Re: [boost] [bgl] Bug in depth_first_search (and therefore topological_sort...)

From: Daniel Mitchell (danmitchell_at_[hidden])
Date: 2006-07-25 13:39:43

Loïc Joly <loic.joly <at> reportive.com> writes:

> 
> Daniel Mitchell a écrit :
> 
> > I'm not sure I'd call that a bug; after all, the graph must contain at 
least a 
> > source vertex for DFS to be sensible. I would say that having a non-empty 
> > graph is a pre-condition for calling DFS.
> 
> It may be so for depth-first-search, I'm not a domain expert at all. In 
> that case, maybe just adding this requirement to the doc would be enough.
> 
> However, for topological_sort, this goes against my expectations. 
> std::sort on an empty STL sequence may be useless, it is however defined 
> and does the right thing. And it allows to write generic code easily, 
> without requiring the user to check anything before. I do not see any 
> reason why topological_sort would not behave the same.
> 

I guess adding a simple test such as

if( vertices( g ).first == vertices( g ).second ) return;

at the beginning of topological_sort wouldn't hurt.