#8425: BipartiteGraph add_edge allows bipartite property to be violated.
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Reporter: rhinton | Owner: rhinton
Type: defect | Status: needs_work
Priority: major | Milestone: sage-4.4
Component: graph theory | Keywords: BipartiteGraph, add_edge
Author: Ryan Hinton | Upstream: N/A
Reviewer: | Merged:
Work_issues: |
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Comment(by rhinton):
Thanks for helping! Sorry for the slow response: apparently trac decided
to stop sending me email notifications.
Your suggestions are good. They would make BipartiteGraph much easier to
work with. Not that the current approach is invalid -- some people might
take offense if their left/right sets started changing without permission.
Of course, we can always add a keyword flag to prevent set modification
and essentially keep the current behavior.
My selfish suggestion is to allow this patch to go through because it
fixes an important deficiency in BipartiteGraph. Right now BG is broken.
This patch fixes it, although it doesn't handle the left/right sets
automatically. I would love to see an additional ticket to add this
convenience. (I'm happy to review it!) In particular, this handling
would make the left/right keywords for add_vertex optional and obviate
some of the dirty tricks I played during BipartiteGraph initialization.
The docstring test shows that an exception is raised. Would you like me
to add verbiage above saying that it is an error for the two endpoints to
be in the same partition?
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/8425#comment:7>
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