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+<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
+<html>
+<head>
+<meta http-equiv="content-type" content="text/html; charset=UTF-8">
+<title>Mu - 061text.mu</title>
+<meta name="Generator" content="Vim/7.4">
+<meta name="plugin-version" content="vim7.4_v2">
+<meta name="syntax" content="none">
+<meta name="settings" content="use_css,pre_wrap,no_foldcolumn,expand_tabs,prevent_copy=">
+<meta name="colorscheme" content="minimal">
+<style type="text/css">
+<!--
+pre { white-space: pre-wrap; font-family: monospace; color: #eeeeee; background-color: #080808; }
+body { font-size: 12pt; font-family: monospace; color: #eeeeee; background-color: #080808; }
+* { font-size: 12pt; font-size: 1em; }
+.muRecipe { color: #ff8700; }
+.muData { color: #ffff00; }
+.muScenario { color: #00af00; }
+.Delimiter { color: #800080; }
+.Comment { color: #9090ff; }
+.Constant { color: #00a0a0; }
+.Special { color: #c00000; }
+.muControl { color: #c0a020; }
+-->
+</style>
+
+<script type='text/javascript'>
+<!--
+
+-->
+</script>
+</head>
+<body>
+<pre id='vimCodeElement'>
+<span class="Comment"># Some useful helpers for dealing with text (arrays of characters)</span>
+
+<span class="Comment"># to-text-line gets called implicitly in various places</span>
+<span class="Comment"># define it to be identical to 'to-text' by default</span>
+<span class="muRecipe">def</span> to-text-line x:_elem<span class="muRecipe"> -&gt; </span>y:address:array:character [
+  <span class="Constant">local-scope</span>
+  <span class="Constant">load-ingredients</span>
+  y<span class="Special"> &lt;- </span>to-text x
+]
+
+<span class="Comment"># variant for arrays (since we can't pass them around otherwise)</span>
+<span class="muRecipe">def</span> array-to-text-line x:address:array:_elem<span class="muRecipe"> -&gt; </span>y:address:array:character [
+  <span class="Constant">local-scope</span>
+  <span class="Constant">load-ingredients</span>
+  y<span class="Special"> &lt;- </span>to-text *x
+]
+
+<span class="muRecipe">def</span> equal a:address:array:character, b:address:array:character<span class="muRecipe"> -&gt; </span>result:boolean [
+  <span class="Constant">local-scope</span>
+  <span class="Constant">load-ingredients</span>
+  a-len:number<span class="Special"> &lt;- </span>length *a
+  b-len:number<span class="Special"> &lt;- </span>length *b
+  <span class="Comment"># compare lengths</span>
+  <span class="Delimiter">{</span>
+    trace <span class="Constant">99</span>, <span class="Constant">[text-equal]</span>, <span class="Constant">[comparing lengths]</span>
+    length-equal?:boolean<span class="Special"> &lt;- </span>equal a-len, b-len
+    <span class="muControl">break-if</span> length-equal?
+    <span class="muControl">return</span> <span class="Constant">0</span>
+  <span class="Delimiter">}</span>
+  <span class="Comment"># compare each corresponding character</span>
+  trace <span class="Constant">99</span>, <span class="Constant">[text-equal]</span>, <span class="Constant">[comparing characters]</span>
+  i:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
+  <span class="Delimiter">{</span>
+    done?:boolean<span class="Special"> &lt;- </span>greater-or-equal i, a-len
+    <span class="muControl">break-if</span> done?
+    a2:character<span class="Special"> &lt;- </span>index *a, i
+    b2:character<span class="Special"> &lt;- </span>index *b, i
+    <span class="Delimiter">{</span>
+      chars-match?:boolean<span class="Special"> &lt;- </span>equal a2, b2
+      <span class="muControl">break-if</span> chars-match?
+      <span class="muControl">return</span> <span class="Constant">0</span>
+    <span class="Delimiter">}</span>
+    i<span class="Special"> &lt;- </span>add i, <span class="Constant">1</span>
+    <span class="muControl">loop</span>
+  <span class="Delimiter">}</span>
+  <span class="muControl">return</span> <span class="Constant">1</span>
+]
+
+<span class="muScenario">scenario</span> text-equal-reflexive [
+  run [
+    <span class="Constant">local-scope</span>
+    x:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
+    <span class="Constant">10</span>:boolean/<span class="Special">raw &lt;- </span>equal x, x
+  ]
+  memory-should-contain [
+    <span class="Constant">10</span><span class="Special"> &lt;- </span><span class="Constant">1</span>  <span class="Comment"># x == x for all x</span>
+  ]
+]
+
+<span class="muScenario">scenario</span> text-equal-identical [
+  run [
+    <span class="Constant">local-scope</span>
+    x:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
+    y:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
+    <span class="Constant">10</span>:boolean/<span class="Special">raw &lt;- </span>equal x, y
+  ]
+  memory-should-contain [
+    <span class="Constant">10</span><span class="Special"> &lt;- </span><span class="Constant">1</span>  <span class="Comment"># abc == abc</span>
+  ]
+]
+
+<span class="muScenario">scenario</span> text-equal-distinct-lengths [
+  run [
+    <span class="Constant">local-scope</span>
+    x:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
+    y:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abcd]</span>
+    <span class="Constant">10</span>:boolean/<span class="Special">raw &lt;- </span>equal x, y
+  ]
+  memory-should-contain [
+    <span class="Constant">10</span><span class="Special"> &lt;- </span><span class="Constant">0</span>  <span class="Comment"># abc != abcd</span>
+  ]
+  trace-should-contain [
+    text-equal: comparing lengths
+  ]
+  trace-should-not-contain [
+    text-equal: comparing characters
+  ]
+]
+
+<span class="muScenario">scenario</span> text-equal-with-empty [
+  run [
+    <span class="Constant">local-scope</span>
+    x:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
+    y:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abcd]</span>
+    <span class="Constant">10</span>:boolean/<span class="Special">raw &lt;- </span>equal x, y
+  ]
+  memory-should-contain [
+    <span class="Constant">10</span><span class="Special"> &lt;- </span><span class="Constant">0</span>  <span class="Comment"># &quot;&quot; != abcd</span>
+  ]
+]
+
+<span class="muScenario">scenario</span> text-equal-common-lengths-but-distinct [
+  run [
+    <span class="Constant">local-scope</span>
+    x:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
+    y:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abd]</span>
+    <span class="Constant">10</span>:boolean/<span class="Special">raw &lt;- </span>equal x, y
+  ]
+  memory-should-contain [
+    <span class="Constant">10</span><span class="Special"> &lt;- </span><span class="Constant">0</span>  <span class="Comment"># abc != abd</span>
+  ]
+]
+
+<span class="Comment"># A new type to help incrementally construct texts.</span>
+<span class="muData">container</span> buffer [
+  length:number
+  data:address:array:character
+]
+
+<span class="muRecipe">def</span> new-buffer capacity:number<span class="muRecipe"> -&gt; </span>result:address:buffer [
+  <span class="Constant">local-scope</span>
+  <span class="Constant">load-ingredients</span>
+  result<span class="Special"> &lt;- </span>new <span class="Constant">buffer:type</span>
+  *result<span class="Special"> &lt;- </span>put *result, <span class="Constant">length:offset</span>, <span class="Constant">0</span>
+  data:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">character:type</span>, capacity
+  *result<span class="Special"> &lt;- </span>put *result, <span class="Constant">data:offset</span>, data
+  <span class="muControl">return</span> result
+]
+
+<span class="muRecipe">def</span> grow-buffer in:address:buffer<span class="muRecipe"> -&gt; </span>in:address:buffer [
+  <span class="Constant">local-scope</span>
+  <span class="Constant">load-ingredients</span>
+  <span class="Comment"># double buffer size</span>
+  olddata:address:array:character<span class="Special"> &lt;- </span>get *in, <span class="Constant">data:offset</span>
+  oldlen:number<span class="Special"> &lt;- </span>length *olddata
+  newlen:number<span class="Special"> &lt;- </span>multiply oldlen, <span class="Constant">2</span>
+  newdata:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">character:type</span>, newlen
+  *in<span class="Special"> &lt;- </span>put *in, <span class="Constant">data:offset</span>, newdata
+  <span class="Comment"># copy old contents</span>
+  i:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
+  <span class="Delimiter">{</span>
+    done?:boolean<span class="Special"> &lt;- </span>greater-or-equal i, oldlen
+    <span class="muControl">break-if</span> done?
+    src:character<span class="Special"> &lt;- </span>index *olddata, i
+    *newdata<span class="Special"> &lt;- </span>put-index *newdata, i, src
+    i<span class="Special"> &lt;- </span>add i, <span class="Constant">1</span>
+    <span class="muControl">loop</span>
+  <span class="Delimiter">}</span>
+]
+
+<span class="muRecipe">def</span> buffer-full? in:address:buffer<span class="muRecipe"> -&gt; </span>result:boolean [
+  <span class="Constant">local-scope</span>
+  <span class="Constant">load-ingredients</span>
+  len:number<span class="Special"> &lt;- </span>get *in, <span class="Constant">length:offset</span>
+  s:address:array:character<span class="Special"> &lt;- </span>get *in, <span class="Constant">data:offset</span>
+  capacity:number<span class="Special"> &lt;- </span>length *s
+  result<span class="Special"> &lt;- </span>greater-or-equal len, capacity
+]
+
+<span class="Comment"># most broadly applicable definition of append to a buffer: just call to-text</span>
+<span class="muRecipe">def</span> append buf:address:buffer, x:_elem<span class="muRecipe"> -&gt; </span>buf:address:buffer [
+  <span class="Constant">local-scope</span>
+  <span class="Constant">load-ingredients</span>
+  text:address:array:character<span class="Special"> &lt;- </span>to-text x
+  len:number<span class="Special"> &lt;- </span>length *text
+  i:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
+  <span class="Delimiter">{</span>
+    done?:boolean<span class="Special"> &lt;- </span>greater-or-equal i, len
+    <span class="muControl">break-if</span> done?
+    c:character<span class="Special"> &lt;- </span>index *text, i
+    buf<span class="Special"> &lt;- </span>append buf, c
+    i<span class="Special"> &lt;- </span>add i, <span class="Constant">1</span>
+    <span class="muControl">loop</span>
+  <span class="Delimiter">}</span>
+]
+
+<span class="muRecipe">def</span> append in:address:buffer, c:character<span class="muRecipe"> -&gt; </span>in:address:buffer [
+  <span class="Constant">local-scope</span>
+  <span class="Constant">load-ingredients</span>
+  len:number<span class="Special"> &lt;- </span>get *in, <span class="Constant">length:offset</span>
+  <span class="Delimiter">{</span>
+    <span class="Comment"># backspace? just drop last character if it exists and return</span>
+    backspace?:boolean<span class="Special"> &lt;- </span>equal c, <span class="Constant">8/backspace</span>
+    <span class="muControl">break-unless</span> backspace?
+    empty?:boolean<span class="Special"> &lt;- </span>lesser-or-equal len, <span class="Constant">0</span>
+    <span class="muControl">return-if</span> empty?
+    len<span class="Special"> &lt;- </span>subtract len, <span class="Constant">1</span>
+    *in<span class="Special"> &lt;- </span>put *in, <span class="Constant">length:offset</span>, len
+    <span class="muControl">return</span>
+  <span class="Delimiter">}</span>
+  <span class="Delimiter">{</span>
+    <span class="Comment"># grow buffer if necessary</span>
+    full?:boolean<span class="Special"> &lt;- </span>buffer-full? in
+    <span class="muControl">break-unless</span> full?
+    in<span class="Special"> &lt;- </span>grow-buffer in
+  <span class="Delimiter">}</span>
+  s:address:array:character<span class="Special"> &lt;- </span>get *in, <span class="Constant">data:offset</span>
+  *s<span class="Special"> &lt;- </span>put-index *s, len, c
+  len<span class="Special"> &lt;- </span>add len, <span class="Constant">1</span>
+  *in<span class="Special"> &lt;- </span>put *in, <span class="Constant">length:offset</span>, len
+]
+
+<span class="muScenario">scenario</span> buffer-append-works [
+  run [
+    <span class="Constant">local-scope</span>
+    x:address:buffer<span class="Special"> &lt;- </span>new-buffer <span class="Constant">3</span>
+    s1:address:array:character<span class="Special"> &lt;- </span>get *x, <span class="Constant">data:offset</span>
+    c:character<span class="Special"> &lt;- </span>copy <span class="Constant">97/a</span>
+    x<span class="Special"> &lt;- </span>append x, c
+    c:character<span class="Special"> &lt;- </span>copy <span class="Constant">98/b</span>
+    x<span class="Special"> &lt;- </span>append x, c
+    c:character<span class="Special"> &lt;- </span>copy <span class="Constant">99/c</span>
+    x<span class="Special"> &lt;- </span>append x, c
+    s2:address:array:character<span class="Special"> &lt;- </span>get *x, <span class="Constant">data:offset</span>
+    <span class="Constant">10</span>:boolean/<span class="Special">raw &lt;- </span>equal s1, s2
+    <span class="Constant">11</span>:array:character/<span class="Special">raw &lt;- </span>copy *s2
+<span class="Constant">    +buffer-filled</span>
+    c:character<span class="Special"> &lt;- </span>copy <span class="Constant">100/d</span>
+    x<span class="Special"> &lt;- </span>append x, c
+    s3:address:array:character<span class="Special"> &lt;- </span>get *x, <span class="Constant">data:offset</span>
+    <span class="Constant">20</span>:boolean/<span class="Special">raw &lt;- </span>equal s1, s3
+    <span class="Constant">21</span>:number/<span class="Special">raw &lt;- </span>get *x, <span class="Constant">length:offset</span>
+    <span class="Constant">30</span>:array:character/<span class="Special">raw &lt;- </span>copy *s3
+  ]
+  memory-should-contain [
+    <span class="Comment"># before +buffer-filled</span>
+    <span class="Constant">10</span><span class="Special"> &lt;- </span><span class="Constant">1</span>   <span class="Comment"># no change in data pointer</span>
+    <span class="Constant">11</span><span class="Special"> &lt;- </span><span class="Constant">3</span>   <span class="Comment"># size of data</span>
+    <span class="Constant">12</span><span class="Special"> &lt;- </span><span class="Constant">97</span>  <span class="Comment"># data</span>
+    <span class="Constant">13</span><span class="Special"> &lt;- </span><span class="Constant">98</span>
+    <span class="Constant">14</span><span class="Special"> &lt;- </span><span class="Constant">99</span>
+    <span class="Comment"># in the end</span>
+    <span class="Constant">20</span><span class="Special"> &lt;- </span><span class="Constant">0</span>   <span class="Comment"># data pointer has grown</span>
+    <span class="Constant">21</span><span class="Special"> &lt;- </span><span class="Constant">4</span>   <span class="Comment"># final length</span>
+    <span class="Constant">30</span><span class="Special"> &lt;- </span><span class="Constant">6</span>   <span class="Comment"># but data's capacity has doubled</span>
+    <span class="Constant">31</span><span class="Special"> &lt;- </span><span class="Constant">97</span>  <span class="Comment"># data</span>
+    <span class="Constant">32</span><span class="Special"> &lt;- </span><span class="Constant">98</span>
+    <span class="Constant">33</span><span class="Special"> &lt;- </span><span class="Constant">99</span>
+    <span class="Constant">34</span><span class="Special"> &lt;- </span><span class="Constant">100</span>
+    <span class="Constant">35</span><span class="Special"> &lt;- </span><span class="Constant">0</span>
+    <span class="Constant">36</span><span class="Special"> &lt;- </span><span class="Constant">0</span>
+  ]
+]
+
+<span class="muScenario">scenario</span> buffer-append-handles-backspace [
+  run [
+    <span class="Constant">local-scope</span>
+    x:address:buffer<span class="Special"> &lt;- </span>new-buffer <span class="Constant">3</span>
+    c:character<span class="Special"> &lt;- </span>copy <span class="Constant">97/a</span>
+    x<span class="Special"> &lt;- </span>append x, c
+    c:character<span class="Special"> &lt;- </span>copy <span class="Constant">98/b</span>
+    x<span class="Special"> &lt;- </span>append x, c
+    c:character<span class="Special"> &lt;- </span>copy <span class="Constant">8/backspace</span>
+    x<span class="Special"> &lt;- </span>append x, c
+    s:address:array:character<span class="Special"> &lt;- </span>buffer-to-array x
+    <span class="Constant">10</span>:array:character/<span class="Special">raw &lt;- </span>copy *s
+  ]
+  memory-should-contain [
+    <span class="Constant">10</span><span class="Special"> &lt;- </span><span class="Constant">1</span>   <span class="Comment"># length</span>
+    <span class="Constant">11</span><span class="Special"> &lt;- </span><span class="Constant">97</span>  <span class="Comment"># contents</span>
+    <span class="Constant">12</span><span class="Special"> &lt;- </span><span class="Constant">0</span>
+  ]
+]
+
+<span class="muRecipe">def</span> buffer-to-array in:address:buffer<span class="muRecipe"> -&gt; </span>result:address:array:character [
+  <span class="Constant">local-scope</span>
+  <span class="Constant">load-ingredients</span>
+  <span class="Delimiter">{</span>
+    <span class="Comment"># propagate null buffer</span>
+    <span class="muControl">break-if</span> in
+    <span class="muControl">return</span> <span class="Constant">0</span>
+  <span class="Delimiter">}</span>
+  len:number<span class="Special"> &lt;- </span>get *in, <span class="Constant">length:offset</span>
+  s:address:array:character<span class="Special"> &lt;- </span>get *in, <span class="Constant">data:offset</span>
+  <span class="Comment"># we can't just return s because it is usually the wrong length</span>
+  result<span class="Special"> &lt;- </span>new <span class="Constant">character:type</span>, len
+  i:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
+  <span class="Delimiter">{</span>
+    done?:boolean<span class="Special"> &lt;- </span>greater-or-equal i, len
+    <span class="muControl">break-if</span> done?
+    src:character<span class="Special"> &lt;- </span>index *s, i
+    *result<span class="Special"> &lt;- </span>put-index *result, i, src
+    i<span class="Special"> &lt;- </span>add i, <span class="Constant">1</span>
+    <span class="muControl">loop</span>
+  <span class="Delimiter">}</span>
+]
+
+<span class="muRecipe">def</span> append a:address:array:character, b:address:array:character<span class="muRecipe"> -&gt; </span>result:address:array:character [
+  <span class="Constant">local-scope</span>
+  <span class="Constant">load-ingredients</span>
+  <span class="Comment"># handle null addresses</span>
+  <span class="muControl">reply-unless</span> a, b
+  <span class="muControl">reply-unless</span> b, a
+  <span class="Comment"># result = new character[a.length + b.length]</span>
+  a-len:number<span class="Special"> &lt;- </span>length *a
+  b-len:number<span class="Special"> &lt;- </span>length *b
+  result-len:number<span class="Special"> &lt;- </span>add a-len, b-len
+  result<span class="Special"> &lt;- </span>new <span class="Constant">character:type</span>, result-len
+  <span class="Comment"># copy a into result</span>
+  result-idx:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
+  i:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
+  <span class="Delimiter">{</span>
+    <span class="Comment"># while i &lt; a.length</span>
+    a-done?:boolean<span class="Special"> &lt;- </span>greater-or-equal i, a-len
+    <span class="muControl">break-if</span> a-done?
+    <span class="Comment"># result[result-idx] = a[i]</span>
+    in:character<span class="Special"> &lt;- </span>index *a, i
+    *result<span class="Special"> &lt;- </span>put-index *result, result-idx, in
+    i<span class="Special"> &lt;- </span>add i, <span class="Constant">1</span>
+    result-idx<span class="Special"> &lt;- </span>add result-idx, <span class="Constant">1</span>
+    <span class="muControl">loop</span>
+  <span class="Delimiter">}</span>
+  <span class="Comment"># copy b into result</span>
+  i<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
+  <span class="Delimiter">{</span>
+    <span class="Comment"># while i &lt; b.length</span>
+    b-done?:boolean<span class="Special"> &lt;- </span>greater-or-equal i, b-len
+    <span class="muControl">break-if</span> b-done?
+    <span class="Comment"># result[result-idx] = a[i]</span>
+    in:character<span class="Special"> &lt;- </span>index *b, i
+    *result<span class="Special"> &lt;- </span>put-index *result, result-idx, in
+    i<span class="Special"> &lt;- </span>add i, <span class="Constant">1</span>
+    result-idx<span class="Special"> &lt;- </span>add result-idx, <span class="Constant">1</span>
+    <span class="muControl">loop</span>
+  <span class="Delimiter">}</span>
+]
+
+<span class="muScenario">scenario</span> text-append-1 [
+  run [
+    <span class="Constant">local-scope</span>
+    x:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[hello,]</span>
+    y:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[ world!]</span>
+    z:address:array:character<span class="Special"> &lt;- </span>append x, y
+    <span class="Constant">10</span>:array:character/<span class="Special">raw &lt;- </span>copy *z
+  ]
+  memory-should-contain [
+    <span class="Constant">10</span>:array:character<span class="Special"> &lt;- </span><span class="Constant">[hello, world!]</span>
+  ]
+]
+
+<span class="muScenario">scenario</span> text-append-null [
+  run [
+    <span class="Constant">local-scope</span>
+    x:address:array:character<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
+    y:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[ world!]</span>
+    z:address:array:character<span class="Special"> &lt;- </span>append x, y
+    <span class="Constant">10</span>:array:character/<span class="Special">raw &lt;- </span>copy *z
+  ]
+  memory-should-contain [
+    <span class="Constant">10</span>:array:character<span class="Special"> &lt;- </span><span class="Constant">[ world!]</span>
+  ]
+]
+
+<span class="muScenario">scenario</span> text-append-null-2 [
+  run [
+    <span class="Constant">local-scope</span>
+    x:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[hello,]</span>
+    y:address:array:character<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
+    z:address:array:character<span class="Special"> &lt;- </span>append x, y
+    <span class="Constant">10</span>:array:character/<span class="Special">raw &lt;- </span>copy *z
+  ]
+  memory-should-contain [
+    <span class="Constant">10</span>:array:character<span class="Special"> &lt;- </span><span class="Constant">[hello,]</span>
+  ]
+]
+
+<span class="muScenario">scenario</span> replace-character-in-text [
+  run [
+    <span class="Constant">local-scope</span>
+    x:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
+    x<span class="Special"> &lt;- </span>replace x, <span class="Constant">98/b</span>, <span class="Constant">122/z</span>
+    <span class="Constant">10</span>:array:character/<span class="Special">raw &lt;- </span>copy *x
+  ]
+  memory-should-contain [
+    <span class="Constant">10</span>:array:character<span class="Special"> &lt;- </span><span class="Constant">[azc]</span>
+  ]
+]
+
+<span class="muRecipe">def</span> replace s:address:array:character, oldc:character, newc:character, from:number/optional<span class="muRecipe"> -&gt; </span>s:address:array:character [
+  <span class="Constant">local-scope</span>
+  <span class="Constant">load-ingredients</span>
+  len:number<span class="Special"> &lt;- </span>length *s
+  i:number<span class="Special"> &lt;- </span>find-next s, oldc, from
+  done?:boolean<span class="Special"> &lt;- </span>greater-or-equal i, len
+  <span class="muControl">return-if</span> done?, s/same-as-ingredient:<span class="Constant">0</span>
+  *s<span class="Special"> &lt;- </span>put-index *s, i, newc
+  i<span class="Special"> &lt;- </span>add i, <span class="Constant">1</span>
+  s<span class="Special"> &lt;- </span>replace s, oldc, newc, i
+]
+
+<span class="muScenario">scenario</span> replace-character-at-start [
+  run [
+    <span class="Constant">local-scope</span>
+    x:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
+    x<span class="Special"> &lt;- </span>replace x, <span class="Constant">97/a</span>, <span class="Constant">122/z</span>
+    <span class="Constant">10</span>:array:character/<span class="Special">raw &lt;- </span>copy *x
+  ]
+  memory-should-contain [
+    <span class="Constant">10</span>:array:character<span class="Special"> &lt;- </span><span class="Constant">[zbc]</span>
+  ]
+]
+
+<span class="muScenario">scenario</span> replace-character-at-end [
+  run [
+    <span class="Constant">local-scope</span>
+    x:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
+    x<span class="Special"> &lt;- </span>replace x, <span class="Constant">99/c</span>, <span class="Constant">122/z</span>
+    <span class="Constant">10</span>:array:character/<span class="Special">raw &lt;- </span>copy *x
+  ]
+  memory-should-contain [
+    <span class="Constant">10</span>:array:character<span class="Special"> &lt;- </span><span class="Constant">[abz]</span>
+  ]
+]
+
+<span class="muScenario">scenario</span> replace-character-missing [
+  run [
+    <span class="Constant">local-scope</span>
+    x:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
+    x<span class="Special"> &lt;- </span>replace x, <span class="Constant">100/d</span>, <span class="Constant">122/z</span>
+    <span class="Constant">10</span>:array:character/<span class="Special">raw &lt;- </span>copy *x
+  ]
+  memory-should-contain [
+    <span class="Constant">10</span>:array:character<span class="Special"> &lt;- </span><span class="Constant">[abc]</span>
+  ]
+]
+
+<span class="muScenario">scenario</span> replace-all-characters [
+  run [
+    <span class="Constant">local-scope</span>
+    x:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[banana]</span>
+    x<span class="Special"> &lt;- </span>replace x, <span class="Constant">97/a</span>, <span class="Constant">122/z</span>
+    <span class="Constant">10</span>:array:character/<span class="Special">raw &lt;- </span>copy *x
+  ]
+  memory-should-contain [
+    <span class="Constant">10</span>:array:character<span class="Special"> &lt;- </span><span class="Constant">[bznznz]</span>
+  ]
+]
+
+<span class="Comment"># replace underscores in first with remaining args</span>
+<span class="muRecipe">def</span> interpolate template:address:array:character<span class="muRecipe"> -&gt; </span>result:address:array:character [
+  <span class="Constant">local-scope</span>
+  <span class="Constant">load-ingredients</span>  <span class="Comment"># consume just the template</span>
+  <span class="Comment"># compute result-len, space to allocate for result</span>
+  tem-len:number<span class="Special"> &lt;- </span>length *template
+  result-len:number<span class="Special"> &lt;- </span>copy tem-len
+  <span class="Delimiter">{</span>
+    <span class="Comment"># while ingredients remain</span>
+    a:address:array:character, arg-received?:boolean<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
+    <span class="muControl">break-unless</span> arg-received?
+    <span class="Comment"># result-len = result-len + arg.length - 1 (for the 'underscore' being replaced)</span>
+    a-len:number<span class="Special"> &lt;- </span>length *a
+    result-len<span class="Special"> &lt;- </span>add result-len, a-len
+    result-len<span class="Special"> &lt;- </span>subtract result-len, <span class="Constant">1</span>
+    <span class="muControl">loop</span>
+  <span class="Delimiter">}</span>
+  <span class="Constant">rewind-ingredients</span>
+  _<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>  <span class="Comment"># skip template</span>
+  result<span class="Special"> &lt;- </span>new <span class="Constant">character:type</span>, result-len
+  <span class="Comment"># repeatedly copy sections of template and 'holes' into result</span>
+  result-idx:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
+  i:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
+  <span class="Delimiter">{</span>
+    <span class="Comment"># while arg received</span>
+    a:address:array:character, arg-received?:boolean<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
+    <span class="muControl">break-unless</span> arg-received?
+    <span class="Comment"># copy template into result until '_'</span>
+    <span class="Delimiter">{</span>
+      <span class="Comment"># while i &lt; template.length</span>
+      tem-done?:boolean<span class="Special"> &lt;- </span>greater-or-equal i, tem-len
+      <span class="muControl">break-if</span> tem-done?, <span class="Constant">+done:label</span>
+      <span class="Comment"># while template[i] != '_'</span>
+      in:character<span class="Special"> &lt;- </span>index *template, i
+      underscore?:boolean<span class="Special"> &lt;- </span>equal in, <span class="Constant">95/_</span>
+      <span class="muControl">break-if</span> underscore?
+      <span class="Comment"># result[result-idx] = template[i]</span>
+      *result<span class="Special"> &lt;- </span>put-index *result, result-idx, in
+      i<span class="Special"> &lt;- </span>add i, <span class="Constant">1</span>
+      result-idx<span class="Special"> &lt;- </span>add result-idx, <span class="Constant">1</span>
+      <span class="muControl">loop</span>
+    <span class="Delimiter">}</span>
+    <span class="Comment"># copy 'a' into result</span>
+    j:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
+    <span class="Delimiter">{</span>
+      <span class="Comment"># while j &lt; a.length</span>
+      arg-done?:boolean<span class="Special"> &lt;- </span>greater-or-equal j, a-len
+      <span class="muControl">break-if</span> arg-done?
+      <span class="Comment"># result[result-idx] = a[j]</span>
+      in:character<span class="Special"> &lt;- </span>index *a, j
+      *result<span class="Special"> &lt;- </span>put-index *result, result-idx, in
+      j<span class="Special"> &lt;- </span>add j, <span class="Constant">1</span>
+      result-idx<span class="Special"> &lt;- </span>add result-idx, <span class="Constant">1</span>
+      <span class="muControl">loop</span>
+    <span class="Delimiter">}</span>
+    <span class="Comment"># skip '_' in template</span>
+    i<span class="Special"> &lt;- </span>add i, <span class="Constant">1</span>
+    <span class="muControl">loop</span>  <span class="Comment"># interpolate next arg</span>
+  <span class="Delimiter">}</span>
+<span class="Constant">  +done</span>
+  <span class="Comment"># done with holes; copy rest of template directly into result</span>
+  <span class="Delimiter">{</span>
+    <span class="Comment"># while i &lt; template.length</span>
+    tem-done?:boolean<span class="Special"> &lt;- </span>greater-or-equal i, tem-len
+    <span class="muControl">break-if</span> tem-done?
+    <span class="Comment"># result[result-idx] = template[i]</span>
+    in:character<span class="Special"> &lt;- </span>index *template, i
+    *result<span class="Special"> &lt;- </span>put-index *result, result-idx, in
+    i<span class="Special"> &lt;- </span>add i, <span class="Constant">1</span>
+    result-idx<span class="Special"> &lt;- </span>add result-idx, <span class="Constant">1</span>
+    <span class="muControl">loop</span>
+  <span class="Delimiter">}</span>
+]
+
+<span class="muScenario">scenario</span> interpolate-works [
+  run [
+    <span class="Constant">local-scope</span>
+    x:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc_ghi]</span>
+    y:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[def]</span>
+    z:address:array:character<span class="Special"> &lt;- </span>interpolate x, y
+    <span class="Constant">10</span>:array:character/<span class="Special">raw &lt;- </span>copy *z
+  ]
+  memory-should-contain [
+    <span class="Constant">10</span>:array:character<span class="Special"> &lt;- </span><span class="Constant">[abcdefghi]</span>
+  ]
+]
+
+<span class="muScenario">scenario</span> interpolate-at-start [
+  run [
+    <span class="Constant">local-scope</span>
+    x:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[_, hello!]</span>
+    y:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
+    z:address:array:character<span class="Special"> &lt;- </span>interpolate x, y
+    <span class="Constant">10</span>:array:character/<span class="Special">raw &lt;- </span>copy *z
+  ]
+  memory-should-contain [
+    <span class="Constant">10</span>:array:character<span class="Special"> &lt;- </span><span class="Constant">[abc, hello!]</span>
+    <span class="Constant">22</span><span class="Special"> &lt;- </span><span class="Constant">0</span>  <span class="Comment"># out of bounds</span>
+  ]
+]
+
+<span class="muScenario">scenario</span> interpolate-at-end [
+  run [
+    x:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[hello, _]</span>
+    y:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
+    z:address:array:character<span class="Special"> &lt;- </span>interpolate x, y
+    <span class="Constant">10</span>:array:character/<span class="Special">raw &lt;- </span>copy *z
+  ]
+  memory-should-contain [
+    <span class="Constant">10</span>:array:character<span class="Special"> &lt;- </span><span class="Constant">[hello, abc]</span>
+  ]
+]
+
+<span class="Comment"># result:boolean &lt;- space? c:character</span>
+<span class="muRecipe">def</span> space? c:character<span class="muRecipe"> -&gt; </span>result:boolean [
+  <span class="Constant">local-scope</span>
+  <span class="Constant">load-ingredients</span>
+  <span class="Comment"># most common case first</span>
+  result<span class="Special"> &lt;- </span>equal c, <span class="Constant">32/space</span>
+  <span class="muControl">return-if</span> result
+  result<span class="Special"> &lt;- </span>equal c, <span class="Constant">10/newline</span>
+  <span class="muControl">return-if</span> result
+  result<span class="Special"> &lt;- </span>equal c, <span class="Constant">9/tab</span>
+  <span class="muControl">return-if</span> result
+  result<span class="Special"> &lt;- </span>equal c, <span class="Constant">13/carriage-return</span>
+  <span class="muControl">return-if</span> result
+  <span class="Comment"># remaining uncommon cases in sorted order</span>
+  <span class="Comment"># <a href="http://unicode.org">http://unicode.org</a> code-points in unicode-set Z and Pattern_White_Space</span>
+  result<span class="Special"> &lt;- </span>equal c, <span class="Constant">11/ctrl-k</span>
+  <span class="muControl">return-if</span> result
+  result<span class="Special"> &lt;- </span>equal c, <span class="Constant">12/ctrl-l</span>
+  <span class="muControl">return-if</span> result
+  result<span class="Special"> &lt;- </span>equal c, <span class="Constant">133/ctrl-0085</span>
+  <span class="muControl">return-if</span> result
+  result<span class="Special"> &lt;- </span>equal c, <span class="Constant">160/no-break-space</span>
+  <span class="muControl">return-if</span> result
+  result<span class="Special"> &lt;- </span>equal c, <span class="Constant">5760/ogham-space-mark</span>
+  <span class="muControl">return-if</span> result
+  result<span class="Special"> &lt;- </span>equal c, <span class="Constant">8192/en-quad</span>
+  <span class="muControl">return-if</span> result
+  result<span class="Special"> &lt;- </span>equal c, <span class="Constant">8193/em-quad</span>
+  <span class="muControl">return-if</span> result
+  result<span class="Special"> &lt;- </span>equal c, <span class="Constant">8194/en-space</span>
+  <span class="muControl">return-if</span> result
+  result<span class="Special"> &lt;- </span>equal c, <span class="Constant">8195/em-space</span>
+  <span class="muControl">return-if</span> result
+  result<span class="Special"> &lt;- </span>equal c, <span class="Constant">8196/three-per-em-space</span>
+  <span class="muControl">return-if</span> result
+  result<span class="Special"> &lt;- </span>equal c, <span class="Constant">8197/four-per-em-space</span>
+  <span class="muControl">return-if</span> result
+  result<span class="Special"> &lt;- </span>equal c, <span class="Constant">8198/six-per-em-space</span>
+  <span class="muControl">return-if</span> result
+  result<span class="Special"> &lt;- </span>equal c, <span class="Constant">8199/figure-space</span>
+  <span class="muControl">return-if</span> result
+  result<span class="Special"> &lt;- </span>equal c, <span class="Constant">8200/punctuation-space</span>
+  <span class="muControl">return-if</span> result
+  result<span class="Special"> &lt;- </span>equal c, <span class="Constant">8201/thin-space</span>
+  <span class="muControl">return-if</span> result
+  result<span class="Special"> &lt;- </span>equal c, <span class="Constant">8202/hair-space</span>
+  <span class="muControl">return-if</span> result
+  result<span class="Special"> &lt;- </span>equal c, <span class="Constant">8206/left-to-right</span>
+  <span class="muControl">return-if</span> result
+  result<span class="Special"> &lt;- </span>equal c, <span class="Constant">8207/right-to-left</span>
+  <span class="muControl">return-if</span> result
+  result<span class="Special"> &lt;- </span>equal c, <span class="Constant">8232/line-separator</span>
+  <span class="muControl">return-if</span> result
+  result<span class="Special"> &lt;- </span>equal c, <span class="Constant">8233/paragraph-separator</span>
+  <span class="muControl">return-if</span> result
+  result<span class="Special"> &lt;- </span>equal c, <span class="Constant">8239/narrow-no-break-space</span>
+  <span class="muControl">return-if</span> result
+  result<span class="Special"> &lt;- </span>equal c, <span class="Constant">8287/medium-mathematical-space</span>
+  <span class="muControl">return-if</span> result
+  result<span class="Special"> &lt;- </span>equal c, <span class="Constant">12288/ideographic-space</span>
+]
+
+<span class="muRecipe">def</span> trim s:address:array:character<span class="muRecipe"> -&gt; </span>result:address:array:character [
+  <span class="Constant">local-scope</span>
+  <span class="Constant">load-ingredients</span>
+  len:number<span class="Special"> &lt;- </span>length *s
+  <span class="Comment"># left trim: compute start</span>
+  start:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
+  <span class="Delimiter">{</span>
+    <span class="Delimiter">{</span>
+      at-end?:boolean<span class="Special"> &lt;- </span>greater-or-equal start, len
+      <span class="muControl">break-unless</span> at-end?
+      result<span class="Special"> &lt;- </span>new <span class="Constant">character:type</span>, <span class="Constant">0</span>
+      <span class="muControl">return</span>
+    <span class="Delimiter">}</span>
+    curr:character<span class="Special"> &lt;- </span>index *s, start
+    whitespace?:boolean<span class="Special"> &lt;- </span>space? curr
+    <span class="muControl">break-unless</span> whitespace?
+    start<span class="Special"> &lt;- </span>add start, <span class="Constant">1</span>
+    <span class="muControl">loop</span>
+  <span class="Delimiter">}</span>
+  <span class="Comment"># right trim: compute end</span>
+  end:number<span class="Special"> &lt;- </span>subtract len, <span class="Constant">1</span>
+  <span class="Delimiter">{</span>
+    not-at-start?:boolean<span class="Special"> &lt;- </span>greater-than end, start
+    assert not-at-start?, <span class="Constant">[end ran up against start]</span>
+    curr:character<span class="Special"> &lt;- </span>index *s, end
+    whitespace?:boolean<span class="Special"> &lt;- </span>space? curr
+    <span class="muControl">break-unless</span> whitespace?
+    end<span class="Special"> &lt;- </span>subtract end, <span class="Constant">1</span>
+    <span class="muControl">loop</span>
+  <span class="Delimiter">}</span>
+  <span class="Comment"># result = new character[end+1 - start]</span>
+  new-len:number<span class="Special"> &lt;- </span>subtract end, start, <span class="Constant">-1</span>
+  result:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">character:type</span>, new-len
+  <span class="Comment"># copy the untrimmed parts between start and end</span>
+  i:number<span class="Special"> &lt;- </span>copy start
+  j:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
+  <span class="Delimiter">{</span>
+    <span class="Comment"># while i &lt;= end</span>
+    done?:boolean<span class="Special"> &lt;- </span>greater-than i, end
+    <span class="muControl">break-if</span> done?
+    <span class="Comment"># result[j] = s[i]</span>
+    src:character<span class="Special"> &lt;- </span>index *s, i
+    *result<span class="Special"> &lt;- </span>put-index *result, j, src
+    i<span class="Special"> &lt;- </span>add i, <span class="Constant">1</span>
+    j<span class="Special"> &lt;- </span>add j, <span class="Constant">1</span>
+    <span class="muControl">loop</span>
+  <span class="Delimiter">}</span>
+]
+
+<span class="muScenario">scenario</span> trim-unmodified [
+  run [
+    <span class="Constant">local-scope</span>
+    x:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
+    y:address:array:character<span class="Special"> &lt;- </span>trim x
+    <span class="Constant">1</span>:array:character/<span class="Special">raw &lt;- </span>copy *y
+  ]
+  memory-should-contain [
+    <span class="Constant">1</span>:array:character<span class="Special"> &lt;- </span><span class="Constant">[abc]</span>
+  ]
+]
+
+<span class="muScenario">scenario</span> trim-left [
+  run [
+    <span class="Constant">local-scope</span>
+    x:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[  abc]</span>
+    y:address:array:character<span class="Special"> &lt;- </span>trim x
+    <span class="Constant">1</span>:array:character/<span class="Special">raw &lt;- </span>copy *y
+  ]
+  memory-should-contain [
+    <span class="Constant">1</span>:array:character<span class="Special"> &lt;- </span><span class="Constant">[abc]</span>
+  ]
+]
+
+<span class="muScenario">scenario</span> trim-right [
+  run [
+    <span class="Constant">local-scope</span>
+    x:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc  ]</span>
+    y:address:array:character<span class="Special"> &lt;- </span>trim x
+    <span class="Constant">1</span>:array:character/<span class="Special">raw &lt;- </span>copy *y
+  ]
+  memory-should-contain [
+    <span class="Constant">1</span>:array:character<span class="Special"> &lt;- </span><span class="Constant">[abc]</span>
+  ]
+]
+
+<span class="muScenario">scenario</span> trim-left-right [
+  run [
+    <span class="Constant">local-scope</span>
+    x:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[  abc   ]</span>
+    y:address:array:character<span class="Special"> &lt;- </span>trim x
+    <span class="Constant">1</span>:array:character/<span class="Special">raw &lt;- </span>copy *y
+  ]
+  memory-should-contain [
+    <span class="Constant">1</span>:array:character<span class="Special"> &lt;- </span><span class="Constant">[abc]</span>
+  ]
+]
+
+<span class="muScenario">scenario</span> trim-newline-tab [
+  run [
+    <span class="Constant">local-scope</span>
+    x:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[  abc</span>
+<span class="Constant">]</span>
+    y:address:array:character<span class="Special"> &lt;- </span>trim x
+    <span class="Constant">1</span>:array:character/<span class="Special">raw &lt;- </span>copy *y
+  ]
+  memory-should-contain [
+    <span class="Constant">1</span>:array:character<span class="Special"> &lt;- </span><span class="Constant">[abc]</span>
+  ]
+]
+
+<span class="muRecipe">def</span> find-next text:address:array:character, pattern:character, idx:number<span class="muRecipe"> -&gt; </span>next-index:number [
+  <span class="Constant">local-scope</span>
+  <span class="Constant">load-ingredients</span>
+  len:number<span class="Special"> &lt;- </span>length *text
+  <span class="Delimiter">{</span>
+    eof?:boolean<span class="Special"> &lt;- </span>greater-or-equal idx, len
+    <span class="muControl">break-if</span> eof?
+    curr:character<span class="Special"> &lt;- </span>index *text, idx
+    found?:boolean<span class="Special"> &lt;- </span>equal curr, pattern
+    <span class="muControl">break-if</span> found?
+    idx<span class="Special"> &lt;- </span>add idx, <span class="Constant">1</span>
+    <span class="muControl">loop</span>
+  <span class="Delimiter">}</span>
+  <span class="muControl">return</span> idx
+]
+
+<span class="muScenario">scenario</span> text-find-next [
+  run [
+    <span class="Constant">local-scope</span>
+    x:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[a/b]</span>
+    <span class="Constant">10</span>:number/<span class="Special">raw &lt;- </span>find-next x, <span class="Constant">47/slash</span>, <span class="Constant">0/start-index</span>
+  ]
+  memory-should-contain [
+    <span class="Constant">10</span><span class="Special"> &lt;- </span><span class="Constant">1</span>
+  ]
+]
+
+<span class="muScenario">scenario</span> text-find-next-empty [
+  run [
+    <span class="Constant">local-scope</span>
+    x:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
+    <span class="Constant">10</span>:number/<span class="Special">raw &lt;- </span>find-next x, <span class="Constant">47/slash</span>, <span class="Constant">0/start-index</span>
+  ]
+  memory-should-contain [
+    <span class="Constant">10</span><span class="Special"> &lt;- </span><span class="Constant">0</span>
+  ]
+]
+
+<span class="muScenario">scenario</span> text-find-next-initial [
+  run [
+    <span class="Constant">local-scope</span>
+    x:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[/abc]</span>
+    <span class="Constant">10</span>:number/<span class="Special">raw &lt;- </span>find-next x, <span class="Constant">47/slash</span>, <span class="Constant">0/start-index</span>
+  ]
+  memory-should-contain [
+    <span class="Constant">10</span><span class="Special"> &lt;- </span><span class="Constant">0</span>  <span class="Comment"># prefix match</span>
+  ]
+]
+
+<span class="muScenario">scenario</span> text-find-next-final [
+  run [
+    <span class="Constant">local-scope</span>
+    x:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc/]</span>
+    <span class="Constant">10</span>:number/<span class="Special">raw &lt;- </span>find-next x, <span class="Constant">47/slash</span>, <span class="Constant">0/start-index</span>
+  ]
+  memory-should-contain [
+    <span class="Constant">10</span><span class="Special"> &lt;- </span><span class="Constant">3</span>  <span class="Comment"># suffix match</span>
+  ]
+]
+
+<span class="muScenario">scenario</span> text-find-next-missing [
+  run [
+    <span class="Constant">local-scope</span>
+    x:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abcd]</span>
+    <span class="Constant">10</span>:number/<span class="Special">raw &lt;- </span>find-next x, <span class="Constant">47/slash</span>, <span class="Constant">0/start-index</span>
+  ]
+  memory-should-contain [
+    <span class="Constant">10</span><span class="Special"> &lt;- </span><span class="Constant">4</span>  <span class="Comment"># no match</span>
+  ]
+]
+
+<span class="muScenario">scenario</span> text-find-next-invalid-index [
+  run [
+    <span class="Constant">local-scope</span>
+    x:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
+    <span class="Constant">10</span>:number/<span class="Special">raw &lt;- </span>find-next x, <span class="Constant">47/slash</span>, <span class="Constant">4/start-index</span>
+  ]
+  memory-should-contain [
+    <span class="Constant">10</span><span class="Special"> &lt;- </span><span class="Constant">4</span>  <span class="Comment"># no change</span>
+  ]
+]
+
+<span class="muScenario">scenario</span> text-find-next-first [
+  run [
+    <span class="Constant">local-scope</span>
+    x:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[ab/c/]</span>
+    <span class="Constant">10</span>:number/<span class="Special">raw &lt;- </span>find-next x, <span class="Constant">47/slash</span>, <span class="Constant">0/start-index</span>
+  ]
+  memory-should-contain [
+    <span class="Constant">10</span><span class="Special"> &lt;- </span><span class="Constant">2</span>  <span class="Comment"># first '/' of multiple</span>
+  ]
+]
+
+<span class="muScenario">scenario</span> text-find-next-second [
+  run [
+    <span class="Constant">local-scope</span>
+    x:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[ab/c/]</span>
+    <span class="Constant">10</span>:number/<span class="Special">raw &lt;- </span>find-next x, <span class="Constant">47/slash</span>, <span class="Constant">3/start-index</span>
+  ]
+  memory-should-contain [
+    <span class="Constant">10</span><span class="Special"> &lt;- </span><span class="Constant">4</span>  <span class="Comment"># second '/' of multiple</span>
+  ]
+]
+
+<span class="Comment"># search for a pattern of multiple characters</span>
+<span class="Comment"># fairly dumb algorithm</span>
+<span class="muRecipe">def</span> find-next text:address:array:character, pattern:address:array:character, idx:number<span class="muRecipe"> -&gt; </span>next-index:number [
+  <span class="Constant">local-scope</span>
+  <span class="Constant">load-ingredients</span>
+  first:character<span class="Special"> &lt;- </span>index *pattern, <span class="Constant">0</span>
+  <span class="Comment"># repeatedly check for match at current idx</span>
+  len:number<span class="Special"> &lt;- </span>length *text
+  <span class="Delimiter">{</span>
+    <span class="Comment"># does some unnecessary work checking even when there isn't enough of text left</span>
+    done?:boolean<span class="Special"> &lt;- </span>greater-or-equal idx, len
+    <span class="muControl">break-if</span> done?
+    found?:boolean<span class="Special"> &lt;- </span>match-at text, pattern, idx
+    <span class="muControl">break-if</span> found?
+    idx<span class="Special"> &lt;- </span>add idx, <span class="Constant">1</span>
+    <span class="Comment"># optimization: skip past indices that definitely won't match</span>
+    idx<span class="Special"> &lt;- </span>find-next text, first, idx
+    <span class="muControl">loop</span>
+  <span class="Delimiter">}</span>
+  <span class="muControl">return</span> idx
+]
+
+<span class="muScenario">scenario</span> find-next-text-1 [
+  run [
+    <span class="Constant">local-scope</span>
+    x:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
+    y:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[bc]</span>
+    <span class="Constant">10</span>:number/<span class="Special">raw &lt;- </span>find-next x, y, <span class="Constant">0</span>
+  ]
+  memory-should-contain [
+    <span class="Constant">10</span><span class="Special"> &lt;- </span><span class="Constant">1</span>
+  ]
+]
+
+<span class="muScenario">scenario</span> find-next-text-2 [
+  run [
+    <span class="Constant">local-scope</span>
+    x:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abcd]</span>
+    y:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[bc]</span>
+    <span class="Constant">10</span>:number/<span class="Special">raw &lt;- </span>find-next x, y, <span class="Constant">1</span>
+  ]
+  memory-should-contain [
+    <span class="Constant">10</span><span class="Special"> &lt;- </span><span class="Constant">1</span>
+  ]
+]
+
+<span class="muScenario">scenario</span> find-next-no-match [
+  run [
+    <span class="Constant">local-scope</span>
+    x:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
+    y:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[bd]</span>
+    <span class="Constant">10</span>:number/<span class="Special">raw &lt;- </span>find-next x, y, <span class="Constant">0</span>
+  ]
+  memory-should-contain [
+    <span class="Constant">10</span><span class="Special"> &lt;- </span><span class="Constant">3</span>  <span class="Comment"># not found</span>
+  ]
+]
+
+<span class="muScenario">scenario</span> find-next-suffix-match [
+  run [
+    <span class="Constant">local-scope</span>
+    x:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abcd]</span>
+    y:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[cd]</span>
+    <span class="Constant">10</span>:number/<span class="Special">raw &lt;- </span>find-next x, y, <span class="Constant">0</span>
+  ]
+  memory-should-contain [
+    <span class="Constant">10</span><span class="Special"> &lt;- </span><span class="Constant">2</span>
+  ]
+]
+
+<span class="muScenario">scenario</span> find-next-suffix-match-2 [
+  run [
+    <span class="Constant">local-scope</span>
+    x:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abcd]</span>
+    y:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[cde]</span>
+    <span class="Constant">10</span>:number/<span class="Special">raw &lt;- </span>find-next x, y, <span class="Constant">0</span>
+  ]
+  memory-should-contain [
+    <span class="Constant">10</span><span class="Special"> &lt;- </span><span class="Constant">4</span>  <span class="Comment"># not found</span>
+  ]
+]
+
+<span class="Comment"># checks if pattern matches at index 'idx'</span>
+<span class="muRecipe">def</span> match-at text:address:array:character, pattern:address:array:character, idx:number<span class="muRecipe"> -&gt; </span>result:boolean [
+  <span class="Constant">local-scope</span>
+  <span class="Constant">load-ingredients</span>
+  pattern-len:number<span class="Special"> &lt;- </span>length *pattern
+  <span class="Comment"># check that there's space left for the pattern</span>
+  <span class="Delimiter">{</span>
+    x:number<span class="Special"> &lt;- </span>length *text
+    x<span class="Special"> &lt;- </span>subtract x, pattern-len
+    enough-room?:boolean<span class="Special"> &lt;- </span>lesser-or-equal idx, x
+    <span class="muControl">break-if</span> enough-room?
+    <span class="muControl">return</span> <span class="Constant">0/not-found</span>
+  <span class="Delimiter">}</span>
+  <span class="Comment"># check each character of pattern</span>
+  pattern-idx:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
+  <span class="Delimiter">{</span>
+    done?:boolean<span class="Special"> &lt;- </span>greater-or-equal pattern-idx, pattern-len
+    <span class="muControl">break-if</span> done?
+    c:character<span class="Special"> &lt;- </span>index *text, idx
+    exp:character<span class="Special"> &lt;- </span>index *pattern, pattern-idx
+    <span class="Delimiter">{</span>
+      match?:boolean<span class="Special"> &lt;- </span>equal c, exp
+      <span class="muControl">break-if</span> match?
+      <span class="muControl">return</span> <span class="Constant">0/not-found</span>
+    <span class="Delimiter">}</span>
+    idx<span class="Special"> &lt;- </span>add idx, <span class="Constant">1</span>
+    pattern-idx<span class="Special"> &lt;- </span>add pattern-idx, <span class="Constant">1</span>
+    <span class="muControl">loop</span>
+  <span class="Delimiter">}</span>
+  <span class="muControl">return</span> <span class="Constant">1/found</span>
+]
+
+<span class="muScenario">scenario</span> match-at-checks-pattern-at-index [
+  run [
+    <span class="Constant">local-scope</span>
+    x:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
+    y:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[ab]</span>
+    <span class="Constant">10</span>:boolean/<span class="Special">raw &lt;- </span>match-at x, y, <span class="Constant">0</span>
+  ]
+  memory-should-contain [
+    <span class="Constant">10</span><span class="Special"> &lt;- </span><span class="Constant">1</span>  <span class="Comment"># match found</span>
+  ]
+]
+
+<span class="muScenario">scenario</span> match-at-reflexive [
+  run [
+    <span class="Constant">local-scope</span>
+    x:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
+    <span class="Constant">10</span>:boolean/<span class="Special">raw &lt;- </span>match-at x, x, <span class="Constant">0</span>
+  ]
+  memory-should-contain [
+    <span class="Constant">10</span><span class="Special"> &lt;- </span><span class="Constant">1</span>  <span class="Comment"># match found</span>
+  ]
+]
+
+<span class="muScenario">scenario</span> match-at-outside-bounds [
+  run [
+    <span class="Constant">local-scope</span>
+    x:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
+    y:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[a]</span>
+    <span class="Constant">10</span>:boolean/<span class="Special">raw &lt;- </span>match-at x, y, <span class="Constant">4</span>
+  ]
+  memory-should-contain [
+    <span class="Constant">10</span><span class="Special"> &lt;- </span><span class="Constant">0</span>  <span class="Comment"># never matches</span>
+  ]
+]
+
+<span class="muScenario">scenario</span> match-at-empty-pattern [
+  run [
+    <span class="Constant">local-scope</span>
+    x:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
+    y:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
+    <span class="Constant">10</span>:boolean/<span class="Special">raw &lt;- </span>match-at x, y, <span class="Constant">0</span>
+  ]
+  memory-should-contain [
+    <span class="Constant">10</span><span class="Special"> &lt;- </span><span class="Constant">1</span>  <span class="Comment"># always matches empty pattern given a valid index</span>
+  ]
+]
+
+<span class="muScenario">scenario</span> match-at-empty-pattern-outside-bound [
+  run [
+    <span class="Constant">local-scope</span>
+    x:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
+    y:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
+    <span class="Constant">10</span>:boolean/<span class="Special">raw &lt;- </span>match-at x, y, <span class="Constant">4</span>
+  ]
+  memory-should-contain [
+    <span class="Constant">10</span><span class="Special"> &lt;- </span><span class="Constant">0</span>  <span class="Comment"># no match</span>
+  ]
+]
+
+<span class="muScenario">scenario</span> match-at-empty-text [
+  run [
+    <span class="Constant">local-scope</span>
+    x:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
+    y:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
+    <span class="Constant">10</span>:boolean/<span class="Special">raw &lt;- </span>match-at x, y, <span class="Constant">0</span>
+  ]
+  memory-should-contain [
+    <span class="Constant">10</span><span class="Special"> &lt;- </span><span class="Constant">0</span>  <span class="Comment"># no match</span>
+  ]
+]
+
+<span class="muScenario">scenario</span> match-at-empty-against-empty [
+  run [
+    <span class="Constant">local-scope</span>
+    x:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
+    <span class="Constant">10</span>:boolean/<span class="Special">raw &lt;- </span>match-at x, x, <span class="Constant">0</span>
+  ]
+  memory-should-contain [
+    <span class="Constant">10</span><span class="Special"> &lt;- </span><span class="Constant">1</span>  <span class="Comment"># matches because pattern is also empty</span>
+  ]
+]
+
+<span class="muScenario">scenario</span> match-at-inside-bounds [
+  run [
+    <span class="Constant">local-scope</span>
+    x:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
+    y:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[bc]</span>
+    <span class="Constant">10</span>:boolean/<span class="Special">raw &lt;- </span>match-at x, y, <span class="Constant">1</span>
+  ]
+  memory-should-contain [
+    <span class="Constant">10</span><span class="Special"> &lt;- </span><span class="Constant">1</span>  <span class="Comment"># match</span>
+  ]
+]
+
+<span class="muScenario">scenario</span> match-at-inside-bounds-2 [
+  run [
+    <span class="Constant">local-scope</span>
+    x:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
+    y:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[bc]</span>
+    <span class="Constant">10</span>:boolean/<span class="Special">raw &lt;- </span>match-at x, y, <span class="Constant">0</span>
+  ]
+  memory-should-contain [
+    <span class="Constant">10</span><span class="Special"> &lt;- </span><span class="Constant">0</span>  <span class="Comment"># no match</span>
+  ]
+]
+
+<span class="muRecipe">def</span> split s:address:array:character, delim:character<span class="muRecipe"> -&gt; </span>result:address:array:address:array:character [
+  <span class="Constant">local-scope</span>
+  <span class="Constant">load-ingredients</span>
+  <span class="Comment"># empty text? return empty array</span>
+  len:number<span class="Special"> &lt;- </span>length *s
+  <span class="Delimiter">{</span>
+    empty?:boolean<span class="Special"> &lt;- </span>equal len, <span class="Constant">0</span>
+    <span class="muControl">break-unless</span> empty?
+    result<span class="Special"> &lt;- </span>new <span class="Delimiter">{</span>(address array character): type<span class="Delimiter">}</span>, <span class="Constant">0</span>
+    <span class="muControl">return</span>
+  <span class="Delimiter">}</span>
+  <span class="Comment"># count #pieces we need room for</span>
+  count:number<span class="Special"> &lt;- </span>copy <span class="Constant">1</span>  <span class="Comment"># n delimiters = n+1 pieces</span>
+  idx:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
+  <span class="Delimiter">{</span>
+    idx<span class="Special"> &lt;- </span>find-next s, delim, idx
+    done?:boolean<span class="Special"> &lt;- </span>greater-or-equal idx, len
+    <span class="muControl">break-if</span> done?
+    idx<span class="Special"> &lt;- </span>add idx, <span class="Constant">1</span>
+    count<span class="Special"> &lt;- </span>add count, <span class="Constant">1</span>
+    <span class="muControl">loop</span>
+  <span class="Delimiter">}</span>
+  <span class="Comment"># allocate space</span>
+  result<span class="Special"> &lt;- </span>new <span class="Delimiter">{</span>(address array character): type<span class="Delimiter">}</span>, count
+  <span class="Comment"># repeatedly copy slices start..end until delimiter into result[curr-result]</span>
+  curr-result:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
+  start:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
+  <span class="Delimiter">{</span>
+    <span class="Comment"># while next delim exists</span>
+    done?:boolean<span class="Special"> &lt;- </span>greater-or-equal start, len
+    <span class="muControl">break-if</span> done?
+    end:number<span class="Special"> &lt;- </span>find-next s, delim, start
+    <span class="Comment"># copy start..end into result[curr-result]</span>
+    dest:address:array:character<span class="Special"> &lt;- </span>copy-range s, start, end
+    *result<span class="Special"> &lt;- </span>put-index *result, curr-result, dest
+    <span class="Comment"># slide over to next slice</span>
+    start<span class="Special"> &lt;- </span>add end, <span class="Constant">1</span>
+    curr-result<span class="Special"> &lt;- </span>add curr-result, <span class="Constant">1</span>
+    <span class="muControl">loop</span>
+  <span class="Delimiter">}</span>
+]
+
+<span class="muScenario">scenario</span> text-split-1 [
+  run [
+    <span class="Constant">local-scope</span>
+    x:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[a/b]</span>
+    y:address:array:address:array:character<span class="Special"> &lt;- </span>split x, <span class="Constant">47/slash</span>
+    <span class="Constant">10</span>:number/<span class="Special">raw &lt;- </span>length *y
+    a:address:array:character<span class="Special"> &lt;- </span>index *y, <span class="Constant">0</span>
+    b:address:array:character<span class="Special"> &lt;- </span>index *y, <span class="Constant">1</span>
+    <span class="Constant">20</span>:array:character/<span class="Special">raw &lt;- </span>copy *a
+    <span class="Constant">30</span>:array:character/<span class="Special">raw &lt;- </span>copy *b
+  ]
+  memory-should-contain [
+    <span class="Constant">10</span><span class="Special"> &lt;- </span><span class="Constant">2</span>  <span class="Comment"># length of result</span>
+    <span class="Constant">20</span>:array:character<span class="Special"> &lt;- </span><span class="Constant">[a]</span>
+    <span class="Constant">30</span>:array:character<span class="Special"> &lt;- </span><span class="Constant">[b]</span>
+  ]
+]
+
+<span class="muScenario">scenario</span> text-split-2 [
+  run [
+    <span class="Constant">local-scope</span>
+    x:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[a/b/c]</span>
+    y:address:array:address:array:character<span class="Special"> &lt;- </span>split x, <span class="Constant">47/slash</span>
+    <span class="Constant">10</span>:number/<span class="Special">raw &lt;- </span>length *y
+    a:address:array:character<span class="Special"> &lt;- </span>index *y, <span class="Constant">0</span>
+    b:address:array:character<span class="Special"> &lt;- </span>index *y, <span class="Constant">1</span>
+    c:address:array:character<span class="Special"> &lt;- </span>index *y, <span class="Constant">2</span>
+    <span class="Constant">20</span>:array:character/<span class="Special">raw &lt;- </span>copy *a
+    <span class="Constant">30</span>:array:character/<span class="Special">raw &lt;- </span>copy *b
+    <span class="Constant">40</span>:array:character/<span class="Special">raw &lt;- </span>copy *c
+  ]
+  memory-should-contain [
+    <span class="Constant">10</span><span class="Special"> &lt;- </span><span class="Constant">3</span>  <span class="Comment"># length of result</span>
+    <span class="Constant">20</span>:array:character<span class="Special"> &lt;- </span><span class="Constant">[a]</span>
+    <span class="Constant">30</span>:array:character<span class="Special"> &lt;- </span><span class="Constant">[b]</span>
+    <span class="Constant">40</span>:array:character<span class="Special"> &lt;- </span><span class="Constant">[c]</span>
+  ]
+]
+
+<span class="muScenario">scenario</span> text-split-missing [
+  run [
+    <span class="Constant">local-scope</span>
+    x:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
+    y:address:array:address:array:character<span class="Special"> &lt;- </span>split x, <span class="Constant">47/slash</span>
+    <span class="Constant">10</span>:number/<span class="Special">raw &lt;- </span>length *y
+    a:address:array:character<span class="Special"> &lt;- </span>index *y, <span class="Constant">0</span>
+    <span class="Constant">20</span>:array:character/<span class="Special">raw &lt;- </span>copy *a
+  ]
+  memory-should-contain [
+    <span class="Constant">10</span><span class="Special"> &lt;- </span><span class="Constant">1</span>  <span class="Comment"># length of result</span>
+    <span class="Constant">20</span>:array:character<span class="Special"> &lt;- </span><span class="Constant">[abc]</span>
+  ]
+]
+
+<span class="muScenario">scenario</span> text-split-empty [
+  run [
+    <span class="Constant">local-scope</span>
+    x:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
+    y:address:array:address:array:character<span class="Special"> &lt;- </span>split x, <span class="Constant">47/slash</span>
+    <span class="Constant">10</span>:number/<span class="Special">raw &lt;- </span>length *y
+  ]
+  memory-should-contain [
+    <span class="Constant">10</span><span class="Special"> &lt;- </span><span class="Constant">0</span>  <span class="Comment"># empty result</span>
+  ]
+]
+
+<span class="muScenario">scenario</span> text-split-empty-piece [
+  run [
+    <span class="Constant">local-scope</span>
+    x:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[a/b//c]</span>
+    y:address:array:address:array:character<span class="Special"> &lt;- </span>split x:address:array:character, <span class="Constant">47/slash</span>
+    <span class="Constant">10</span>:number/<span class="Special">raw &lt;- </span>length *y
+    a:address:array:character<span class="Special"> &lt;- </span>index *y, <span class="Constant">0</span>
+    b:address:array:character<span class="Special"> &lt;- </span>index *y, <span class="Constant">1</span>
+    c:address:array:character<span class="Special"> &lt;- </span>index *y, <span class="Constant">2</span>
+    d:address:array:character<span class="Special"> &lt;- </span>index *y, <span class="Constant">3</span>
+    <span class="Constant">20</span>:array:character/<span class="Special">raw &lt;- </span>copy *a
+    <span class="Constant">30</span>:array:character/<span class="Special">raw &lt;- </span>copy *b
+    <span class="Constant">40</span>:array:character/<span class="Special">raw &lt;- </span>copy *c
+    <span class="Constant">50</span>:array:character/<span class="Special">raw &lt;- </span>copy *d
+  ]
+  memory-should-contain [
+    <span class="Constant">10</span><span class="Special"> &lt;- </span><span class="Constant">4</span>  <span class="Comment"># length of result</span>
+    <span class="Constant">20</span>:array:character<span class="Special"> &lt;- </span><span class="Constant">[a]</span>
+    <span class="Constant">30</span>:array:character<span class="Special"> &lt;- </span><span class="Constant">[b]</span>
+    <span class="Constant">40</span>:array:character<span class="Special"> &lt;- </span><span class="Constant">[]</span>
+    <span class="Constant">50</span>:array:character<span class="Special"> &lt;- </span><span class="Constant">[c]</span>
+  ]
+]
+
+<span class="muRecipe">def</span> split-first text:address:array:character, delim:character<span class="muRecipe"> -&gt; </span>x:address:array:character, y:address:array:character [
+  <span class="Constant">local-scope</span>
+  <span class="Constant">load-ingredients</span>
+  <span class="Comment"># empty text? return empty texts</span>
+  len:number<span class="Special"> &lt;- </span>length *text
+  <span class="Delimiter">{</span>
+    empty?:boolean<span class="Special"> &lt;- </span>equal len, <span class="Constant">0</span>
+    <span class="muControl">break-unless</span> empty?
+    x:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
+    y:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
+    <span class="muControl">return</span>
+  <span class="Delimiter">}</span>
+  idx:number<span class="Special"> &lt;- </span>find-next text, delim, <span class="Constant">0</span>
+  x:address:array:character<span class="Special"> &lt;- </span>copy-range text, <span class="Constant">0</span>, idx
+  idx<span class="Special"> &lt;- </span>add idx, <span class="Constant">1</span>
+  y:address:array:character<span class="Special"> &lt;- </span>copy-range text, idx, len
+]
+
+<span class="muScenario">scenario</span> text-split-first [
+  run [
+    <span class="Constant">local-scope</span>
+    x:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[a/b]</span>
+    y:address:array:character, z:address:array:character<span class="Special"> &lt;- </span>split-first x, <span class="Constant">47/slash</span>
+    <span class="Constant">10</span>:array:character/<span class="Special">raw &lt;- </span>copy *y
+    <span class="Constant">20</span>:array:character/<span class="Special">raw &lt;- </span>copy *z
+  ]
+  memory-should-contain [
+    <span class="Constant">10</span>:array:character<span class="Special"> &lt;- </span><span class="Constant">[a]</span>
+    <span class="Constant">20</span>:array:character<span class="Special"> &lt;- </span><span class="Constant">[b]</span>
+  ]
+]
+
+<span class="muRecipe">def</span> copy-range buf:address:array:character, start:number, end:number<span class="muRecipe"> -&gt; </span>result:address:array:character [
+  <span class="Constant">local-scope</span>
+  <span class="Constant">load-ingredients</span>
+  <span class="Comment"># if end is out of bounds, trim it</span>
+  len:number<span class="Special"> &lt;- </span>length *buf
+  end:number<span class="Special"> &lt;- </span>min len, end
+  <span class="Comment"># allocate space for result</span>
+  len<span class="Special"> &lt;- </span>subtract end, start
+  result:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">character:type</span>, len
+  <span class="Comment"># copy start..end into result[curr-result]</span>
+  src-idx:number<span class="Special"> &lt;- </span>copy start
+  dest-idx:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
+  <span class="Delimiter">{</span>
+    done?:boolean<span class="Special"> &lt;- </span>greater-or-equal src-idx, end
+    <span class="muControl">break-if</span> done?
+    src:character<span class="Special"> &lt;- </span>index *buf, src-idx
+    *result<span class="Special"> &lt;- </span>put-index *result, dest-idx, src
+    src-idx<span class="Special"> &lt;- </span>add src-idx, <span class="Constant">1</span>
+    dest-idx<span class="Special"> &lt;- </span>add dest-idx, <span class="Constant">1</span>
+    <span class="muControl">loop</span>
+  <span class="Delimiter">}</span>
+]
+
+<span class="muScenario">scenario</span> text-copy-copies-partial-text [
+  run [
+    <span class="Constant">local-scope</span>
+    x:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
+    y:address:array:character<span class="Special"> &lt;- </span>copy-range x, <span class="Constant">1</span>, <span class="Constant">3</span>
+    <span class="Constant">1</span>:array:character/<span class="Special">raw &lt;- </span>copy *y
+  ]
+  memory-should-contain [
+    <span class="Constant">1</span>:array:character<span class="Special"> &lt;- </span><span class="Constant">[bc]</span>
+  ]
+]
+
+<span class="muScenario">scenario</span> text-copy-out-of-bounds [
+  run [
+    <span class="Constant">local-scope</span>
+    x:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
+    y:address:array:character<span class="Special"> &lt;- </span>copy-range x, <span class="Constant">2</span>, <span class="Constant">4</span>
+    <span class="Constant">1</span>:array:character/<span class="Special">raw &lt;- </span>copy *y
+  ]
+  memory-should-contain [
+    <span class="Constant">1</span>:array:character<span class="Special"> &lt;- </span><span class="Constant">[c]</span>
+  ]
+]
+
+<span class="muScenario">scenario</span> text-copy-out-of-bounds-2 [
+  run [
+    <span class="Constant">local-scope</span>
+    x:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
+    y:address:array:character<span class="Special"> &lt;- </span>copy-range x, <span class="Constant">3</span>, <span class="Constant">3</span>
+    <span class="Constant">1</span>:array:character/<span class="Special">raw &lt;- </span>copy *y
+  ]
+  memory-should-contain [
+    <span class="Constant">1</span>:array:character<span class="Special"> &lt;- </span><span class="Constant">[]</span>
+  ]
+]
+</pre>
+</body>
+</html>
+<!-- vim: set foldmethod=manual : -->