Ancestors and descendants

[<gvdmoort AT skynet.be>]

Hello,

At first sight, your library seems to fit with my needs. But I don't find in
the API an easy way to get the set of all the descendants or ancestors of a
given node in a directed graph. For the descendants, it's possible to use the 
BreadthFirstIterator, but for the ancestors ? Is it necessary to make an
"inversed copy" of the graph ?

I don't find mention of directed or undirected graphs. Can a graph mix 
directed
and undirected edges ? 

Thanks in advance,

gvdm