[Boost-users] How to get a graph that does not accept parallel edges?

How do I declare a graph that does not allow parallel edges? I have come up with this but IMO it is sort of, well, kludgey: typedef adjacency_list<setS, vecS, bidirectionalS> Graph; This works because std::set does not like multiple entries. But what if for performance reasons (say) I want a listS or vecS instead of setS? In adjacency_list.hpp I find: template <> struct parallel_edge_traits<setS> { typedef disallow_parallel_edge_tag type; }; Which suggest the existence of a more elegant mechanism. Anybody know what that is? Eric