Hi, I encountered the following problem : a successive call with equal parameters u, v, and g of ============================================================ std::pair<edge_descriptor, bool> add_edge( vertex_descriptor u , vertex_descriptor v , adjacency_list& g ) ============================================================ yields both times "RESULT.second == true". But the documentation states, that only in case it is NOT PRESENT it should be true, which is obviously wrong for the second call. If I use the "edge(u,v,g)" method to check if the edge exists I get the correct result of "edge(u,v,g).second == false" before the first call and "edge(u,v,g).second == true" after the first and before the second call. So the problem is all about the add_edge function and I think it's more a bug than a feature. Because otherwise the bool-flag is obsolete or reports something totally different. Cheers, Martin ============================================================ The boost graph class I use ============================================================ //! The properties available for the nodes of a CoreGraph typedef boost::property< boost::vertex_index_t, size_t , boost::property< boost::vertex_name_t, std::string > > CoreGraph_NodeProperties; //! The properties available for the edges of a CoreGraph typedef boost::property< boost::edge_name_t, std::string > CoreGraph_EdgeProperties; //! The definition of a the internal graph representation typedef boost::adjacency_list< boost::vecS , boost::vecS , boost::undirectedS , CoreGraph_NodeProperties , CoreGraph_EdgeProperties > CoreGraph; ============================================================