#16397: Symbolic cmp
-------------------------------------+-------------------------------------
Reporter: vbraun | Owner:
Type: defect | Status: needs_review
Priority: critical | Milestone: sage-7.1
Component: symbolics | Resolution:
Keywords: | Merged in:
Authors: Volker Braun, | Reviewers:
Ralf Stephan | Work issues:
Report Upstream: N/A | Commit:
Branch: public/16397-1 | 06ea5a9957bcfd03fa1476f7651b2d9400e9e36b
Dependencies: | Stopgaps: #19465
-------------------------------------+-------------------------------------
Description changed by rws:
Old description:
> In the symbolic ring, cmp implements the print comparison which is
> probably not what you envisioned:
> {{{
> sage: cmp(1, sqrt(2)) # mathematically correct, uses rich comparison
> -1
> sage: cmp(SR(1), sqrt(2)) # unexpectedly, you get the print sort order
> 1
> }}}
> Everybody who coerces to same parents internally before comparing trips
> over this, for example the real lazy field:
> {{{
> sage: RLF(1) < RLF(sqrt(2))
> False
> }}}
> This also makes `RealSet` unusable with symbolics:
> {{{
> sage: RealSet((0, pi),[pi, pi],(pi,4))
> [pi, 4)
> sage: RealSet((0, pi),[0, pi],(pi,4))
> [pi, 4)
> sage: RealSet((0, pi),[0, 3.5],(pi,4))
> (pi, 4)
> }}}
New description:
In the symbolic ring, cmp implements the print comparison which is
probably not what you envisioned:
{{{
sage: cmp(1, sqrt(2)) # mathematically correct, uses rich comparison
-1
sage: cmp(SR(1), sqrt(2)) # unexpectedly, you get the print sort order
1
sage: cmp(log(8), 3*log(2))
-1
}}}
Everybody who coerces to same parents internally before comparing trips
over this, for example the real lazy field:
{{{
sage: RLF(1) < RLF(sqrt(2))
False
}}}
This also makes `RealSet` unusable with symbolics:
{{{
sage: RealSet((0, pi),[pi, pi],(pi,4))
[pi, 4)
sage: RealSet((0, pi),[0, pi],(pi,4))
[pi, 4)
sage: RealSet((0, pi),[0, 3.5],(pi,4))
(pi, 4)
}}}
--
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Ticket URL: <http://trac.sagemath.org/ticket/16397#comment:25>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
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