#10963: More functorial constructions
-------------------------------------+-------------------------------------
Reporter: nthiery | Owner: stumpc5
Type: enhancement | Status: needs_info
Priority: major | Milestone: sage-6.2
Component: categories | Resolution:
Keywords: days54 | Merged in:
Authors: Nicolas M. Thiéry | Reviewers: Simon King, Frédéric
Report Upstream: N/A | Chapoton
Branch: | Work issues:
public/ticket/10963-doc- | Commit:
distributive | f1b6804c499bfdc9cd8a864f81f739d80783122d
Dependencies: #11224, #8327, | Stopgaps:
#10193, #12895, #14516, #14722, |
#13589, #14471, #15069, #15094, |
#11688, #13394, #15150, #15506, |
#15757, #15759 |
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Comment (by SimonKing):
Hi Nicolas!
Welcome back...
Can you also please address my confusion about the following (see
comment:535).
{{{
sage: Semigroups().Finite
Cached version of <function Finite at 0xa4c2c6c>
sage: Semigroups().__class__.Finite
<class 'sage.categories.finite_semigroups.FiniteSemigroups'>
}}}
`Semigroups` has a class attribute called `"Finite"`, that is a lazily
imported class `FiniteSemigroups`. Fine.
The (unique) instance of `Semigroups` does, however, ''not'' inherit the
attribute `"Finite"` from its class. Instead, it provides a cached method.
Calling this cached method `Semigroups().Finite` does, however, just
return an instance of `Semigroups.Finite`.
The three questions are:
1. ''Why'' is `Semigroups.Finite` overridden on instances of `Semigroups`?
After all, calling `Semigroups.Finite()` returns the same thing as
`Semigroups().Finite()` (and is cached as well).
2. ''How'' is `Semigroups.Finite` overridden on instances of `Semigroups`?
I simply don't see at what point the cached method is put into
`Semigroups().__dict__`.
3. ''Where'' can the answers to 1. and 2. be found in the docs?
Best regards,
Simon
--
Ticket URL: <http://trac.sagemath.org/ticket/10963#comment:548>
Sage <http://www.sagemath.org>
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