#9695: AdditiveAbelianGroup, __call__ is misleading and complicated
-----------------------+----------------------------------------------------
Reporter: rbeezer | Owner: AlexGhitza
Type: defect | Status: new
Priority: major | Milestone: sage-4.5.2
Component: algebra | Keywords:
Author: | Upstream: N/A
Reviewer: | Merged:
Work_issues: |
-----------------------+----------------------------------------------------
The {{{__call__}}} functions for {{{AdditiveAbelianGroup}}} and
{{{AdditiveAbelianGroupWrapper}}} don't behave as I would expect, nor as
the doctests would lead one to believe.
Documentation for the wrapper class says:
{{{
...or an iterable (in which case the result is the corresponding
product of the generators of self).
}}}
It seems that the iterable instead gives a linear combination of the
generators used in the "optimized" version of the quotient modules. Most
(all?) of the doctests use examples where the number of invariants is
equal to the number of original generators, so the optimization is trivial
and the situations below are not exposed.
See #9694 for an example of working around this.
Here, I'd expect {{{M([1,1,1])}}} to be {{{M.0+M.1+M.2}}}, and not an
error
{{{
sage: E = EllipticCurve('30a2')
sage: pts = [E(4,-7,1), E(7/4, -11/8, 1), E(3, -2, 1)]
sage: M = AdditiveAbelianGroupWrapper(pts[0].parent(), pts, [3, 2, 2])
sage: M.gens()
((4 : -7 : 1), (7/4 : -11/8 : 1), (3 : -2 : 1))
sage: M([1,1,1])
---------------------------------------------------------------------------
TypeError Traceback (most recent call
last)
/sage/sage-4.5.2.rc1/devel/sage-main/<ipython console> in <module>()
/sage/sage-4.5.2.rc1/local/lib/python2.6/site-
packages/sage/groups/additive_abelian/additive_abelian_wrapper.pyc in
__call__(self, x, check)
234 elif x.parent() is self.universe():
235 return AdditiveAbelianGroupWrapperElement(self,
self._discrete_log(x), element = x)
--> 236 return
addgp.AdditiveAbelianGroup_fixed_gens.__call__(self, x, check)
237
238 class
AdditiveAbelianGroupWrapperElement(addgp.AdditiveAbelianGroupElement):
/sage/sage-4.5.2.rc1/local/lib/python2.6/site-
packages/sage/modules/fg_pid/fgp_module.pyc in __call__(self, x, check)
481 x =
self.optimized()[0].V().linear_combination_of_basis(x)
482 except ValueError, msg:
--> 483 raise TypeError, msg
484 elif isinstance(x, FGP_Element):
485 x = x.lift()
TypeError: length of v must be at most the number of rows of self
}}}
No problem when the number of invariants equal the number of generators:
{{{
sage: G=AdditiveAbelianGroup([17])
sage: a=G([12])
sage: a
(12)
}}}
The problem case again, up in the base class
{{{
sage: H=AdditiveAbelianGroup([3,7])
sage: b=H([12])
sage: b
(0, 4)
sage: c=H([2,3])
---------------------------------------------------------------------------
TypeError Traceback (most recent call
last)
/sage/sage-4.5.2.rc1/devel/sage-main/<ipython console> in <module>()
/sage/sage-4.5.2.rc1/local/lib/python2.6/site-
packages/sage/modules/fg_pid/fgp_module.pyc in __call__(self, x, check)
481 x =
self.optimized()[0].V().linear_combination_of_basis(x)
482 except ValueError, msg:
--> 483 raise TypeError, msg
484 elif isinstance(x, FGP_Element):
485 x = x.lift()
TypeError: length of v must be at most the number of rows of self
}}}
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/9695>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
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