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MLton
20241230
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<h1>ImplementSuffix</h1>
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<div id="content">
<div id="preamble">
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<div class="paragraph">
<p><a href="#">ImplementSuffix</a> is a pass for the <a href="SXML">SXML</a>
<a href="IntermediateLanguage">IntermediateLanguage</a>, invoked from <a href="SXMLSimplify">SXMLSimplify</a>.</p>
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<h2 id="_description">Description</h2>
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<div class="paragraph">
<p>This pass implements the <code>TopLevel_setSuffix</code> primitive, which
installs a function to exit the program.</p>
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<h2 id="_implementation">Implementation</h2>
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<div class="ulist">
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<p><a href="https://github.com/MLton/mlton/blob/master/mlton/xml/implement-suffix.fun"><code>implement-suffix.fun</code></a></p>
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<h2 id="_details_and_notes">Details and Notes</h2>
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<div class="paragraph">
<p><a href="#">ImplementSuffix</a> works by introducing a new <code>ref</code> cell to contain
the function of type <code>unit -&gt; unit</code> that should be called on program
exit.</p>
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<ul>
<li>
<p>The following code (appropriately alpha-converted) is appended to the beginning of the <a href="SXML">SXML</a> program:</p>
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<pre class="rouge highlight"><code data-lang="sml"><span class="kr">val</span> <span class="nv">z_0</span> <span class="p">=</span>
  <span class="kr">fn</span> <span class="n">a_0</span> <span class="p">=&gt;</span>
  <span class="kr">let</span>
    <span class="kr">val</span> <span class="nv">x_0</span> <span class="p">=</span>
      <span class="s2">"toplevel suffix not installed"</span>
    <span class="kr">val</span> <span class="nv">x_1</span> <span class="p">=</span>
      <span class="n">MLton_bug</span> <span class="p">(</span><span class="n">x_0</span><span class="p">)</span>
  <span class="kr">in</span>
    <span class="n">x_1</span>
  <span class="kr">end</span>
<span class="kr">val</span> <span class="nv">topLevelSuffixCell</span> <span class="p">=</span>
  <span class="n">Ref_ref</span> <span class="p">(</span><span class="n">z_0</span><span class="p">)</span></code></pre>
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<p>Any occurrence of</p>
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<div class="content">
<pre class="rouge highlight"><code data-lang="sml"><span class="kr">val</span> <span class="nv">x_0</span> <span class="p">=</span>
  <span class="n">TopLevel_setSuffix</span> <span class="p">(</span><span class="n">f_0</span><span class="p">)</span></code></pre>
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<p>is rewritten to</p>
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<div class="listingblock">
<div class="content">
<pre class="rouge highlight"><code data-lang="sml"><span class="kr">val</span> <span class="nv">x_0</span> <span class="p">=</span>
  <span class="n">Ref_assign</span> <span class="p">(</span><span class="n">topLevelSuffixCell</span><span class="p">,</span> <span class="n">f_0</span><span class="p">)</span></code></pre>
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</li>
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<p>The following code (appropriately alpha-converted) is appended to the end of the <a href="SXML">SXML</a> program:</p>
<div class="listingblock">
<div class="content">
<pre class="rouge highlight"><code data-lang="sml"><span class="kr">val</span> <span class="nv">f_0</span> <span class="p">=</span>
  <span class="n">Ref_deref</span> <span class="p">(</span><span class="n">topLevelSuffixCell</span><span class="p">)</span>
<span class="kr">val</span> <span class="nv">z_0</span> <span class="p">=</span>
  <span class="p">()</span>
<span class="kr">val</span> <span class="nv">x_0</span> <span class="p">=</span>
  <span class="n">f_0</span> <span class="n">z_0</span></code></pre>
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Last updated Thu Oct 21 15:53:06 2021 -0400 by Matthew Fluet.
<a href="https://github.com/MLton/mlton/commits/master/doc/guide/src/ImplementSuffix.adoc">Log</a>
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