Re: [Boost-users] Graph: Trying to filter on custom properties

Subject: Re: [Boost-users] Graph: Trying to filter on custom properties
From: Daniel Hofmann (daniel_at_[hidden])
Date: 2016-07-28 13:29:50

Your get_filtered_graph function has to take a graph type and return a
filtered graph type for your graph. Those two are not the same type.

Here's an example signature for: graph in, filtered graph out.

    template <typename G, typename EdgePred>
    bgl::filtered_graph<G, EdgePred> filterd(G& g, EdgePred pred);

And here is a small self contained example for filtered graphs:

https://gist.github.com/daniel-j-h/ceb53abffa4b3cb3ab37

Cheers,
Daniel J H

On 07/28/2016 04:55 PM, Amit Prakash Ambasta wrote:
> How should I be writing the get_filtered_graph in a generic way?
> 
> #include <map>
> #include <string>
> #include <vector>
> #include <iostream>
> 
> #include <boost/graph/adjacency_list.hpp>
> #include <boost/property_map/property_map.hpp>
> #include <boost/graph/filtered_graph.hpp>
> #include <boost/graph/graph_utility.hpp>
> 
> template <typename F> struct EdgeProperty {
>     F features;
> 
>     EdgeProperty() = default;
> 
>     EdgeProperty(const F& f) : features(f) {}
> };
> 
> template <typename EM, typename F>
> struct filtered_edge {
>     F filters;
>     EM emap;
> 
>     filtered_edge() = default;
>     filtered_edge(EM emap_, F filters_) : emap(emap_), filters(filters_) {}
> 
>     template <typename E> bool operator()(const E& e) {
>         auto e_prop = get(emap, e);
>         auto e_feat = e_prop.features;
> 
>         for (auto it: e_feat) {
>             if (get(e_feat, it.first) != it.second) {
>                 return false;
>             }
>         }
>         return true;
>     }
> };
> 
> template<typename G, typename F> G get_filtered_graph(G& g, F& filters) {
>     typedef filtered_edge<boost::property_map<G, EdgeProperty<F> >, F>
> filter_fn;
>     filter_fn filter{get(&EdgeProperty<F>::features, g), filters};
>     boost::filtered_graph<G, filter_fn> fg(g, filter);
>     return fg;
> }
> 
> typedef std::map<std::string, int> dict;
> 
> typedef boost::adjacency_list<
>         boost::vecS,
>         boost::vecS,
>         boost::directedS,
>         boost::no_property,
>         EdgeProperty<dict>
>> Graph;
> 
> Graph create_empty_graph() noexcept {
>     return {};
> }
> 
> int main() {
>     const char* name = "ABCDE";
>     auto g = create_empty_graph();
>     auto v0 = boost::add_vertex(g);
>     auto v1 = boost::add_vertex(g);
>     auto v2 = boost::add_vertex(g);
> 
>     dict d01;
>     d01["a"] = 1;
> 
>     dict d12;
>     d12["b"] = 1;
> 
>     dict fil;
>     fil["a"] = 1;
> 
>     auto ep01 = EdgeProperty<dict>{
>         dict{}
>     };
>     boost::add_edge(v0, v1, d01, g);
>     boost::add_edge(v1, v2, d12, g);
> 
>     std::cout << "Before filter" << std::endl;
>     boost::print_graph(g, name);
>     auto fg = get_filtered_graph(g, fil);
> 
>     std::cout << "After filter" << std::endl;
>     boost::print_graph(fg, name);
> 
>     Graph ga;
> }
> 
> 
> _______________________________________________
> Boost-users mailing list
> Boost-users_at_[hidden]
> http://lists.boost.org/mailman/listinfo.cgi/boost-users
>