#11309: Sage sees - x + y > 0, - y + x >= 0, and x - y > 0 as equivalent
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Reporter: tnv |
Owner: burcin
Type: defect |
Status: positive_review
Priority: major |
Milestone: sage-5.1
Component: symbolics |
Resolution:
Keywords: inequality equality relational sd31 __richcmp__ sd40.5 |
Work issues:
Report Upstream: N/A |
Reviewers: Karl-Dieter Crisman, ThanhVu Nguyen
Authors: Keshav Kini, Burcin Erocal |
Merged in:
Dependencies: |
Stopgaps:
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Comment (by tnv):
Hi, may be I've missed something but these patches still break things as
listed in my comment:24.
{{{
(prepatched)
sage: (- x + y == 0) == (0 == -x + y)
True
sage: (-x + y == 0) == (0 == -x + y)
True
sage: (x < y) == (y > x)
True
(postpatched)
sage: (- x + y == 0) == (0 == -x + y)
False
sage: (-x + y == 0) == (0 == -x + y)
False
sage: (x < y) == (y > x)
False
}}}
The main reason why I report this in the first place is because of this
error in which multiplying by -1 does not switch the sign. I think they
are related but not sure.
{{{
sage: -1 * (x<5)
-x < -5
}}}
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/11309#comment:53>
Sage <http://www.sagemath.org>
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