Thanks again for a reply. Excuse my confusion and lack of understanding, but I don't yet understand what you explain below: "You can store a copy of the color map in the edge filter predicate" I think I get this, is this what you mean (here are the definitions for this part): typedef adjacency_list < vecS, vecS, directedS, property< vertex_color_t, default_color_type, property< vertex_type_t, VertexType > >
Graph;
typedef property_map<Graph, vertex_color_t>::type VertexColorMap; template <typename Graph, typename VertexColorMap> struct valid_edge { valid_edge() { } valid_edge(Graph& graph, VertexColorMap color_map) : m_graph(graph), m_color_map(color_map) { } template <typename Edge> bool operator()(const Edge& e) const { return ( Color::gray() != get(m_color_map, target(e, m_graph)) ); } VertexColorMap m_color_map; Graph& m_graph; }; And the code to setup the above: valid_edge<Graph, VertexColorMap> filter(m_graph, get(vertex_color, m_graph)); filtered_graph<Graph, valid_edge<Graph, VertexColorMap> > fg(m_graph, filter); But the next part of what you write isn't clear: "pass the same color map to depth_first_search; then you filter out any edges whose targets are gray" So which graph gets sorted with depth_first_search? The filter graph I presume? But I thought the constructor for filter_graph will call the predicate function for every edge without having to do a depth_first_search??? Also, if the predicate has only a copy of the vertex color map then how are the results from depth_first_search going to be reflected in the predicate object? Anyways, those last two steps don't make sense yet. Thanks for a clarification. Yours, Elisha
What test is there to determine whether an edge is a back-edge that can be used inside a filter predicate of the filter_graph?
You can use the (vertex) color map to determine if an edge is a back edge. You can store a copy of the color map in the edge filter predicate, and pass the same color map to depth_first_search; then you filter out any edges whose targets are gray.
Doug
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