Re: [Boost-users] accessing internal graph properties via vertex-iterators directly?

From: Doug Gregor (dgregor_at_[hidden])
Date: 2004-11-29 11:27:31

On Nov 29, 2004, at 9:17 AM, Sebastian Weber wrote:
> (*vi).stuff = 4;
>
> With this, one would save a lookup in the data-structures and the 
> vertice-iterator concept would be far more logic to me, concernig 
> internal property handling.
[snip]

> I don't know the BGL internals and how this behaviour is optimally 
> programmed with the BGL.
[snip]
> I hope my point is clear.

We considered this syntax (you might be able to find the discussion on 
the Boost developers list; GMane is running a bit slow for me at the 
moment). The basic problem is that we would need both const- and 
non-const vertex and edge descriptors (because the constness of the 
internal properties is now tied to the descriptors), which then means 
that we need const vertex iterators, const edge iterators, const out 
iterators, etc... it would very quickly become a nightmare for users 
and developers alike, because we would have twice as many iterator and 
descriptor types to deal with.

On the performance side, it would make copying descriptors more 
expensive (e.g., with VertexListS=vecS, a vertex descriptor is just an 
integer; it would have to go to _at least_ a pointer). On the other 
side, I don't see that this would help performance much when accessing 
internal properties.

        Doug