Re: [Boost-users] [graph] Is reverse_graph<> read-only?

On Fri, 18 Feb 2011, Cedric Laczny wrote:

Hi Jeremiah,

On Friday, 18. February 2011 00:14:08 Jeremiah Willcock wrote:

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On Fri, 18 Feb 2011, al.zatv wrote:

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Jeremiah Willcock писал(а) в своём письме Fri, 18 Feb

2011 01:49:27 +0300:

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Is reverse_graph<> in Boost::Graph Library, read-only?

It appears to be read-only. It should be possible to add mutation; it just isn't there yet. Do you need that feature?

Yes. My program build two trees in the same graph. First tree is "forward". Second tree is "backward": build by the same algorithm, but in reverse order. So I need add_vertex and add_edge for reverse trees. I wrote them this way (please look if I'm correct - because I'm a newbie and can make stupid errors).

Do those versions work? I forgot whether edge_descriptors in the original graph are implicitly convertible to edge_descriptors in the reverse_graph; your implementations require that.

Just of pure interest, where do you see this requirement in the code? It's not that I doubt the fact that it actually is like this but I am interested in knowing how this can be seen in these short, two functions?

He's directly returning the result of add_edge() on the underlying graph as a pair without explicitly converting the underlying graph's edge_descriptor to the reverse_graph's version. Anyway, it turns out that the descriptors are exactly the same between the underlying and reverse graphs; that is not documented, however.

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Your code would be easy to fix for the other case, though.

Again, I would really like to know how.

See above about the types being the same. If not, there is no documented way to do the conversion. -- Jeremiah Willcock