On 18/06/2013 10:28, Szymon Gatner wrote:

2013/6/18 Andreas Fabri <andreas.fabri@geometryfactory.com <mailto:andreas.fabri@geometryfactory.com>>

Hello,

I am wondering what the function boost::graph_traits<G>::null___vertex() http://www.boost.org/doc/libs/__1_53_0/libs/graph/doc/Graph.__html <http://www.boost.org/doc/libs/1_53_0/libs/graph/doc/Graph.html> is for, and why there is no equivalent function null_edge()

Because often you will want to assign some data to point back to a vertex. I mean, a graph holds a vertex -> custom data mapping, but that custom data will want to keep vertex id back. Thing is it has to store some "invalid" value before mapping happens and that is when null_vertex() helps. I hope that is clear enough.

and why is it not the same for edges? andreas

Cheers

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