Re: [Boost-users] Re: BGL: adjacency list, EdgeList, VertexList

From: Doug Gregor (dgregor_at_[hidden])
Date: 2005-03-18 14:22:20

On Mar 18, 2005, at 1:53 AM, S wrote:
> Here is a situation where typedefs for EdgeList etc can prove to be 
> very useful.
>
> template < class graph_type >
> void foo( graph_type& g )
> {
>     // I would like to create another graph type which depends
>     // on the value of the template parameter graph_type
>     // e.g.
>
>     typedef adjacency_list< graph_type::EdgeList,
>                             graph_type::VertexList,
>                             undirectedS
>> another_graph_type;
>     // note that graph_type could have been directedS or bidirectionalS
>     // but I would like to ignore that when creating another_graph_type
>
>     another_graph_type ag;
>     copy_graph( g, ag );
>     // and so we have an undirected version of the input graph - g
> }

To be really picky, since "graph_type" has to be an adjacency list 
anyway, one possibility is to do this:

template<typename OutEdgeListS, typename VertexListS, typename 
DirectedS,
                   typename VertexProperty, typename EdgeProperty, 
typename EdgeListS>
void foo(adjacency_list<OutEdgeListS, VertexListS, DirectedS, 
VertexProperty, EdgeProperty, EdgeListS>& g)
{
   // ...
}

It is a bit verbose, but in a sense it is more "correct" because it 
more accurately reflects the parameter type.

> What do you think?

I had originally thought you wanted something different. I'm not at all 
opposed to providing these typedefs. I'm just about to check in changes 
that provide the typedefs out_edge_list_selector, vertex_list_selector, 
directed_selector, and edge_list_selector for the OutEdgeListS, 
VertexListS, DirectedS, and EdgeListS template parameters, 
respectively.

        Doug