Just to say that Jenny and I sorted this out off-list (essentially by replacing QQ wuth ZZ).
John On Sep 10, 7:27 pm, Robert Bradshaw <rober...@math.washington.edu> wrote: > On Sep 10, 2009, at 5:24 AM, J. Cooley wrote: > > > Hi > > > I'm trying to write some code involving isogenies that will work over > > different types of fields (at least rational and finite and hopefully > > number fields too.) > > Cool. > > > Part of the code includes the line: > > > fp.numerator()-j*fp.denominator() where fp is a polynomial in t over > > Qt = FractionField(PolynomialRing(QQ,'t') > > What is j? > > > > > > > for the elliptic curve > > E = EllipticCurve([1,0,1,4, -6]); E > > > we have > > sage: E.j_invariant() > > 9938375/21952 > > sage: type(E.j_invariant()) > > <type 'sage.rings.rational.Rational'> > > and this works fine > > > but for > > sage: E = EllipticCurve(GF(13^4, 'a'),[2,8]) > > sage: E.j_invariant() > > 4 > > sage: type(E.j_invariant()) > > <type 'sage.rings.finite_field_givaro.FiniteField_givaroElement'> > > > and so I get the error > > TypeError: unsupported operand parent(s) for '-': 'Univariate > > Polynomial Ring in t over Rational Field' and 'Univariate Polynomial > > Ring in t over Finite Field in a of size 13^4' > > > I have tried replacing j with QQ(j), but I got the error > > TypeError: Unable to coerce 4 (<type > > 'sage.rings.finite_field_givaro.FiniteField_givaroElement'>) to > > Rational > > > Not quite sure how to proceed! > > It looks like you're trying to mix rational numbers and elements of GF > (13^4), which shouldn't work, but it's unclear from the above > examples where the mixing is occurring. Could you give the code that > leads up to the error? > > - Robert --~--~---------~--~----~------------~-------~--~----~ To post to this group, send an email to sage-devel@googlegroups.com To unsubscribe from this group, send an email to sage-devel-unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/sage-devel URLs: http://www.sagemath.org -~----------~----~----~----~------~----~------~--~---
