#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 |
-------------------------------------+-------------------------------------
Comment (by nthiery):
Replying to [comment:548 SimonKing]:
> Can you also please address my confusion about the following (see
comment:535).
Oops, thanks for the reminder.
> The three questions are:
> 1. ''Why'' is `Semigroups.Finite` overridden on instances of
`Semigroups`?
So that, when {{{C}}} is a category, {{{C.Finite}}} always points to
the original {{{Finite}}} method, whether C implements or not this
axiom (an implementation detail). In particular, introspection with
{{{C.Finite?}}} always nicely gives the documentation of the axiom
from the {{{Finite}}} method.
> 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__`.
That's implemented in `CategoryWithAxiom.__classget__`.
> 3. ''Where'' can the answers to 1. and 2. be found in the docs?
See, in the category_with_axiom file, the notes in the section "Simple
case involving a single predefined axiom", the section "Defining a new
axiom" and the documentation of `CategoryWithAxiom.__classget__`.
I just spent some time refactoring those pieces of documentation with
your specific questions in mind. I hope it's better now!
Commit to come in a couple minutes when I'll have finished recompiling
Sage and tested my changes ...
> After all, calling `Semigroups.Finite()` returns the same thing as
`Semigroups().Finite()` (and is cached as well).
Indeed the overriding of `Semigroups().Finite` would not be absolutely
necessary if we only cared about `Semigroups().Finite()` working, and not
about introspection as above.
Still `Semigroups.Finite()` kind of works by "fluke" at
this point. I am not sure we want to support this syntax in the long
run. See also the section "Making the category with axiom directly
callable".
Cheers,
Nicolas
--
Ticket URL: <http://trac.sagemath.org/ticket/10963#comment:549>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
--
You received this message because you are subscribed to the Google Groups
"sage-trac" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to [email protected].
To post to this group, send email to [email protected].
Visit this group at http://groups.google.com/group/sage-trac.
For more options, visit https://groups.google.com/groups/opt_out.
