A3(list(P)) works here -- answering the easier of your two questions!

John Cremona


On Apr 19, 2:33 am, vdelecroix <[email protected]> wrote:
> Hello,
>
> I'm trying to implement an algorithm for factorization of bivariate
> polynomials. A step of the algorithm is Hensel lifting and I was not
> able to coerce a Taylor development of degree k into a Taylor
> development of degree k+1. More precisely, I have a polynomial in the
> quotient ring R[t] / (t^k) and I want to see it in R[t] / (t^(k+1)). I
> would like to use the quotient rings because many calculus are done in
> each of them.
>
> My two attempts were the followings
> {{{
> sage: K.<t> = PolynomialRing(QQ,'t')
> sage: A2 = QuotientRing(K, Ideal(t^2))
> sage: A3 = QuotientRing(K, Ideal(t^3))
> sage: P = A2(t^4 + 3*t + 1)
>
> }}}
>
> First method: try to coerce
> {{{
> sage: A3(P)
> Traceback (click to the left of this block for traceback)
> ...
> TypeError: Unable to coerce 3*tbar + 1 (<class
> 'sage.rings.polynomial.polynomial_quotient_ring_element.PolynomialQuotie
> \
> ntRingElement'>) to Rational
>
> }}}
>
> Second method substitute
> {{{
> sage: P.substitute(t=A3.gen()).parent()
> sage: P.parent()
> Univariate Quotient Polynomial Ring in tbar over Rational Field with
> modulus t^2
>
> }}}
>
> Is Hensel lifting yet implemented in Sage ? Does anybody have a
> solution for this particular problem ?
>
> Thanks,
> Vincent
>
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