On Mon, Mar 21, 2011 at 10:35:55PM +0100, Nicolas M. Thiery wrote:
> 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?
Well, yes, there is one tricky point with the current organization of
the code, where first the WeylCharacterRing is defined, and then the
WeightRing is constructed from it. Then of course it's a bit
inconvenient to define the product of the former from that of the
latter. But that would be easy to change internaly, even without
changing the current interface. And then one could use the generic
ambient/lift/retract mechanism for subquotients.
> Thanks! I'll have a look now.
I just pushed my changes on the Sage-Combinat queue. The code uses
standard coercion now. In the process, I have factored out a couple
functions to the ambient space (from_vector_notation, the coerce_E6
and friends). It's not polished (see the TODO's) but all test pass.
I have left for the record the construction of the partial morphism
from the WeightRing to the WeylCharacterRing even if it is not
currently registered as a conversion (I had a little glitch there, and
it's time to go to bed). Even if not registered as a conversion; that
could be a useful function for the user, so you may want to keep it
and document it.
I won't touch the thing tomorrow, so feel free to fold all the 7922
patches together for a better overview.
Cheers,
Nicolas
--
Nicolas M. Thiéry "Isil" <nthi...@users.sf.net>
http://Nicolas.Thiery.name/
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