181 lines
4.8 KiB
HTML
181 lines
4.8 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>Bidirectional</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>
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<A NAME="concept:BidirectionalGraph"></A>
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BidirectionalGraph
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</H2>
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<P>
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The BidirectionalGraph concept refines <a
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href="./IncidenceGraph.html">IncidenceGraph</a> and adds the
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requirement for efficient access to the in-edges of each vertex. This
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concept is separated from <a
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href="./IncidenceGraph.html">IncidenceGraph</a> because for directed
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graphs efficient access to in-edges typically requires more storage
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space, and many algorithms do not require access to in-edges. For
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undirected graphs this is not an issue, since the <TT>in_edges()</TT>
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and <TT>out_edges()</TT> functions are the same, they both return the
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edges incident to the vertex.
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<H3>Refinement of</H3>
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<a href="./IncidenceGraph.html">IncidenceGraph</a>
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<h3>Notation</h3>
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<Table>
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<TR>
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<TD><tt>G</tt></TD>
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<TD>A type that is a model of Graph.</TD>
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</TR>
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<TR>
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<TD><tt>g</tt></TD>
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<TD>An object of type <tt>G</tt>.</TD>
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</TR>
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<TR>
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<TD><tt>v</tt></TD>
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<TD>An object of type <tt>boost::graph_traits<G>::vertex_descriptor</tt>.</TD>
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</TR>
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</table>
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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>bidirectional_graph_tag</tt>.
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</td>
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</tr>
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<TR>
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<TD><pre>boost::graph_traits<G>::in_edge_iterator</pre>
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An in-edge iterator for a vertex <i>v</i> provides access to the
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in-edges of <i>v</i>. As such, the value type of an in-edge iterator
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is the edge descriptor type of its graph. An in-edge iterator must
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meet the requirements of <a href="../../utility/MultiPassInputIterator.html">MultiPassInputIterator</a>.
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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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<td><a name="sec:in-edges"><TT>in_edges(v, g)</TT></a></TD>
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<TD>
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Returns an iterator-range providing access to the
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in-edges (for directed graphs) or incident edges (for
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undirected graphs) of vertex <TT>v</TT> in graph <TT>g</TT>.
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For both directed and undirected graphs, the target of
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an out-edge is required to be vertex <tt>v</tt> and the
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source is required to be a vertex that is adjacent to <tt>v</tt>.
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<br>
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Return type: <TT>std::pair<in_edge_iterator, in_edge_iterator></TT>
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</TD>
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</TR>
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<tr>
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<TD><TT>in_degree(v, g)</TT></TD>
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<TD>
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Returns the number of in-edges (for directed graphs) or the
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number of incident edges (for undirected graphs) of vertex <TT>v</TT>
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in graph <TT>g</TT>.<br>
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Return type: <TT>degree_size_type</TT>
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</TD>
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</TR>
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<tr>
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<TD><TT>degree(v, g)</TT></TD>
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<TD>Returns the number of in-edges plus out-edges (for directed graphs) or the
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number of incident edges (for undirected graphs) of vertex <TT>v</TT>
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in graph <TT>g</TT>.<br>
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Return type: <TT>degree_size_type</TT>
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</TD>
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</TR>
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</Table>
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<H3>Models</H3>
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<ul>
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<li><a href="./adjacency_list.html"><tt>adjacency_list</tt></a> with <tt>Directed=bidirectionalS</tt></li>
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<li><a href="./adjacency_list.html"><tt>adjacency_list</tt></a> with <tt>Directed=undirectedS</tt></li>
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</ul>
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<H3>Complexity guarantees</H3>
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The <TT>in_edges()</TT> function is required to be constant time. The
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<tt>in_degree()</tt> and <tt>degree()</tt> functions must be linear in
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the number of in-edges (for directed graphs) or incident edges (for
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undirected graphs).
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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>Concept Checking Class</H3>
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<PRE>
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template <class G>
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struct BidirectionalGraphConcept
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{
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typedef typename boost::graph_traits<G>::in_edge_iterator
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in_edge_iterator;
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void constraints() {
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BOOST_CONCEPT_ASSERT(( IncidenceGraphConcept<G> ));
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BOOST_CONCEPT_ASSERT(( MultiPassInputIteratorConcept<in_edge_iterator> ));
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p = in_edges(v, g);
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n = in_degree(v, g);
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n = degree(v, g);
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e = *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 = in_edges(v, g);
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n = in_degree(v, g);
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n = degree(v, g);
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e = *p.first;
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}
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std::pair<in_edge_iterator, in_edge_iterator> p;
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typename boost::graph_traits<G>::vertex_descriptor v;
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typename boost::graph_traits<G>::edge_descriptor e;
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typename boost::graph_traits<G>::degree_size_type n;
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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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