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<Title>Boost Graph Library: opposite</Title>
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<H1><A NAME="sec:opposite"></A>
<TT>opposite</TT>
</H1>

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<TR><TH ALIGN="LEFT"><B>Complexity:</B></TH>
<TD ALIGN="LEFT"><i>O(1)</i>
</TD>
</TR>

<TR><TH ALIGN="LEFT"><B>Where Defined:</B></TH>
<TD ALIGN="LEFT">
<a href="../../../boost/graph/graph_utility.hpp"><TT>boost/graph/graph_utility.hpp</TT></a>
</TD>

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<P>
<PRE>
  template &lt;class Graph&gt;
  typename graph_traits&lt;Graph&gt;::vertex_descriptor
  opposite(typename graph_traits&lt;Graph&gt;::edge_descriptor e,
           typename graph_traits&lt;Graph&gt;::vertex_descriptor v,
           const Graph& g)
</pre>

Given an edge and a vertex which must be incident to the edge, this
function returns the opposite vertex. So if <tt>v</tt> is the source
vertex, this function returns the target vertex. If <tt>v</tt> is the
target, then this function returns the source vertex.

<h3>Example</h3>

<pre>
edge_descriptor e;
...
vertex_descriptor u, v;
tie(u, v) = incident(e, g);
assert(v == opposite(e, u, g));
assert(u == opposite(e, v, g));
</pre>

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<TABLE>
<TR valign=top>
<TD nowrap>Copyright &copy; 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>)<br>
<A HREF="http://www.boost.org/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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