doc/guide/localhost/ImplementSuffix

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  26 <h1>ImplementSuffix</h1>
  27 </div>
  28 <div id="content">
  29 <div id="preamble">
  30 <div class="sectionbody">
  31 <div class="paragraph"><p><a href="ImplementSuffix">ImplementSuffix</a> is a pass for the <a href="SXML">SXML</a>
  32 <a href="IntermediateLanguage">IntermediateLanguage</a>, invoked from <a href="SXMLSimplify">SXMLSimplify</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 implements the <span class="monospaced">TopLevel_setSuffix</span> primitive, which
  39 installs a function to exit the program.</p></div>
  40 </div>
  41 </div>
  42 <div class="sect1">
  43 <h2 id="_implementation">Implementation</h2>
  44 <div class="sectionbody">
  45 <div class="ulist"><ul>
  46 <li>
  47 <p>
  48 <a href="https://github.com/MLton/mlton/blob/master/mlton/xml/implement-suffix.fun"><span class="monospaced">implement-suffix.fun</span></a>
  49 </p>
  50 </li>
  51 </ul></div>
  52 </div>
  53 </div>
  54 <div class="sect1">
  55 <h2 id="_details_and_notes">Details and Notes</h2>
  56 <div class="sectionbody">
  57 <div class="paragraph"><p><a href="ImplementSuffix">ImplementSuffix</a> works by introducing a new <span class="monospaced">ref</span> cell to contain
  58 the function of type <span class="monospaced">unit -&gt; unit</span> that should be called on program
  59 exit.</p></div>
  60 <div class="ulist"><ul>
  61 <li>
  62 <p>
  63 The following code (appropriately alpha-converted) is appended to the beginning of the <a href="SXML">SXML</a> program:
  64 </p>
  65 <div class="listingblock">
  66 <div class="content"><div class="highlight"><pre><span class="k">val</span><span class="w"> </span><span class="n">z_0</span><span class="w"> </span><span class="p">=</span><span class="w"></span>
  67 <span class="w">  </span><span class="k">fn</span><span class="w"> </span><span class="n">a_0</span><span class="w"> </span><span class="p">=&gt;</span><span class="w"></span>
  68 <span class="w">  </span><span class="k">let</span><span class="w"></span>
  69 <span class="w">    </span><span class="k">val</span><span class="w"> </span><span class="n">x_0</span><span class="w"> </span><span class="p">=</span><span class="w"></span>
  70 <span class="w">      </span><span class="s">&quot;toplevel suffix not installed&quot;</span><span class="w"></span>
  71 <span class="w">    </span><span class="k">val</span><span class="w"> </span><span class="n">x_1</span><span class="w"> </span><span class="p">=</span><span class="w"></span>
  72 <span class="w">      </span><span class="n">MLton_bug</span><span class="w"> </span><span class="p">(</span><span class="n">x_0</span><span class="p">)</span><span class="w"></span>
  73 <span class="w">  </span><span class="k">in</span><span class="w"></span>
  74 <span class="w">    </span><span class="n">x_1</span><span class="w"></span>
  75 <span class="w">  </span><span class="k">end</span><span class="w"></span>
  76 <span class="k">val</span><span class="w"> </span><span class="n">topLevelSuffixCell</span><span class="w"> </span><span class="p">=</span><span class="w"></span>
  77 <span class="w">  </span><span class="n">Ref_ref</span><span class="w"> </span><span class="p">(</span><span class="n">z_0</span><span class="p">)</span><span class="w"></span>
  78 </pre></div></div></div>
  79 </li>
  80 <li>
  81 <p>
  82 Any occurrence of
  83 </p>
  84 <div class="listingblock">
  85 <div class="content"><div class="highlight"><pre><span class="k">val</span><span class="w"> </span><span class="n">x_0</span><span class="w"> </span><span class="p">=</span><span class="w"></span>
  86 <span class="w">  </span><span class="n">TopLevel_setSuffix</span><span class="w"> </span><span class="p">(</span><span class="n">f_0</span><span class="p">)</span><span class="w"></span>
  87 </pre></div></div></div>
  88 <div class="paragraph"><p>is rewritten to</p></div>
  89 <div class="listingblock">
  90 <div class="content"><div class="highlight"><pre><span class="k">val</span><span class="w"> </span><span class="n">x_0</span><span class="w"> </span><span class="p">=</span><span class="w"></span>
  91 <span class="w">  </span><span class="n">Ref_assign</span><span class="w"> </span><span class="p">(</span><span class="n">topLevelSuffixCell</span><span class="p">,</span><span class="w"> </span><span class="n">f_0</span><span class="p">)</span><span class="w"></span>
  92 </pre></div></div></div>
  93 </li>
  94 <li>
  95 <p>
  96 The following code (appropriately alpha-converted) is appended to the end of the <a href="SXML">SXML</a> program:
  97 </p>
  98 <div class="listingblock">
  99 <div class="content"><div class="highlight"><pre><span class="k">val</span><span class="w"> </span><span class="n">f_0</span><span class="w"> </span><span class="p">=</span><span class="w"></span>
 100 <span class="w">  </span><span class="n">Ref_deref</span><span class="w"> </span><span class="p">(</span><span class="n">topLevelSuffixCell</span><span class="p">)</span><span class="w"></span>
 101 <span class="k">val</span><span class="w"> </span><span class="n">z_0</span><span class="w"> </span><span class="p">=</span><span class="w"></span>
 102 <span class="w">  </span><span class="p">()</span><span class="w"></span>
 103 <span class="k">val</span><span class="w"> </span><span class="n">x_0</span><span class="w"> </span><span class="p">=</span><span class="w"></span>
 104 <span class="w">  </span><span class="n">f_0</span><span class="w"> </span><span class="n">z_0</span><span class="w"></span>
 105 </pre></div></div></div>
 106 </li>
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