h parameter is
used in the default expressions for <tt class="docutils literal">root_vertex</tt>,
<tt class="docutils literal">index_map</tt> and <tt class="docutils literal">color_map</tt>.</p>
<pre class="compound-middle literal-block">
(required (<strong>graph</strong>, *) )
(optional
  (visitor,           *, boost::dfs_visitor&lt;&gt;())
  (root_vertex,       *, *vertices(<strong>graph</strong>).first)
  (index_map,         *, get(boost::vertex_index,<strong>graph</strong>))
  (in_out(color_map), *,
   