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| <Head> |
| <Title>AdjacencyGraph</Title> |
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| |
| <H2><A NAME="concept:AdjacencyGraph"></A> |
| AdjacencyGraph |
| </H2> |
| |
| The AdjacencyGraph concept provides and interface for efficient access |
| of the adjacent vertices to a vertex in a graph. This is quite similar |
| to the <a href="./IncidenceGraph.html">IncidenceGraph</a> concept (the |
| target of an out-edge is an adjacent vertex). Both concepts are |
| provided because in some contexts there is only concern for the |
| vertices, whereas in other contexts the edges are also important. |
| |
| <H3>Refinement of</H3> |
| |
| <a href="Graph.html">Graph</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>adjacency_graph_tag</tt>. |
| </td> |
| </tr> |
| |
| <TR> |
| <TD><pre>boost::graph_traits<G>::adjacency_iterator</pre> |
| An adjacency iterator for a vertex <i>v</i> provides access to the |
| vertices adjacent to <i>v</i>. As such, the value type of an |
| adjacency iterator is the vertex descriptor type of its graph. An |
| adjacency 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:adjacent-vertices"><TT>adjacent_vertices(v, g)</TT></a></TD> |
| <TD> |
| Returns an iterator-range providing access to the vertices adjacent to |
| vertex <TT>v</TT> in graph <TT>g</TT>.<a |
| href="#1">[1]</a> |
| |
| <br> Return type: |
| <TT>std::pair<adjacency_iterator, adjacency_iterator></TT> |
| </TD> |
| </TR> |
| |
| </table> |
| |
| <H3>Complexity guarantees</H3> |
| |
| The <TT>adjacent_vertices()</TT> function must return in constant time. |
| |
| <H3>See Also</H3> |
| |
| <a href="./graph_concepts.html">Graph concepts</a>, |
| <a href="./adjacency_iterator.html"><tt>adjacency_iterator</tt></a> |
| |
| <H3>Concept Checking Class</H3> |
| |
| <PRE> |
| template <class G> |
| struct AdjacencyGraphConcept |
| { |
| typedef typename boost::graph_traits<G>::adjacency_iterator |
| adjacency_iterator; |
| void constraints() { |
| function_requires< IncidenceGraphConcept<G> >(); |
| function_requires< MultiPassInputIteratorConcept<adjacency_iterator> >(); |
| |
| p = adjacent_vertices(v, g); |
| v = *p.first; |
| const_constraints(g); |
| } |
| void const_constraints(const G& g) { |
| p = adjacent_vertices(v, g); |
| } |
| std::pair<adjacency_iterator,adjacency_iterator> p; |
| typename boost::graph_traits<G>::vertex_descriptor v; |
| G g; |
| }; |
| </PRE> |
| |
| <h3>Design Rationale</h3> |
| |
| The AdjacencyGraph concept is somewhat frivolous since <a |
| href="./IncidenceGraph.html">IncidenceGraph</a> really covers the same |
| functionality (and more). The AdjacencyGraph concept exists because |
| there are situations when <tt>adjacent_vertices()</tt> is more |
| convenient to use than <tt>out_edges()</tt>. If you are constructing a |
| graph class and do not want to put in the extra work of creating an |
| adjacency iterator, have no fear. There is an adaptor class named <a |
| href="./adjacency_iterator.html"> <tt>adjacency_iterator</tt></a> that |
| you can use to create an adjacency iterator out of an out-edge |
| iterator. |
| |
| <h3>Notes</h3> |
| |
| <a name="1">[1]</a> The case of a |
| <I>multigraph</I> (where multiple edges can connect the same two |
| vertices) brings up an issue as to whether the iterators returned by |
| the <TT>adjacent_vertices()</TT> function access a range that |
| includes each adjacent vertex once, or whether it should match the |
| behavior of the <TT>out_edges()</TT> function, and access a |
| range that may include an adjacent vertex more than once. For now the |
| behavior is defined to match that of <TT>out_edges()</TT>, |
| though this decision may need to be reviewed in light of more |
| experience with graph algorithm implementations. |
| |
| |
| |
| <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>) |
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