doc/guide/localhost/LambdaFree

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  22 <a href="./Home">MLton 20180207</a>
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  26 <h1>LambdaFree</h1>
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  29 <div id="preamble">
  30 <div class="sectionbody">
  31 <div class="paragraph"><p><a href="LambdaFree">LambdaFree</a> is an analysis pass for the <a href="SXML">SXML</a>
  32 <a href="IntermediateLanguage">IntermediateLanguage</a>, invoked from <a href="ClosureConvert">ClosureConvert</a>.</p></div>
  33 </div>
  34 </div>
  35 <div class="sect1">
  36 <h2 id="_description">Description</h2>
  37 <div class="sectionbody">
  38 <div class="paragraph"><p>This pass descends the entire <a href="SXML">SXML</a> program and attaches a property
  39 to each <span class="monospaced">Lambda</span> <span class="monospaced">PrimExp.t</span> in the program.  Then, you can use
  40 <span class="monospaced">lambdaFree</span> and <span class="monospaced">lambdaRec</span> to get free variables of that <span class="monospaced">Lambda</span>.</p></div>
  41 </div>
  42 </div>
  43 <div class="sect1">
  44 <h2 id="_implementation">Implementation</h2>
  45 <div class="sectionbody">
  46 <div class="ulist"><ul>
  47 <li>
  48 <p>
  49 <a href="https://github.com/MLton/mlton/blob/master/mlton/closure-convert/lambda-free.sig"><span class="monospaced">lambda-free.sig</span></a>
  50 </p>
  51 </li>
  52 <li>
  53 <p>
  54 <a href="https://github.com/MLton/mlton/blob/master/mlton/closure-convert/lambda-free.fun"><span class="monospaced">lambda-free.fun</span></a>
  55 </p>
  56 </li>
  57 </ul></div>
  58 </div>
  59 </div>
  60 <div class="sect1">
  61 <h2 id="_details_and_notes">Details and Notes</h2>
  62 <div class="sectionbody">
  63 <div class="paragraph"><p>For <span class="monospaced">Lambda</span>-s bound in a <span class="monospaced">Fun</span> dec, <span class="monospaced">lambdaFree</span> gives the union of
  64 the frees of the entire group of mutually recursive functions.  Hence,
  65 <span class="monospaced">lambdaFree</span> for every <span class="monospaced">Lambda</span> in a single <span class="monospaced">Fun</span> dec is the same.
  66 Furthermore, for a <span class="monospaced">Lambda</span> bound in a <span class="monospaced">Fun</span> dec, <span class="monospaced">lambdaRec</span> gives
  67 the list of other functions bound in the same dec defining that
  68 <span class="monospaced">Lambda</span>.</p></div>
  69 <div class="paragraph"><p>For example:</p></div>
  70 <div class="listingblock">
  71 <div class="content monospaced">
  72 <pre>val rec f = fn x =&gt; ... y ... g ... f ...
  73 and g = fn z =&gt; ... f ... w ...</pre>
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  75 <div class="listingblock">
  76 <div class="content monospaced">
  77 <pre>lambdaFree(fn x =&gt;) = [y, w]
  78 lambdaFree(fn z =&gt;) = [y, w]
  79 lambdaRec(fn x =&gt;) = [g, f]
  80 lambdaRec(fn z =&gt;) = [f]</pre>
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