#5065: elliptic curve torsion subgroup doesn't know it's identity
---------------------------+------------------------------------------------
Reporter: boothby | Owner: was
Type: defect | Status: new
Priority: minor | Milestone:
Component: number theory | Keywords:
---------------------------+------------------------------------------------
The torsion subgroup of an elliptic curve appears to be quite broken -- it
barfs when trying to coerce in 0,
{{{
sage: E = EllipticCurve(1)
sage: T = E.torsion_subgroup()
sage: T(0)
...
...
TypeError: Argument x (= 0) is of wrong type.
}}}
further, it returns a mysterious 1 when coercing in a 1
{{{
sage: a = T(1); a
1
sage: b = T.gens()[0]-T.gens()[0]; b
(0 : 1 : 0)
sage: a+b
TypeError: unsupported operand parent(s) for '+': 'Abelian group of points
on Elliptic Curve defined by y^2 + x*y + y = x^3 - 19*x + 26 over Rational
Field' and 'Torsion Subgroup isomorphic to Multiplicative Abelian Group
isomorphic to C6 x C2 associated to the Elliptic Curve defined by y^2 +
x*y + y = x^3 - 19*x + 26 over Rational Field'
}}}
Yet, it's all cool with the original curve.
{{{
sage: E(0)
(0 : 1 : 0)
sage: E(1)
...
...
TypeError: v (=(1,)) must have 3 components
sage:
}}}
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/5065>
Sage <http://sagemath.org/>
Sage - Open Source Mathematical Software: Building the Car Instead of
Reinventing the Wheel
--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups
"sage-trac" group.
To post to this group, send email to [email protected]
To unsubscribe from this group, send email to
[email protected]
For more options, visit this group at
http://groups.google.com/group/sage-trac?hl=en
-~----------~----~----~----~------~----~------~--~---
