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<a href='https://github.com/akkartik/mu/blob/master/same-fringe.mu'>https://github.com/akkartik/mu/blob/master/same-fringe.mu</a>
<pre id='vimCodeElement'>
<span id="L1" class="LineNr"> 1 </span><span class="Comment"># The 'same fringe' problem: <a href="http://wiki.c2.com/?SameFringeProblem">http://wiki.c2.com/?SameFringeProblem</a></span>
<span id="L2" class="LineNr"> 2 </span><span class="Comment"># Example program demonstrating coroutines using Mu's delimited continuations.</span>
<span id="L3" class="LineNr"> 3 </span><span class="Comment">#</span>
<span id="L4" class="LineNr"> 4 </span><span class="Comment"># Expected output:</span>
<span id="L5" class="LineNr"> 5 </span><span class="Comment"># 1</span>
<span id="L6" class="LineNr"> 6 </span><span class="Comment"># (i.e. that the two given trees x and y have the same leaves, in the same</span>
<span id="L7" class="LineNr"> 7 </span><span class="Comment"># order from left to right)</span>
<span id="L8" class="LineNr"> 8 </span>
<span id="L9" class="LineNr"> 9 </span><span class="muData">container</span> <a href='same-fringe.mu.html#L9'>tree</a>:_elem [
<span id="L10" class="LineNr">10 </span> val:_elem
<span id="L11" class="LineNr">11 </span> left:&:<a href='same-fringe.mu.html#L9'>tree</a>:_elem
<span id="L12" class="LineNr">12 </span> right:&:<a href='same-fringe.mu.html#L9'>tree</a>:_elem
<span id="L13" class="LineNr">13 </span>]
<span id="L14" class="LineNr">14 </span>
<span id="L15" class="LineNr">15 </span><span class="muRecipe">def</span> <a href='same-fringe.mu.html#L15'>main</a> [
<span id="L16" class="LineNr">16 </span> <span class="Constant">local-scope</span>
<span id="L17" class="LineNr">17 </span> <span class="Comment"># x: ((a b) c)</span>
<span id="L18" class="LineNr">18 </span> <span class="Comment"># y: (a (b c))</span>
<span id="L19" class="LineNr">19 </span> a:&:<a href='same-fringe.mu.html#L9'>tree</a>:num <span class="Special"><-</span> new-tree<span class="Constant"> 3</span>
<span id="L20" class="LineNr">20 </span> b:&:<a href='same-fringe.mu.html#L9'>tree</a>:num <span class="Special"><-</span> new-tree<span class="Constant"> 4</span>
<span id="L21" class="LineNr">21 </span> c:&:<a href='same-fringe.mu.html#L9'>tree</a>:num <span class="Special"><-</span> new-tree<span class="Constant"> 5</span>
<span id="L22" class="LineNr">22 </span> x1:&:<a href='same-fringe.mu.html#L9'>tree</a>:num <span class="Special"><-</span> new-tree a, b
<span id="L23" class="LineNr">23 </span> x:&:<a href='same-fringe.mu.html#L9'>tree</a>:num <span class="Special"><-</span> new-tree x1, c
<span id="L24" class="LineNr">24 </span> y1:&:<a href='same-fringe.mu.html#L9'>tree</a>:num <span class="Special"><-</span> new-tree b, c
<span id="L25" class="LineNr">25 </span> y:&:<a href='same-fringe.mu.html#L9'>tree</a>:num <span class="Special"><-</span> new-tree a, y1
<span id="L26" class="LineNr">26 </span> result:bool <span class="Special"><-</span> <a href='same-fringe.mu.html#L30'>same-fringe</a> x, y
<span id="L27" class="LineNr">27 </span> $print result <span class="Constant">10/newline</span>
<span id="L28" class="LineNr">28 </span>]
<span id="L29" class="LineNr">29 </span>
<span id="L30" class="LineNr">30 </span><span class="muRecipe">def</span> <a href='same-fringe.mu.html#L30'>same-fringe</a> a:&:<a href='same-fringe.mu.html#L9'>tree</a>:_elem, b:&:<a href='same-fringe.mu.html#L9'>tree</a>:_elem<span class="muRecipe"> -> </span>result:bool [
<span id="L31" class="LineNr">31 </span> <span class="Constant">local-scope</span>
<span id="L32" class="LineNr">32 </span> <span class="Constant">load-inputs</span>
<span id="L33" class="LineNr">33 </span> k1:continuation <span class="Special"><-</span> <span class="muControl">call-with-continuation-mark</span> <span class="Constant">100/mark</span>, <a href='same-fringe.mu.html#L48'>process</a>, a
<span id="L34" class="LineNr">34 </span> k2:continuation <span class="Special"><-</span> <span class="muControl">call-with-continuation-mark</span> <span class="Constant">100/mark</span>, <a href='same-fringe.mu.html#L48'>process</a>, b
<span id="L35" class="LineNr">35 </span> <span class="Delimiter">{</span>
<span id="L36" class="LineNr">36 </span> k1, x:_elem, a-done?:bool <span class="Special"><-</span> call k1
<span id="L37" class="LineNr">37 </span> k2, y:_elem, b-done?:bool <span class="Special"><-</span> call k2
<span id="L38" class="LineNr">38 </span> <span class="muControl">break-if</span> a-done?
<span id="L39" class="LineNr">39 </span> <span class="muControl">break-if</span> b-done?
<span id="L40" class="LineNr">40 </span> match?:bool <span class="Special"><-</span> equal x, y
<span id="L41" class="LineNr">41 </span> <span class="muControl">return-unless</span> match?,<span class="Constant"> false</span>
<span id="L42" class="LineNr">42 </span> <span class="muControl"> loop</span>
<span id="L43" class="LineNr">43 </span> <span class="Delimiter">}</span>
<span id="L44" class="LineNr">44 </span> result <span class="Special"><-</span> and a-done?, b-done?
<span id="L45" class="LineNr">45 </span>]
<span id="L46" class="LineNr">46 </span>
<span id="L47" class="LineNr">47 </span><span class="Comment"># harness around traversal</span>
<span id="L48" class="LineNr">48 </span><span class="muRecipe">def</span> <a href='same-fringe.mu.html#L48'>process</a> t:&:<a href='same-fringe.mu.html#L9'>tree</a>:_elem [
<span id="L49" class="LineNr">49 </span> <span class="Constant">local-scope</span>
<span id="L50" class="LineNr">50 </span> <span class="Constant">load-inputs</span>
<span id="L51" class="LineNr">51 </span> <span class="muControl">return-continuation-until-mark</span> <span class="Constant">100/mark</span> <span class="Comment"># initial</span>
<span id="L52" class="LineNr">52 </span> <a href='same-fringe.mu.html#L59'>traverse</a> t
<span id="L53" class="LineNr">53 </span> zero-val:&:_elem <span class="Special"><-</span> new <span class="Constant">_elem:type</span>
<span id="L54" class="LineNr">54 </span> <span class="muControl">return-continuation-until-mark</span> <span class="Constant">100/mark</span>, *zero-val,<span class="Constant"> true/done</span> <span class="Comment"># final</span>
<span id="L55" class="LineNr">55 </span> assert<span class="Constant"> false</span>, <span class="Constant">[continuation called past done]</span>
<span id="L56" class="LineNr">56 </span>]
<span id="L57" class="LineNr">57 </span>
<span id="L58" class="LineNr">58 </span><span class="Comment"># core traversal</span>
<span id="L59" class="LineNr">59 </span><span class="muRecipe">def</span> <a href='same-fringe.mu.html#L59'>traverse</a> t:&:<a href='same-fringe.mu.html#L9'>tree</a>:_elem [
<span id="L60" class="LineNr">60 </span> <span class="Constant">local-scope</span>
<span id="L61" class="LineNr">61 </span> <span class="Constant">load-inputs</span>
<span id="L62" class="LineNr">62 </span> <span class="muControl">return-unless</span> t
<span id="L63" class="LineNr">63 </span> l:&:<a href='same-fringe.mu.html#L9'>tree</a>:_elem <span class="Special"><-</span> get *t, <span class="Constant">left:offset</span>
<span id="L64" class="LineNr">64 </span> <a href='same-fringe.mu.html#L59'>traverse</a> l
<span id="L65" class="LineNr">65 </span> r:&:<a href='same-fringe.mu.html#L9'>tree</a>:_elem <span class="Special"><-</span> get *t, <span class="Constant">right:offset</span>
<span id="L66" class="LineNr">66 </span> <a href='same-fringe.mu.html#L59'>traverse</a> r
<span id="L67" class="LineNr">67 </span> <span class="muControl">return-if</span> l
<span id="L68" class="LineNr">68 </span> <span class="muControl">return-if</span> r
<span id="L69" class="LineNr">69 </span> <span class="Comment"># leaf</span>
<span id="L70" class="LineNr">70 </span> v:_elem <span class="Special"><-</span> get *t, <span class="Constant">val:offset</span>
<span id="L71" class="LineNr">71 </span> <span class="muControl">return-continuation-until-mark</span> <span class="Constant">100/mark</span>, v,<span class="Constant"> false/not-done</span>
<span id="L72" class="LineNr">72 </span>]
<span id="L73" class="LineNr">73 </span>
<span id="L74" class="LineNr">74 </span><span class="Comment"># details</span>
<span id="L75" class="LineNr">75 </span>
<span id="L76" class="LineNr">76 </span><span class="muRecipe">def</span> new-tree x:_elem<span class="muRecipe"> -> </span>result:&:<a href='same-fringe.mu.html#L9'>tree</a>:_elem [
<span id="L77" class="LineNr">77 </span> <span class="Constant">local-scope</span>
<span id="L78" class="LineNr">78 </span> <span class="Constant">load-inputs</span>
<span id="L79" class="LineNr">79 </span> result <span class="Special"><-</span> new <span class="Delimiter">{</span>(tree _elem): type<span class="Delimiter">}</span>
<span id="L80" class="LineNr">80 </span> put *result, <span class="Constant">val:offset</span>, x
<span id="L81" class="LineNr">81 </span>]
<span id="L82" class="LineNr">82 </span>
<span id="L83" class="LineNr">83 </span><span class="muRecipe">def</span> new-tree l:&:<a href='same-fringe.mu.html#L9'>tree</a>:_elem, r:&:<a href='same-fringe.mu.html#L9'>tree</a>:_elem<span class="muRecipe"> -> </span>result:&:<a href='same-fringe.mu.html#L9'>tree</a>:_elem [
<span id="L84" class="LineNr">84 </span> <span class="Constant">local-scope</span>
<span id="L85" class="LineNr">85 </span> <span class="Constant">load-inputs</span>
<span id="L86" class="LineNr">86 </span> result <span class="Special"><-</span> new <span class="Delimiter">{</span>(tree _elem): type<span class="Delimiter">}</span>
<span id="L87" class="LineNr">87 </span> put *result, <span class="Constant">left:offset</span>, l
<span id="L88" class="LineNr">88 </span> put *result, <span class="Constant">right:offset</span>, r
<span id="L89" class="LineNr">89 </span>]
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