<HTML>
<!--
     Copyright (c) Jeremy Siek 2000
    
     Distributed under the Boost Software License, Version 1.0.
     (See accompanying file LICENSE_1_0.txt or copy at
     http://www.boost.org/LICENSE_1_0.txt)
  -->
<Head>
<Title>Boost Graph Library: Depth-First Visit</Title>
<BODY BGCOLOR="#ffffff" LINK="#0000ee" TEXT="#000000" VLINK="#551a8b" 
        ALINK="#ff0000"> 
<IMG SRC="../../../boost.png" 
     ALT="C++ Boost" width="277" height="86"> 

<BR Clear>

<H2><A NAME="sec:dfs"></A>
<img src="figs/python.gif" alt="(Python)"/>
<TT>depth_first_visit</TT>
</H2>


<P>
<PRE>
template &lt;class <a href="./IncidenceGraph.html">IncidenceGraph</a>, class <a href="./DFSVisitor.html">DFSVisitor</a>, class ColorMap&gt;
void depth_first_visit(IncidenceGraph& g,
  typename graph_traits&lt;IncidenceGraph&gt;::vertex_descriptor s, 
  DFSVisitor&amp; vis, ColorMap color)

template &lt;class <a href="./IncidenceGraph.html">IncidenceGraph</a>, class <a href="./DFSVisitor.html">DFSVisitor</a>, class ColorMap, 
          class TerminatorFunc&gt;
void depth_first_visit(IncidenceGraph& g,
  typename graph_traits&lt;IncidenceGraph&gt;::vertex_descriptor s, 
  DFSVisitor&amp; vis, ColorMap color, TerminatorFunc func = TerminatorFunc())
</PRE>

<P>
This function visits all of the vertices in the same connected
component as the source vertex <tt>s</tt>, using the <a
href="./graph_theory_review.html#sec:dfs-algorithm">depth-first
pattern</a>. The main purpose of the function is for the
implementation of <TT>depth_first_search()</TT> though sometimes it is
useful on its own. 

<p>
The <tt>DFSVisitor</tt> supplied by the user determines what
actions are taken at each event-point within the algorithm.

<p>
The <tt>ColorMap</tt> is used by the algorithm to keep track
of which vertices have been visited.

<p>The second variant can be used, for example, to find all marked vertices
reachable from a start vertex by a path which does not contain any another
marked vertices.


<P>

<h3>Where Defined:</h3>

<a href="../../../boost/graph/depth_first_search.hpp"><TT>boost/graph/depth_first_search.hpp</TT></a>


<h3>Parameters</h3>

IN <tt>IncidenceGraph&amp; g</tt>
<blockquote>
A directed or undirected graph. The graph's type must be a model of
<a href="./IncidenceGraph.html">Incidence Graph</a>.<br>

<b>Python</b>: The parameter is named <tt>graph</tt>.
</blockquote>

IN: <tt>vertex_descriptor s</tt>
<blockquote>
  The source vertex from which to start the search.<br>

  <b>Python</b>: The parameter is named <tt>root_vertex</tt>.
</blockquote>

IN: <tt>DFSVisitor visitor</tt>
<blockquote>
  A visitor object that is invoked inside the algorithm at the
  event-points specified by the <a href="./DFSVisitor.html">DFS
  Visitor</a> concept. The visitor object is passed by value <a
  href="#1">[1]</a>.<br>

  <b>Python</b>: The parameter should be an object that derives from
  the <a href="DFSVisitor.html#python"><tt>DFSVisitor</tt></a> type of
  the graph.
</blockquote>

UTIL: <tt>ColorMap color</tt>
<blockquote>
  This is used by the algorithm to keep track of its progress through
  the graph. The type <tt>ColorMap</tt> must be a model of <a
  href="../../property_map/doc/ReadWritePropertyMap.html">Read/Write
  Property Map</a> and its key type must be the graph's vertex
  descriptor type and the value type of the color map map must model
  <a href="./ColorValue.html">Color Value</a>.<br>

  <b>Python</b>: The color map must be a <tt>vertex_color_map</tt> for
  the graph.
</blockquote>

IN: <tt>TerminatorFunc func</tt>
<blockquote>
A function object callable with two parameters - the descriptor of
vertex and the graph instance - and returning bool. The call is made
immediately after call to 'discover_vertex' visitor
event. If <tt>true</tt> is returned, the out edges of the vertex are
not examined, as if they don't exist.<br>

  <b>Python</b>: Unsupported parameter.
</blockquote>
<P>

<h3>Complexity</h3>

Time complexity is <i>O(E)</i>.


<h3>Notes</h3>

<p><a name="1">[1]</a> 
  Since the visitor parameter is passed by value, if your visitor
  contains state then any changes to the state during the algorithm
  will be made to a copy of the visitor object, not the visitor object
  passed in. Therefore you may want the visitor to hold this state by
  pointer or reference.


<br>
<HR>
<TABLE>
<TR valign=top>
<TD nowrap>Copyright &copy; 2000-2001</TD><TD>
<A HREF="http://www.boost.org/people/jeremy_siek.htm">Jeremy Siek</A>, Indiana University (<A HREF="mailto:jsiek@osl.iu.edu">jsiek@osl.iu.edu</A>)
</TD></TR></TABLE>

</BODY>
</HTML>