#15470: reduce() on QQ(x) doesn't know how to factor out integers
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Reporter: darij | Owner:
Type: defect | Status: new
Priority: major | Milestone: sage-5.13
Component: algebra | Keywords: fraction field, rational
Merged in: | functions, reduce
Reviewers: | Authors:
Work issues: | Report Upstream: N/A
Commit: | Branch:
Stopgaps: | Dependencies:
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{{{
sage: Qx = PolynomialRing(QQ, 'x').fraction_field()
sage: x = Qx.gen()
sage: s = (2*(x+1)) / (2*(x+2))
sage: s
(2*x + 2)/(2*x + 4)
sage: s.reduce()
sage: s
(2*x + 2)/(2*x + 4)
sage:
}}}
Same behavior for multivariate rational functions. Note, however, that it
reduces the integers if the fraction is a constant:
{{{
sage: s = (2*(x+1)) / (2*(x+1))
sage: s
1
}}}
I don't know if it's a bug strictly speaking (the result returned isn't
false, and it compares equal with the cancelled version), but it's a major
annoyance to me because seeing this behaviour I'm no longer sure if I can
trust Sage to cancel out nonconstant polynomials reliably.
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Ticket URL: <http://trac.sagemath.org/ticket/15470>
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