On Thu, Oct 29, 2009 at 02:33:04AM -0700, javier wrote:
>
>
>
> On Oct 29, 12:38 am, "Nicolas M. Thiery" <nicolas.thi...@u-psud.fr>
> wrote:
> > Again, that's just how it used to be. Do we have an agreement for
> > having both:
> >
> > PartiallyOrderedSets()
> > TotallyOrderedSets()
> >
> > I haven't Wikipedia under hand. But since an OrderedMonoid is a
> > partially ordered set there, I assume that OrderedSets could be an
> > alias for PartiallyOrderedSets.
> >
> > Please everybody vote!
>
> If I have to choose, my vote goes for PartiallyOrderedSets() (and
> would add the frequently used alias "poset"). I don't see the need for
> TotallyOrderedSets() at the moment, but someone might think
> differently and it probably won't hurt to have both of them.
Ok. Anyone else comments? Franco?
> > > vector_spaces.py
> > > Concerning the super_categories, why to return Modules(R)? It is not
> > > a different category. IMO we should return Sets() or something like
> > > that.
> >
> > Yes, they are equal. However, as in a previous similar situation
> > (CommutativeRingIdeals w.r.t. RingIdeals), keeping them separate
> > allows for putting in Modules(R) all the mathematical information and
> > code that is generic to any module, and in VectorSpaces(R) those which
> > are specific to vector spaces. At the same time, from the callers
> > point of view, typing Modules(QQ) could automatically return
> > VectorSpaces(QQ).
>
> I agree with keeping the code separate, what I don't think is that
> Modules(QQ) should be the output of supercategories for VectorSpaces
> (QQ) since they are the same one. If Modules(QQ) returns automatically
> VectorSpaces(QQ) then one would have something like this:
>
> sage: C = VectorSpacess(QQ); C
> Vector spaces over rational field
> C.supercategories()
> [Vector spaces over rational fields]
Sure. I should have mentioned that this requires a little technical
trick so that VectorSpaces(QQ).super_categories() can call the actual
Modules(QQ), bypassing the automatic rewriting to VectorSpaces(QQ).
Typically, we could recycle the former RingModules to be the actual
category, and Modules be a function returning either RingModules or
VectorSpaces. Or put an option like Modules(QQ, rewrite = False). That
technical decision is the main reason why I wanted to postpone this
feature. And implement all similar features at the same time to ensure
consistency.
> i.e supercatergories returning exactly the same category. My proposal
> is just to return as supercategories Modules(R).supercategories()
> instead of Modules(R).
But then (at least with the current architecture), VectorSpaces(QQ)
would not inherit from all the code that is implemented in
Modules(QQ).
Cheers,
Nicolas
--
Nicolas M. Thiéry "Isil" <nthi...@users.sf.net>
http://Nicolas.Thiery.name/
--~--~---------~--~----~------------~-------~--~----~
To post to this group, send an email to sage-devel@googlegroups.com
To unsubscribe from this group, send an email to
sage-devel-unsubscr...@googlegroups.com
For more options, visit this group at http://groups.google.com/group/sage-devel
URL: http://www.sagemath.org
-~----------~----~----~----~------~----~------~--~---
