<HTML> <!-- Copyright (c) Jeremy Siek, Lie-Quan Lee, and Andrew Lumsdaine 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: Visitor Concepts</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> <H1><A NAME="sec:visitor-concepts"></A> Visitor Concepts </H1> <P> The visitor concepts plays the same role in BGL as <a href="http://www.sgi.com/tech/stl/functors.html">functors</a> play in the STL. Functors provide a mechanism for extending an algorithm; for customizing what is done at each step of the algorithm. Visitors allow the user to insert their own operations at various steps within a graph algorithm. Unlike the STL algorithms, graph algorithms typically have multiple event points where one may want to insert a call-back via a functor. Therefore visitors do not have a single <tt>operator()</tt> method like a functor, but instead have several methods that correspond to the various event points. Each algorithm has a different set of event points, which are described by the following visitor concepts: <ul> <li> <a href="./BFSVisitor.html">BFS Visitor</a> <li> <a href="./DFSVisitor.html">DFS Visitor</a> <li> <a href="./DijkstraVisitor.html">Dijkstra Visitor</a> <li> <a href="./BellmanFordVisitor.html">Bellman Ford Visitor</a> <li> <a href="./AStarVisitor.html">A* Visitor</a> <li> <a href="./EventVisitor.html">Event Visitor</a> <li> <a href="./PlanarFaceVisitor.html">Planar Face Visitor</a> <li> <a href="./TSPTourVisitor.html">TSP Tour Visitor</a> </ul> <br> <HR> <TABLE> <TR valign=top> <TD nowrap>Copyright © 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>)<br> <A HREF="http://www.boost.org/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>