#16830: Can't multiply a linear morphism defined by a matrix by an element of
the
base field
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Reporter: nthiery | Owner:
Type: defect | Status: new
Priority: major | Milestone:
Component: linear algebra | Resolution:
Keywords: | Merged in:
Authors: | Reviewers:
Report Upstream: N/A | Work issues:
Branch: | Commit:
Dependencies: | Stopgaps:
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Comment (by nthiery):
Replying to [comment:2 nbruin]:
> That looks like the category machinery is not cooperating with
> coercion properly. The scalar multiplication should be there
> according to the categories:
Well, categories are doing nothing here but stating the math. This
issue is really about the concrete class VectorSpaceMorphism for
morphisms defined by a matrix which is responsible for implementing
multiplication by scalars, and apparently does not.
> By the way, going up the inheritance in the code:
> {{{
> sage: sage.modules.vector_space_homspace.VectorSpaceHomspace.mro()
> [sage.modules.vector_space_homspace.VectorSpaceHomspace,
> sage.modules.free_module_homspace.FreeModuleHomspace,
> sage.categories.homset.HomsetWithBase,
> sage.categories.homset.Homset,
> sage.structure.parent.Set_generic,
> sage.structure.parent.Parent,
> sage.structure.category_object.CategoryObject,
> sage.structure.sage_object.SageObject,
> object]
> }}}
> and reading the code, it's completely unclear how `parent(phi)` got
those module categories attached to it. It would have to happen somewhere
in `sage.modules.vector_space_homspace.VectorSpaceHomspace,
sage.modules.free_module_homspace.FreeModuleHomspace` but none of those
classes have an `__init__`.
The setting of the category for a homset is handled generically in
Homset.__init__.
Cheers,
Nicolas
--
Ticket URL: <http://trac.sagemath.org/ticket/16830#comment:3>
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