On Tue, Dec 7, 2010 at 4:29 PM, luisfe <lftab...@yahoo.es> wrote: > On Dec 7, 5:03 pm, andrew ewart <aewartma...@googlemail.com> wrote: > > I have the following code > > > > P.<x0,x1,y0,y1,y2,y3> = PolynomialRing(QQ,order='degrevlex') > > I = Ideal(x0^4-y0,x0^3*x1-y1,x0*x1^3-y2,x1^4-y3) > > print I > > R.<y0,y1,y2,y3> = PolynomialRing(QQ,order='degrevlex') > > I1=Ideal(1) > > J=I.intersection(I1) > > print J > > but gives error > > File "/usr/local/sage/sage-4.6/local/lib/python2.6/site-packages/sage/ > > rings/polynomial/multi_polynomial_ideal.py", line 369, in wrapper > > return func(*args, **kwds) > > File "/usr/local/sage/sage-4.6/local/lib/python2.6/site-packages/ > > sage/rings/polynomial/multi_polynomial_ideal.py", line 1327, in > > intersection > > raise ValueError, "other must be an ideal in the ring of self, but > > it isn't." > > ValueError: other must be an ideal in the ring of self, but it isn't. > > > > becuase I doesnt lie in R > > so how do I change this so that sage will be happy for I, an ideal in > > P, intersecting with any ideal in R > > (also R is supposed to be a subring of P where the x0 and x1 are > > removed) > > Sort answer, you cannot intersect ideals in different rings. > Note that I1 is an ideal of ZZ since you wrote Ideal(1) which is > assumed to be 1 in ZZ. > > You could define the ideal 1 in R as (for instance) > > I1 = Ideal(R(1)) > I2 = I1.change_ring(P) # Now it is an ideal in P with the same > generators as I1 > I2.intersection(I) > Ideal (x1^4 - y3, x0*x1^3 - y2, x0^3*x1 - y1, x0^4 - y0) of > Multivariate Polynomial Ring in x0, x1, y0, y1, y2, y3 over Rational > Field > > -- > 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<sage-support%2bunsubscr...@googlegroups.com> > For more options, visit this group at > http://groups.google.com/group/sage-support > URL: http://www.sagemath.org >
I thought I1=R=<1> also the intersection should be in R, not just in P, so how is this achieved? -- 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
