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- Copyright (c) Jeremy Siek 2000
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- <Head>
- <Title>Bidirectional</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:BidirectionalGraph"></A>
- BidirectionalGraph
- </H2>
- <P>
- The BidirectionalGraph concept refines <a
- href="./IncidenceGraph.html">IncidenceGraph</a> and adds the
- requirement for efficient access to the in-edges of each vertex. This
- concept is separated from <a
- href="./IncidenceGraph.html">IncidenceGraph</a> because for directed
- graphs efficient access to in-edges typically requires more storage
- space, and many algorithms do not require access to in-edges. For
- undirected graphs this is not an issue, since the <TT>in_edges()</TT>
- and <TT>out_edges()</TT> functions are the same, they both return the
- edges incident to the vertex.
- <H3>Refinement of</H3>
- <a href="./IncidenceGraph.html">IncidenceGraph</a>
- <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>
- <TR>
- <TD><tt>v</tt></TD>
- <TD>An object of type <tt>boost::graph_traits<G>::vertex_descriptor</tt>.</TD>
- </TR>
- </table>
- <H3>Associated Types</H3>
- <Table border>
- <tr>
- <td><tt>boost::graph_traits<G>::traversal_category</tt><br><br>
- This tag type must be convertible to <tt>bidirectional_graph_tag</tt>.
- </td>
- </tr>
- <TR>
- <TD><pre>boost::graph_traits<G>::in_edge_iterator</pre>
- An in-edge iterator for a vertex <i>v</i> provides access to the
- in-edges of <i>v</i>. As such, the value type of an in-edge iterator
- is the edge descriptor type of its graph. An in-edge iterator must
- meet the requirements of <a href="../../utility/MultiPassInputIterator.html">MultiPassInputIterator</a>.
- </TD>
- </TR>
- </Table>
- <h3>Valid Expressions</h3>
- <Table border>
- <tr>
- <td><a name="sec:in-edges"><TT>in_edges(v, g)</TT></a></TD>
- <TD>
- Returns an iterator-range providing access to the
- in-edges (for directed graphs) or incident edges (for
- undirected graphs) of vertex <TT>v</TT> in graph <TT>g</TT>.
- For both directed and undirected graphs, the target of
- an out-edge is required to be vertex <tt>v</tt> and the
- source is required to be a vertex that is adjacent to <tt>v</tt>.
- <br>
- Return type: <TT>std::pair<in_edge_iterator, in_edge_iterator></TT>
- </TD>
- </TR>
- <tr>
- <TD><TT>in_degree(v, g)</TT></TD>
- <TD>
- Returns the number of in-edges (for directed graphs) or the
- number of incident edges (for undirected graphs) of vertex <TT>v</TT>
- in graph <TT>g</TT>.<br>
- Return type: <TT>degree_size_type</TT>
- </TD>
- </TR>
- <tr>
- <TD><TT>degree(v, g)</TT></TD>
- <TD>Returns the number of in-edges plus out-edges (for directed graphs) or the
- number of incident edges (for undirected graphs) of vertex <TT>v</TT>
- in graph <TT>g</TT>.<br>
- Return type: <TT>degree_size_type</TT>
- </TD>
- </TR>
- </Table>
- <H3>Models</H3>
- <ul>
- <li><a href="./adjacency_list.html"><tt>adjacency_list</tt></a> with <tt>Directed=bidirectionalS</tt></li>
- <li><a href="./adjacency_list.html"><tt>adjacency_list</tt></a> with <tt>Directed=undirectedS</tt></li>
- </ul>
- <H3>Complexity guarantees</H3>
- The <TT>in_edges()</TT> function is required to be constant time. The
- <tt>in_degree()</tt> and <tt>degree()</tt> functions must be linear in
- the number of in-edges (for directed graphs) or incident edges (for
- undirected graphs).
- <H3>See Also</H3>
- <a href="./graph_concepts.html">Graph concepts</a>
- <H3>Concept Checking Class</H3>
- <PRE>
- template <class G>
- struct BidirectionalGraphConcept
- {
- typedef typename boost::graph_traits<G>::in_edge_iterator
- in_edge_iterator;
- void constraints() {
- BOOST_CONCEPT_ASSERT(( IncidenceGraphConcept<G> ));
- BOOST_CONCEPT_ASSERT(( MultiPassInputIteratorConcept<in_edge_iterator> ));
- p = in_edges(v, g);
- n = in_degree(v, g);
- n = degree(v, g);
- e = *p.first;
- const_constraints(g);
- }
- void const_constraints(const G& g) {
- p = in_edges(v, g);
- n = in_degree(v, g);
- n = degree(v, g);
- e = *p.first;
- }
- std::pair<in_edge_iterator, in_edge_iterator> p;
- typename boost::graph_traits<G>::vertex_descriptor v;
- typename boost::graph_traits<G>::edge_descriptor e;
- typename boost::graph_traits<G>::degree_size_type n;
- G g;
- };
- </PRE>
- <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>
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