Add method is_bipartite to BipartiteGraph

[dcoudert]

A member of class BipartiteGraph is obviously bipartite, so we can avoid to test it.

[dcoudert]

If you have in mind a smarter way to handle initialization, please share it. The branch is in public, so you can implement it directly.

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New commits:

​d239b5e

trac #28198: is_bipartite for BipartiteGraph

[vdelecroix]

Insteed of having a weird and mostly useless special case

+        if not hasattr(self, 'left') or not hasattr(self, 'right'):
+            # This case may occur during the initialization (i.e., in __init__)
+            return GenericGraph.is_bipartite(self, certificate=certificate)

Why don't you call GenericGraph.is_bipartite(self) in __init__ instead of `self.is_bipartite()?

[git]

Branch pushed to git repo; I updated commit sha1. New commits:

​564fa99

proposition of simplification for 28198

[git]

Branch pushed to git repo; I updated commit sha1. New commits:

​c909cdc

trac #28198: small correction

[dcoudert]

I agree with your improvement. I did a small correction to avoid this issue

sage: a = b = set()
sage: a.add(1)
sage: b
{1}

For me this ticket is good to go. I let you conclude. Thank you.

[vdelecroix]

• I don't like so much the duplication in the BipartiteGraph.__init__.
• The sets_from_colors would be more natural if it would return ans instead of ans.values(). That is it would transform a dictionary k -> v in v -> {keys with that values}.

Is that ok if I try something to fix these.

[dcoudert]

Sure, the branch is in public so that we can interact (and I'm not the author of the commit "proposition of simplification for 28198")

[git]

Branch pushed to git repo; I updated commit sha1. New commits:

​f2e3d83

cleanup

[vdelecroix]

I like it better now :-)

[git]

Branch pushed to git repo; I updated commit sha1. New commits:

​17d5401

even simpler

[dcoudert]

we can simplify more putting the content of sets_from_colors inside _upgrade_from_graph, no ?

[vdelecroix]

make sense

[git]

Branch pushed to git repo; I updated commit sha1. New commits:

​0436491

trac #28198: more simplifications

[dcoudert]

Should be good now.

[vdelecroix]

good for me at least

[dcoudert]

Thank you.