Multivariate polynomials: libsingular vs. polydict

[Robert Samal]

Hi,

I'm trying to compute something using multivariate polynomials, and am struggling to understand the relation between polynomials of type <type 'sage.rings.polynomial.multi_polynomial_libsingular.MPolynomial_libsingular'>
and of type <class 'sage.rings.polynomial.multi_polynomial_element.MPolynomial_polydict'>.

How does one create one or the other? And, mainly: how can one convert from one to the other?

What happened to me is that I unwillingly created some polynomial of one type and some of the other and than methods like P.coefficient(Q.monomials()[0]) object that they got argument of wrong type. (Here P and Q are polynomials of the respective types.)

I'm sorry for not giving specific lines how to reproduce this, but -- in this case this is the point ... I got my polynomials P and Q over the course of several days and don't quite understand what happened.

Thanks!

  Robert

[Martin Albrecht]

Hi,

On Wednesday 05 Sep 2012, Robert Samal wrote:
> Hi,
>
> I'm trying to compute something using multivariate polynomials, and am
> struggling to understand the relation between polynomials of type <type
> 'sage.rings.polynomial.multi_polynomial_libsingular.MPolynomial_libsingular
> '> and of type <class
> 'sage.rings.polynomial.multi_polynomial_element.MPolynomial_polydict'>.
>
> How does one create one or the other? And, mainly: how can one convert from
> one to the other?

It shouldn't happen that you can create two polynomials of different types
polydict vs. libsingular for the same ring.

> What happened to me is that I unwillingly created some polynomial of one
> type and some of the other and than methods like
> P.coefficient(Q.monomials()[0]) object that they got argument of wrong
> type. (Here P and Q are polynomials of the respective types.)

If you have a ring P and and an element f in Q, doesn't P(f) work? If all else
fails, there's always P(str(f)).

> I'm sorry for not giving specific lines how to reproduce this, but -- in
> this case this is the point ... I got my polynomials P and Q over the
> course of several days and don't quite understand what happened.
>
> Thanks!
>
> Robert

Cheers,
Martin

--
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