155 lines
4.1 KiB
HTML
155 lines
4.1 KiB
HTML
<HTML>
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<!--
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Copyright (c) Jeremy Siek 2000
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Distributed under the Boost Software License, Version 1.0.
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(See accompanying file LICENSE_1_0.txt or copy at
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http://www.boost.org/LICENSE_1_0.txt)
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-->
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<Head>
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<Title>VertexListGraph</Title>
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<BODY BGCOLOR="#ffffff" LINK="#0000ee" TEXT="#000000" VLINK="#551a8b"
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ALINK="#ff0000">
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<IMG SRC="../../../boost.png"
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ALT="C++ Boost" width="277" height="86">
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<BR Clear>
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<H2><A NAME="concept:VertexListGraph">
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VertexListGraph
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</H2>
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The <I>VertexListGraph</I> concept refines the <a
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href="./Graph.html">Graph</a> concept, and adds the requirement for
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efficient traversal of all the vertices in the graph.
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<H3>Refinement of</H3>
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<a href="./Graph.html">Graph</a>
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<H3>Associated Types</H3>
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<Table border>
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<tr>
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<td><tt>boost::graph_traits<G>::traversal_category</tt><br><br>
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This tag type must be convertible to <tt>vertex_list_graph_tag</tt>.
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</td>
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</tr>
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<TR>
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<TD><tt>boost::graph_traits<G>::vertex_iterator</tt><br><br>
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A vertex iterator (obtained via <TT>vertices(g)</TT>) provides access
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to all of the vertices in a graph. A vertex iterator type must meet
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the requirements of <a
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href="../../utility/MultiPassInputIterator.html">MultiPassInputIterator</a>. The
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value type of the vertex iterator must be the vertex descriptor of the
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graph.
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</TD>
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</TR>
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<tr>
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<td><tt>boost::graph_traits<G>::vertices_size_type</tt><br><br>
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The unsigned integer type used to represent the number of vertices
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in the graph.
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</td>
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</tr>
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</table>
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<h3>Valid Expressions</h3>
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<table border>
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<tr>
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<th>Name</th><th>Expression</th><th>Return Type</th><th>Description</th>
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</tr>
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<tr>
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<td>Vertex Set of the Graph</td>
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<td><a name="sec:vertices"><TT>vertices(g)</TT></a></TD>
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<TD><TT>std::pair<vertex_iterator, vertex_iterator></TT></TD>
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<TD>
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Returns an iterator-range providing access to all the vertices in the
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graph<TT>g</TT>.
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</TD>
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</TR>
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<tr>
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<td>Number of Vertices in the Graph </td>
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<td><TT>num_vertices(g)</TT></TD>
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<TD><TT>vertices_size_type</TT></TD>
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<TD>Returns the number of vertices in the graph <TT>g</TT>.</TD>
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</TR>
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</TABLE>
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<H3>Complexity guarantees</H3>
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<P>
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The <TT>vertices()</TT> function must return in constant time.
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<H3>See Also</H3>
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<a href="./graph_concepts.html">Graph concepts</a>
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<H3>Design Rationale</H3>
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One issue in the design of this concept is whether to include the
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refinement from the <a href="./IncidenceGraph.html">IncidenceGraph</a>
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and <a href="./AdjacencyGraph.html">AdjacencyGraph</a> concepts. The
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ability to traverse the vertices of a graph is orthogonal to
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traversing out-edges, so it would make sense to have a VertexListGraph
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concept that only includes vertex traversal. However, such a concept
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would no longer really be a graph, but would just be a set, and the
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STL already has concepts for dealing with such things. However, there
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are many BGL algorithms that need to traverse the vertices and
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out-edges of a graph, so for convenience a concept is needed that
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groups these requirements together, hence the VertexListGraph concept.
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<H3>Concept Checking Class</H3>
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<P>
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<PRE>
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template <class G>
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struct VertexListGraphConcept
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{
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typedef typename boost::graph_traits<G>::vertex_iterator
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vertex_iterator;
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void constraints() {
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BOOST_CONCEPT_ASSERT(( IncidenceGraphConcept<G> ));
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BOOST_CONCEPT_ASSERT(( AdjacencyGraphConcept<G> ));
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BOOST_CONCEPT_ASSERT(( MultiPassInputIteratorConcept<vertex_iterator> ));
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p = vertices(g);
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V = num_vertices(g);
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v = *p.first;
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const_constraints(g);
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}
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void const_constraints(const G& g) {
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p = vertices(g);
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V = num_vertices(g);
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v = *p.first;
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}
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std::pair<vertex_iterator, vertex_iterator> p;
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typename boost::graph_traits<G>::vertex_descriptor v;
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typename boost::graph_traits<G>::vertices_size_type V;
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G g;
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};
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</PRE>
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<br>
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<HR>
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<TABLE>
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<TR valign=top>
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<TD nowrap>Copyright © 2000-2001</TD><TD>
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<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>)
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</TD></TR></TABLE>
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</BODY>
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</HTML>
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