Hi, I originally wanted to construct an undirected graph from a directed graph and vice versa. For this purpose i tried to use template <class EdgeIterator> adjacency_list(EdgeIterator first, EdgeIterator last, vertices_size_type n, edges_size_type m = 0, const GraphProperty& p = GraphProperty()) as shown in http://www.boost.org/doc/libs/1_47_0/libs/graph/doc/adjacency_list.html but i do not even manage to construct a graph from the same type with this constructor. What am i missing? Please have a look at the example below. If you uncomment the last two lines, the code will not compile. // begin code #include <iostream> #include #include int main(int argc, char** argv) { typedef boost::adjacency_list < boost::listS, boost::vecS, boost::directedS> Dgraph; typedef boost::adjacency_list < boost::listS, boost::vecS, boost::undirectedS> Graph; Dgraph g(5); add_edge (0,1,g);add_edge (2,3,g);add_edge (4,5,g); print_graph (g, boost::get(boost::vertex_index, g)); boost::graph_traits<Dgraph>::edge_iterator i1 = (edges(g)).first; boost::graph_traits<Dgraph>::edge_iterator i2 = (edges(g)).second; // Dgraph g2 = Dgraph (i1, i2, num_vertices (g), num_edges (g)); // print_graph (g2, boost::get(boost::vertex_index, g2)); return 0; } // end code best regards Christoph