On Sat, Mar 19, 2011 at 07:37:25AM -0700, Daniel Bump wrote:
> Well, what you are suggesting is a little tricky. Two
> rings will be created at the same time, and the
> multiplication will be implemented by coercing from
> the WeylCharacterRing to the WeightRing, multiplying,
> and coercing back.
Why tricky? After all, that's the standard implementation of
e.g. quotient rings like IntegerModRing (admittedly with
optimizations). And it should be just a couple lines to set up since
anyway the reciprocal morphisms are already implemented.
Admitted, finding exactly which lines shall be added can be tricky the
first time in the current state of the documentation and examples. A
good starting point could be:
sage: Semigroups().Subquotients().example()
> And I see no benefit to the user.
It is mostly beneficial to the developers indeed. But also to the
curious user who will dig into the multiplication code.
Besides, if Sage is aware that the WeylCharacterRing is a subring of
the WeightRing which itself is isomorphic to a Laurent polynomial
ring, then WeylCharacterRing could in the long run automatically
inherit from some fancy tools around factorization or Gröbner basis
calculations. And that would come back to the user.
> > With the sage-combinat patches applied, you get about 20 occurences :-)
> >
> > See typically sage/categories/examples/realizations.py.
> >
> > Alternatively, if you push your current version on the sage-combinat
> > server, I can probably handle this change on Monday.
>
> I added a patch to the queue called trac_7922-revisions.patch.
> The patch trac_7922-rebased-4.7.alpha1 that is posted on the
> trac server equals the sum of the four patches:
>
> 91 A trac_7922-rebased-4.6.1
> 92 A trac_7922-doc.patch
> 93 A trac_7922-review-nt.patch
> 94 A trac_7922-revisions.patch
Thanks! I'll have a look now.
> I moved the guarded patch trac_7922-hash-nt.patch later.
Yup.
Cheers,
Nicolas
--
Nicolas M. Thiéry "Isil" <nthi...@users.sf.net>
http://Nicolas.Thiery.name/
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