<HTML> <!-- -- Copyright (c) Jeremy Siek, Lie-Quan Lee, and Andrew Lumsdaine 2000 -- -- Permission to use, copy, modify, distribute and sell this software -- and its documentation for any purpose is hereby granted without fee, -- provided that the above copyright notice appears in all copies and -- that both that copyright notice and this permission notice appear -- in supporting documentation. We make no -- representations about the suitability of this software for any -- purpose. It is provided "as is" without express or implied warranty. --> <Head> <Title>Boost Graph Library: BFSVisitor</Title> <BODY BGCOLOR="#ffffff" LINK="#0000ee" TEXT="#000000" VLINK="#551a8b" ALINK="#ff0000"> <IMG SRC="../../../c++boost.gif" ALT="C++ Boost" width="277" height="86"> <BR Clear> <H1>BFS Visitor Concept</H1> This concept defines the visitor interface for <a href="./breadth_first_search.html"><tt>breadth_first_search()</tt></a>. Users can define a class with the BFS Visitor interface and pass and object of the class to <tt>breadth_first_search()</tt>, thereby augmenting the actions taken during the graph search. <h3>Refinement of</h3> <a href="../../utility/CopyConstructible.html">Copy Constructible</a> (copying a visitor should be a lightweight operation). <h3>Notation</h3> <Table> <TR> <TD><tt>V</tt></TD> <TD>A type that is a model of BFS Visitor.</TD> </TR> <TR> <TD><tt>vis</tt></TD> <TD>An object of type <tt>V</tt>.</TD> </TR> <TR> <TD><tt>G</tt></TD> <TD>A type that is a model of Graph.</TD> </TR> <TR> <TD><tt>g</tt></TD> <TD>An object of type <tt>G</tt>.</TD> </TR> <TR> <TD><tt>e</tt></TD> <TD>An object of type <tt>boost::graph_traits<G>::edge_descriptor</tt>.</TD> </TR> <TR> <TD><tt>s,u</tt></TD> <TD>An object of type <tt>boost::graph_traits<G>::vertex_descriptor</tt>.</TD> </TR> </table> <h3>Associated Types</h3> none <p> <h3>Valid Expressions</h3> <table border> <tr> <th>Name</th><th>Expression</th><th>Return Type</th><th>Description</th> </tr> <tr> <td>Initialize Vertex</td> <td><tt>vis.initialize_vertex(s, g)</tt></td> <td><tt>void</tt></td> <td> This is invoked on every vertex of the graph before the start of the graph search. </td> </tr> <tr> <td>Discover Vertex</td> <td><tt>vis.discover_vertex(u, g)</tt></td> <td><tt>void</tt></td> <td> This is invoked when a vertex is encountered for the first time. </td> </tr> <tr> <td>Examine Vertex</td> <td><tt>vis.examine_vertex(u, g)</tt></td> <td><tt>void</tt></td> <td> This is invoked on a vertex as it is popped from the queue. This happens immediately before <tt>examine_edge()</tt> is invoked on each of the out-edges of vertex <tt>u</tt>. </td> </tr> <tr> <td>Examine Edge</td> <td><tt>vis.examine_edge(e, g)</tt></td> <td><tt>void</tt></td> <td> This is invoked on every out-edge of each vertex after it is discovered. </td> </tr> <tr> <td>Tree Edge</td> <td><tt>vis.tree_edge(e, g)</tt></td> <td><tt>void</tt></td> <td> This is invoked on each edge as it becomes a member of the edges that form the search tree.</td> </tr> <tr> <td>Non-Tree Edge</td> <td><tt>vis.non_tree_edge(e, g)</tt></td> <td><tt>void</tt></td> <td> This is invoked on back or cross edges for directed graphs and cross edges for undirected graphs. </td> </tr> <tr> <td>Gray Target</td> <td><tt>vis.gray_target(e, g)</tt></td> <td><tt>void</tt></td> <td> This is invoked on the subset of non-tree edges who's target vertex is colored gray at the time of examination. The color gray indicates that the vertex is currently in the queue. </td> </tr> <tr> <td>Black Target</td> <td><tt>vis.black_target(e, g)</tt></td> <td><tt>void</tt></td> <td> This is invoked on the subset of non-tree edges who's target vertex is colored black at the time of examination. The color black indicates that the vertex has been removed from the queue. </td> </tr> <tr> <td>Finish Vertex</td> <td><tt>vis.finish_vertex(u, g)</tt></td> <td><tt>void</tt></td> <td> This invoked on a vertex after all of its out edges have been added to the search tree and all of the adjacent vertices have been discovered (but before the out-edges of the adjacent vertices have been examined). </td> </tr> </table> <h3>Models</h3> <ul> <li><a href="./bfs_visitor.html"><tt>bfs_visitor</tt></a> </ul> <h3>See also</h3> <a href="./visitor_concepts.html">Visitor concepts</a> <br> <HR> <TABLE> <TR valign=top> <TD nowrap>Copyright © 2000-2001</TD><TD> <A HREF="../../../people/jeremy_siek.htm">Jeremy Siek</A>, Indiana University (<A HREF="mailto:jsiek@osl.iu.edu">jsiek@osl.iu.edu</A>)<br> <A HREF="../../../people/liequan_lee.htm">Lie-Quan Lee</A>, Indiana University (<A HREF="mailto:llee@cs.indiana.edu">llee@cs.indiana.edu</A>)<br> <A HREF=http://www.osl.iu.edu/~lums>Andrew Lumsdaine</A>, Indiana University (<A HREF="mailto:lums@osl.iu.edu">lums@osl.iu.edu</A>) </TD></TR></TABLE> </BODY> </HTML>