<HTML>
<!--
      (C) Copyright David Abrahams and Jeremy Siek 2000.
    
     Distributed under the Boost Software License, Version 1.0.
     (See accompanying file LICENSE_1_0.txt or copy at
     http://www.boost.org/LICENSE_1_0.txt)
  -->
<Head>
<Title>Boost Graph Library: Reverse Graph Adaptor</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>


<H1><A NAME="sec:reverse-graph-adaptor"></A>
</h1>
<pre>
reverse_graph&lt;<a href="./BidirectionalGraph.html">BidirectionalGraph</a>, GraphReference&gt;
</pre>

The <tt>reverse_graph</tt> adaptor flips the in-edges and out-edges of
a <a href="./BidirectionalGraph.html">BidirectionalGraph</a>,
effectively transposing the graph. The construction of the
<tt>reverse_graph</tt> is constant time, providing a highly efficient
way to obtain a transposed-view of a graph.


<H3>Example</H3>

The example from <a
href="../example/reverse-graph-eg.cpp"><tt>examples/reverse-graph-eg.cpp</tt></a>.

<pre>
int
main()
{
  typedef boost::adjacency_list&lt; 
    boost::vecS, boost::vecS, boost::bidirectionalS,
  &gt; Graph;
  
  Graph G(5);
  boost::add_edge(0, 2, G);
  boost::add_edge(1, 1, G);
  boost::add_edge(1, 3, G);
  boost::add_edge(1, 4, G);
  boost::add_edge(2, 1, G);
  boost::add_edge(2, 3, G);
  boost::add_edge(2, 4, G);
  boost::add_edge(3, 1, G);
  boost::add_edge(3, 4, G);
  boost::add_edge(4, 0, G);
  boost::add_edge(4, 1, G);

  std::cout &lt;&lt; &quot;original graph:&quot; &lt;&lt; std::endl;
  boost::print_graph(G, boost::get(boost::vertex_index, G));

  std::cout &lt;&lt; std::endl &lt;&lt; &quot;reversed graph:&quot; &lt;&lt; std::endl;
  boost::print_graph(boost::make_reverse_graph(G), 
                     boost::get(boost::vertex_index, G));


  return 0;
}
</pre>
The output is:
<pre>
original graph:
0 --&gt; 2 
1 --&gt; 1 3 4 
2 --&gt; 1 3 4 
3 --&gt; 1 4 
4 --&gt; 0 1 

reversed graph:
0 --&gt; 4 
1 --&gt; 1 2 3 4 
2 --&gt; 0 
3 --&gt; 1 2 
4 --&gt; 1 2 3 
</pre>

<H3>Template Parameters</H3>

<P>
<TABLE border>
<TR>
<th>Parameter</th><th>Description</th><th>Default</th>
</tr>

<TR><TD><TT>BidirectionalGraph</TT></TD>
<TD>The graph type to be adapted.</TD>
<TD>&nbsp;</TD>
</TR>

<TR><TD><TT>GraphReference</TT></TD>
<TD>This type should be <tt>const&nbsp;BidirectionalGraph&amp;</tt>
if you want to create a const reverse graph, or <tt>BidirectionalGraph&amp;</tt> if you want to create a non-const reverse graph.</TD>
<TD><tt>const&nbsp;BidirectionalGraph&amp;</tt></TD>
</TR>


</table>


<H3>Model of</H3>

<P>
<a href="./BidirectionalGraph.html">BidirectionalGraph</a>
and optionally
<a href="./VertexListGraph.html">VertexListGraph</a>
and <a href="./PropertyGraph.html">PropertyGraph</a>


<H3>Where Defined</H3>

<P>
<a href="../../../boost/graph/reverse_graph.hpp"><TT>boost/graph/reverse_graph.hpp</TT></a>


<H2>Associated Types</H2>

<hr>

<tt>graph_traits&lt;reverse_graph&gt;::vertex_descriptor</tt>
<br><br>
The type for the vertex descriptors associated with the
<TT>reverse_graph</TT>.

<hr>

<tt>graph_traits&lt;reverse_graph&gt;::edge_descriptor</tt>
<br><br>
The type for the edge descriptors associated with the
<TT>reverse_graph</TT>.

<hr>

<tt>graph_traits&lt;reverse_graph&gt;::vertex_iterator</tt>
<br><br>
The type for the iterators returned by <TT>vertices()</TT>.

<hr>

<tt>graph_traits&lt;reverse_graph&gt;::edge_iterator</tt>
<br><br>
The type for the iterators returned by <TT>edges()</TT>.

<hr>


<tt>graph_traits&lt;reverse_graph&gt;::out_edge_iterator</tt>
<br><br>
The type for the iterators returned by <TT>out_edges()</TT>.

<hr>

<tt>graph_traits&lt;reverse_graph&gt;::adjacency_iterator</tt>
<br><br>
The type for the iterators returned by <TT>adjacent_vertices()</TT>.

<hr>

<tt>graph_traits&lt;reverse_graph&gt;::directed_category</tt>
<br><br>
Provides information about whether the graph is
directed (<TT>directed_tag</TT>) or undirected
(<TT>undirected_tag</TT>).

<hr>

<tt>graph_traits&lt;reverse_graph&gt;::edge_parallel_category</tt>
<br><br>
This describes whether the graph class allows the insertion of
parallel edges (edges with the same source and target). The two tags
are <TT>allow_parallel_edge-_tag</TT> and
<TT>disallow_parallel_edge_tag</TT>. The
<TT>setS</TT> and <TT>hash_setS</TT> variants disallow
parallel edges while the others allow parallel edges.

<hr>

<tt>graph_traits&lt;reverse_graph&gt;::vertices_size_type</tt>
<br><br>
The type used for dealing with the number of vertices in the graph.

<hr>

<tt>graph_traits&lt;reverse_graph&gt;::edge_size_type</tt>
<br><br>
The type used for dealing with the number of edges in the graph.

<hr>

<tt>graph_traits&lt;reverse_graph&gt;::degree_size_type</tt>
<br><br>
The type used for dealing with the number of edges incident to a vertex
in the graph.

<hr>

<tt>property_map&lt;reverse_graph, PropertyTag&gt;::type</tt><br>
and<br>
<tt>property_map&lt;reverse_graph, PropertyTag&gt;::const_type</tt>
<br><br>
The property map type for vertex or edge properties in the graph. The
specific property is specified by the <TT>PropertyTag</TT> template argument,
and must match one of the properties specified in the
<TT>VertexProperty</TT> or <TT>EdgeProperty</TT> for the graph.

<hr>


<H2>Member Functions</H2>

<hr>

<pre>
reverse_graph(BidirectionalGraph&amp;&nbsp;g)
</pre>
Constructor. Create a reversed (transposed) view of the graph <tt>g</tt>.

<hr>

<H2>Non-Member Functions</H2>

<hr>

<pre>
template &lt;class BidirectionalGraph&gt;
reverse_graph&lt;BidirectionalGraph, BidirectionalGraph&amp;&gt;
make_reverse_graph(BidirectionalGraph&amp; g);

template &lt;class BidirectionalGraph&gt;
reverse_graph&lt;BidirectionalGraph, const BidirectionalGraph&amp;&gt;
make_reverse_graph(const BidirectionalGraph&amp; g)

</pre>
Helper function for creating a <tt>reverse_graph</tt>.

<hr>

<pre>
std::pair&lt;vertex_iterator,&nbsp;vertex_iterator&gt;
vertices(const reverse_graph&amp; g)
</pre>
Returns an iterator-range providing access to the vertex set of graph
<tt>g</tt>.

<hr>

<pre>
std::pair&lt;out_edge_iterator,&nbsp;out_edge_iterator&gt;
out_edges(vertex_descriptor&nbsp;v, const&nbsp;reverse_graph&amp;&nbsp;g)
</pre>
Returns an iterator-range providing access to the out-edges of vertex
<tt>v</tt> in graph <tt>g</tt>. These out-edges correspond to the
in-edges of the adapted graph.

<hr>

<pre>
std::pair&lt;in_edge_iterator,&nbsp;in_edge_iterator&gt;
in_edges(vertex_descriptor&nbsp;v, const&nbsp;reverse_graph&amp;&nbsp;g)
</pre>
Returns an iterator-range providing access to the in-edges of vertex
<tt>v</tt> in graph <tt>g</tt>. These in-edges correspond to the
out edges of the adapted graph.

<hr>

<pre>
std::pair&lt;adjacency_iterator,&nbsp;adjacency__iterator&gt;
adjacent_vertices(vertex_descriptor&nbsp;v, const&nbsp;reverse_graph&amp;&nbsp;g)
</pre>
Returns an iterator-range providing access to the adjacent vertices of vertex
<tt>v</tt> in graph <tt>g</tt>.

<hr>

<pre>
vertex_descriptor
source(edge_descriptor&nbsp;e, const&nbsp;reverse_graph&amp;&nbsp;g)
</pre>
Returns the source vertex of edge <tt>e</tt>.

<hr>

<pre>
vertex_descriptor
target(edge_descriptor&nbsp;e, const&nbsp;reverse_graph&amp;&nbsp;g)
</pre>
Returns the target vertex of edge <tt>e</tt>.

<hr>

<pre>
degree_size_type
out_degree(vertex_descriptor&nbsp;u, const&nbsp;reverse_graph&amp;&nbsp;g)
</pre>
Returns the number of edges leaving vertex <tt>u</tt>.

<hr>

<pre>
degree_size_type
in_degree(vertex_descriptor&nbsp;u, const&nbsp;reverse_graph&amp;&nbsp;g)
</pre>
Returns the number of edges entering vertex <tt>u</tt>. This operation
is only available if <TT>bidirectionalS</TT> was specified for
the <TT>Directed</TT> template parameter.

<hr>

<pre>
vertices_size_type
num_vertices(const reverse_graph&amp; g)
</pre>
Returns the number of vertices in the graph <tt>g</tt>.

<hr>

<pre>
vertex_descriptor
vertex(vertices_size_type&nbsp;n, const&nbsp;reverse_graph&amp;&nbsp;g)
</pre>
Returns the nth vertex in the graph's vertex list.

<hr>

<pre>
std::pair&lt;edge_descriptor, bool&gt;
edge(vertex_descriptor&nbsp;u, vertex_descriptor&nbsp;v,
     const&nbsp;reverse_graph&amp;&nbsp;g)
</pre>
Returns the edge connecting vertex <tt>u</tt> to vertex <tt>v</tt> in
graph <tt>g</tt>.

<hr>

<pre>
template &lt;class <a href="./PropertyTag.html">PropertyTag</a>&gt;
property_map&lt;reverse_graph, PropertyTag&gt;::type
get(PropertyTag, reverse_graph&amp; g)

template &lt;class <a href="./PropertyTag.html">PropertyTag</a>&gt;
property_map&lt;reverse_graph, Tag&gt;::const_type
get(PropertyTag, const reverse_graph&amp; g)
</pre>
Returns the property map object for the vertex property specified by
<TT>PropertyTag</TT>. The <TT>PropertyTag</TT> must match one of the
properties specified in the graph's <TT>VertexProperty</TT> template
argument.

<hr>

<pre>
template &lt;class <a href="./PropertyTag.html">PropertyTag</a>, class X&gt;
typename property_traits&lt;property_map&lt;reverse_graph, PropertyTag&gt;::const_type&gt;::value_type
get(PropertyTag, const reverse_graph&amp; g, X x)
</pre>
This returns the property value for <tt>x</tt>, which is either
a vertex or edge descriptor.
<hr>

<pre>
template &lt;class <a href="./PropertyTag.html">PropertyTag</a>, class X, class Value&gt;
void
put(PropertyTag, const reverse_graph&amp; g, X x, const Value&amp; value)
</pre>
This sets the property value for <tt>x</tt> to
<tt>value</tt>. <tt>x</tt> is either a vertex or edge descriptor.
<tt>Value</tt> must be convertible to
<tt>typename property_traits&lt;property_map&lt;reverse_graph, PropertyTag&gt;::type&gt::value_type</tt>

<hr>

<pre>
template &lt;class GraphProperties, class <a href="./PropertyTag.html#GraphPropertyTag">GraphPropertyTag</a>&gt;
typename property_value&lt;GraphProperties, GraphPropertyTag&gt;::type&amp;
get_property(reverse_graph&amp; g, GraphPropertyTag);
</pre>
Return the property specified by <tt>GraphPropertyTag</tt> that is
attached to the graph object <tt>g</tt>. The <tt>property_value</tt>
traits class is defined in <a
href="../../../boost/pending/property.hpp"><tt>boost/pending/property.hpp</tt></a>.

<hr>

<pre>
template &lt;class GraphProperties, class <a href="./PropertyTag.html#GraphPropertyTag">GraphPropertyTag</a>&gt;
const typename property_value&lt;GraphProperties, GraphPropertyTag&gt;::type&amp;
get_property(const reverse_graph&amp; g, GraphPropertyTag);
</pre>
Return the property specified by <tt>GraphPropertyTag</tt> that is
attached to the graph object <tt>g</tt>.  The <tt>property_value</tt>
traits class is defined in <a
href="../../../boost/pending/property.hpp"><tt>boost/pending/property.hpp</tt></a>.

<hr>

<br>
<HR>
<TABLE>
<TR valign=top>
<TD nowrap>Copyright &copy; 2000-2001</TD><TD>
<a HREF="http://www.boost.org/people/dave_abrahams.htm">Dave Abrahams</a>
(<A HREF="mailto:david.abrahams@rcn.com">david.abrahams@rcn.com</A>)<br>
<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>)<br>
</TD></TR></TABLE>

</BODY>
</HTML>