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

28 Jul 2016

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

Daniel Hofmann