#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: needs_review
Priority: major |
Milestone: sage-5.0
Component: symbolics |
Resolution:
Keywords: inequality equality relational sd31 __richcmp__ | 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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Changes (by kini):
* status: needs_work => needs_review
Old description:
> -x + y > 0 and x - y > 0 are treated the same in Sage.
>
> {{{
> #!python
> sage: version()
> 'Sage Version 4.6.2, Release Date: 2011-02-25'
>
> sage: (-x +y < 0) in [x -y < 0]
> True
>
> Set([-x +y >= 0,x -y >= 0])
> {-x + y >= 0}
> }}}
>
> and they have the same Hash
>
> {{{
> #!python
> sage: var('x,y')
> (x, y)
> sage: hash(-x + y > 0 )
> 1221566266
> sage: hash(-x + y >= 0 )
> 1221566266
> sage: hash(x - y >= 0 )
> 1221566266
> sage: hash(-y + x >= 0 )
> 1221566266
> sage: hash(x - y > 0 )
> 1221566266
> }}}
>
> It seems to me that Sage treats `>`, `>=`, and `==` the same (see #7660).
> If this is true then it's a serious problem and needs to be addressed.
New description:
-x + y > 0 and x - y > 0 are treated the same in Sage.
{{{
#!python
sage: version()
'Sage Version 4.6.2, Release Date: 2011-02-25'
sage: (-x +y < 0) in [x -y < 0]
True
Set([-x +y >= 0,x -y >= 0])
{-x + y >= 0}
}}}
and they have the same Hash
{{{
#!python
sage: var('x,y')
(x, y)
sage: hash(-x + y > 0 )
1221566266
sage: hash(-x + y >= 0 )
1221566266
sage: hash(x - y >= 0 )
1221566266
sage: hash(-y + x >= 0 )
1221566266
sage: hash(x - y > 0 )
1221566266
}}}
It seems to me that Sage treats `>`, `>=`, and `==` the same (see #7660).
If this is true then it's a serious problem and needs to be addressed.
Apply:
1. [attachment:trac_11309-fix-comparison-of-comparisons.patch]
1. [attachment:trac_11309-equate-flipped-comparisons.patch]
--
Comment:
Added a new patch. Burcin, can you look over it to make sure I'm doing
this the right way? In particular are those operator comparisons
optimizable somehow?
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/11309#comment:37>
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