#10963: More functorial constructions
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Reporter: nthiery | Owner: stumpc5
Type: enhancement | Status: needs_review
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 | Commit:
Dependencies: #11224, #8327, | 478de48553d203516cddb47e0cb89c34ccc210ee
#10193, #12895, #14516, #14722, | Stopgaps:
#13589, #14471, #15069, #15094, |
#11688, #13394, #15150, #15506 |
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Comment (by SimonKing):
Replying to [comment:331 nbruin]:
> Right. I was expecting something like that. The fact that each has to
refer to the other is suspicious to me.
+1.
> What is the scenario that makes this absolutely necessary to be there
right from the start? Wouldn't it be possible for there to be only one
link? Perhaps when that link is actually exercised the other one can be
put in place.
You can not know what end of the link will be called first. The user could
first do `FinitePermutationGroups()`, or `PermutationGroups().Finite()`.
You
have no way to know what will happen first. Of course, you can make it so
that
starting with one end of the link will make the other and of the link
work. But you don't know at what end you start and thus need to implement
''both'' directions of the link.
... unless you forget to think about the ''ends'' of the link, and start
thinking about
the ''link'' itself---and make it so that any attempt to access either end
of
the link will use the information that is stored in the link (see the
suggestion in my previous post).
> My default reaction would be that !FiniteDimensionalAlgebras needs to
know about Algebras because it needs to inherit the properties of
Algebras, but is it absolutely necessary for Algebras to know about a
!FiniteDimensional version, even before it is instantiated?
I think so.
> My default would be that `FiniteDimensionalAlgebras` only registers
itself with `Algebras` when it gets instantiated, if that is necessary at
all. That requires finding a solution for `Algebras().FiniteDimensional()`
(is that how you call it?) when that happens before
`FiniteDimensionalAlgebras` gets imported. Does that happen at all?
Sure. This is the default scenario.
--
Ticket URL: <http://trac.sagemath.org/ticket/10963#comment:333>
Sage <http://www.sagemath.org>
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