[Boost-users] BGL: using an edge_descriptor as key in a map

Hi, is it possible to use an edge_descriptor (boost::graph_traits<G>::edge_descriptor) as key in a map? I intend to write a visitor class which sets a boolean to each edge, and therefore I need the edge as key. The result of my first try is, that the compiler complains about the missing '<' operator of the key in the map. Best regards Stefan Rauch