Re: [Boost-users] Graph: create_subgraph not defined

On Jun 24, 2010, at 10:12 AM, Jeremiah Willcock wrote:

Note that G0 is of type subgraph<...>, not adjacency_list<...> like you were using. Could that be the issue?

Yes, that's definitely something I was doing wrong. After rereading the docs, I see now that subgraphs must be of a special subgraph class type, but I don't understand why. Conceptually speaking, I see no reason for this class to exist. For example, when implementing a generic tree structure, there's no need to have separate "Node" and "Subnode" classes; all nodes can be of type "Node". The top-level node is distinguished simply by the fact that it has no parents. For the same reason, the top-level graph in a hierarchy of graphs can have the same type as any of its children (and vice versa). The way Boost implements this concept seems overly complicated. Design issues aside, I'm now trying to modify my graph code to use subgraphs. To start off, I thought I would try changing my adjacency_list to subgraph. Theoretically, my code should still work the same way, right? But I'm getting compiler errors when calling get(). Pasted below is an example of the problem. The error is: subgraph.cpp: In function ‘int main(int, char**)’: subgraph.cpp:19: error: conversion from ‘boost ::subgraph_global_property_map , boost::no_property, boost::listS> >*, boost::adj_list_edge_property_map, boost::edge_index_t>, boost::edge_index_t>’ to non-scalar type ‘boost::subgraph_global_property_map, boost::edge_index_t>, boost::edge_index_t>’ requested Any suggestions how to fix this? Thanks, Trevor #include #include using namespace boost; class MyVertex { public: virtual ~MyVertex() {} }; class MyGraph : public subgraph > > { }; typedef property_map::type EdgeIndexMap; int main(int,char*[]) { MyGraph g; EdgeIndexMap edgeMap = get(edge_index, g); return 0; }