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 -~----------~----~----~----~------~----~------~--~---
