On Mar 6, 2008, at 11:20 AM, David wrote:
> > I am trying to use the reduce() command on a rational pollynomial. I > first clear the denominator by multiplying by the denominator but when > I use reduce() I get an error. When I print out the polynomial it is > no longer rational but SAGE doesn't like it. I would appriciate any > advice. Below is an example script with ouput. Thank you. The following may help explain the issue: sage: v = 6/7 sage: type(v) <type 'sage.rings.rational.Rational'> sage: type(7*v) <type 'sage.rings.rational.Rational'> Just "clearing denominators" doesn't change the ring to which the elements belong. All you did was produce a rational polynomial whose coefficients all have denominator 1 :-} Sage makes a distinction between "ZZ" (integers) and "QQ" (rationals). Even though "QQ" contains "ZZ" (at some level), Sage doesn't always switch from one ring to a larger or smaller ring (or homomorphic image, more generally). There are rules for when and how this is done (search for coercion on this or the sage-devel lists for the seamy underbelly of this subject :-}), but these only apply when "combining" elements from different "parents". You can do something like this, if you need to. sage: Zx.<x>=PolynomialRing(ZZ) sage: Qx.<x>=PolynomialRing(QQ) sage: f=x-v sage: type(f) <class 'sage.rings.polynomial.polynomial_element_generic.Polynomial_rational_de nse'> sage: type(7*f) <class 'sage.rings.polynomial.polynomial_element_generic.Polynomial_rational_de nse'> sage: g=Zx(7*f) sage: g 7*x - 6 sage: type(g) <type 'sage.rings.polynomial.polynomial_integer_dense_ntl.Polynomial_integer_d ense_ntl'> HTH Justin -- Justin C. Walker, Curmudgeon-at-Large () The ASCII Ribbon Campaign /\ Help Cure HTML Email --~--~---------~--~----~------------~-------~--~----~ To post to this group, send email to sage-support@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/sage-support URLs: http://www.sagemath.org -~----------~----~----~----~------~----~------~--~---
