pedef.
The prototype of the finalization, comparison and hashing functions are:
</p><pre>
        value <span class=font-it>final-fn</span>(<span class=font-it>ty</span> * x);
        int <span class=font-it>compare-fn</span>(<span class=font-it>ty</span> * x, <span class=font-it>ty</span> * y);
        long <span class=font-it>hash-fn</span>(<span class=font-it>ty</span> * x);
</pre><p>
That is, their arguments are passed by reference. The comparison
function must return an integer that is negative, zero, 