D graph library

[w0rp]

On Wednesday, 15 May 2013 at 17:59:01 UTC, Joseph Rushton 
Wakeling wrote:
> Maybe I'm being harsh, but I was assuming you might actually 
> throw an error if
> someone tries to add an edge that already exists (although 
> perhaps you'd want to
> avoid throwing in order not to hit performance).

I don't think that's too useful or necessary. A graph is at its 
heart a pair (V, E) where V is the vertex set and E is the edge 
set. So addNode is really just V' = V ∪ {n} for some node n. I 
think it's best to just allow redundantly adding a node, which 
ought to be an O(1) function.