 literal">graph</tt> parameter.  That might not seem to be a problem at first;
after all, if the arguments don't match the requirements imposed by
the implementation of <tt class="docutils literal">depth_first_search</tt>, a compilation error
will occur later, when its body is instantiated.</p>
<p>There are at least three problems with very general function
signatures.</p>
<ol class="arabic simple">
<li>By the time our <tt class="docutils literal">depth_first_search</tt> is instantiated, it has
been selecte