#17364: Homset categories should be subcategories of the category of all homsets
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Reporter: nthiery | Owner:
Type: defect | Status: needs_review
Priority: major | Milestone: sage-6.5
Component: categories | Resolution:
Keywords: | Merged in:
Authors: Nicolas M. Thiéry | Reviewers:
Report Upstream: N/A | Work issues:
Branch: | Commit:
u/nthiery/all_homsets_category_should_be_subcategories_of_the_category_of_all_homsets|
0925390c0d1eacabd75bb24c815d30124c8e8a2b
Dependencies: | Stopgaps:
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Comment (by nthiery):
Hi Peter,
Replying to [comment:8 pbruin]:
> I am not sure that this ticket solves all difficulties with
> determining the supercategories of Hom set categories.
Thanks for checking whether everything is correct.
> For example (both before and after this ticket):
> {{{
> sage: HeckeModules(ZZ).is_subcategory(Modules(ZZ))
...
> }}}
> Note that the fact that Hom sets of modules are Abelian groups is not
reflected in the output of the last command.
This is not about the infrastructure (which is the theme of this
ticket), but about what Sage knows about Hecke modules (which is what
the TODO I left is about):
- If the category Hecke modules is a full subcategory of the category
of modules, Sage should be told about this by implementing
`HeckeModules.additional_structure` to return `None`.
- Otherwise, one needs to state explicitly that
`HeckeModules(ZZ).Homsets()` is a subcategory of `AbelianGroups()`
(or whatever appropriate) in
`HeckeModules.Homsets.extra_super_categories`.
Cheers,
Nicolas
--
Ticket URL: <http://trac.sagemath.org/ticket/17364#comment:9>
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