Added boost header

test/external/boost/graph/lookup_edge.hpp

@@ -0,0 +1,50 @@
+//=======================================================================
+// Copyright 2009 Trustees of Indiana University
+// Author: Jeremiah Willcock
+//
+// 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)
+//=======================================================================
+
+#ifndef BOOST_GRAPH_LOOKUP_EDGE_HPP
+#define BOOST_GRAPH_LOOKUP_EDGE_HPP
+
+#include <utility>
+#include <boost/config.hpp>
+#include <boost/utility/enable_if.hpp>
+#include <boost/graph/graph_traits.hpp>
+
+// lookup_edge: a function that acts like edge() but falls back to out_edges()
+// and a search when edge() is not provided.
+
+namespace boost {
+
+  template <typename Graph>
+  std::pair<typename boost::graph_traits<Graph>::edge_descriptor, bool>
+  lookup_edge(typename boost::graph_traits<Graph>::vertex_descriptor src,
+              typename boost::graph_traits<Graph>::vertex_descriptor tgt,
+              const Graph& g,
+              typename boost::enable_if<is_adjacency_matrix<Graph>, int>::type = 0) {
+    return edge(src, tgt, g);
+  }
+
+  template <typename Graph>
+  std::pair<typename boost::graph_traits<Graph>::edge_descriptor, bool>
+  lookup_edge(typename boost::graph_traits<Graph>::vertex_descriptor src,
+              typename boost::graph_traits<Graph>::vertex_descriptor tgt,
+              const Graph& g,
+              typename boost::disable_if<is_adjacency_matrix<Graph>, int>::type = 0) {
+    typedef typename boost::graph_traits<Graph>::out_edge_iterator it;
+    typedef typename boost::graph_traits<Graph>::edge_descriptor edesc;
+    std::pair<it, it> oe = out_edges(src, g);
+    for (; oe.first != oe.second; ++oe.first) {
+      edesc e = *oe.first;
+      if (target(e, g) == tgt) return std::make_pair(e, true);
+    }
+    return std::make_pair(edesc(), false);
+  }
+
+}
+
+#endif // BOOST_GRAPH_LOOKUP_EDGE_HPP