#10667: Morphisms and Objects of Categories
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Reporter: SimonKing | Owner: nthiery
Type: enhancement | Status: needs_work
Priority: major | Milestone: sage-5.0
Component: categories | Keywords: objects
morphisms containment
Work_issues: Cope with non-unique number fields | Upstream: N/A
Reviewer: | Author: Simon King
Merged: | Dependencies: #9138,
#11115, #11780
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Comment(by SimonKing):
Replying to [comment:58 nthiery]:
> I am not very keen on having a class inherit (indirectly) from
> UniqueRepresentation, and then hacking it's way around to actually not
> have to implement the unique representation protocole. I'd rather only
> inherit explicitly from UniqueRepresentation when I mean it.
Yes, what I did doesn't fully convince me.
With my patch, the `Rings().HomCategory.ParentMethods` inherits from
`UniqueRepresentation`, and since `NumberFields()` is a sub-category of
`Rings()`, the default `NumberFields().hom_category().parent_class
inherits from `UniqueRepresentation` as well.
But it would be possible to have a custom
`NumberFields().HomCategory.ParentMethods`, similar to the custom
`Rings().HomCategory.ParentMethods`.
While `Rings().hom_category().parent_class` with my patch inherits from
`UniqueRepresentation` and (via classcall) from either
`sage.rings.homset.RingHomset_generic` or
`sage.rings.homset.RingHomset_quo_ring`, one could have
`NumberFields().hom_category().parent_class` inherit from
`sage.rings.number_field.morphism.NumberFieldHomset`, but not from
`UniqueRepresentation`.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/10667#comment:60>
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