Re: [Boost-Users] [BGL] Vertex removal without iterator invalidation?

From: Jeremy Siek (jsiek_at_[hidden])
Date: 2002-08-01 11:06:00

Hi Erik,

On Thu, 1 Aug 2002, Erik Arner wrote:
yg-boo>
yg-boo> Yet another question from the BGL newbie...
yg-boo>
yg-boo> I understand that performing remove_vertex() on graphs with
yg-boo> vertexList=vecS will result in invalidated itarors and descriptors for
yg-boo> the graph.
yg-boo>
yg-boo> However, some toy examples i made suggest that if I remove a vertex in
yg-boo> such a graph, the vertex descriptors and vertex iterators for vertices
yg-boo> with *lower* ID than the removed vertex remain valid after removal,
yg-boo> while those for higher ID vertices are invalidated.
yg-boo>
yg-boo> Is this a true feature of a graph with Vertexlist=vecS, or is my
yg-boo> observation a mere coincidence? Is it safe to write code that exploits
yg-boo> this "feature"?

Yes, that is indeed a true feature.

yg-boo> If it indeed is a feature, I can construct a sorted list of vertices to
yg-boo> remove, and remove the vertices in descending order in an easy fashion.

That sounds plausible.

Cheers,
Jeremy

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 Jeremy Siek                          http://php.indiana.edu/~jsiek/
 Ph.D. Student, Indiana Univ. B'ton   email: jsiek_at_[hidden]
 C++ Booster (http://www.boost.org)   office phone: [phone]
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