Re: [Boost-users] Newbie question: add_edge()

From: Doug Gregor (dgregor_at_[hidden])
Date: 2004-06-26 21:33:15

On Jun 26, 2004, at 5:33 AM, Tim Rowe wrote:
> On Fri, 25 Jun 2004 16:53:51 -0500, Doug Gregor wrote:
>> Exactly. When the type of the vertex list for an adjacency list is
>> "vecS", the descriptors are just integers. It tends to make many
>> things much easier when this is the case!
>
> Thanks -- is that documented? I couldn't find it.

*Technically* yes, it's documented, as in "you could find something in 
the docs that says that this is the case." Granted, it's an aside in 
the description of add_edge for an adjacency_list:
   "VertexList selector is vecS, and if either vertex descriptor u or v 
(which are integers) has a value greater than the current number of 
vertices in the graph, the graph is enlarged so that the number of 
vertices is std::max(u,v) + 1."

I'm going to add a more obvious description into the documentation for 
our upcoming release. Thanks for pointing out how  confusing this was!

>  And what about when the type of the vertex list is something else -- 
> is the type of boost::graph_traits<G>::vertex_descriptor available to 
> the user for anything more than declaring variables to identify 
> vertices?

Nope, that's it: a vertex descriptor just describes a particular vertex 
when coupled with an appropriate graph.

        Doug