Re: [Boost-users] [BGL, Graph] listS and property maps

From: Aaron Windsor (aaron.windsor_at_[hidden])
Date: 2005-11-15 20:00:01

On 11/15/05, Stephane Grabli <Stephane.Grabli_at_[hidden]> wrote:
> Hi,
>
> I'm new to the BGL and I'm trying to use the strong_components
> algorithm, defined this way:
>
> template <class Graph, class ComponentMap, class P, class T, class R>
> typename property_traits<ComponentMap>::value_type
> strong_components(Graph& g, ComponentMap comp,
>     const bgl_named_params<P, T, R>& params = all defaults)
>
> with a graph
> defined like this:
>
> typedef adjacency_list<listS,listS,directedS> Graph;
>
> (in particular using listS for vertices storage).
>
> Does anyone know how I should declare the ComponentMap property map?
> I couldn't figure this out from the documentation and the examples I've
> seen all assume that a vecS type storage is used for vertices in the graph.
> Thanks!
>
> Stephane

Here's one way to do it:
(1) declare an interior vertex index map.
(2) initialize the interior vertex index map.
(3) compose the interior vertex index map with a vector property map.

For step (1), just replace your graph declaration with

typedef adjacency_list<listS, listS, directedS,
property<vertex_index_t, std::size_t> > Graph;

For step (2), see the code in the BGL FAQ, #5 (http://tinyurl.com/9skck)

For step (3), first #include <boost/vector_property_map.hpp>, then:

typedef graph_traits<Graph>::vertices_size_type v_size_t; //the range
of ComponentMap
vector_property_map< v_size_t, property_map<Graph, vertex_index_t>::type >
     component_map( num_vertices(g), get(vertex_index,g) );  //g is an
instance of Graph

Now your component_map is ready to use. I haven't tested this code, of course.

Aaron