Re: [Boost-users] Re: [boost] [BGL] forced client complexity

From: Jeremy Siek (jsiek_at_[hidden])
Date: 2004-03-31 14:18:59

Hi Doug,

On Mar 31, 2004, at 1:52 PM, Douglas Paul Gregor wrote:
> The only thing I've ever found complex in the BGL is actually forming a
> graph type out of adjacency_list. Every single time I need a graph I 
> have
> to read through the adjacency_list documentation to figure out what to 
> do,
> although often I just copy the typedef from somewhere else. Simplified
> graph adaptors could really help here.

Right. In particular, the way internal properties are dealt with is 
rather
cumbersome.

> There's a lot we could do in the way of syntactic sugar. For instance, 
> I'd
> love to be able to easily loop over the edges in a graph without 
> dealing
> with iterators directly:
>
>   Graph g;
>   for(Graph::vertex_descriptor u, v; (u, v) = G; ) {
>     // do something with edge (u, v)
>   }
>
> The same thing can be applied to, e.g., adjacent vertices:
>
>   for(Graph::vertex_descriptor v; v = adj(u, g); ) {
>     // v is adjacent to u
>   }
>
> Since vertex descriptors tend to be iterators or indices, this could be
> implemented just as efficiently as the corresponding iterator loop, but
> it's a simpler idiom.

Looks neat. How would that be implemented? I hope it doesn't require
storing something in the graph object itself that keeps track of
the progress of the iteration.

BTW, for those who like macros, there's 
boost/graph/iteration_macros.hpp.

Cheers,
Jeremy

_______________________________________________
Jeremy Siek <jsiek_at_[hidden]>
http://www.osl.iu.edu/~jsiek
Ph.D. Student, Indiana University Bloomington
Graduating in August 2004 and looking for work
C++ Booster (http://www.boost.org)
_______________________________________________