#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 nthiery):
Replying to [comment:53 SimonKing]:
> Why would one not want uniqueness for temporarily created parents? When
the same parent is frequently created, then it is more efficient to just
use a cache. Or are you concerned that one creates too many different
parents that will stay in cache forever?
Possibly so. Or about creating many different parents that each need a
lot of input data, or maybe some non hashable data; and maybe you need
each such parent only once. So the overhead in time or code complexity
of guaranteeing unique representation would not be worth it.
Honestly, I don't have a specific use case, just a bad feeling about
it.
> But I think it would be a good idea to add a `X._reduce_from_cache()`
method to `UniqueRepresentation`: It would remove any item of
`X.__class__.__classcall__.cache` whose value is (equal to) X,
+1. I am not sure about the name though. What about something like
_delete_from_cache instead?
> and then it would try `X._reduce_from_homset_cache()` as well (which
> would of course only be available for rings).
UniqueRepresentation is meant to also be used by non Parents. So I'd
rather have nothing Parent-related in it. On the other hand, Parent
could overload UniqueRepresentation's method to also call that for
homsets.
Cheers,
Nicolas
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Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/10667#comment:57>
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