#20435: factorisation of polynomials over integers has wrong parent
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Reporter: chapoton | Owner:
Type: defect | Status: new
Priority: major | Milestone: sage-7.2
Component: algebra | Resolution:
Keywords: | Merged in:
Authors: | Reviewers:
Report Upstream: N/A | Work issues:
Branch: | Commit:
Dependencies: | Stopgaps:
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Changes (by chapoton):
* cc: tscrim, jdemeyer (added)
Old description:
> {{{
> sage: x,y=polygen(ZZ,'x,y')
> sage: p=x**2-y**2
> sage: p.parent()
> Multivariate Polynomial Ring in x, y over Integer Ring
> sage: factor(p)
> (x - y) * (x + y)
> sage: factor(p)[0][0].parent()
> Multivariate Polynomial Ring in x, y over Multivariate Polynomial Ring in
> x, y over Integer Ring
> }}}
New description:
{{{
sage: x,y=polygen(ZZ,'x,y')
sage: p=x**2-y**2
sage: p.parent()
Multivariate Polynomial Ring in x, y over Integer Ring
sage: factor(p)
(x - y) * (x + y)
sage: factor(p)[0][0].parent()
Multivariate Polynomial Ring in x, y over Multivariate Polynomial Ring in
x, y over Integer Ring
}}}
but no problem over QQ
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Ticket URL: <http://trac.sagemath.org/ticket/20435#comment:1>
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