Re: [Boost-users] BGL: filtered_graph and breadth_first_search.

Aaron Windsor wrote:

Your predicate should have const member functions - replace

bool operator()(const vertex_t &v) {}

bool operator()(const edge_t &e) {}

with bool operator()(const vertex_t &v) const {}

bool operator()(const edge_t &e) const {}

and it should compile.

Thanks, it indeed compiles fine. Is there are other restrictions on using filtered_graph with breadth_first_search? The problem is that predicates of a filtered_graph should be Default Constructable, and it seems that even though in an example in a documentation of filtered_graph predicate has instance members, predicates of filtered_graphs which are used in breadth_first_search couldn't have any non-static members, because at some stage during the search predicates are default-constructed, and values of it's members are lost - for example, in order to be able to implement my idea of an induced subgraph, I would like each predicate instance to have a pointer to a graph to which filtering is going to be applied (see an example below). Is it somehow possible to let predicates to a filtered_graph have instance variables? Of course it is possible to use globals or static members, but this is a bad solution. P.S.: it seems that an idea of an induced graph can be realized by using 'subgraph' adaptor, but in a general case having predicates with instance members or some equivalent of instance members looks like a good thing - if at least it have been possible to get a reference to a graph given it's edge or vertex the problem would have been much easier to solve, but unfortunately it seems that graph's edge/vertex doesn't know anything about a graph it belongs to. Predicate example: ---------------------------------------------------------------- template class induced_graph_filter { public: typedef typename graph_traits<Graph>::edge_descriptor edge_t; typedef typename graph_traits<Graph>::vertex_descriptor vertex_t; induced_graph_filter() {} induced_graph_filter(Graph *g, VertexCont *vert) : m_g(g), m_vert(vert) {} bool operator()(const vertex_t &v) const { if (this::m_vert->find(v) != this::m_vert->end()) return true; return false; } bool operator()(const edge_t &e) const { if (m_vert->find(source(e, *m_g)) != m_vert->end() && m_vert->find(target(e, *m_g)) != m_vert->end()) { return true; } return false; } Graph *m_g; VertexCont *m_vert; }; ---------------------------------------------------------------- VertexCont can be, for example, a set or list of vertices of an induced subgraph.