#3056: [with patch, with positive review] bug with polynomials over power series
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Reporter: kedlaya | Owner: roed
Type: defect | Status: new
Priority: major | Milestone: sage-3.3
Component: basic arithmetic | Resolution:
Keywords: polynomials, power series, Karatsuba |
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Old description:
> The first computation of z^2 is incorrect, whereas the second is correct:
> {{{
> sage: C.<t> = PowerSeriesRing(ZZ)
> sage: D.<s> = PolynomialRing(C)
> sage: z = (1 + O(t)) + t*s^2
> sage: z^2
> t^2*s^4 + 1 + O(t)
> sage: z._mul_generic(z)
> t^2*s^4 + (2*t + O(t^2))*s^2 + 1 + O(t)
> }}}
New description:
The first computation of {{{z^2}}} is incorrect, whereas the second is
correct:
{{{
sage: C.<t> = PowerSeriesRing(ZZ)
sage: D.<s> = PolynomialRing(C)
sage: z = (1 + O(t)) + t*s^2
sage: z^2
t^2*s^4 + 1 + O(t)
sage: z._mul_generic(z)
t^2*s^4 + (2*t + O(t^2))*s^2 + 1 + O(t)
}}}
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/3056#comment:7>
Sage <http://sagemath.org/>
Sage - Open Source Mathematical Software: Building the Car Instead of
Reinventing the Wheel
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