Re: [Boost-users] BGL: a quick question on bundled properties and graph traits

From: Elvanör (elvanor2004_at_[hidden])
Date: 2005-03-16 20:10:40

Since nobody answered my first question, I had to look up myself on the 
code and found some kind of answer (at least, it works for me).

I just use, if I have a graph of type Graph (it is in fact an adjacency 
list, but that is unimportant),

typedef typename Graph:vertex_bundled VertexType;

But I am still wondering if it is the "correct solution". For me it 
works, however I don't understand why I use directly 
Graph:vertex_bundled and not some kind of 
graph_traits<Graph>::vertex_bundled thing...

I am new to traits (be it for STL iterators or Boost Graphs ) and don't 
understand how it works internally (I just understand the basic concept 
yet, and know how to use them). What is the whole purpose of having a 
graph_traits class if something as simple as Graph:vertex_bundled 
works? Why am I doing things like 
graph_traits<Graph>::vertex_descriptor instead of just 
Graph::vertex_descriptor then ??

Any help would be appreciated, and I still think the documentation 
should mention how to get the type of the bundled properties.

Jean-Noël Rivasseau

> Hello,
>
> How can I get the type of my vertex properties if I use bundled 
> properties as internal properties?
>
> My example is this one:
>
> typedef adjacency_list<mapS, vecS, undirectedS, myClass> Graph;
>
> // and in one function:
>
> template <class graph>
>
> void myFunction (Graph & g)
> {
>
> // Here I need to declare an object of type myClass... how can I get 
> this type using graph_traits ??
>
> }
>
> Thanks. Again, the documentation on bundled properties really need to 
> be improved, IMHO. All the information I could find was relevant to 
> the old property maps mechanism...
>
> Jean-Noël
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