Apparently, this is caused by a problem in degree() which is used in polynomial(). In your example:
sage: pol2.degree(q) 0 sage: pol2.degree(p) 3 You get the expected behavior if you bring q into pol2.parent() explicitly: sage: q=pol2.parent()(q) sage: pol2.degree(q),pol2.polynomial(q) (3, 4*q^3 + 3*q + 2) So, this seems like an error to me. In the implementation of degree() the line reading return singular_polynomial_deg(p, (<MPolynomial_libsingular>x)._poly, r) should probably be changed (x is the generator passed to the method). But maybe somebody who knows more about the singular/sage connection can say more about this. cheers, julian * rafaeldleon <rafaeldl...@gmail.com> [2011-07-25 12:31:29 -0700]: > Hello all, > > I don´t know if the following is an error in the implementation of the > method polynomial > or if I am using it in a way that is not intended, but it seems that > the use of the method > polynomial changes when I am in a polynomial ring with 2 or with 3 > variables. > > pol and pol2 are the "same" polynomial in rings with 3 or 2 variables > resp. and > the method pol.polynomial(q) and pol2.polynomial(q) return different > answers. > > > sage: R.<p,q,t>=ZZ[] > sage: pol=2+3*q+4*q^3;pol > 4*q^3 + 3*q + 2 > sage: parent(pol) > Multivariate Polynomial Ring in p, q, t over Integer Ring > sage: pol2=pol.polynomial(t).coefficients()[0];pol2 > 4*q^3 + 3*q + 2 > sage: parent(pol2) > Multivariate Polynomial Ring in p, q over Integer Ring > sage: pol2.polynomial(q) > 2 > sage: pol.polynomial(q) > 4*q^3 + 3*q + 2 > > Can anyone give me some insight about why I am getting these > different answers? > > Thanks! > > Rafael > > -- > To post to this group, send email to sage-support@googlegroups.com > To unsubscribe from this group, send email to > sage-support+unsubscr...@googlegroups.com > For more options, visit this group at > http://groups.google.com/group/sage-support > URL: http://www.sagemath.org -- To post to this group, send email to sage-support@googlegroups.com To unsubscribe from this group, send email to sage-support+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/sage-support URL: http://www.sagemath.org
