#19016: A more naive sage.structure.element.__hash__
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Reporter: ncohen | Owner:
Type: defect | Status: needs_review
Priority: blocker | Milestone: sage-6.9
Component: misc | Resolution:
Keywords: | Merged in:
Authors: Nathann Cohen | Reviewers:
Report Upstream: N/A | Work issues:
Branch: u/ncohen/19016 | Commit:
Dependencies: | Stopgaps:
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Changes (by ncohen):
* status: new => needs_review
* branch: => u/ncohen/19016
Old description:
> As reported on sage-devel [1], the default hash function implemented in
> `Element` makes it very likely that `hash` and `==` will not agree. With
> this branch, the hash is constant and set to 0, making it less likely.
> Incidentally, it fixes the following bug:
> {{{
> sage: G = groups.presentation.Cyclic(4)
> sage: G.cayley_graph().vertices()
> [1, a, a^2, a^-2, a^3, a^-1]
> }}}
>
> Nathann
>
> [1]
New description:
As reported on sage-devel [1], the default hash function implemented in
`Element` makes it very likely that `hash` and `==` will not agree. With
this branch, the hash is constant and set to 0, making it less likely.
Incidentally, it fixes the following bug:
{{{
sage: G = groups.presentation.Cyclic(4)
sage: G.cayley_graph().vertices()
[1, a, a^2, a^-2, a^3, a^-1]
}}}
Nathann
[1] https://groups.google.com/d/topic/sage-devel/6rXKkF87Gtc/discussion
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Ticket URL: <http://trac.sagemath.org/ticket/19016#comment:1>
Sage <http://www.sagemath.org>
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