Chris@16: //=======================================================================
Chris@16: // Copyright 2009 Trustees of Indiana University
Chris@16: // Author: Jeremiah Willcock
Chris@16: //
Chris@16: // Distributed under the Boost Software License, Version 1.0. (See
Chris@16: // accompanying file LICENSE_1_0.txt or copy at
Chris@16: // http://www.boost.org/LICENSE_1_0.txt)
Chris@16: //=======================================================================
Chris@16: 
Chris@16: #ifndef BOOST_GRAPH_LOOKUP_EDGE_HPP
Chris@16: #define BOOST_GRAPH_LOOKUP_EDGE_HPP
Chris@16: 
Chris@16: #include <utility>
Chris@16: #include <boost/config.hpp>
Chris@16: #include <boost/utility/enable_if.hpp>
Chris@16: #include <boost/graph/graph_traits.hpp>
Chris@16: 
Chris@16: // lookup_edge: a function that acts like edge() but falls back to out_edges()
Chris@16: // and a search when edge() is not provided.
Chris@16: 
Chris@16: namespace boost {
Chris@16: 
Chris@16:   template <typename Graph>
Chris@16:   std::pair<typename boost::graph_traits<Graph>::edge_descriptor, bool>
Chris@16:   lookup_edge(typename boost::graph_traits<Graph>::vertex_descriptor src,
Chris@16:               typename boost::graph_traits<Graph>::vertex_descriptor tgt,
Chris@16:               const Graph& g,
Chris@16:               typename boost::enable_if<is_adjacency_matrix<Graph>, int>::type = 0) {
Chris@16:     return edge(src, tgt, g);
Chris@16:   }
Chris@16: 
Chris@16:   template <typename Graph>
Chris@16:   std::pair<typename boost::graph_traits<Graph>::edge_descriptor, bool>
Chris@16:   lookup_edge(typename boost::graph_traits<Graph>::vertex_descriptor src,
Chris@16:               typename boost::graph_traits<Graph>::vertex_descriptor tgt,
Chris@16:               const Graph& g,
Chris@16:               typename boost::disable_if<is_adjacency_matrix<Graph>, int>::type = 0) {
Chris@16:     typedef typename boost::graph_traits<Graph>::out_edge_iterator it;
Chris@16:     typedef typename boost::graph_traits<Graph>::edge_descriptor edesc;
Chris@16:     std::pair<it, it> oe = out_edges(src, g);
Chris@16:     for (; oe.first != oe.second; ++oe.first) {
Chris@16:       edesc e = *oe.first;
Chris@16:       if (target(e, g) == tgt) return std::make_pair(e, true);
Chris@16:     }
Chris@16:     return std::make_pair(edesc(), false);
Chris@16:   }
Chris@16: 
Chris@16: }
Chris@16: 
Chris@16: #endif // BOOST_GRAPH_LOOKUP_EDGE_HPP