boost::graph : implementation independent way of getting edge from a pair of vertices

Question

I had a look at the Boost graph concepts, but it does not provide any interface of getting any edge from a pair over vertices. I have tried:

boost::graph_traits<G>::edge_descriptor edge(u, v); // does not work

but it requires an additional pointer to property type. How can I get that?

Answer 1

The third parameter for boost::edge() is your graph.

Note also that the function does not return the edge descriptor directly, but a pair containing the edge descriptor and a Boolean depending on the existence of the edge

Something like this:

G myGraph;   // construct the graph
....         // populate it
....         // select a pair of vertices u, v

// get the edge between the vertices, if it exists
typedef boost::graph_traits<G>::edge_descriptor edge_t;
edge_t found_edge;
std::pair < edge_t, bool > p = boost::edge( u, v, myGraph ); 
if( ! p.second) {
   // edge does not exist
   ...
} else {
   found_edge = p.first;
   ...
}