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<Head>
<Title>Boost Graph Library: Graph Traits</Title>
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<H1><A NAME=""></A>
<pre>
graph_traits<<a href="./Graph.html">Graph</a>>
</pre>
</H1>
Just like the <a
href="http://www.sgi.com/tech/stl/iterator_traits.html">
iterators</a> of STL, graphs have <b>associated types</b>. As stated
in the various <a href="./graph_concepts.html">graph concepts</a>, a
graph has quite a few associated types: <tt>vertex_descriptor</tt>,
<tt>edge_descriptor</tt>, <tt>out_edge_iterator</tt>, etc.. Any
particular graph concepts will not require that all of the following
associated types be defined. When implementing a graph class that
fullfils one or more graph concepts, for associated types that are not
required by the concepts, it is ok to use <tt>void</tt> as the type
(when using nested typedefs inside the graph class), or to leave the
typedef out of the <tt>graph_traits</tt> specialization for the graph
class.
<pre>
template <typename Graph>
struct graph_traits {
typedef typename Graph::vertex_descriptor vertex_descriptor;
typedef typename Graph::edge_descriptor edge_descriptor;
typedef typename Graph::adjacency_iterator adjacency_iterator;
typedef typename Graph::out_edge_iterator out_edge_iterator;
typedef typename Graph::in_edge_iterator in_edge_iterator;
typedef typename Graph::vertex_iterator vertex_iterator;
typedef typename Graph::edge_iterator edge_iterator;
typedef typename Graph::directed_category directed_category;
typedef typename Graph::edge_parallel_category edge_parallel_category;
typedef typename Graph::traversal_category traversal_category;
typedef typename Graph::vertices_size_type vertices_size_type;
typedef typename Graph::edges_size_type edges_size_type;
typedef typename Graph::degree_size_type degree_size_type;
};
</pre>
<h3>Where Defined</h3>
<a href="../../../boost/graph/graph_traits.hpp"><tt>boost/graph/graph_traits.hpp</tt></a>
<H3>Template Parameters</H3>
<P>
<TABLE border>
<TR>
<th>Parameter</th><th>Description</th>
</tr>
<TR><TD><TT>Graph</TT></TD>
<TD>
The graph type whose associated types are being accessed.
</TD>
</TR>
</table>
<h3>Model of</h3>
<a
href="http://www.sgi.com/tech/stl/DefaultConstructible.html">DefaultConstructible</a> and
<a href="http://www.sgi.com/tech/stl/Assignable.html">Assignable</a>
<h3>Type Requirements</h3>
<ul>
<li><tt>Graph</tt> is a model of one of the <a
href="./graph_concepts.html">graph concepts</a>.
</ul>
<H2>Members</H2>
<p>
<table border>
<tr>
<th>Member</th><th>Description</th>
</tr>
<tr>
<td><tt>
vertex_descriptor
</tt></td>
<td>
The type for the objects used to identity vertices in the graph.
</td>
</tr>
<tr>
<td><tt>
edge_descriptor
</tt></td>
<td>
The type for the objects used to identity edges in the graph.
</td>
</tr>
<tr>
<td><tt>
adjacency_iterator
</tt></td>
<td>
The type for the iterators that traverse the vertices adjacent
to a vertex.
</td>
</tr>
<tr>
<td><tt>
out_edge_iterator
</tt></td>
<td>
The type for the iterators that traverse through the out-edges
of a vertex.
</td>
</tr>
<tr>
<td><tt>
in_edge_iterator
</tt></td>
<td>
The type for the iterators that traverse through the in-edges
of a vertex.
</td>
</tr>
<tr>
<td><tt>
vertex_iterator
</tt></td>
<td>
The type for the iterators that traverse through the complete vertex
set of the graph.
</td>
</tr>
<tr>
<td><tt>
edge_iterator
</tt></td>
<td>
The type for the iterators that traverse through the complete edge
set of the graph.
</td>
</tr>
<tr>
<td><tt>
directed_category
</tt></td>
<td>
This says whether the graph is undirected (<tt>undirected_tag</tt>)
or directed (<tt>directed_tag</tt>).
</td>
</tr>
<tr>
<td><tt>
edge_parallel_category
</tt></td>
<td>
This says whether the graph allows parallel edges to be inserted
(<tt>allow_parallel_edge_tag</tt>) or if it automatically removes
parallel edges (<tt>disallow_parallel_edge_tag</tt>).
</td>
</tr>
<tr>
<td><tt>
traversal_category
</tt></td>
<td>
The ways in which the vertices in the graph can be traversed.
The traversal category tags are:
<tt>incidence_graph_tag, adjacency_graph_tag,
bidirectional_graph_tag, vertex_list_graph_tag,
edge_list_graph_tag, vertex_and_edge_list_graph_tag,
adjacency_matrix_tag</tt>. You can also create your own
tag which should inherit from one of the above.
</td>
</tr>
<tr>
<td><tt>
vertices_size_type
</tt></td>
<td>
The unsigned integer type used for representing the number of
vertices in the graph.
</td>
</tr>
<tr>
<td><tt>
edge_size_type
</tt></td>
<td>
The unsigned integer type used for representing the number of
edge in the graph.
</td>
</tr>
<tr>
<td><tt>
degree_size_type
</tt></td>
<td>
The unsigned integer type used for representing the degree
of vertices in the graph.
</td>
</tr>
</table>
<br>
<HR>
<TABLE>
<TR valign=top>
<TD nowrap>Copyright © 2000-2001</TD><TD>
<A HREF="../../../people/jeremy_siek.htm">Jeremy Siek</A>,
Indiana University (<A
HREF="mailto:jsiek@osl.iu.edu">jsiek@osl.iu.edu</A>)<br>
<A HREF="../../../people/liequan_lee.htm">Lie-Quan Lee</A>, Indiana University (<A HREF="mailto:llee@cs.indiana.edu">llee@cs.indiana.edu</A>)<br>
<A HREF=http://www.osl.iu.edu/~lums>Andrew Lumsdaine</A>,
Indiana University (<A
HREF="mailto:lums@osl.iu.edu">lums@osl.iu.edu</A>)
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