boost/graph/lookup_edge.hpp

0001 //=======================================================================
0002 // Copyright 2009 Trustees of Indiana University
0003 // Author: Jeremiah Willcock
0004 //
0005 // Distributed under the Boost Software License, Version 1.0. (See
0006 // accompanying file LICENSE_1_0.txt or copy at
0007 // http://www.boost.org/LICENSE_1_0.txt)
0008 //=======================================================================
0009
0010 #ifndef BOOST_GRAPH_LOOKUP_EDGE_HPP
0011 #define BOOST_GRAPH_LOOKUP_EDGE_HPP
0012
0013 #include <utility>
0014 #include <boost/config.hpp>
0015 #include <boost/utility/enable_if.hpp>
0016 #include <boost/graph/graph_traits.hpp>
0017
0018 // lookup_edge: a function that acts like edge() but falls back to out_edges()
0019 // and a search when edge() is not provided.
0020
0021 namespace boost
0022 {
0023
0024 template < typename Graph >
0025 std::pair< typename boost::graph_traits< Graph >::edge_descriptor, bool >
0026 lookup_edge(typename boost::graph_traits< Graph >::vertex_descriptor src,
0027     typename boost::graph_traits< Graph >::vertex_descriptor tgt,
0028     const Graph& g,
0029     typename boost::enable_if< is_adjacency_matrix< Graph >, int >::type = 0)
0030 {
0031     return edge(src, tgt, g);
0032 }
0033
0034 template < typename Graph >
0035 std::pair< typename boost::graph_traits< Graph >::edge_descriptor, bool >
0036 lookup_edge(typename boost::graph_traits< Graph >::vertex_descriptor src,
0037     typename boost::graph_traits< Graph >::vertex_descriptor tgt,
0038     const Graph& g,
0039     typename boost::disable_if< is_adjacency_matrix< Graph >, int >::type = 0)
0040 {
0041     typedef typename boost::graph_traits< Graph >::out_edge_iterator it;
0042     typedef typename boost::graph_traits< Graph >::edge_descriptor edesc;
0043     std::pair< it, it > oe = out_edges(src, g);
0044     for (; oe.first != oe.second; ++oe.first)
0045     {
0046         edesc e = *oe.first;
0047         if (target(e, g) == tgt)
0048             return std::make_pair(e, true);
0049     }
0050     return std::make_pair(edesc(), false);
0051 }
0052
0053 }
0054
0055 #endif // BOOST_GRAPH_LOOKUP_EDGE_HPP