#19257: pushout wrong when using coercion_reversed in construction functor
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Reporter: dkrenn | Owner:
Type: defect | Status: new
Priority: major | Milestone: sage-6.9
Component: categories | Resolution:
Keywords: | Merged in:
Authors: | Reviewers:
Report Upstream: N/A | Work issues:
Branch: | Commit:
Dependencies: | Stopgaps:
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Description changed by dkrenn:
Old description:
> In `sage.categories.pushout.SubspaceFunctor` we have the example
> {{{
> sage: M = ZZ^3
> sage: S = M.submodule([(1,2,3),(4,5,6)]); S
> Free module of degree 3 and rank 2 over Integer Ring
> Echelon basis matrix:
> [1 2 3]
> [0 3 6]
> sage: S.construction()
> (SubspaceFunctor,
> Ambient free module of rank 3 over the principal ideal domain Integer
> Ring)
> }}}
> The subspace functor uses `coercion_reversed=True`. The pushout
> sage: sage.categories.pushout.pushout(S, M)
> Ambient free module of rank 3 over the principal ideal domain Integer
> Ring
> }}}
> is wrong; it should be `ZZ^3`. Consequently
> {{{
> sage: cm = sage.structure.element.get_coercion_model()
> sage: cm.common_parent(S, M)
> Ambient free module of rank 3 over the principal ideal domain Integer
> Ring
> }}}
> also gives the wrong result.
New description:
In `sage.categories.pushout.SubspaceFunctor` we have the example
{{{
sage: M = ZZ^3
sage: S = M.submodule([(1,2,3),(4,5,6)]); S
Free module of degree 3 and rank 2 over Integer Ring
Echelon basis matrix:
[1 2 3]
[0 3 6]
sage: S.construction()
(SubspaceFunctor,
Ambient free module of rank 3 over the principal ideal domain Integer
Ring)
}}}
The subspace functor uses `coercion_reversed=True`. The pushout
{{{
sage: sage.categories.pushout.pushout(S, M)
Ambient free module of rank 3 over the principal ideal domain Integer Ring
}}}
is wrong; it should be `ZZ^3`.
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Ticket URL: <http://trac.sagemath.org/ticket/19257#comment:1>
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