
  object:_elem<span class="Special"> &lt;- </span>first, list
  list<span class="Special"> &lt;- </span>rest list
  temp<span class="Special"> &lt;- </span>push object, temp
  result<span class="Special"> &lt;- </span>reverse list, temp
]

<span class="muScenario">scenario</span> reverse-list [
  <span class="Constant">local-scope</span>
  list:&amp;:list:number<span class="Special"> &lt;- </span>push <span class="Constant">1</span>, <span class="Constant">0</span>
  list<span class="Special"> &lt;- </span>push <span class="Constant">2</span>, list
  list<span class="Special"> &lt;- </span>push <span class="Constant">3</span>, list
  run [
    stash <span class="Constant">[list:]</span>, list
    list<span class="Special"> &lt;- </span>reverse list
    stash <span class="Constant">[reversed:]</span>, list
  ]
  trace-should-contain [
    app: list: <span class="Constant">3</span><span class="muRecipe"> -&gt; </span><span class="Constant">2</span><span class="muRecipe"> -&gt; </span><span class="Constant">1</span>
    app: reversed: <span class="Constant">1</span><span class="muRecipe"> -&gt; </span><span class="Constant">2</span><span class="muRecipe"> -&gt; </span><span class="Constant">3</span>
  ]
]

<span class="muRecipe">def</span> to-text in:&amp;:list:_elem<span class="muRecipe"> -&gt; </span>result:text [
  <span class="Constant">local-scope</span>
  <span class="Constant">load-ingredients</span>
  buf:&amp;:buffer<span class="Special"> &lt;- </span>new-buffer <span class="Constant">80</span>
  buf<span class="Special"> &lt;- </span>to-buffer in, buf
  result<span class="Special"> &lt;- </span>buffer-to-array buf
]

<span class="Comment"># variant of 'to-text' which stops printing after a few elements (and so is robust to cycles)</span>
<span class="muRecipe">def</span> to-text-line in:&amp;:list:_elem<span class="muRecipe"> -&gt; </span>result:text [
  <span class="Constant">local-scope</span>
  <span class="Constant">load-ingredients</span>
  buf:&amp;:buffer<span class="Special"> &lt;- </span>new-buffer <span class="Constant">80</span>
  buf<span class="Special"> &lt;- </span>to-buffer in, buf, <span class="Constant">6</span>  <span class="Comment"># max elements to display</span>
  result<span class="Special"> &lt;- </span>buffer-to-array buf
]

<span class="muRecipe">def</span> to-buffer in:&amp;:list:_elem, buf:&amp;:buffer<span class="muRecipe"> -&gt; </span>buf:&amp;:buffer [
  <span class="Constant">local-scope</span>
  <span class="Constant">load-ingredients</span>
  <span class="Delimiter">{</span>
    <span class="muControl">break-if</span> in
    buf<span class="Special"> &lt;- </span>append buf, <span class="Constant">[[]</span>]
    <span class="muControl">return</span>
  <span class="Delimiter">}</span>
  <span class="Comment"># append in.value to buf</span>
  val:_elem<span class="Special"> &lt;- </span>get *in, <span class="Constant">value:offset</span>
  buf<span class="Special"> &lt;- </span>append buf, val
  <span class="Comment"># now prepare next</span>
  next:&amp;:list:_elem<span class="Special"> &lt;- </span>rest in
  nextn:num<span class="Special"> &lt;- </span>copy next
  <span class="muControl">return-unless</span> next
  buf<span class="Special"> &lt;- </span>append buf, <span class="Constant">[ -&gt; ]</span>
  <span class="Comment"># and recurse</span>
  remaining:num, optional-ingredient-found?:bool<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
  <span class="Delimiter">{</span>
    <span class="muControl">break-if</span> optional-ingredient-found?
    <span class="Comment"># unlimited recursion</span>
    buf<span class="Special"> &lt;- </span>to-buffer next, buf
    <span class="muControl">return</span>
  <span class="Delimiter">}</span>
  <span class="Delimiter">{</span>
    <span class="muControl">break-unless</span> remaining
    <span class="Comment"># limited recursion</span>
    remaining<span class="Special"> &lt;- </span>subtract remaining, <span class="Constant">1</span>
    buf<span class="Special"> &lt;- </span>to-buffer next, buf, remaining
    <span class="muControl">return</span>
  <span class="Delimiter">}</span>
  <span class="Comment"># past recursion depth; insert ellipses and stop</span>
  append buf, <span class="Constant">[...]</span>
]

<span class="muScenario">scenario</span> stash-empty-list [
  <span class="Constant">local-scope</span>
  x:&amp;:list:num<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
  run [
    stash x
  ]
  trace-should-contain [
    app: <span class="Constant">[]</span>
  ]
]
</pre>
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