al"><span class="pre">vertices(graph).first</span></tt> are ill-formed for the given <tt class="docutils literal">graph</tt>
arguments, both calls will compile, and each one will print
exactly the same thing.</p>
</div>
<!-- @example.prepend('''
#include <boost/parameter.hpp>
#include <iostream>

BOOST_PARAMETER_NAME(graph)
BOOST_PARAMETER_NAME(visitor)
BOOST_PARAMETER_NAME(root_vertex)
BOOST_PARAMETER_NAME(index_map)
BOOST_PARAMETER_NAME(color_map)''') -->
<!-- @example.replace_emphasis('''
, (required
   