#14229: Remove vacuous solutions from solve
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Reporter: ppurka | Owner: burcin
Type: enhancement | Status: new
Priority: major | Milestone: sage-5.8
Component: symbolics | Resolution:
Keywords: | Work issues:
Report Upstream: N/A | Reviewers:
Authors: | Merged in:
Dependencies: | Stopgaps:
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Description changed by ppurka:
Old description:
> Sometimes solve and its variants tend to report vacuous solutions. A
> recent one from [http://ask.sagemath.org/question/2324/how-to-print-out-
> maxima-commands-being-used-by ask.sagemath] is the following:
> {{{
> sage: x,y = var('x,y')
> sage: solve([x^2*y^2 <= x^2*y, x^2*y^2 > x^2*y],[x,y])
> [[x == 0, 1 < y, 0 != 0], [x == 0, y < 0, 0 != 0]]
> }}}
>
> Shouldn't we remove these meaningless solutions? The attached patch
> contains a potential solution. If it seems reasonable, then similar
> changes could be introduced in `solve_ineq`.
New description:
Sometimes solve and its variants tend to report vacuous solutions. A
recent one from [http://ask.sagemath.org/question/2324/how-to-print-out-
maxima-commands-being-used-by ask.sagemath] is the following:
{{{
sage: x,y = var('x,y')
sage: solve([x^2*y^2 <= x^2*y, x^2*y^2 > x^2*y],[x,y])
[[x == 0, 1 < y, 0 != 0], [x == 0, y < 0, 0 != 0]]
}}}
Shouldn't we remove these meaningless solutions? The attached patch
contains a potential solution. If it seems reasonable, then similar
changes could be introduced in `solve_ineq`.
The output of the above command after this patch is as expected:
{{{
sage: x,y = var('x,y')
sage: solve([x^2*y^2 <= x^2*y, x^2*y^2 > x^2*y],[x,y])
[]
}}}
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Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/14229#comment:2>
Sage <http://www.sagemath.org>
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