parison
    and hash functions, either for performance/security concerns,
    or because keys are not hashable/comparable with the polymorphic builtins.
<p>

    For instance, one might want to specialize a table for integer keys:
    </p><pre class="codepre"><code class="code">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<span class="keyword">module</span>&nbsp;<span class="constructor">IntHash</span>&nbsp;=<br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<span class="keyword">struct</span><br>
&nbsp;&nbsp;&nbs