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 For more options, visit this group at http://groups.google.com/group/sage-support URL: http://www.sagemath.org
