Re: [Boost-users] [BGL] IncidenceGraph and out_edges

Subject: Re: [Boost-users] [BGL] IncidenceGraph and out_edges
From: Andrew Sutton (andrew.n.sutton_at_[hidden])
Date: 2009-06-18 07:40:42

> I dont see why this requirement is one of the esoteric ones as traversing
> the
> set of all vertices incident to another vertex is a often used operation
> and I
> still do not undertand why out_edges is used for this. Why is there no
> explicit function for this purpose?

For an undirected graph there is, by definition/no source or target vertex
implicit in the edge. And yet, source() and target() are still required for
an undirected graph to behave properly with virtually every BGL algorithm. I
used the term "esoteric" because this requires you to apply directional
semantics to undirected edges, which is somewhat contradictory and imposes
some interesting implementation requirements.

The out_edges() requirement is a badly stated requirement that is trying to
describe source/target requirements for undirected graphs, but do so in a
way that precludes an implementation of graphs that contain loops. As such
you should probably ignore the requirement.

Explicit function for what?

Andrew Sutton
andrew.n.sutton_at_[hidden]