html/034exclusive_container.cc.html


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<span class="Comment">//: Exclusive containers contain exactly one of a fixed number of 'variants'</span>
<span class="Comment">//: of different types.</span>
<span class="Comment">//:</span>
<span class="Comment">//: They also implicitly contain a tag describing precisely which variant is</span>
<span class="Comment">//: currently stored in them.</span>

<span class="Delimiter">:(before &quot;End Mu Types Initialization&quot;)</span>
<span class="Comment">//: We'll use this container as a running example, with two integer elements.</span>
<span class="Delimiter">{</span>
type_number tmp = Type_number[<span class="Constant">&quot;integer-or-point&quot;</span>] = Next_type_number++<span class="Delimiter">;</span>
Type[tmp]<span class="Delimiter">.</span>size = <span class="Constant">2</span><span class="Delimiter">;</span>
Type[tmp]<span class="Delimiter">.</span>kind = exclusive_container<span class="Delimiter">;</span>
Type[tmp]<span class="Delimiter">.</span>name = <span class="Constant">&quot;integer-or-point&quot;</span><span class="Delimiter">;</span>
<span class="CommentedCode">//? cout &lt;&lt; tmp &lt;&lt; &quot;: &quot; &lt;&lt; Type[tmp].elements.size() &lt;&lt; '\n'; //? 1</span>
vector&lt;type_number&gt; t1<span class="Delimiter">;</span>
t1<span class="Delimiter">.</span>push_back<span class="Delimiter">(</span>integer<span class="Delimiter">);</span>
Type[tmp]<span class="Delimiter">.</span>elements<span class="Delimiter">.</span>push_back<span class="Delimiter">(</span>t1<span class="Delimiter">);</span>
<span class="CommentedCode">//? cout &lt;&lt; Type[tmp].elements.size() &lt;&lt; '\n'; //? 1</span>
vector&lt;type_number&gt; t2<span class="Delimiter">;</span>
t2<span class="Delimiter">.</span>push_back<span class="Delimiter">(</span>point<span class="Delimiter">);</span>
Type[tmp]<span class="Delimiter">.</span>elements<span class="Delimiter">.</span>push_back<span class="Delimiter">(</span>t2<span class="Delimiter">);</span>
<span class="CommentedCode">//? cout &lt;&lt; Type[tmp].elements.size() &lt;&lt; '\n'; //? 1</span>
<span class="CommentedCode">//? cout &lt;&lt; &quot;point: &quot; &lt;&lt; point &lt;&lt; '\n'; //? 1</span>
Type[tmp]<span class="Delimiter">.</span>element_names<span class="Delimiter">.</span>push_back<span class="Delimiter">(</span><span class="Constant">&quot;i&quot;</span><span class="Delimiter">);</span>
Type[tmp]<span class="Delimiter">.</span>element_names<span class="Delimiter">.</span>push_back<span class="Delimiter">(</span><span class="Constant">&quot;p&quot;</span><span class="Delimiter">);</span>
<span class="Delimiter">}</span>

<span class="Delimiter">:(scenario copy_exclusive_container)</span>
<span class="Comment"># Copying exclusive containers copies all their contents and an extra location for the tag.</span>
recipe main [
  <span class="Constant">1</span>:integer<span class="Special"> &lt;- </span>copy <span class="Constant">1</span>:literal  <span class="Comment"># 'point' variant</span>
  <span class="Constant">2</span>:integer<span class="Special"> &lt;- </span>copy <span class="Constant">34</span>:literal
  <span class="Constant">3</span>:integer<span class="Special"> &lt;- </span>copy <span class="Constant">35</span>:literal
  <span class="Constant">4</span>:integer-or-point<span class="Special"> &lt;- </span>copy <span class="Constant">1</span>:integer-or-point
]
<span class="traceContains">+mem: storing 1 in location 4</span>
<span class="traceContains">+mem: storing 34 in location 5</span>
<span class="traceContains">+mem: storing 35 in location 6</span>

<span class="Delimiter">:(before &quot;End size_of(types) Cases&quot;)</span>
if <span class="Delimiter">(</span>t<span class="Delimiter">.</span>kind == exclusive_container<span class="Delimiter">)</span> <span class="Delimiter">{</span>
  <span class="Comment">// size of an exclusive container is the size of its largest variant</span>
  <span class="Comment">// (So like containers, it can't contain arrays.)</span>
<span class="CommentedCode">//?   cout &lt;&lt; &quot;--- &quot; &lt;&lt; types[0] &lt;&lt; ' ' &lt;&lt; t.size &lt;&lt; '\n'; //? 1</span>
<span class="CommentedCode">//?   cout &lt;&lt; &quot;point: &quot; &lt;&lt; Type_number[&quot;point&quot;] &lt;&lt; &quot; &quot; &lt;&lt; Type[Type_number[&quot;point&quot;]].name &lt;&lt; &quot; &quot; &lt;&lt; Type[Type_number[&quot;point&quot;]].size &lt;&lt; '\n'; //? 1</span>
<span class="CommentedCode">//?   cout &lt;&lt; t.name &lt;&lt; ' ' &lt;&lt; t.size &lt;&lt; ' ' &lt;&lt; t.elements.size() &lt;&lt; '\n'; //? 1</span>
  size_t result = <span class="Constant">0</span><span class="Delimiter">;</span>
  for <span class="Delimiter">(</span>index_t i = <span class="Constant">0</span><span class="Delimiter">;</span> i &lt; t<span class="Delimiter">.</span>size<span class="Delimiter">;</span> ++i<span class="Delimiter">)</span> <span class="Delimiter">{</span>
    size_t tmp = size_of<span class="Delimiter">(</span>t<span class="Delimiter">.</span>elements[i]<span class="Delimiter">);</span>
<span class="CommentedCode">//?     cout &lt;&lt; i &lt;&lt; &quot;: &quot; &lt;&lt; t.elements[i][0] &lt;&lt; ' ' &lt;&lt; tmp &lt;&lt; ' ' &lt;&lt; result &lt;&lt; '\n'; //? 1</span>
    if <span class="Delimiter">(</span>tmp &gt; result<span class="Delimiter">)</span> result = tmp<span class="Delimiter">;</span>
  <span class="Delimiter">}</span>
  <span class="Comment">// ...+1 for its tag.</span>
  <span class="Identifier">return</span> result+<span class="Constant">1</span><span class="Delimiter">;</span>
<span class="Delimiter">}</span>

<span class="SalientComment">//:: To access variants of an exclusive container, use 'maybe-convert'.</span>
<span class="Comment">//: It always returns an address (so that you can modify it) or null (to</span>
<span class="Comment">//: signal that the conversion failed (because the container contains a</span>
<span class="Comment">//: different variant).</span>

<span class="Comment">//: 'maybe-convert' requires a literal in ingredient 1. We'll use a synonym</span>
<span class="Comment">//: called 'variant'.</span>
<span class="Delimiter">:(before &quot;End Mu Types Initialization&quot;)</span>
Type_number[<span class="Constant">&quot;variant&quot;</span>] = <span class="Constant">0</span><span class="Delimiter">;</span>

<span class="Delimiter">:(scenario maybe_convert)</span>
recipe main [
  <span class="Constant">12</span>:integer<span class="Special"> &lt;- </span>copy <span class="Constant">1</span>:literal
  <span class="Constant">13</span>:integer<span class="Special"> &lt;- </span>copy <span class="Constant">35</span>:literal
  <span class="Constant">14</span>:integer<span class="Special"> &lt;- </span>copy <span class="Constant">36</span>:literal
  <span class="Constant">20</span>:address:point<span class="Special"> &lt;- </span>maybe-convert <span class="Constant">12</span>:integer-or-point<span class="Delimiter">,</span> <span class="Constant">1</span>:variant
]
<span class="traceContains">+mem: storing 13 in location 20</span>

<span class="Delimiter">:(scenario maybe_convert_fail)</span>
recipe main [
  <span class="Constant">12</span>:integer<span class="Special"> &lt;- </span>copy <span class="Constant">1</span>:literal
  <span class="Constant">13</span>:integer<span class="Special"> &lt;- </span>copy <span class="Constant">35</span>:literal
  <span class="Constant">14</span>:integer<span class="Special"> &lt;- </span>copy <span class="Constant">36</span>:literal
  <span class="Constant">20</span>:address:point<span class="Special"> &lt;- </span>maybe-convert <span class="Constant">12</span>:integer-or-point<span class="Delimiter">,</span> <span class="Constant">0</span>:variant
]
<span class="traceContains">+mem: storing 0 in location 20</span>

<span class="Delimiter">:(before &quot;End Primitive Recipe Declarations&quot;)</span>
MAYBE_CONVERT<span class="Delimiter">,</span>
<span class="Delimiter">:(before &quot;End Primitive Recipe Numbers&quot;)</span>
Recipe_number[<span class="Constant">&quot;maybe-convert&quot;</span>] = MAYBE_CONVERT<span class="Delimiter">;</span>
<span class="Delimiter">:(before &quot;End Primitive Recipe Implementations&quot;)</span>
case MAYBE_CONVERT: <span class="Delimiter">{</span>
  trace<span class="Delimiter">(</span><span class="Constant">&quot;run&quot;</span><span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;ingredient 0 is &quot;</span> &lt;&lt; current_instruction<span class="Delimiter">().</span>ingredients[<span class="Constant">0</span>]<span class="Delimiter">.</span>name<span class="Delimiter">;</span>
  reagent base = canonize<span class="Delimiter">(</span>current_instruction<span class="Delimiter">().</span>ingredients[<span class="Constant">0</span>]<span class="Delimiter">);</span>
  index_t base_address = base<span class="Delimiter">.</span>value<span class="Delimiter">;</span>
  type_number base_type = base<span class="Delimiter">.</span>types[<span class="Constant">0</span>]<span class="Delimiter">;</span>
  assert<span class="Delimiter">(</span>Type[base_type]<span class="Delimiter">.</span>kind == exclusive_container<span class="Delimiter">);</span>
  trace<span class="Delimiter">(</span><span class="Constant">&quot;run&quot;</span><span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;ingredient 1 is &quot;</span> &lt;&lt; current_instruction<span class="Delimiter">().</span>ingredients[<span class="Constant">1</span>]<span class="Delimiter">.</span>name<span class="Delimiter">;</span>
  assert<span class="Delimiter">(</span>isa_literal<span class="Delimiter">(</span>current_instruction<span class="Delimiter">().</span>ingredients[<span class="Constant">1</span>]<span class="Delimiter">));</span>
  index_t tag = current_instruction<span class="Delimiter">().</span>ingredients[<span class="Constant">1</span>]<span class="Delimiter">.</span>value<span class="Delimiter">;</span>
  vector&lt;long long int&gt; result<span class="Delimiter">;</span>
  if <span class="Delimiter">(</span>tag == static_cast&lt;index_t&gt;<span class="Delimiter">(</span>Memory[base_address]<span class="Delimiter">))</span> <span class="Delimiter">{</span>
    result<span class="Delimiter">.</span>push_back<span class="Delimiter">(</span>base_address+<span class="Constant">1</span><span class="Delimiter">);</span>
  <span class="Delimiter">}</span>
  else <span class="Delimiter">{</span>
    result<span class="Delimiter">.</span>push_back<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">);</span>
  <span class="Delimiter">}</span>
  write_memory<span class="Delimiter">(</span>current_instruction<span class="Delimiter">().</span>products[<span class="Constant">0</span>]<span class="Delimiter">,</span> result<span class="Delimiter">);</span>
  <span class="Identifier">break</span><span class="Delimiter">;</span>
<span class="Delimiter">}</span>
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