#19302: Stopgap for Element.__hash__
-------------------------+-------------------------------------------------
Reporter: | Owner:
ncohen | Status: needs_review
Type: | Milestone: sage-6.9
defect | Resolution:
Priority: | Merged in:
blocker | Reviewers:
Component: misc | Work issues:
Keywords: | Commit:
Authors: | c84d7c704e90b5c762964118af6d06b59b9478fc
Nathann Cohen | Stopgaps:
Report Upstream: N/A |
Branch: |
public/19302 |
Dependencies: |
-------------------------+-------------------------------------------------
Comment (by vdelecroix):
I am ok with the stopgap. But I would like more consensus from developers.
The most problem I have is that it is very intrusive
{{{
sage: G = FreeGroup(2)
sage: x,y = G.gens()
sage: H = G / [x**2, y**2]
/opt/sage/src/bin/sage-ipython:1:
********************************************************************************
The __hash__ method of Element is broken. Beware of any
function that relies on it, as it may return wrong results.
This issue is being tracked at
http://trac.sagemath.org/sage_trac/ticket/19302.
********************************************************************************
}}}
or
{{{
sage: p = Polyhedron([(1,1),(2,3),(4,5),(6,7)])
sage: F = p.faces(2)
/opt/sage/local/lib/python2.7/site-
packages/sage/graphs/generic_graph.py:19557:
********************************************************************************
The __hash__ method of Element is broken. Beware of any function that
relies on it, as it may return wrong results.
This issue is being tracked at
http://trac.sagemath.org/sage_trac/ticket/19302.
********************************************************************************
}}}
... which means that many people will run into that trouble. But
"annoying" is better than "wrong". This is why I tend to agree with the
proposal.
Another option, would be to move some of the commits from #19016 here
(e.g. it would at least avoid the error on polyhedron). At the same time
it will decrease the complexity of #19016 which is good. What do you
think?
Vincent
--
Ticket URL: <http://trac.sagemath.org/ticket/19302#comment:3>
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