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<title>Identifier - MLton Standard ML Compiler (SML Compiler)</title>
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      Identifier
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In <a href="StandardML">Standard ML</a>, there are syntactically two kinds of identifiers. 
    <ul>

    <li>
<p>
 Alphanumeric: starts with a letter or prime (<tt>'</tt>) and is  followed by letters, digits, primes and underbars (<tt>_</tt>). 
</p>
<p>
 Examples: <tt>abc</tt>, <tt>ABC123</tt>, <tt>Abc_123</tt>, <tt>'a</tt>. 
</p>
</li>
    <li class="gap">
<p>
 Symbolic: a sequence of the following 
<pre> ! % &amp; $ # + - / : &lt; = &gt; ? @ | ~ ` ^ | *</pre>
</p>
<p>
 Examples: <tt>+=</tt>, <tt>&lt;=</tt>, <tt>&gt;&gt;</tt>, <tt>$</tt>. 
</p>
</li>

    </ul>


<p>
With the exception of <tt>=</tt>, reserved words can not be identifiers. 
</p>
<p>
There are a number of different classes of identifiers, some of which have additional syntactic rules. 
</p>

    <ul>

    <li>
<p>
 Identifiers not starting with a prime. 
</p>
</li>

        <ul>

        <li>
<p>
 value identifier (includes variables and constructors) 
</p>
</li>
        <li>
<p>
 type constructor 
</p>
</li>
        <li>
<p>
 structure identifier 
</p>
</li>
        <li>
<p>
 signature identifier 
</p>
</li>
        <li>
<p>
 functor identifier 
</p>
</li>

        </ul>


    <li class="gap">
<p>
 Identifiers starting with a prime. 
</p>
</li>

        <ul>

        <li>
<p>
 type variable (must start with prime) 
</p>
</li>

        </ul>


    <li class="gap">
<p>
 Identifiers + numeric labels (<tt>1</tt>, <tt>2</tt>, ...). 
</p>
</li>

        <ul>

        <li>
<p>
 record label 
</p>
</li>
</ul>

</ul>

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<p>
<hr>
Last edited on 2005-01-18 15:02:21 by <span title="cfs32.cs.cornell.edu"><a href="MatthewFluet">MatthewFluet</a></span>.
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