Re: [Boost-users] filtered graph

From: Douglas Gregor (dgregor_at_[hidden])
Date: 2004-12-22 09:25:19

Please post in plain text in the future. HTML-formatted messages are 
hard to read in some e-mail readers.

On Dec 22, 2004, at 5:35 AM, Matthias Linkenheil wrote:
>  template <typename EdgeCapacityMap>
>  struct positive_edge_capacity {
>    positive_edge_capacity() { }
>    positive_edge_capacity(EdgeCapacityMap capacity) : 
> m_capacity(capacity) { }
>    template <typename Edge>
>    bool operator()(const Edge& e) const {
>      return 0 < boost::get(m_capacity, e);
>    }
>    EdgeCapacityMap m_capacity;
>  };
>  ...
>
>    typedef adjacency_list_traits<vecS, vecS, directedS> Traits;
>    typedef property<vertex_index_t, int> VertexProperties;
>    typedef property<edge_capacity_t, double,
>            property<edge_residual_capacity_t, double,
>            property<edge_reverse_t, Traits::edge_descriptor> > > 
> EdgeProperties;
>    typedef adjacency_list<vecS, vecS, directedS, VertexProperties, 
> EdgeProperties > Graph;
>
>    typedef graph_traits<Graph>::edge_descriptor edge_descriptor;
>    typedef graph_traits<Graph>::vertex_descriptor vertex_descriptor;
>    const int V = x_size*y_size;
>    Graph g(V);
>   
>    property_map<Graph, vertex_index_t>::type vid = get(vertex_index, 
> g);
>    property_map<Graph, edge_capacity_t>::type cap = get(edge_capacity, 
> g);
>    property_map<Graph, edge_reverse_t>::type rev_edge = 
> get(edge_reverse, g);
>    property_map<Graph, edge_residual_capacity_t >::type res_cap = 
> get(edge_residual_capacity, g);
>  ...
>   edmunds_karp_max_flow(g, s, t);
>  ...

Probably okay so far...

>    positive_edge_capacity<cap> filter(get(edge_capacity, g));
>    filtered_graph<Graph, positive_edge_capacity<cap> > fg(g, filter);

I'm assuming you get an error here? That's because "cap" is an object, 
not a type, so you can't use it in a template. You'll need to get the 
type of it first:

   typedef property_map<Graph, edge_capacity_t>::type CapacityMap;
   positive_edge_capacity<CapacityMap> filter(get(edge_capacity, g));
   filtered_graph<Graph, positive_edge_capacity<CapacityMap> > fg(g, 
filter);

        Doug