#10963: More functorial constructions
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Reporter: nthiery | Owner: stumpc5
Type: enhancement | Status: needs_info
Priority: major | Milestone: sage-6.1
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 | 3e2003ded77192465cc3e99fec7fa64dae998950
Dependencies: #11224, #8327, | Stopgaps:
#10193, #12895, #14516, #14722, |
#13589, #14471, #15069, #15094, |
#11688, #13394, #15150, #15506 |
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Comment (by pbruin):
Replying to [comment:491 nthiery]:
> I reviewed your commit 98a4407, and changed a couple more things
> (3e2003d). Please review the latter!
Thanks for looking at it! There seems to be a typo (12963 instead of
10963 in various places). Didn't you run into problems with using
`deprecated_function_alias()` everywhere? I tried this first, but (if I
recall correctly) when running doctests there was a problem due to a
circular import, and another error caused by applying
`deprecated_function_alias()` to a `cached_method`.
As for which of `summand_embedding()` and `cartesian_embedding()` in
`CombinatorialFreeModule` is the "real" one: you probably wanted to make
the definitions look more symmetrical, and of course it makes no practical
difference. Just to explain my motivation for doing it the other way
around than for `*_projection()`: for a direct sum it is the embeddings
that exist by definition, while for a Cartesian product is is the
projections. The fact that you do have a `cartesian_embedding()` in this
setting follows from a theorem (product = sum for modules), not a
definition, so it seemed more natural to regard `summand_embedding()` as
the "primary" notion.
--
Ticket URL: <http://trac.sagemath.org/ticket/10963#comment:494>
Sage <http://www.sagemath.org>
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