  <code class="code">compare</code> applied to cyclic structures may not terminate.
</p><p>

   The <code class="code">compare</code> function can be used as the comparison function
   required by the <a href="Set.Make.html"><code class="code"><span class="constructor">Set</span>.<span class="constructor">Make</span></code></a> and <a href="Map.Make.html"><code class="code"><span class="constructor">Map</span>.<span class="constructor">Make</span></code></a> functors, as well as
   the <a href="List.html#VA