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<a href="./Home">MLton 20130715</a>
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<h1>Utilities</h1>
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<div class="paragraph"><p>This page is a collection of basic utilities used in the examples on
various pages.  See</p></div>
<div class="ulist"><ul>
<li>
<p>
<a href="InfixingOperators">InfixingOperators</a>, and
</p>
</li>
<li>
<p>
<a href="ProductType">ProductType</a>
</p>
</li>
</ul></div>
<div class="paragraph"><p>for longer discussions on some of these utilities.</p></div>
<div class="listingblock">
<div class="content"><div class="highlight"><pre><span></span><span class="cm">(* Operator precedence table *)</span>
<span class="kr">infix</span>   <span class="mi">8</span>  <span class="n">*</span> <span class="n">/</span> <span class="n">div</span> <span class="n">mod</span>        <span class="cm">(* +1 from Basis Library *)</span>
<span class="kr">infix</span>   <span class="mi">7</span>  <span class="n">+</span> <span class="n">-</span> <span class="n">^</span>              <span class="cm">(* +1 from Basis Library *)</span>
<span class="kr">infixr</span>  <span class="mi">6</span>  <span class="n">::</span> <span class="n">@</span>               <span class="cm">(* +1 from Basis Library *)</span>
<span class="kr">infix</span>   <span class="mi">5</span>  <span class="p">=</span> <span class="n">&lt;&gt;</span> <span class="n">&gt;</span> <span class="n">&gt;=</span> <span class="n">&lt;</span> <span class="n">&lt;=</span>     <span class="cm">(* +1 from Basis Library *)</span>
<span class="kr">infix</span>   <span class="mi">4</span>  <span class="n">&lt;\</span> <span class="n">\&gt;</span>
<span class="kr">infixr</span>  <span class="mi">4</span>  <span class="n">&lt;/</span> <span class="n">/&gt;</span>
<span class="kr">infix</span>   <span class="mi">3</span>  <span class="n">o</span>
<span class="kr">infix</span>   <span class="mi">2</span>  <span class="n">&gt;|</span>
<span class="kr">infixr</span>  <span class="mi">2</span>  <span class="n">|&lt;</span>
<span class="kr">infix</span>   <span class="mi">1</span>  <span class="n">:=</span>                 <span class="cm">(* -2 from Basis Library *)</span>
<span class="kr">infix</span>   <span class="mi">0</span>  <span class="n">before</span> <span class="n">&amp;</span>

<span class="cm">(* Some basic combinators *)</span>
<span class="kr">fun</span> <span class="nf">const</span> <span class="n">x</span> <span class="p">_</span> <span class="p">=</span> <span class="n">x</span>
<span class="kr">fun</span> <span class="nf">cross</span> <span class="p">(</span><span class="n">f</span><span class="p">,</span> <span class="n">g</span><span class="p">)</span> <span class="p">(</span><span class="n">x</span><span class="p">,</span> <span class="n">y</span><span class="p">)</span> <span class="p">=</span> <span class="p">(</span><span class="n">f</span> <span class="n">x</span><span class="p">,</span> <span class="n">g</span> <span class="n">y</span><span class="p">)</span>
<span class="kr">fun</span> <span class="nf">curry</span> <span class="n">f</span> <span class="n">x</span> <span class="n">y</span> <span class="p">=</span> <span class="n">f</span> <span class="p">(</span><span class="n">x</span><span class="p">,</span> <span class="n">y</span><span class="p">)</span>
<span class="kr">fun</span> <span class="nf">fail</span> <span class="n">e</span> <span class="p">_</span> <span class="p">=</span> <span class="kr">raise</span> <span class="n">e</span>
<span class="kr">fun</span> <span class="nf">id</span> <span class="n">x</span> <span class="p">=</span> <span class="n">x</span>

<span class="cm">(* Product type *)</span>
<span class="kr">datatype</span> <span class="p">(</span><span class="nd">&#39;a</span><span class="p">,</span> <span class="nd">&#39;b</span><span class="p">)</span> <span class="kt">product</span> <span class="p">=</span> <span class="nc">&amp;</span> <span class="kr">of</span> <span class="nd">&#39;a</span> <span class="n">*</span> <span class="nd">&#39;b</span>

<span class="cm">(* Sum type *)</span>
<span class="kr">datatype</span> <span class="p">(</span><span class="nd">&#39;a</span><span class="p">,</span> <span class="nd">&#39;b</span><span class="p">)</span> <span class="kt">sum</span> <span class="p">=</span> <span class="nc">INL</span> <span class="kr">of</span> <span class="nd">&#39;a</span> <span class="p">|</span> <span class="nc">INR</span> <span class="kr">of</span> <span class="nd">&#39;b</span>

<span class="cm">(* Some type shorthands *)</span>
<span class="kr">type</span> <span class="nd">&#39;a</span> <span class="kt">uop</span> <span class="p">=</span> <span class="nd">&#39;a</span> <span class="p">-&gt;</span> <span class="nd">&#39;a</span>
<span class="kr">type</span> <span class="nd">&#39;a</span> <span class="kt">fix</span> <span class="p">=</span> <span class="nd">&#39;a</span> <span class="n">uop</span> <span class="p">-&gt;</span> <span class="nd">&#39;a</span>
<span class="kr">type</span> <span class="nd">&#39;a</span> <span class="kt">thunk</span> <span class="p">=</span> <span class="n">unit</span> <span class="p">-&gt;</span> <span class="nd">&#39;a</span>
<span class="kr">type</span> <span class="nd">&#39;a</span> <span class="kt">effect</span> <span class="p">=</span> <span class="nd">&#39;a</span> <span class="p">-&gt;</span> <span class="n">unit</span>
<span class="kr">type</span> <span class="p">(</span><span class="nd">&#39;a</span><span class="p">,</span> <span class="nd">&#39;b</span><span class="p">)</span> <span class="kt">emb</span> <span class="p">=</span> <span class="p">(</span><span class="nd">&#39;a</span> <span class="p">-&gt;</span> <span class="nd">&#39;b</span><span class="p">)</span> <span class="n">*</span> <span class="p">(</span><span class="nd">&#39;b</span> <span class="p">-&gt;</span> <span class="nd">&#39;a</span><span class="p">)</span>

<span class="cm">(* Infixing, sectioning, and application operators *)</span>
<span class="kr">fun</span> <span class="nf">x</span> <span class="n">&lt;\</span> <span class="n">f</span> <span class="p">=</span> <span class="kr">fn</span> <span class="n">y</span> <span class="p">=&gt;</span> <span class="n">f</span> <span class="p">(</span><span class="n">x</span><span class="p">,</span> <span class="n">y</span><span class="p">)</span>
<span class="kr">fun</span> <span class="nf">f</span> <span class="n">\&gt;</span> <span class="n">y</span> <span class="p">=</span> <span class="n">f</span> <span class="n">y</span>
<span class="kr">fun</span> <span class="nf">f</span> <span class="n">/&gt;</span> <span class="n">y</span> <span class="p">=</span> <span class="kr">fn</span> <span class="n">x</span> <span class="p">=&gt;</span> <span class="n">f</span> <span class="p">(</span><span class="n">x</span><span class="p">,</span> <span class="n">y</span><span class="p">)</span>
<span class="kr">fun</span> <span class="nf">x</span> <span class="n">&lt;/</span> <span class="n">f</span> <span class="p">=</span> <span class="n">f</span> <span class="n">x</span>

<span class="cm">(* Piping operators *)</span>
<span class="kr">val</span> <span class="nv">op</span><span class="n">&gt;|</span> <span class="p">=</span> <span class="kr">op</span><span class="n">&lt;/</span>
<span class="kr">val</span> <span class="nv">op</span><span class="n">|&lt;</span> <span class="p">=</span> <span class="kr">op</span><span class="n">\&gt;</span>
</pre></div></div></div>
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