#15964: Remove superfluous import statement in ell_point
-------------------------------+----------------------------
Reporter: cremona | Owner:
Type: defect | Status: new
Priority: minor | Milestone: sage-6.2
Component: elliptic curves | Keywords:
Merged in: | Authors:
Reviewers: | Report Upstream: N/A
Work issues: | Branch:
Commit: | Dependencies:
Stopgaps: |
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As reported on sage-devel, in Sage 6.1.1 this works as designed:
{{{
sage: N = 1715761513
sage: E = EllipticCurve(Integers(N),[3,-13])
sage: P = E(2,1)
sage: LCM([2..60])*P
...ZeroDivisionError: Inverse of 1520944668 does not exist (characteristic
= 1715761513 = 26927*63719)
}}}
but this fails in the wrong way:
{{{
N = 35
E = EllipticCurve(Integers(N),[5,1])
P = E(0,1)
LCM([2..6])*P
...
UnboundLocalError: local variable 'ZZ' referenced before assignment
}}}
The problem is that there are two places where the fail condiction can be
triggered (and in this situation this happens by design, as it is used to
detect the fact that the modulus is not prime and factor it): one in
addition of points and one in duplication. In the latter there is an
explicit "import ZZ" while in the former there is not. This could be
fixed by deleting the import on line 708 (thus relying on the import at
the top of the file in line 130), or by deleting line 130 (since ZZ is not
referred to elsehere in the file) and inderting a copy of line 708 before
line 696.
--
Ticket URL: <http://trac.sagemath.org/ticket/15964>
Sage <http://www.sagemath.org>
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