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| <Head> |
| <Title>Bidirectional</Title> |
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| |
| <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() { |
| function_requires< IncidenceGraphConcept<G> >(); |
| function_requires< MultiPassInputIteratorConcept<in_edge_iterator> >(); |
| |
| p = in_edges(v, g); |
| e = *p.first; |
| const_constraints(g); |
| } |
| void const_constraints(const G& g) { |
| p = in_edges(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; |
| 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> |
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