<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>Graph</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="concept:Graph"></A> Graph </H2> <P> The Graph concept contains a few requirements that are common to all the graph concepts. These include some associated types for <tt>vertex_descriptor</tt>, <tt>edge_descriptor</tt>, etc. One should note that a model of Graph is <B>not</B> required to be a model of <a href="http://www.sgi.com/tech/stl/Assignable.html">Assignable</a>, so algorithms should pass graph objects by reference. <P> <h3>Notation</h3> <Table> <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> </table> <H3>Associated Types</H3> <table border> <tr> <td><pre>boost::graph_traits<G>::vertex_descriptor</pre> A vertex descriptor corresponds to a unique vertex in an abstract graph instance. A vertex descriptor must be <a href="http://www.sgi.com/tech/stl/DefaultConstructible.html">Default Constructible</a>, <a href="http://www.sgi.com/tech/stl/Assignable.html">Assignable</a>, and <a href="http://www.sgi.com/tech/stl/EqualityComparable.html">Equality Comparable</a>. </td> </tr> <tr> <td><pre>boost::graph_traits<G>::edge_descriptor</pre> An edge descriptor corresponds to a unique edge <i>(u,v)</i> in a graph. An edge descriptor must be <a href="http://www.sgi.com/tech/stl/DefaultConstructible.html">Default Constructible</I>, <a href="http://www.sgi.com/tech/stl/Assignable.html">Assignable</a>, and <a href="http://www.sgi.com/tech/stl/EqualityComparable.html">Equality Comparable</a>. </td> </tr> <tr> <td><pre>boost::graph_traits<G>::directed_category</pre> This type shall be convertible to <TT>directed_tag</TT> or <TT>undirected_tag</TT>. </td> </tr> <tr> <td><pre>boost::graph_traits<G>::edge_parallel_category</pre> This describes whether the graph class allows the insertion of parallel edges (edges with the same source and target). The two tags are <TT>allow_parallel_edge_tag</TT> and <TT>disallow_parallel_edge_tag</TT>. </td> </tr> <tr> <td><pre>boost::graph_traits<G>::traversal_category</pre> This describes the ways in which the vertices and edges of the graph can be visited. The choices are <TT>incidence_graph_tag</TT>, <TT>adjacency_graph_tag</TT>, <TT>bidirectional_graph_tag</TT>, <TT>vertex_list_graph_tag</TT>, <TT>edge_list_graph_tag</TT>, and <TT>adjacency_matrix_tag</TT>. </td> </tr> </table> <H3>Valid Expressions</H3> <table border> <tr> <td><pre>boost::graph_traits<G>::null_vertex()</pre></td></TD> <td> Returns a special <tt>boost::graph_traits<G>::vertex_descriptor</tt> object which does not refer to any vertex of graph object which type is <tt>G</tt>. <td> </tr> </table> <H3>Concept Checking Class</H3> <PRE> template <class G> struct GraphConcept { typedef typename boost::graph_traits<G>::vertex_descriptor vertex_descriptor; typedef typename boost::graph_traits<G>::edge_descriptor edge_descriptor; typedef typename boost::graph_traits<G>::directed_category directed_category; typedef typename boost::graph_traits<G>::edge_parallel_category edge_parallel_category; typedef typename boost::graph_traits<G>::traversal_category traversal_category; void constraints() { function_requires< DefaultConstructibleConcept<vertex_descriptor> >(); function_requires< EqualityComparableConcept<vertex_descriptor> >(); function_requires< AssignableConcept<vertex_descriptor> >(); function_requires< DefaultConstructibleConcept<edge_descriptor> >(); function_requires< EqualityComparableConcept<edge_descriptor> >(); function_requires< AssignableConcept<edge_descriptor> >(); } G g; }; </PRE> <H3>See Also</H3> <a href="./graph_concepts.html">Graph concepts</a> <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>) </TD></TR></TABLE> </BODY> </HTML>