#15906: solve should solve inequalities that are operated on
-------------------------------+------------------------
Reporter: rws | Owner:
Type: enhancement | Status: new
Priority: major | Milestone: sage-6.2
Component: symbolics | Resolution:
Keywords: | Merged in:
Authors: | Reviewers:
Report Upstream: N/A | Work issues:
Branch: | Commit:
Dependencies: #7660 | Stopgaps:
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Description changed by rws:
Old description:
> In #7660 inequalities will be handled differently, and e.g. multiplying
> `x>1` with `-1` will yield `-(x>1)`. These formal expressions cannot be
> solved because---after applying the patch in #7660 they are parsed as
> arithmetic:
> {{{
> sage: solve(-(x > 1),x)
> ...
> RuntimeError: ECL says: THROW: The catch MACSYMA-QUIT is undefined.
> }}}
> {{{
> sage: solve_ineq((x>1)*(-1),[x,y])
> #0: solve_rat_ineq(ineq=-(x > 1))
> ...
> TypeError: ECL says: Error executing code in Maxima: solve_rat_ineq: -(x
> > 1) is not an inequality.
> }}}
> Since, by definition, operations on both lhs and rhs do not change the
> outcome, in one of the above two cases the outer op should be stripped
> away and the result solved.
>
> This ticket depends on #7660 having been implemented as proposed, as
> without you couldn't doctest it.
New description:
In #7660 inequalities will be handled differently, and e.g. multiplying
`x>1` with `-1` will yield `-(x>1)`. These formal expressions cannot be
solved because---after applying the patch in #7660 they are parsed as
arithmetic:
{{{
sage: solve(-(x > 1),x)
...
RuntimeError: ECL says: THROW: The catch MACSYMA-QUIT is undefined.
}}}
{{{
sage: solve_ineq((x>1)*(-1),[x,y])
#0: solve_rat_ineq(ineq=-(x > 1))
...
TypeError: ECL says: Error executing code in Maxima: solve_rat_ineq: -(x
> 1) is not an inequality.
}}}
Since, by definition, simple operations (+,-,*,/) on both lhs and rhs do
not change the outcome, in one of the above two cases the outer op should
be stripped away and the result solved.
This ticket depends on #7660 having been implemented as proposed, as
without you couldn't doctest it.
--
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Ticket URL: <http://trac.sagemath.org/ticket/15906#comment:1>
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