Hello, I'm constructing an undirected graph using the following graph, but the last line failed to compile. I'm using two property maps to associate a char type and a std::string type of properties to the vertices and edges of the graph, respectively. std::map<elem_id_t, char> vmap; std::map<edge_id_t, std::string> emap; typedef boost::associative_property_map< std::map<elem_id_t, char> > vpmap_t; typedef boost::associative_property_map< std::map<edge_id_t, std::string> > epmap_t; vpmap_t vpmap(vmap); epmap_t epmap(emap); typedef boost::adjacency_list<boost::vecS, boost::vecS, boost::undirectedS, vpmap_t, epmap_t> graph_t; typedef boost::graph_traits<graph_t>::vertex_descriptor vertex_descriptor; typedef boost::graph_traits<graph_t>::edge_descriptor edge_descriptor; graph_t g; vertex_descriptor v[5]; v[0] = add_vertex(g); put(vpmap, v[0], '0'); //vpmap[v[0]] = '0'; // this line also does not work v[1] = add_vertex(g); put(vpmap, v[1], '1'); v[2] = add_vertex(g); put(vpmap, v[2], '2'); v[3] = add_vertex(g); put(vpmap, v[3], '3'); v[4] = add_vertex(g); put(vpmap, v[4], '4'); edge_descriptor e; bool inserted; boost::tie(e, inserted) = add_edge(v[0], v[1], g); // this line failed to be compiled put(epmap, e, std::string("01")); What's wrong? Any help will be appriciated. min2max