#2952: [with patch, needs work] LaurentPolynomialRing coercion error
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Reporter: mhansen | Owner: roed
Type: defect | Status: needs_work
Priority: critical | Milestone: sage-6.2
Component: coercion | Resolution:
Keywords: laurent polynomials | Merged in:
Authors: | Reviewers:
Report Upstream: N/A | Work issues:
Branch: | Commit:
Dependencies: | Stopgaps:
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Comment (by pbruin):
It seems the underlying problem is that
`LaurentPolynomial_mpair.__pow__()` can return Laurent polynomials whose
coefficients do not lie in its base ring, but in its fraction field:
{{{
sage: R.<q>=QQ[]
sage: L.<x,y,z> = LaurentPolynomialRing(R)
sage: g=z^-1
sage: parent(g)
Multivariate Laurent Polynomial Ring in x, y, z over Univariate Polynomial
Ring in q over Rational Field
sage: parent(g.coefficients()[0])
Fraction Field of Univariate Polynomial Ring in q over Rational Field
}}}
The last line should simply be `Univariate ...`
A slightly unrelated note: `z^-1` still lies in `L` (ignoring this bug),
but `1/z` and `~z` return elements of the fraction field of `L`.
--
Ticket URL: <http://trac.sagemath.org/ticket/2952#comment:9>
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