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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 "End Mu Types Initialization")</span>
<span class="Comment">//: We'll use this container as a running example, with two number elements.</span>
<span class="Delimiter">{</span>
type_ordinal tmp = Type_ordinal[<span class="Constant">"number-or-point"</span>] = Next_type_ordinal++<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">"number-or-point"</span><span class="Delimiter">;</span>
vector<type_ordinal> t1<span class="Delimiter">;</span>
t1<span class="Delimiter">.</span>push_back<span class="Delimiter">(</span>number<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>
vector<type_ordinal> 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>
Type[tmp]<span class="Delimiter">.</span>element_names<span class="Delimiter">.</span>push_back<span class="Delimiter">(</span><span class="Constant">"i"</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">"p"</span><span class="Delimiter">);</span>
<span class="Delimiter">}</span>
<span class="Comment">//: Tests in this layer often explicitly setup memory before reading it as an</span>
<span class="Comment">//: array. Don't do this in general. I'm tagging exceptions with /raw to</span>
<span class="Comment">//: avoid warnings.</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>:number<span class="Special"> <- </span>copy <span class="Constant">1</span>:literal <span class="Comment"># 'point' variant</span>
<span class="Constant">2</span>:number<span class="Special"> <- </span>copy <span class="Constant">34</span>:literal
<span class="Constant">3</span>:number<span class="Special"> <- </span>copy <span class="Constant">35</span>:literal
<span class="Constant">4</span>:number-<span class="Normal">or</span>-point<span class="Special"> <- </span>copy <span class="Constant">1</span>:number-<span class="Normal">or</span>-point/<span class="Special">raw</span> <span class="Comment"># unsafe</span>
]
<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 "End size_of(types) Cases")</span>
<span class="Normal">if</span> <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="Normal">long</span> <span class="Normal">long</span> <span class="Normal">int</span> result = <span class="Constant">0</span><span class="Delimiter">;</span>
<span class="Normal">for</span> <span class="Delimiter">(</span><span class="Normal">long</span> <span class="Normal">long</span> <span class="Normal">int</span> i = <span class="Constant">0</span><span class="Delimiter">;</span> i < t<span class="Delimiter">.</span>size<span class="Delimiter">;</span> ++i<span class="Delimiter">)</span> <span class="Delimiter">{</span>
<span class="Normal">long</span> <span class="Normal">long</span> <span class="Normal">int</span> tmp = size_of<span class="Delimiter">(</span>t<span class="Delimiter">.</span>elements<span class="Delimiter">.</span>at<span class="Delimiter">(</span>i<span class="Delimiter">));</span>
<span class="Normal">if</span> <span class="Delimiter">(</span>tmp > 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 "End Mu Types Initialization")</span>
Type_ordinal[<span class="Constant">"variant"</span>] = <span class="Constant">0</span><span class="Delimiter">;</span>
<span class="Delimiter">:(scenario maybe_convert)</span>
recipe main [
<span class="Constant">12</span>:number<span class="Special"> <- </span>copy <span class="Constant">1</span>:literal
<span class="Constant">13</span>:number<span class="Special"> <- </span>copy <span class="Constant">35</span>:literal
<span class="Constant">14</span>:number<span class="Special"> <- </span>copy <span class="Constant">36</span>:literal
<span class="Constant">20</span>:address:point<span class="Special"> <- </span>maybe-convert <span class="Constant">12</span>:number-<span class="Normal">or</span>-point/<span class="Special">raw</span><span class="Delimiter">,</span> <span class="Constant">1</span>:variant <span class="Comment"># unsafe</span>
]
<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>:number<span class="Special"> <- </span>copy <span class="Constant">1</span>:literal
<span class="Constant">13</span>:number<span class="Special"> <- </span>copy <span class="Constant">35</span>:literal
<span class="Constant">14</span>:number<span class="Special"> <- </span>copy <span class="Constant">36</span>:literal
<span class="Constant">20</span>:address:point<span class="Special"> <- </span>maybe-convert <span class="Constant">12</span>:number-<span class="Normal">or</span>-point/<span class="Special">raw</span><span class="Delimiter">,</span> <span class="Constant">0</span>:variant <span class="Comment"># unsafe</span>
]
<span class="traceContains">+mem: storing 0 in location 20</span>
<span class="Delimiter">:(before "End Primitive Recipe Declarations")</span>
MAYBE_CONVERT<span class="Delimiter">,</span>
<span class="Delimiter">:(before "End Primitive Recipe Numbers")</span>
Recipe_ordinal[<span class="Constant">"maybe-convert"</span>] = MAYBE_CONVERT<span class="Delimiter">;</span>
<span class="Delimiter">:(before "End Primitive Recipe Implementations")</span>
<span class="Normal">case</span> MAYBE_CONVERT: <span class="Delimiter">{</span>
<span class="Normal">if</span> <span class="Delimiter">(</span>SIZE<span class="Delimiter">(</span>ingredients<span class="Delimiter">)</span> != <span class="Constant">2</span><span class="Delimiter">)</span> <span class="Delimiter">{</span>
raise << current_recipe_name<span class="Delimiter">()</span> << <span class="Constant">": 'maybe-convert' expects exactly 2 ingredients in '"</span> << current_instruction<span class="Delimiter">().</span>to_string<span class="Delimiter">()</span> << <span class="Constant">"'</span><span class="cSpecial">\n</span><span class="Constant">"</span> << end<span class="Delimiter">();</span>
<span class="Identifier">break</span><span class="Delimiter">;</span>
<span class="Delimiter">}</span>
reagent base = canonize<span class="Delimiter">(</span>current_instruction<span class="Delimiter">().</span>ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">));</span>
<span class="Normal">long</span> <span class="Normal">long</span> <span class="Normal">int</span> base_address = base<span class="Delimiter">.</span>value<span class="Delimiter">;</span>
type_ordinal base_type = base<span class="Delimiter">.</span>types<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">);</span>
<span class="Normal">if</span> <span class="Delimiter">(</span>Type[base_type]<span class="Delimiter">.</span>kind != exclusive_container<span class="Delimiter">)</span> <span class="Delimiter">{</span>
raise << current_recipe_name <span class="Delimiter">()</span> << <span class="Constant">": first ingredient of 'maybe-convert' should be an exclusive-container, but got "</span> << base<span class="Delimiter">.</span>original_string << <span class="cSpecial">'\n'</span> << end<span class="Delimiter">();</span>
<span class="Identifier">break</span><span class="Delimiter">;</span>
<span class="Delimiter">}</span>
<span class="Normal">if</span> <span class="Delimiter">(</span>!is_literal<span class="Delimiter">(</span>current_instruction<span class="Delimiter">().</span>ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">1</span><span class="Delimiter">)))</span> <span class="Delimiter">{</span>
raise << current_recipe_name<span class="Delimiter">()</span> << <span class="Constant">": second ingredient of 'maybe-convert' should have type 'variant', but got "</span> << current_instruction<span class="Delimiter">().</span>ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">1</span><span class="Delimiter">).</span>original_string << <span class="cSpecial">'\n'</span> << end<span class="Delimiter">();</span>
<span class="Identifier">break</span><span class="Delimiter">;</span>
<span class="Delimiter">}</span>
<span class="Normal">long</span> <span class="Normal">long</span> <span class="Normal">int</span> tag = current_instruction<span class="Delimiter">().</span>ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">1</span><span class="Delimiter">).</span>value<span class="Delimiter">;</span>
<span class="Normal">long</span> <span class="Normal">long</span> <span class="Normal">int</span> result<span class="Delimiter">;</span>
<span class="Normal">if</span> <span class="Delimiter">(</span>tag == <span class="Normal">static_cast</span><<span class="Normal">long</span> <span class="Normal">long</span> <span class="Normal">int</span>><span class="Delimiter">(</span>Memory[base_address]<span class="Delimiter">))</span> <span class="Delimiter">{</span>
result = base_address+<span class="Constant">1</span><span class="Delimiter">;</span>
<span class="Delimiter">}</span>
<span class="Normal">else</span> <span class="Delimiter">{</span>
result = <span class="Constant">0</span><span class="Delimiter">;</span>
<span class="Delimiter">}</span>
products<span class="Delimiter">.</span>resize<span class="Delimiter">(</span><span class="Constant">1</span><span class="Delimiter">);</span>
products<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">).</span>push_back<span class="Delimiter">(</span>result<span class="Delimiter">);</span>
<span class="Identifier">break</span><span class="Delimiter">;</span>
<span class="Delimiter">}</span>
<span class="SalientComment">//:: Allow exclusive containers to be defined in mu code.</span>
<span class="Delimiter">:(scenario exclusive_container)</span>
exclusive-container foo [
<span class="Normal">x</span>:number
<span class="Normal">y</span>:number
]
<span class="traceContains">+parse: reading exclusive-container foo</span>
<span class="traceContains">+parse: element name: x</span>
<span class="traceContains">+parse: type: 1</span>
<span class="traceContains">+parse: element name: y</span>
<span class="traceContains">+parse: type: 1</span>
<span class="Delimiter">:(before "End Command Handlers")</span>
<span class="Normal">else</span> <span class="Normal">if</span> <span class="Delimiter">(</span>command == <span class="Constant">"exclusive-container"</span><span class="Delimiter">)</span> <span class="Delimiter">{</span>
insert_container<span class="Delimiter">(</span>command<span class="Delimiter">,</span> exclusive_container<span class="Delimiter">,</span> in<span class="Delimiter">);</span>
<span class="Delimiter">}</span>
<span class="SalientComment">//:: To construct exclusive containers out of variant types, use 'merge'.</span>
<span class="Delimiter">:(scenario lift_to_exclusive_container)</span>
exclusive-container foo [
<span class="Normal">x</span>:number
<span class="Normal">y</span>:number
]
recipe main [
<span class="Constant">1</span>:number<span class="Special"> <- </span>copy <span class="Constant">34</span>:literal
<span class="Constant">2</span>:foo<span class="Special"> <- </span>merge <span class="Constant">0</span>:literal/x<span class="Delimiter">,</span> <span class="Constant">1</span>:number
<span class="Constant">4</span>:foo<span class="Special"> <- </span>merge <span class="Constant">1</span>:literal/x<span class="Delimiter">,</span> <span class="Constant">1</span>:number
]
<span class="traceContains">+mem: storing 0 in location 2</span>
<span class="traceContains">+mem: storing 34 in location 3</span>
<span class="traceContains">+mem: storing 1 in location 4</span>
<span class="traceContains">+mem: storing 34 in location 5</span>
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