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<a href='https://github.com/akkartik/mu/blob/master/076continuation.cc'>https://github.com/akkartik/mu/blob/master/076continuation.cc</a>
<pre id='vimCodeElement'>
<span id="L1" class="LineNr"> 1 </span><span class="Comment">//: Continuations are a powerful primitive for constructing advanced kinds of</span>
<span id="L2" class="LineNr"> 2 </span><span class="Comment">//: control *policies* like back-tracking.</span>
<span id="L3" class="LineNr"> 3 </span><span class="Comment">//:</span>
<span id="L4" class="LineNr"> 4 </span><span class="Comment">//: In Mu, continuations are first-class and delimited, and are constructed</span>
<span id="L5" class="LineNr"> 5 </span><span class="Comment">//: out of two primitives:</span>
<span id="L6" class="LineNr"> 6 </span><span class="Comment">//:</span>
<span id="L7" class="LineNr"> 7 </span><span class="Comment">//: * 'call-with-continuation-mark' marks the top of the call stack and then</span>
<span id="L8" class="LineNr"> 8 </span><span class="Comment">//: calls the provided recipe.</span>
<span id="L9" class="LineNr"> 9 </span><span class="Comment">//: * 'return-continuation-until-mark' copies the top of the stack</span>
<span id="L10" class="LineNr"> 10 </span><span class="Comment">//: until the mark, and returns it as the result of</span>
<span id="L11" class="LineNr"> 11 </span><span class="Comment">//: 'call-with-continuation-mark' (which might be a distant ancestor on the</span>
<span id="L12" class="LineNr"> 12 </span><span class="Comment">//: call stack; intervening calls don't return)</span>
<span id="L13" class="LineNr"> 13 </span><span class="Comment">//:</span>
<span id="L14" class="LineNr"> 14 </span><span class="Comment">//: The resulting slice of the stack can now be called just like a regular</span>
<span id="L15" class="LineNr"> 15 </span><span class="Comment">//: recipe.</span>
<span id="L16" class="LineNr"> 16 </span><span class="Comment">//:</span>
<span id="L17" class="LineNr"> 17 </span><span class="Comment">//: See the example programs continuation*.mu to get a sense for the</span>
<span id="L18" class="LineNr"> 18 </span><span class="Comment">//: possibilities.</span>
<span id="L19" class="LineNr"> 19 </span><span class="Comment">//:</span>
<span id="L20" class="LineNr"> 20 </span><span class="Comment">//: Refinements:</span>
<span id="L21" class="LineNr"> 21 </span><span class="Comment">//: * You can call a single continuation multiple times, and it will preserve</span>
<span id="L22" class="LineNr"> 22 </span><span class="Comment">//: the state of its local variables at each stack frame between calls.</span>
<span id="L23" class="LineNr"> 23 </span><span class="Comment">//: The stack frames of a continuation are not destroyed until the</span>
<span id="L24" class="LineNr"> 24 </span><span class="Comment">//: continuation goes out of scope. See continuation2.mu.</span>
<span id="L25" class="LineNr"> 25 </span><span class="Comment">//: * 'return-continuation-until-mark' doesn't consume the mark, so you can</span>
<span id="L26" class="LineNr"> 26 </span><span class="Comment">//: return multiple continuations based on a single mark. In combination</span>
<span id="L27" class="LineNr"> 27 </span><span class="Comment">//: with the fact that 'return-continuation-until-mark' can return from</span>
<span id="L28" class="LineNr"> 28 </span><span class="Comment">//: regular calls, just as long as there was an earlier call to</span>
<span id="L29" class="LineNr"> 29 </span><span class="Comment">//: 'call-with-continuation-mark', this gives us a way to create resumable</span>
<span id="L30" class="LineNr"> 30 </span><span class="Comment">//: recipes. See continuation3.mu.</span>
<span id="L31" class="LineNr"> 31 </span><span class="Comment">//: * 'return-continuation-until-mark' can take ingredients to return just</span>
<span id="L32" class="LineNr"> 32 </span><span class="Comment">//: like other 'return' instructions. It just implicitly also returns a</span>
<span id="L33" class="LineNr"> 33 </span><span class="Comment">//: continuation as the first result. See continuation4.mu.</span>
<span id="L34" class="LineNr"> 34 </span><span class="Comment">//: * Conversely, you can pass ingredients to a continuation when calling it,</span>
<span id="L35" class="LineNr"> 35 </span><span class="Comment">//: to make it available to products of 'return-continuation-until-mark'.</span>
<span id="L36" class="LineNr"> 36 </span><span class="Comment">//: See continuation5.mu.</span>
<span id="L37" class="LineNr"> 37 </span><span class="Comment">//: * There can be multiple continuation marks on the stack at once;</span>
<span id="L38" class="LineNr"> 38 </span><span class="Comment">//: 'call-with-continuation-mark' and 'return-continuation-until-mark' both</span>
<span id="L39" class="LineNr"> 39 </span><span class="Comment">//: need to pass in a tag to coordinate on the correct mark. This allows us</span>
<span id="L40" class="LineNr"> 40 </span><span class="Comment">//: to save multiple continuations for different purposes (say if one is</span>
<span id="L41" class="LineNr"> 41 </span><span class="Comment">//: for exceptions) with overlapping stack frames. See exception.mu.</span>
<span id="L42" class="LineNr"> 42 </span><span class="Comment">//:</span>
<span id="L43" class="LineNr"> 43 </span><span class="Comment">//: Inspired by James and Sabry, "Yield: Mainstream delimited continuations",</span>
<span id="L44" class="LineNr"> 44 </span><span class="Comment">//: Workshop on the Theory and Practice of Delimited Continuations, 2011.</span>
<span id="L45" class="LineNr"> 45 </span><span class="Comment">//: <a href="https://www.cs.indiana.edu/~sabry/papers/yield.pdf">https://www.cs.indiana.edu/~sabry/papers/yield.pdf</a></span>
<span id="L46" class="LineNr"> 46 </span><span class="Comment">//:</span>
<span id="L47" class="LineNr"> 47 </span><span class="Comment">//: Caveats:</span>
<span id="L48" class="LineNr"> 48 </span><span class="Comment">//: * At the moment we can't statically type-check continuations. So we raise</span>
<span id="L49" class="LineNr"> 49 </span><span class="Comment">//: runtime errors for a call that doesn't return a continuation when the</span>
<span id="L50" class="LineNr"> 50 </span><span class="Comment">//: caller expects, or one that returns a continuation when the caller</span>
<span id="L51" class="LineNr"> 51 </span><span class="Comment">//: doesn't expect it. This shouldn't cause memory corruption, though.</span>
<span id="L52" class="LineNr"> 52 </span><span class="Comment">//: There should still be no way to lookup addresses that aren't allocated.</span>
<span id="L53" class="LineNr"> 53 </span>
<span id="L54" class="LineNr"> 54 </span><span class="Delimiter">:(before "End Mu Types Initialization")</span>
<span id="L55" class="LineNr"> 55 </span><a href='010vm.cc.html#L125'>type_ordinal</a> continuation = <span class="Special">Type_ordinal</span>[<span class="Constant">"continuation"</span>] = <span class="Special">Next_type_ordinal</span>++<span class="Delimiter">;</span>
<span id="L56" class="LineNr"> 56 </span><span class="Special">Type</span>[continuation]<span class="Delimiter">.</span>name = <span class="Constant">"continuation"</span><span class="Delimiter">;</span>
<span id="L57" class="LineNr"> 57 </span>
<span id="L58" class="LineNr"> 58 </span><span class="Comment">//: A continuation can be called like a recipe.</span>
<span id="L59" class="LineNr"> 59 </span><span class="Delimiter">:(before "End <a href='072recipe.cc.html#L335'>is_mu_recipe</a> Atom Cases(r)")</span>
<span id="L60" class="LineNr"> 60 </span><span class="Normal">if</span> <span class="Delimiter">(</span>r<span class="Delimiter">.</span>type<span class="Delimiter">-></span>name == <span class="Constant">"continuation"</span><span class="Delimiter">)</span> <span class="Identifier">return</span><span class="Constant"> true</span><span class="Delimiter">;</span>
<span id="L61" class="LineNr"> 61 </span>
<span id="L62" class="LineNr"> 62 </span><span class="Comment">//: However, it can't be type-checked like most recipes. Pretend it's like a</span>
<span id="L63" class="LineNr"> 63 </span><span class="Comment">//: header-less recipe.</span>
<span id="L64" class="LineNr"> 64 </span><span class="Delimiter">:(after "Begin Reagent->Recipe(r, recipe_header)")</span>
<span id="L65" class="LineNr"> 65 </span><span class="Normal">if</span> <span class="Delimiter">(</span>r<span class="Delimiter">.</span>type<span class="Delimiter">-></span>atom && r<span class="Delimiter">.</span>type<span class="Delimiter">-></span>name == <span class="Constant">"continuation"</span><span class="Delimiter">)</span> <span class="Delimiter">{</span>
<span id="L66" class="LineNr"> 66 </span> result_header<span class="Delimiter">.</span>has_header =<span class="Constant"> false</span><span class="Delimiter">;</span>
<span id="L67" class="LineNr"> 67 </span> <span class="Identifier">return</span> result_header<span class="Delimiter">;</span>
<span id="L68" class="LineNr"> 68 </span><span class="Delimiter">}</span>
<span id="L69" class="LineNr"> 69 </span>
<span id="L70" class="LineNr"> 70 </span><span class="Delimiter">:(scenario delimited_continuation)</span>
<span id="L71" class="LineNr"> 71 </span><span class="muRecipe"><a href='010vm.cc.html#L19'>recipe</a></span> <a href='000organization.cc.html#L113'>main</a> [
<span id="L72" class="LineNr"> 72 </span> <span class="Constant">1</span>:continuation<span class="Special"> <- </span>call-with-continuation-mark <span class="Constant">233</span>/mark<span class="Delimiter">,</span> f<span class="Delimiter">,</span> <span class="Constant">77</span> <span class="Comment"># 77 is an argument to f</span>
<span id="L73" class="LineNr"> 73 </span> <span class="Constant">2</span>:num<span class="Special"> <- </span>copy <span class="Constant">5</span>
<span id="L74" class="LineNr"> 74 </span> <span class="Delimiter">{</span>
<span id="L75" class="LineNr"> 75 </span> <span class="Constant">2</span>:num<span class="Special"> <- </span>call <span class="Constant">1</span>:continuation<span class="Delimiter">,</span> <span class="Constant">2</span>:num <span class="Comment"># jump to 'return-continuation-until-mark' below</span>
<span id="L76" class="LineNr"> 76 </span> <span class="Constant">3</span>:<span class="Normal">bool</span><span class="Special"> <- </span>greater-<span class="Normal">or</span>-equal <span class="Constant">2</span>:num<span class="Delimiter">,</span> <span class="Constant">8</span>
<span id="L77" class="LineNr"> 77 </span> <span class="Identifier">break</span>-<span class="Normal">if</span> <span class="Constant">3</span>:<span class="Normal">bool</span>
<span id="L78" class="LineNr"> 78 </span> loop
<span id="L79" class="LineNr"> 79 </span> <span class="Delimiter">}</span>
<span id="L80" class="LineNr"> 80 </span>]
<span id="L81" class="LineNr"> 81 </span><span class="muRecipe"><a href='010vm.cc.html#L19'>recipe</a></span> f [
<span id="L82" class="LineNr"> 82 </span> <span class="Constant">11</span>:num<span class="Special"> <- </span>next-ingredient
<span id="L83" class="LineNr"> 83 </span> <span class="Constant">12</span>:num<span class="Special"> <- </span>g <span class="Constant">11</span>:num
<span id="L84" class="LineNr"> 84 </span> <span class="Identifier">return</span> <span class="Constant">12</span>:num
<span id="L85" class="LineNr"> 85 </span>]
<span id="L86" class="LineNr"> 86 </span><span class="muRecipe"><a href='010vm.cc.html#L19'>recipe</a></span> g [
<span id="L87" class="LineNr"> 87 </span> <span class="Constant">21</span>:num<span class="Special"> <- </span>next-ingredient
<span id="L88" class="LineNr"> 88 </span> <span class="Constant">22</span>:num<span class="Special"> <- </span><span class="Identifier">return</span>-continuation-until-mark <span class="Constant">233</span>/mark
<span id="L89" class="LineNr"> 89 </span> <span class="Constant">23</span>:num<span class="Special"> <- </span>add <span class="Constant">22</span>:num<span class="Delimiter">,</span> <span class="Constant">1</span>
<span id="L90" class="LineNr"> 90 </span> <span class="Identifier">return</span> <span class="Constant">23</span>:num
<span id="L91" class="LineNr"> 91 </span>]
<span id="L92" class="LineNr"> 92 </span><span class="Comment"># first call of 'g' executes the part before return-continuation-until-mark</span>
<span id="L93" class="LineNr"> 93 </span><span class="traceContains">+mem: storing 77 in location 21</span>
<span id="L94" class="LineNr"> 94 </span><span class="traceContains">+run: {2: "number"} <- copy {5: "literal"}</span>
<span id="L95" class="LineNr"> 95 </span><span class="traceContains">+mem: storing 5 in location 2</span>
<span id="L96" class="LineNr"> 96 </span><span class="Comment"># calls of the continuation execute the part after return-continuation-until-mark</span>
<span id="L97" class="LineNr"> 97 </span><span class="traceContains">+run: {2: "number"} <- call {1: "continuation"}, {2: "number"}</span>
<span id="L98" class="LineNr"> 98 </span><span class="traceContains">+mem: storing 5 in location 22</span>
<span id="L99" class="LineNr"> 99 </span><span class="traceContains">+mem: storing 6 in location 2</span>
<span id="L100" class="LineNr">100 </span><span class="traceContains">+run: {2: "number"} <- call {1: "continuation"}, {2: "number"}</span>
<span id="L101" class="LineNr">101 </span><span class="traceContains">+mem: storing 6 in location 22</span>
<span id="L102" class="LineNr">102 </span><span class="traceContains">+mem: storing 7 in location 2</span>
<span id="L103" class="LineNr">103 </span><span class="traceContains">+run: {2: "number"} <- call {1: "continuation"}, {2: "number"}</span>
<span id="L104" class="LineNr">104 </span><span class="traceContains">+mem: storing 7 in location 22</span>
<span id="L105" class="LineNr">105 </span><span class="traceContains">+mem: storing 8 in location 2</span>
<span id="L106" class="LineNr">106 </span><span class="Comment"># first call of 'g' does not execute the part after return-continuation-until-mark</span>
<span id="L107" class="LineNr">107 </span><span class="traceAbsent">-mem: storing 77 in location 22</span>
<span id="L108" class="LineNr">108 </span><span class="Comment"># calls of the continuation don't execute the part before return-continuation-until-mark</span>
<span id="L109" class="LineNr">109 </span><span class="traceAbsent">-mem: storing 5 in location 21</span>
<span id="L110" class="LineNr">110 </span><span class="traceAbsent">-mem: storing 6 in location 21</span>
<span id="L111" class="LineNr">111 </span><span class="traceAbsent">-mem: storing 7 in location 21</span>
<span id="L112" class="LineNr">112 </span><span class="Comment"># termination</span>
<span id="L113" class="LineNr">113 </span><span class="traceAbsent">-mem: storing 9 in location 2</span>
<span id="L114" class="LineNr">114 </span>
<span id="L115" class="LineNr">115 </span><span class="Delimiter">:(before "End call Fields")</span>
<span id="L116" class="LineNr">116 </span><span class="Normal">int</span> continuation_mark_tag<span class="Delimiter">;</span>
<span id="L117" class="LineNr">117 </span><span class="Delimiter">:(before "End call Constructor")</span>
<span id="L118" class="LineNr">118 </span>continuation_mark_tag = <span class="Constant">0</span><span class="Delimiter">;</span>
<span id="L119" class="LineNr">119 </span>
<span id="L120" class="LineNr">120 </span><span class="Delimiter">:(before "End Primitive Recipe Declarations")</span>
<span id="L121" class="LineNr">121 </span>CALL_WITH_CONTINUATION_MARK<span class="Delimiter">,</span>
<span id="L122" class="LineNr">122 </span><span class="Delimiter">:(before "End Primitive Recipe Numbers")</span>
<span id="L123" class="LineNr">123 </span><span class="Special">Recipe_ordinal</span>[<span class="Constant">"call-with-continuation-mark"</span>] = CALL_WITH_CONTINUATION_MARK<span class="Delimiter">;</span>
<span id="L124" class="LineNr">124 </span><span class="Delimiter">:(before "End Primitive Recipe Checks")</span>
<span id="L125" class="LineNr">125 </span><span class="Normal">case</span> CALL_WITH_CONTINUATION_MARK: <span class="Delimiter">{</span>
<span id="L126" class="LineNr">126 </span> <span class="Normal">if</span> <span class="Delimiter">(</span><a href='001help.cc.html#L141'>SIZE</a><span class="Delimiter">(</span>inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">)</span> < <span class="Constant">2</span><span class="Delimiter">)</span> <span class="Delimiter">{</span>
<span id="L127" class="LineNr">127 </span> <a href='003trace.cc.html#L196'>raise</a> << <a href='013update_operation.cc.html#L25'>maybe</a><span class="Delimiter">(</span>get<span class="Delimiter">(</span><span class="Special">Recipe</span><span class="Delimiter">,</span> r<span class="Delimiter">).</span>name<span class="Delimiter">)</span> << <span class="Constant">"'"</span> << to_original_string<span class="Delimiter">(</span>inst<span class="Delimiter">)</span> << <span class="Constant">"' requires at least two ingredients: a mark number and a <a href='010vm.cc.html#L19'>recipe</a> to call\n"</span> << <a href='003trace.cc.html#L225'>end</a><span class="Delimiter">();</span>
<span id="L128" class="LineNr">128 </span> <span class="Delimiter">}</span>
<span id="L129" class="LineNr">129 </span> <span class="Identifier">break</span><span class="Delimiter">;</span>
<span id="L130" class="LineNr">130 </span><span class="Delimiter">}</span>
<span id="L131" class="LineNr">131 </span><span class="Delimiter">:(before "End Primitive Recipe Implementations")</span>
<span id="L132" class="LineNr">132 </span><span class="Normal">case</span> CALL_WITH_CONTINUATION_MARK: <span class="Delimiter">{</span>
<span id="L133" class="LineNr">133 </span> <span class="Comment">// like call, but mark the current call as a 'base of continuation' call</span>
<span id="L134" class="LineNr">134 </span> <span class="Comment">// before pushing the next one on it</span>
<span id="L135" class="LineNr">135 </span> <span class="Normal">if</span> <span class="Delimiter">(</span><span class="Special">Trace_stream</span><span class="Delimiter">)</span> <span class="Delimiter">{</span>
<span id="L136" class="LineNr">136 </span> ++<span class="Special">Trace_stream</span><span class="Delimiter">-></span>callstack_depth<span class="Delimiter">;</span>
<span id="L137" class="LineNr">137 </span> <a href='003trace.cc.html#L189'>trace</a><span class="Delimiter">(</span><span class="Constant">"trace"</span><span class="Delimiter">)</span> << <span class="Constant">"delimited continuation; incrementing callstack depth to "</span> << <span class="Special">Trace_stream</span><span class="Delimiter">-></span>callstack_depth << <a href='003trace.cc.html#L225'>end</a><span class="Delimiter">();</span>
<span id="L138" class="LineNr">138 </span> assert<span class="Delimiter">(</span><span class="Special">Trace_stream</span><span class="Delimiter">-></span>callstack_depth < <span class="Constant">9000</span><span class="Delimiter">);</span> <span class="Comment">// 9998-101 plus cushion</span>
<span id="L139" class="LineNr">139 </span> <span class="Delimiter">}</span>
<span id="L140" class="LineNr">140 </span> <a href='010vm.cc.html#L33'>instruction</a><span class="Comment">/*</span><span class="Comment">copy</span><span class="Comment">*/</span> caller_instruction = <a href='026call.cc.html#L89'>current_instruction</a><span class="Delimiter">();</span>
<span id="L141" class="LineNr">141 </span> <span class="Special">Current_routine</span><span class="Delimiter">-></span>calls<span class="Delimiter">.</span>front<span class="Delimiter">().</span>continuation_mark_tag = <a href='026call.cc.html#L89'>current_instruction</a><span class="Delimiter">().</span>ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">).</span>value<span class="Delimiter">;</span>
<span id="L142" class="LineNr">142 </span> <span class="Special">Current_routine</span><span class="Delimiter">-></span>calls<span class="Delimiter">.</span>push_front<span class="Delimiter">(</span>call<span class="Delimiter">(</span>ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">1</span><span class="Delimiter">).</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">)));</span>
<span id="L143" class="LineNr">143 </span> <span class="Comment">// drop the mark</span>
<span id="L144" class="LineNr">144 </span> caller_instruction<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>erase<span class="Delimiter">(</span>caller_instruction<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>begin<span class="Delimiter">());</span>
<span id="L145" class="LineNr">145 </span> ingredients<span class="Delimiter">.</span>erase<span class="Delimiter">(</span>ingredients<span class="Delimiter">.</span>begin<span class="Delimiter">());</span>
<span id="L146" class="LineNr">146 </span> <span class="Comment">// drop the callee</span>
<span id="L147" class="LineNr">147 </span> caller_instruction<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>erase<span class="Delimiter">(</span>caller_instruction<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>begin<span class="Delimiter">());</span>
<span id="L148" class="LineNr">148 </span> ingredients<span class="Delimiter">.</span>erase<span class="Delimiter">(</span>ingredients<span class="Delimiter">.</span>begin<span class="Delimiter">());</span>
<span id="L149" class="LineNr">149 </span> finish_call_housekeeping<span class="Delimiter">(</span>caller_instruction<span class="Delimiter">,</span> ingredients<span class="Delimiter">);</span>
<span id="L150" class="LineNr">150 </span> <span class="Identifier">continue</span><span class="Delimiter">;</span>
<span id="L151" class="LineNr">151 </span><span class="Delimiter">}</span>
<span id="L152" class="LineNr">152 </span>
<span id="L153" class="LineNr">153 </span><span class="Delimiter">:(scenario next_ingredient_inside_continuation)</span>
<span id="L154" class="LineNr">154 </span><span class="muRecipe"><a href='010vm.cc.html#L19'>recipe</a></span> <a href='000organization.cc.html#L113'>main</a> [
<span id="L155" class="LineNr">155 </span> call-with-continuation-mark <span class="Constant">233</span>/mark<span class="Delimiter">,</span> f<span class="Delimiter">,</span><span class="Constant"> true</span>
<span id="L156" class="LineNr">156 </span>]
<span id="L157" class="LineNr">157 </span><span class="muRecipe"><a href='010vm.cc.html#L19'>recipe</a></span> f [
<span id="L158" class="LineNr">158 </span> <span class="Constant">10</span>:<span class="Normal">bool</span><span class="Special"> <- </span>next-input
<span id="L159" class="LineNr">159 </span>]
<span id="L160" class="LineNr">160 </span><span class="traceContains">+mem: storing 1 in location 10</span>
<span id="L161" class="LineNr">161 </span>
<span id="L162" class="LineNr">162 </span><span class="Delimiter">:(scenario delimited_continuation_out_of_recipe_variable)</span>
<span id="L163" class="LineNr">163 </span><span class="muRecipe"><a href='010vm.cc.html#L19'>recipe</a></span> <a href='000organization.cc.html#L113'>main</a> [
<span id="L164" class="LineNr">164 </span> <span class="Normal">x</span>:<a href='010vm.cc.html#L19'>recipe</a><span class="Special"> <- </span>copy f
<span id="L165" class="LineNr">165 </span> call-with-continuation-mark <span class="Constant">233</span>/mark<span class="Delimiter">,</span> x<span class="Delimiter">,</span><span class="Constant"> true</span>
<span id="L166" class="LineNr">166 </span>]
<span id="L167" class="LineNr">167 </span><span class="muRecipe"><a href='010vm.cc.html#L19'>recipe</a></span> f [
<span id="L168" class="LineNr">168 </span> <span class="Constant">10</span>:<span class="Normal">bool</span><span class="Special"> <- </span>next-input
<span id="L169" class="LineNr">169 </span>]
<span id="L170" class="LineNr">170 </span><span class="traceContains">+mem: storing 1 in location 10</span>
<span id="L171" class="LineNr">171 </span>
<span id="L172" class="LineNr">172 </span><span class="Comment">//: save the slice of current call stack until the 'call-with-continuation-mark'</span>
<span id="L173" class="LineNr">173 </span><span class="Comment">//: call, and return it as the result.</span>
<span id="L174" class="LineNr">174 </span><span class="Comment">//: todo: implement delimited continuations in Mu's memory</span>
<span id="L175" class="LineNr">175 </span><span class="Delimiter">:(before "End Types")</span>
<span id="L176" class="LineNr">176 </span><span class="Normal">struct</span> delimited_continuation <span class="Delimiter">{</span>
<span id="L177" class="LineNr">177 </span> call_stack frames<span class="Delimiter">;</span>
<span id="L178" class="LineNr">178 </span> <span class="Normal">int</span> nrefs<span class="Delimiter">;</span>
<span id="L179" class="LineNr">179 </span> delimited_continuation<span class="Delimiter">(</span>call_stack::iterator begin<span class="Delimiter">,</span> call_stack::iterator <a href='003trace.cc.html#L225'>end</a><span class="Delimiter">)</span> :frames<span class="Delimiter">(</span>call_stack<span class="Delimiter">(</span>begin<span class="Delimiter">,</span> <a href='003trace.cc.html#L225'>end</a><span class="Delimiter">)),</span> nrefs<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">)</span> <span class="Delimiter">{}</span>
<span id="L180" class="LineNr">180 </span><span class="Delimiter">};</span>
<span id="L181" class="LineNr">181 </span><span class="Delimiter">:(before "End Globals")</span>
<span id="L182" class="LineNr">182 </span>map<<span class="Normal">long</span> <span class="Normal">long</span> <span class="Normal">int</span><span class="Delimiter">,</span> delimited_continuation> <span class="Special">Delimited_continuation</span><span class="Delimiter">;</span>
<span id="L183" class="LineNr">183 </span><span class="Normal">long</span> <span class="Normal">long</span> <span class="Normal">int</span> <span class="Special">Next_delimited_continuation_id</span> = <span class="Constant">1</span><span class="Delimiter">;</span> <span class="Comment">// 0 is null just like an address</span>
<span id="L184" class="LineNr">184 </span><span class="Delimiter">:(before "End Reset")</span>
<span id="L185" class="LineNr">185 </span><span class="Special">Delimited_continuation</span><span class="Delimiter">.</span><a href='050scenario.cc.html#L60'>clear</a><span class="Delimiter">();</span>
<span id="L186" class="LineNr">186 </span><span class="Special">Next_delimited_continuation_id</span> = <span class="Constant">1</span><span class="Delimiter">;</span>
<span id="L187" class="LineNr">187 </span>
<span id="L188" class="LineNr">188 </span><span class="Delimiter">:(before "End Primitive Recipe Declarations")</span>
<span id="L189" class="LineNr">189 </span>RETURN_CONTINUATION_UNTIL_MARK<span class="Delimiter">,</span>
<span id="L190" class="LineNr">190 </span><span class="Delimiter">:(before "End Primitive Recipe Numbers")</span>
<span id="L191" class="LineNr">191 </span><span class="Special">Recipe_ordinal</span>[<span class="Constant">"return-continuation-until-mark"</span>] = RETURN_CONTINUATION_UNTIL_MARK<span class="Delimiter">;</span>
<span id="L192" class="LineNr">192 </span><span class="Delimiter">:(before "End Primitive Recipe Checks")</span>
<span id="L193" class="LineNr">193 </span><span class="Normal">case</span> RETURN_CONTINUATION_UNTIL_MARK: <span class="Delimiter">{</span>
<span id="L194" class="LineNr">194 </span> <span class="Normal">if</span> <span class="Delimiter">(</span>inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>empty<span class="Delimiter">())</span> <span class="Delimiter">{</span>
<span id="L195" class="LineNr">195 </span> <a href='003trace.cc.html#L196'>raise</a> << <a href='013update_operation.cc.html#L25'>maybe</a><span class="Delimiter">(</span>get<span class="Delimiter">(</span><span class="Special">Recipe</span><span class="Delimiter">,</span> r<span class="Delimiter">).</span>name<span class="Delimiter">)</span> << <span class="Constant">"'"</span> << to_original_string<span class="Delimiter">(</span>inst<span class="Delimiter">)</span> << <span class="Constant">"' requires at least one ingredient: a mark tag (number)\n"</span> << <a href='003trace.cc.html#L225'>end</a><span class="Delimiter">();</span>
<span id="L196" class="LineNr">196 </span> <span class="Delimiter">}</span>
<span id="L197" class="LineNr">197 </span> <span class="Identifier">break</span><span class="Delimiter">;</span>
<span id="L198" class="LineNr">198 </span><span class="Delimiter">}</span>
<span id="L199" class="LineNr">199 </span><span class="Delimiter">:(before "End Primitive Recipe Implementations")</span>
<span id="L200" class="LineNr">200 </span><span class="Normal">case</span> RETURN_CONTINUATION_UNTIL_MARK: <span class="Delimiter">{</span>
<span id="L201" class="LineNr">201 </span> <span class="Comment">// I don't know how to think about next-ingredient in combination with</span>
<span id="L202" class="LineNr">202 </span> <span class="Comment">// continuations, so seems cleaner to just kill it. Functions have to read</span>
<span id="L203" class="LineNr">203 </span> <span class="Comment">// their inputs before ever returning a continuation.</span>
<span id="L204" class="LineNr">204 </span> <span class="Special">Current_routine</span><span class="Delimiter">-></span>calls<span class="Delimiter">.</span>front<span class="Delimiter">().</span>ingredient_atoms<span class="Delimiter">.</span><a href='050scenario.cc.html#L60'>clear</a><span class="Delimiter">();</span>
<span id="L205" class="LineNr">205 </span> <span class="Special">Current_routine</span><span class="Delimiter">-></span>calls<span class="Delimiter">.</span>front<span class="Delimiter">().</span>next_ingredient_to_process = <span class="Constant">0</span><span class="Delimiter">;</span>
<span id="L206" class="LineNr">206 </span> <span class="Comment">// copy the current call stack until the most recent marked call</span>
<span id="L207" class="LineNr">207 </span> call_stack::iterator find_base_of_continuation<span class="Delimiter">(</span>call_stack&<span class="Delimiter">,</span> <span class="Normal">int</span><span class="Delimiter">);</span> <span class="Comment">// manual prototype containing '::'</span>
<span id="L208" class="LineNr">208 </span> call_stack::iterator base = find_base_of_continuation<span class="Delimiter">(</span><span class="Special">Current_routine</span><span class="Delimiter">-></span>calls<span class="Delimiter">,</span> <span class="Comment">/*</span><span class="Comment">mark tag</span><span class="Comment">*/</span><a href='026call.cc.html#L89'>current_instruction</a><span class="Delimiter">().</span>ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">).</span>value<span class="Delimiter">);</span>
<span id="L209" class="LineNr">209 </span> <span class="Normal">if</span> <span class="Delimiter">(</span>base == <span class="Special">Current_routine</span><span class="Delimiter">-></span>calls<span class="Delimiter">.</span><a href='003trace.cc.html#L225'>end</a><span class="Delimiter">())</span> <span class="Delimiter">{</span>
<span id="L210" class="LineNr">210 </span> <a href='003trace.cc.html#L196'>raise</a> << <a href='013update_operation.cc.html#L25'>maybe</a><span class="Delimiter">(</span><a href='026call.cc.html#L87'>current_recipe_name</a><span class="Delimiter">())</span> << <span class="Constant">"couldn't find a 'call-with-continuation-mark' to return to with tag "</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>original_string << <span class="cSpecial">'\n'</span> << end<span class="Delimiter">();</span>
<span id="L211" class="LineNr">211 </span> <a href='003trace.cc.html#L196'>raise</a> << <a href='013update_operation.cc.html#L25'>maybe</a><span class="Delimiter">(</span><a href='026call.cc.html#L87'>current_recipe_name</a><span class="Delimiter">())</span> << <span class="Constant">"call stack:\n"</span> << <a href='003trace.cc.html#L225'>end</a><span class="Delimiter">();</span>
<span id="L212" class="LineNr">212 </span> <span class="Normal">for</span> <span class="Delimiter">(</span>call_stack::iterator p = <span class="Special">Current_routine</span><span class="Delimiter">-></span>calls<span class="Delimiter">.</span>begin<span class="Delimiter">();</span> p != <span class="Special">Current_routine</span><span class="Delimiter">-></span>calls<span class="Delimiter">.</span><a href='003trace.cc.html#L225'>end</a><span class="Delimiter">();</span> ++p<span class="Delimiter">)</span>
<span id="L213" class="LineNr">213 </span> <a href='003trace.cc.html#L196'>raise</a> << <a href='013update_operation.cc.html#L25'>maybe</a><span class="Delimiter">(</span><a href='026call.cc.html#L87'>current_recipe_name</a><span class="Delimiter">())</span> << <span class="Constant">" "</span> << get<span class="Delimiter">(</span><span class="Special">Recipe</span><span class="Delimiter">,</span> p<span class="Delimiter">-></span>running_recipe<span class="Delimiter">).</span>name << <span class="cSpecial">'\n'</span> << <a href='003trace.cc.html#L225'>end</a><span class="Delimiter">();</span>
<span id="L214" class="LineNr">214 </span> <span class="Identifier">break</span><span class="Delimiter">;</span>
<span id="L215" class="LineNr">215 </span> <span class="Delimiter">}</span>
<span id="L216" class="LineNr">216 </span> <a href='003trace.cc.html#L189'>trace</a><span class="Delimiter">(</span><span class="Constant">"run"</span><span class="Delimiter">)</span> << <span class="Constant">"creating continuation "</span> << <span class="Special">Next_delimited_continuation_id</span> << <a href='003trace.cc.html#L225'>end</a><span class="Delimiter">();</span>
<span id="L217" class="LineNr">217 </span> <a href='001help.cc.html#L221'>put</a><span class="Delimiter">(</span><span class="Special">Delimited_continuation</span><span class="Delimiter">,</span> <span class="Special">Next_delimited_continuation_id</span><span class="Delimiter">,</span> delimited_continuation<span class="Delimiter">(</span><span class="Special">Current_routine</span><span class="Delimiter">-></span>calls<span class="Delimiter">.</span>begin<span class="Delimiter">(),</span> base<span class="Delimiter">));</span>
<span id="L218" class="LineNr">218 </span> <span class="Normal">while</span> <span class="Delimiter">(</span><span class="Special">Current_routine</span><span class="Delimiter">-></span>calls<span class="Delimiter">.</span>begin<span class="Delimiter">()</span> != base<span class="Delimiter">)</span> <span class="Delimiter">{</span>
<span id="L219" class="LineNr">219 </span> <span class="Normal">if</span> <span class="Delimiter">(</span><span class="Special">Trace_stream</span><span class="Delimiter">)</span> <span class="Delimiter">{</span>
<span id="L220" class="LineNr">220 </span> --<span class="Special">Trace_stream</span><span class="Delimiter">-></span>callstack_depth<span class="Delimiter">;</span>
<span id="L221" class="LineNr">221 </span> assert<span class="Delimiter">(</span><span class="Special">Trace_stream</span><span class="Delimiter">-></span>callstack_depth >= <span class="Constant">0</span><span class="Delimiter">);</span>
<span id="L222" class="LineNr">222 </span> <span class="Delimiter">}</span>
<span id="L223" class="LineNr">223 </span> <span class="Special">Current_routine</span><span class="Delimiter">-></span>calls<span class="Delimiter">.</span>pop_front<span class="Delimiter">();</span>
<span id="L224" class="LineNr">224 </span> <span class="Delimiter">}</span>
<span id="L225" class="LineNr">225 </span> <span class="Comment">// return it as the result of the marked call</span>
<span id="L226" class="LineNr">226 </span> products<span class="Delimiter">.</span>resize<span class="Delimiter">(</span><span class="Constant">1</span><span class="Delimiter">);</span>
<span id="L227" class="LineNr">227 </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><span class="Special">Next_delimited_continuation_id</span><span class="Delimiter">);</span>
<span id="L228" class="LineNr">228 </span> <span class="Comment">// return any other ingredients passed in</span>
<span id="L229" class="LineNr">229 </span> copy<span class="Delimiter">(</span><span class="Comment">/*</span><span class="Comment">skip mark tag</span><span class="Comment">*/</span>++ingredients<span class="Delimiter">.</span>begin<span class="Delimiter">(),</span> ingredients<span class="Delimiter">.</span><a href='003trace.cc.html#L225'>end</a><span class="Delimiter">(),</span> inserter<span class="Delimiter">(</span>products<span class="Delimiter">,</span> products<span class="Delimiter">.</span><a href='003trace.cc.html#L225'>end</a><span class="Delimiter">()));</span>
<span id="L230" class="LineNr">230 </span> ++<span class="Special">Next_delimited_continuation_id</span><span class="Delimiter">;</span>
<span id="L231" class="LineNr">231 </span> <span class="Identifier">break</span><span class="Delimiter">;</span> <span class="Comment">// continue to process rest of marked call</span>
<span id="L232" class="LineNr">232 </span><span class="Delimiter">}</span>
<span id="L233" class="LineNr">233 </span>
<span id="L234" class="LineNr">234 </span><span class="Delimiter">:(code)</span>
<span id="L235" class="LineNr">235 </span>call_stack::iterator find_base_of_continuation<span class="Delimiter">(</span>call_stack& c<span class="Delimiter">,</span> <span class="Normal">int</span> mark_tag<span class="Delimiter">)</span> <span class="Delimiter">{</span>
<span id="L236" class="LineNr">236 </span> <span class="Normal">for</span> <span class="Delimiter">(</span>call_stack::iterator p = c<span class="Delimiter">.</span>begin<span class="Delimiter">();</span> p != c<span class="Delimiter">.</span><a href='003trace.cc.html#L225'>end</a><span class="Delimiter">();</span> ++p<span class="Delimiter">)</span>
<span id="L237" class="LineNr">237 </span> <span class="Normal">if</span> <span class="Delimiter">(</span>p<span class="Delimiter">-></span>continuation_mark_tag == mark_tag<span class="Delimiter">)</span> <span class="Identifier">return</span> p<span class="Delimiter">;</span>
<span id="L238" class="LineNr">238 </span> <span class="Identifier">return</span> c<span class="Delimiter">.</span><a href='003trace.cc.html#L225'>end</a><span class="Delimiter">();</span>
<span id="L239" class="LineNr">239 </span><span class="Delimiter">}</span>
<span id="L240" class="LineNr">240 </span>
<span id="L241" class="LineNr">241 </span><span class="Comment">//: overload 'call' for continuations</span>
<span id="L242" class="LineNr">242 </span><span class="Delimiter">:(after "Begin Call")</span>
<span id="L243" class="LineNr">243 </span><span class="Normal">if</span> <span class="Delimiter">(</span>is_mu_continuation<span class="Delimiter">(</span><a href='026call.cc.html#L89'>current_instruction</a><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="Delimiter">{</span>
<span id="L244" class="LineNr">244 </span> <span class="Comment">// copy multiple calls on to current call stack</span>
<span id="L245" class="LineNr">245 </span> assert<span class="Delimiter">(</span>scalar<span class="Delimiter">(</span>ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">)));</span>
<span id="L246" class="LineNr">246 </span> <a href='003trace.cc.html#L189'>trace</a><span class="Delimiter">(</span><span class="Constant">"run"</span><span class="Delimiter">)</span> << <span class="Constant">"calling continuation "</span> << ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">).</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">)</span> << <a href='003trace.cc.html#L225'>end</a><span class="Delimiter">();</span>
<span id="L247" class="LineNr">247 </span> <span class="Normal">if</span> <span class="Delimiter">(</span>!contains_key<span class="Delimiter">(</span><span class="Special">Delimited_continuation</span><span class="Delimiter">,</span> ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">).</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">)))</span>
<span id="L248" class="LineNr">248 </span> <a href='003trace.cc.html#L196'>raise</a> << <a href='013update_operation.cc.html#L25'>maybe</a><span class="Delimiter">(</span><a href='026call.cc.html#L87'>current_recipe_name</a><span class="Delimiter">())</span> << <span class="Constant">"no such delimited continuation "</span> << <a href='026call.cc.html#L89'>current_instruction</a><span class="Delimiter">().</span>ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">).</span>original_string << <span class="cSpecial">'\n'</span> << <a href='003trace.cc.html#L225'>end</a><span class="Delimiter">();</span>
<span id="L249" class="LineNr">249 </span> <span class="Normal">const</span> call_stack& new_frames = get<span class="Delimiter">(</span><span class="Special">Delimited_continuation</span><span class="Delimiter">,</span> ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">).</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">)).</span>frames<span class="Delimiter">;</span>
<span id="L250" class="LineNr">250 </span> <span class="Normal">for</span> <span class="Delimiter">(</span>call_stack::const_reverse_iterator p = new_frames<span class="Delimiter">.</span>rbegin<span class="Delimiter">();</span> p != new_frames<span class="Delimiter">.</span>rend<span class="Delimiter">();</span> ++p<span class="Delimiter">)</span>
<span id="L251" class="LineNr">251 </span> <span class="Special">Current_routine</span><span class="Delimiter">-></span>calls<span class="Delimiter">.</span>push_front<span class="Delimiter">(</span>*p<span class="Delimiter">);</span>
<span id="L252" class="LineNr">252 </span> <span class="Normal">if</span> <span class="Delimiter">(</span><span class="Special">Trace_stream</span><span class="Delimiter">)</span> <span class="Delimiter">{</span>
<span id="L253" class="LineNr">253 </span> <span class="Special">Trace_stream</span><span class="Delimiter">-></span>callstack_depth += <a href='001help.cc.html#L141'>SIZE</a><span class="Delimiter">(</span>new_frames<span class="Delimiter">);</span>
<span id="L254" class="LineNr">254 </span> <a href='003trace.cc.html#L189'>trace</a><span class="Delimiter">(</span><span class="Constant">"trace"</span><span class="Delimiter">)</span> << <span class="Constant">"calling delimited continuation; growing callstack depth to "</span> << <span class="Special">Trace_stream</span><span class="Delimiter">-></span>callstack_depth << <a href='003trace.cc.html#L225'>end</a><span class="Delimiter">();</span>
<span id="L255" class="LineNr">255 </span> assert<span class="Delimiter">(</span><span class="Special">Trace_stream</span><span class="Delimiter">-></span>callstack_depth < <span class="Constant">9000</span><span class="Delimiter">);</span> <span class="Comment">// 9998-101 plus cushion</span>
<span id="L256" class="LineNr">256 </span> <span class="Delimiter">}</span>
<span id="L257" class="LineNr">257 </span> <span class="Comment">// no call housekeeping; continuations don't support next-ingredient</span>
<span id="L258" class="LineNr">258 </span> copy<span class="Delimiter">(</span><span class="Comment">/*</span><span class="Comment">drop continuation</span><span class="Comment">*/</span>++ingredients<span class="Delimiter">.</span>begin<span class="Delimiter">(),</span> ingredients<span class="Delimiter">.</span><a href='003trace.cc.html#L225'>end</a><span class="Delimiter">(),</span> inserter<span class="Delimiter">(</span>products<span class="Delimiter">,</span> products<span class="Delimiter">.</span>begin<span class="Delimiter">()));</span>
<span id="L259" class="LineNr">259 </span> <span class="Identifier">break</span><span class="Delimiter">;</span> <span class="Comment">// record results of resuming 'return-continuation-until-mark' instruction</span>
<span id="L260" class="LineNr">260 </span><span class="Delimiter">}</span>
<span id="L261" class="LineNr">261 </span>
<span id="L262" class="LineNr">262 </span><span class="Delimiter">:(scenario continuations_can_return_values)</span>
<span id="L263" class="LineNr">263 </span><span class="muRecipe">def</span> <a href='000organization.cc.html#L113'>main</a> [
<span id="L264" class="LineNr">264 </span> local-scope
<span id="L265" class="LineNr">265 </span> <span class="Normal">k</span>:continuation<span class="Delimiter">,</span> <span class="Constant">1</span>:num/<span class="Special">raw <- </span>call-with-continuation-mark <span class="Constant">233</span>/mark<span class="Delimiter">,</span> f
<span id="L266" class="LineNr">266 </span>]
<span id="L267" class="LineNr">267 </span><span class="muRecipe">def</span> f [
<span id="L268" class="LineNr">268 </span> local-scope
<span id="L269" class="LineNr">269 </span> g
<span id="L270" class="LineNr">270 </span>]
<span id="L271" class="LineNr">271 </span><span class="muRecipe">def</span> g [
<span id="L272" class="LineNr">272 </span> local-scope
<span id="L273" class="LineNr">273 </span> <span class="Identifier">return</span>-continuation-until-mark <span class="Constant">233</span>/mark<span class="Delimiter">,</span> <span class="Constant">34</span>
<span id="L274" class="LineNr">274 </span> stash [continuation called]
<span id="L275" class="LineNr">275 </span>]
<span id="L276" class="LineNr">276 </span><span class="traceContains">+mem: storing 34 in location 1</span>
<span id="L277" class="LineNr">277 </span>
<span id="L278" class="LineNr">278 </span><span class="Delimiter">:(scenario continuations_continue_to_matching_mark)</span>
<span id="L279" class="LineNr">279 </span><span class="muRecipe">def</span> <a href='000organization.cc.html#L113'>main</a> [
<span id="L280" class="LineNr">280 </span> local-scope
<span id="L281" class="LineNr">281 </span> <span class="Normal">k</span>:continuation<span class="Delimiter">,</span> <span class="Constant">1</span>:num/<span class="Special">raw <- </span>call-with-continuation-mark <span class="Constant">233</span>/mark<span class="Delimiter">,</span> f
<span id="L282" class="LineNr">282 </span> add <span class="Constant">1</span><span class="Delimiter">,</span> <span class="Constant">1</span>
<span id="L283" class="LineNr">283 </span>]
<span id="L284" class="LineNr">284 </span><span class="muRecipe">def</span> f [
<span id="L285" class="LineNr">285 </span> local-scope
<span id="L286" class="LineNr">286 </span> <span class="Normal">k2</span>:continuation<span class="Special"> <- </span>call-with-continuation-mark <span class="Constant">234</span>/mark<span class="Delimiter">,</span> g
<span id="L287" class="LineNr">287 </span> add <span class="Constant">2</span><span class="Delimiter">,</span> <span class="Constant">2</span>
<span id="L288" class="LineNr">288 </span>]
<span id="L289" class="LineNr">289 </span><span class="muRecipe">def</span> g [
<span id="L290" class="LineNr">290 </span> local-scope
<span id="L291" class="LineNr">291 </span> <span class="Identifier">return</span>-continuation-until-mark <span class="Constant">233</span>/mark<span class="Delimiter">,</span> <span class="Constant">34</span>
<span id="L292" class="LineNr">292 </span> stash [continuation called]
<span id="L293" class="LineNr">293 </span>]
<span id="L294" class="LineNr">294 </span><span class="traceContains">+run: add {1: "literal"}, {1: "literal"}</span>
<span id="L295" class="LineNr">295 </span><span class="traceAbsent">-run: add {2: "literal"}, {2: "literal"}</span>
<span id="L296" class="LineNr">296 </span>
<span id="L297" class="LineNr">297 </span><span class="Comment">//: Allow shape-shifting recipes to return continuations.</span>
<span id="L298" class="LineNr">298 </span>
<span id="L299" class="LineNr">299 </span><span class="Delimiter">:(scenario call_shape_shifting_recipe_with_continuation_mark)</span>
<span id="L300" class="LineNr">300 </span><span class="muRecipe">def</span> <a href='000organization.cc.html#L113'>main</a> [
<span id="L301" class="LineNr">301 </span> <span class="Constant">1</span>:num<span class="Special"> <- </span>call-with-continuation-mark <span class="Constant">233</span>/mark<span class="Delimiter">,</span> f<span class="Delimiter">,</span> <span class="Constant">34</span>
<span id="L302" class="LineNr">302 </span>]
<span id="L303" class="LineNr">303 </span><span class="muRecipe">def</span> f x:_elem<span class="muRecipe"> -> </span>y:_elem [
<span id="L304" class="LineNr">304 </span> local-scope
<span id="L305" class="LineNr">305 </span> load-ingredients
<span id="L306" class="LineNr">306 </span> y<span class="Special"> <- </span>copy x
<span id="L307" class="LineNr">307 </span>]
<span id="L308" class="LineNr">308 </span><span class="traceContains">+mem: storing 34 in location 1</span>
<span id="L309" class="LineNr">309 </span>
<span id="L310" class="LineNr">310 </span><span class="Delimiter">:(before "End resolve_ambiguous_call(r, index, inst, caller_recipe) Special-cases")</span>
<span id="L311" class="LineNr">311 </span><span class="Normal">if</span> <span class="Delimiter">(</span>inst<span class="Delimiter">.</span>name == <span class="Constant">"call-with-continuation-mark"</span><span class="Delimiter">)</span> <span class="Delimiter">{</span>
<span id="L312" class="LineNr">312 </span> <span class="Normal">if</span> <span class="Delimiter">(</span><a href='001help.cc.html#L141'>SIZE</a><span class="Delimiter">(</span>inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">)</span> > <span class="Constant">1</span> && <a href='072recipe.cc.html#L208'>is_recipe_literal</a><span class="Delimiter">(</span>inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Comment">/*</span><span class="Comment">skip mark</span><span class="Comment">*/</span><span class="Constant">1</span><span class="Delimiter">)))</span> <span class="Delimiter">{</span>
<span id="L313" class="LineNr">313 </span> resolve_indirect_continuation_call<span class="Delimiter">(</span>r<span class="Delimiter">,</span> index<span class="Delimiter">,</span> inst<span class="Delimiter">,</span> caller_recipe<span class="Delimiter">);</span>
<span id="L314" class="LineNr">314 </span> <span class="Identifier">return</span><span class="Delimiter">;</span>
<span id="L315" class="LineNr">315 </span> <span class="Delimiter">}</span>
<span id="L316" class="LineNr">316 </span><span class="Delimiter">}</span>
<span id="L317" class="LineNr">317 </span><span class="Delimiter">:(code)</span>
<span id="L318" class="LineNr">318 </span><span class="Normal">void</span> resolve_indirect_continuation_call<span class="Delimiter">(</span><span class="Normal">const</span> <a href='010vm.cc.html#L14'>recipe_ordinal</a> r<span class="Delimiter">,</span> <span class="Normal">int</span> index<span class="Delimiter">,</span> instruction& inst<span class="Delimiter">,</span> <span class="Normal">const</span> recipe& caller_recipe<span class="Delimiter">)</span> <span class="Delimiter">{</span>
<span id="L319" class="LineNr">319 </span> <a href='010vm.cc.html#L33'>instruction</a> inst2<span class="Delimiter">;</span>
<span id="L320" class="LineNr">320 </span> inst2<span class="Delimiter">.</span>name = inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Comment">/*</span><span class="Comment">skip mark</span><span class="Comment">*/</span><span class="Constant">1</span><span class="Delimiter">).</span>name<span class="Delimiter">;</span>
<span id="L321" class="LineNr">321 </span> <span class="Normal">for</span> <span class="Delimiter">(</span><span class="Normal">int</span> i = <span class="Comment">/*</span><span class="Comment">skip mark and <a href='010vm.cc.html#L19'>recipe</a></span><span class="Comment">*/</span><span class="Constant">2</span><span class="Delimiter">;</span> i < <a href='001help.cc.html#L141'>SIZE</a><span class="Delimiter">(</span>inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">);</span> ++i<span class="Delimiter">)</span>
<span id="L322" class="LineNr">322 </span> inst2<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>push_back<span class="Delimiter">(</span>inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span>i<span class="Delimiter">));</span>
<span id="L323" class="LineNr">323 </span> <span class="Normal">for</span> <span class="Delimiter">(</span><span class="Normal">int</span> i = <span class="Comment">/*</span><span class="Comment">skip continuation</span><span class="Comment">*/</span><span class="Constant">1</span><span class="Delimiter">;</span> i < <a href='001help.cc.html#L141'>SIZE</a><span class="Delimiter">(</span>inst<span class="Delimiter">.</span>products<span class="Delimiter">);</span> ++i<span class="Delimiter">)</span>
<span id="L324" class="LineNr">324 </span> inst2<span class="Delimiter">.</span>products<span class="Delimiter">.</span>push_back<span class="Delimiter">(</span>inst<span class="Delimiter">.</span>products<span class="Delimiter">.</span>at<span class="Delimiter">(</span>i<span class="Delimiter">));</span>
<span id="L325" class="LineNr">325 </span> <a href='054static_dispatch.cc.html#L173'>resolve_ambiguous_call</a><span class="Delimiter">(</span>r<span class="Delimiter">,</span> index<span class="Delimiter">,</span> inst2<span class="Delimiter">,</span> caller_recipe<span class="Delimiter">);</span>
<span id="L326" class="LineNr">326 </span> inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Comment">/*</span><span class="Comment">skip mark</span><span class="Comment">*/</span><span class="Constant">1</span><span class="Delimiter">).</span>name = inst2<span class="Delimiter">.</span>name<span class="Delimiter">;</span>
<span id="L327" class="LineNr">327 </span> inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Comment">/*</span><span class="Comment">skip mark</span><span class="Comment">*/</span><span class="Constant">1</span><span class="Delimiter">).</span><a href='010vm.cc.html#L67'>set_value</a><span class="Delimiter">(</span>get<span class="Delimiter">(</span><span class="Special">Recipe_ordinal</span><span class="Delimiter">,</span> inst2<span class="Delimiter">.</span>name<span class="Delimiter">));</span>
<span id="L328" class="LineNr">328 </span><span class="Delimiter">}</span>
<span id="L329" class="LineNr">329 </span>
<span id="L330" class="LineNr">330 </span><span class="Delimiter">:(scenario call_shape_shifting_recipe_with_continuation_mark_and_no_outputs)</span>
<span id="L331" class="LineNr">331 </span><span class="muRecipe">def</span> <a href='000organization.cc.html#L113'>main</a> [
<span id="L332" class="LineNr">332 </span> <span class="Constant">1</span>:continuation<span class="Special"> <- </span>call-with-continuation-mark <span class="Constant">233</span>/mark<span class="Delimiter">,</span> f<span class="Delimiter">,</span> <span class="Constant">34</span>
<span id="L333" class="LineNr">333 </span>]
<span id="L334" class="LineNr">334 </span><span class="muRecipe">def</span> f x:_elem [
<span id="L335" class="LineNr">335 </span> local-scope
<span id="L336" class="LineNr">336 </span> load-ingredients
<span id="L337" class="LineNr">337 </span> <span class="Identifier">return</span>-continuation-until-mark <span class="Constant">233</span>/mark
<span id="L338" class="LineNr">338 </span>]
<span id="L339" class="LineNr">339 </span>$error: <span class="Constant">0</span>
<span id="L340" class="LineNr">340 </span>
<span id="L341" class="LineNr">341 </span><span class="Delimiter">:(scenario continuation1)</span>
<span id="L342" class="LineNr">342 </span><span class="muRecipe">def</span> <a href='000organization.cc.html#L113'>main</a> [
<span id="L343" class="LineNr">343 </span> local-scope
<span id="L344" class="LineNr">344 </span> <span class="Normal">k</span>:continuation<span class="Special"> <- </span>call-with-continuation-mark <span class="Constant">233</span>/mark<span class="Delimiter">,</span> create-yielder
<span id="L345" class="LineNr">345 </span> <span class="Constant">10</span>:num/<span class="Special">raw <- </span>call k
<span id="L346" class="LineNr">346 </span>]
<span id="L347" class="LineNr">347 </span><span class="muRecipe">def</span> create-yielder<span class="muRecipe"> -> </span>n:num [
<span id="L348" class="LineNr">348 </span> local-scope
<span id="L349" class="LineNr">349 </span> load-inputs
<span id="L350" class="LineNr">350 </span> <span class="Identifier">return</span>-continuation-until-mark <span class="Constant">233</span>/mark
<span id="L351" class="LineNr">351 </span> <span class="Identifier">return</span> <span class="Constant">1</span>
<span id="L352" class="LineNr">352 </span>]
<span id="L353" class="LineNr">353 </span><span class="traceContains">+mem: storing 1 in location 10</span>
<span id="L354" class="LineNr">354 </span>$error: <span class="Constant">0</span>
<span id="L355" class="LineNr">355 </span>
<span id="L356" class="LineNr">356 </span><span class="Delimiter">:(code)</span>
<span id="L357" class="LineNr">357 </span><span class="Normal">bool</span> is_mu_continuation<span class="Delimiter">(</span>reagent<span class="Comment">/*</span><span class="Comment">copy</span><span class="Comment">*/</span> x<span class="Delimiter">)</span> <span class="Delimiter">{</span>
<span id="L358" class="LineNr">358 </span> canonize_type<span class="Delimiter">(</span>x<span class="Delimiter">);</span>
<span id="L359" class="LineNr">359 </span> <span class="Identifier">return</span> x<span class="Delimiter">.</span>type && x<span class="Delimiter">.</span>type<span class="Delimiter">-></span>atom && x<span class="Delimiter">.</span>type<span class="Delimiter">-></span>value == get<span class="Delimiter">(</span><span class="Special">Type_ordinal</span><span class="Delimiter">,</span> <span class="Constant">"continuation"</span><span class="Delimiter">);</span>
<span id="L360" class="LineNr">360 </span><span class="Delimiter">}</span>
<span id="L361" class="LineNr">361 </span>
<span id="L362" class="LineNr">362 </span><span class="Comment">// helper for debugging</span>
<span id="L363" class="LineNr">363 </span><span class="Normal">void</span> dump<span class="Delimiter">(</span><span class="Normal">const</span> <span class="Normal">int</span> continuation_id<span class="Delimiter">)</span> <span class="Delimiter">{</span>
<span id="L364" class="LineNr">364 </span> <span class="Normal">if</span> <span class="Delimiter">(</span>!contains_key<span class="Delimiter">(</span><span class="Special">Delimited_continuation</span><span class="Delimiter">,</span> continuation_id<span class="Delimiter">))</span> <span class="Delimiter">{</span>
<span id="L365" class="LineNr">365 </span> <a href='003trace.cc.html#L196'>raise</a> << <span class="Constant">"missing delimited continuation: "</span> << continuation_id << <span class="cSpecial">'\n'</span> << <a href='003trace.cc.html#L225'>end</a><span class="Delimiter">();</span>
<span id="L366" class="LineNr">366 </span> <span class="Identifier">return</span><span class="Delimiter">;</span>
<span id="L367" class="LineNr">367 </span> <span class="Delimiter">}</span>
<span id="L368" class="LineNr">368 </span> delimited_continuation& curr = get<span class="Delimiter">(</span><span class="Special">Delimited_continuation</span><span class="Delimiter">,</span> continuation_id<span class="Delimiter">);</span>
<span id="L369" class="LineNr">369 </span> dump<span class="Delimiter">(</span>curr<span class="Delimiter">.</span>frames<span class="Delimiter">);</span>
<span id="L370" class="LineNr">370 </span><span class="Delimiter">}</span>
</pre>
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