In nutshell: how can I check whether a property map has some given key? The exact problem is as follows. I have graph edges with the property "lambdas" of positive integers, but its the exact meaning is not important here. With the read_graphviz function I am loading graph files which look like this: graph { a; b; c; c -- a [distance="100"]; a -- b [lambdas="8"]; } After I load the file I want to examine which edges have the "lambdas" property, but I don't know how to do this. If I request the property value with the "get" function, I get some random value. My program is at the bottom of this email. The program prints the edge and the value of the "lambdas" property. I get this: (2,0): 33489268 (0,1): 8 The first line is bad: the edge (2,0), i.e. c -- a in my graphviz file, has the reported value of 33489268. The second line is OK. Thanks for reading. Best, Irek ********************************************************************* #include <boost/graph/adjacency_list.hpp> #include <boost/graph/depth_first_search.hpp> #include <boost/graph/iteration_macros.hpp> #include <boost/graph/graphviz.hpp> using namespace boost; typedef boost::adjacency_list<vecS, vecS, undirectedS, property<vertex_name_t, std::string>, property<edge_weight_t, double, property<edge_weight2_t, int> >, no_property > Graph; int main() { Graph g; dynamic_properties dp; dp.property("node_id", get(vertex_name, g)); dp.property("distance", get(edge_weight, g)); dp.property("lambdas", get(edge_weight2, g)); read_graphviz(std::cin, g, dp); typedef boost::property_map<Graph, edge_weight2_t>::type lambdas_t; lambdas_t weight2_map = get(edge_weight2, g); BGL_FORALL_EDGES(e, g, Graph) // Before printing this out I would like to make sure that an edge // has this property. std::cout << e << ": " << get(weight2_map, e) << std::endl; }