#16340: Infrastructure for modelling full subcategories
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Reporter: nthiery | Owner:
Type: enhancement | Status: needs_review
Priority: major | Milestone: sage-6.4
Component: categories | Resolution:
Keywords: full | Merged in:
subcategories, homset | Reviewers: Darij Grinberg,
Authors: Nicolas M. Thiéry | Travis Scrimshaw
Report Upstream: N/A | Work issues:
Branch: | Commit:
public/categories/full_subcategories-16340|
d4c7a88563a397291b6cd5ddadb8f574cc1eedb5
Dependencies: | Stopgaps:
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Comment (by nthiery):
Replying to [comment:29 tscrim]:
> I made some other categories into non-structure categories.
Thanks. I double checked on this, and mostly agree up to one point: I
think Coxeter Groups should be a structure category, the extra
structure being the chosen set of simple generators.
> This made me wonder if we actually want the default category be a
> structure category.
I believe this would be dangerous. Being accidently a structure
category means that your homsets will miss some code that could be
available. So just a missing feature. Whereas being accidently a non
structure category can let your homset inherit from code that is not
applicable which can lead to wrong code.
Besides, all the categories your changed should actually become
CategoryWithAxioms at some point, which will have precisely the
desired effect.
So now one could wonder whether having a CategoryWithAxiom be a non
structure category is not a dangerous default. I believe it's ok,
because for a category with axiom A.B, one only has to be careful
about being a full subcategory or not if A is the category defining
the axiom B. There are not soo many of them.
> I'm going to double-check to make sure I didn't miss any others and
> I'd appreciate if someone else could do the same.
Thanks!
Cheers,
Nicolas
--
Ticket URL: <http://trac.sagemath.org/ticket/16340#comment:33>
Sage <http://www.sagemath.org>
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