1//=======================================================================
2// Copyright 2009 Trustees of Indiana University
3// Author: Jeremiah Willcock
4//
5// Distributed under the Boost Software License, Version 1.0. (See
6// accompanying file LICENSE_1_0.txt or copy at
7// http://www.boost.org/LICENSE_1_0.txt)
8//=======================================================================
9
10#ifndef BOOST_GRAPH_LOOKUP_EDGE_HPP
11#define BOOST_GRAPH_LOOKUP_EDGE_HPP
12
13#include <utility>
14#include <boost/config.hpp>
15#include <boost/utility/enable_if.hpp>
16#include <boost/graph/graph_traits.hpp>
17
18// lookup_edge: a function that acts like edge() but falls back to out_edges()
19// and a search when edge() is not provided.
20
21namespace boost {
22
23 template <typename Graph>
24 std::pair<typename boost::graph_traits<Graph>::edge_descriptor, bool>
25 lookup_edge(typename boost::graph_traits<Graph>::vertex_descriptor src,
26 typename boost::graph_traits<Graph>::vertex_descriptor tgt,
27 const Graph& g,
28 typename boost::enable_if<is_adjacency_matrix<Graph>, int>::type = 0) {
29 return edge(src, tgt, g);
30 }
31
32 template <typename Graph>
33 std::pair<typename boost::graph_traits<Graph>::edge_descriptor, bool>
34 lookup_edge(typename boost::graph_traits<Graph>::vertex_descriptor src,
35 typename boost::graph_traits<Graph>::vertex_descriptor tgt,
36 const Graph& g,
37 typename boost::disable_if<is_adjacency_matrix<Graph>, int>::type = 0) {
38 typedef typename boost::graph_traits<Graph>::out_edge_iterator it;
39 typedef typename boost::graph_traits<Graph>::edge_descriptor edesc;
40 std::pair<it, it> oe = out_edges(src, g);
41 for (; oe.first != oe.second; ++oe.first) {
42 edesc e = *oe.first;
43 if (target(e, g) == tgt) return std::make_pair(e, true);
44 }
45 return std::make_pair(edesc(), false);
46 }
47
48}
49
50#endif // BOOST_GRAPH_LOOKUP_EDGE_HPP
51

source code of boost/boost/graph/lookup_edge.hpp