#128: possible clash for EllipticCurve(j-invariant) signature
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Reporter: nbruin | Owner: was
Type: enhancement | Status: needs_work
Priority: minor | Milestone: sage-4.3.1
Component: elliptic curves | Keywords:
Work_issues: | Author: John Cremona
Upstream: N/A | Reviewer:
Merged: |
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Changes (by nbruin):
* status: needs_review => needs_work
Comment:
The following behaviour is (sort of) documented, but is really painful:
{{{
sage: Q.<y,x>=QQ[]
sage: EllipticCurve(y^2-x^3+1)
NotImplementedError
sage: EllipticCurve(x^3+1)
NotImplementedError
}}}
but:
{{{
sage: Q.<x,y>=QQ[]
sage: EllipticCurve(y^2-x^3+1)
Elliptic Curve defined by y^2 = x^3 - 1 over Rational Field
sage: EllipticCurve(x^3+1)
Elliptic Curve defined by y^2 = x^3 + 1 over Rational Field
}}}
I understand that the heart of this patch is not concerned with this
behaviour, but the patch does change something about bivariate parents too
(lines 280, 282). In particular, there seems to be code there concerned
with swapping {{{x}}} and {{{y}}} so perhaps John could address this as
well?
Incidentally, {{{HyperellipticCurve(x^3+1)}}} in the above example simply
does not work, because it insists on univariate polynomials.
Other weird stuff:
{{{
sage: var("x,y,u,v")
(x, y, u, v)
sage: EllipticCurve(y^2-x^3+1)
Elliptic Curve defined by y^2 = x^3 - 1 over Rational Field
sage: EllipticCurve(v^2-u^3+1)
TypeError
}}}
but I guess that's what you get for using the symbolic ring.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/128#comment:12>
Sage <http://www.sagemath.org>
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