#11552: Fix surjectivity testing for free module morphisms
------------------------------+---------------------------------------------
Reporter: rbeezer | Owner: jason, was
Type: defect | Status: new
Priority: major | Milestone: sage-4.7.2
Component: linear algebra | Keywords:
Work_issues: | Upstream: N/A
Reviewer: | Author:
Merged: | Dependencies:
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Testing for surjectivity of a free module homorphism is probably just fine
for vector spaces, but seems to be broken for modules.
{{{
sage: V = ZZ^2
sage: m = matrix(ZZ, [[1,2],[0,2]])
sage: phi = V.hom(m, V)
sage: phi.lift(vector(ZZ, [0, 1]))
---------------------------------------------------------------------------
ValueError Traceback (most recent call
last)
/sage/dev/devel/sage-main/<ipython console> in <module>()
/sage/dev/local/lib/python2.6/site-
packages/sage/modules/free_module_morphism.pyc in lift(self, x)
375 t = self.domain().linear_combination_of_basis(C)
376 except TypeError:
--> 377 raise ValueError, "element is not in the image"
378 assert self(t) == x
379 return t
ValueError: element is not in the image
sage: phi.is_surjective()
True
}}}
Patch coming up.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/11552>
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