Re: [Boost-users] deciding directed and undirected parameter of adjancency list at runtime .

From: Douglas Gregor (dgregor_at_[hidden])
Date: 2007-09-11 09:39:20

abhishek.v_at_[hidden] wrote:
> I have a function which take an input from the user  whether the graph 
> is directed or undirected.
> I'm declaring graph as follows :-
>
> typedef adjacency_list < vecS, vecS,* undirectedS*, property < 
> vertex_name_t,std::string >, property < edge_name_t, std::string > > 
> Graph;
> Graph g;
>
> Now here the parameter in Bold need to be varied as the user input 
> changes. One method could be i could have two different function 
> say,CreateDirected()
> and CreateUndirected(). But this is not working in my case as i want 
> the declaration should be global so that i can use it throughout my 
> application.  Please help.
That's actually a bit tricky in the BGL, as you've noted. My suggestion 
would be to use bidirectionalS as the directedness tag, which gives you 
a directed graph with access to both the incoming and the outgoing 
edges. Then, it is relatively easy to write a graph adaptor that views 
an existing bidirectional graph as an undirected graph. I that someone 
posted on to the Boost mailing list recently, but I can't find it now :(

    - Doug