#14261: Iwahori-Hecke algebra with several bases
-------------------------------------+-------------------------------------
Reporter: brant | Owner: sage-combinat
Type: enhancement | Status: needs_review
Priority: major | Milestone: sage-5.12
Component: combinatorics | Resolution:
Keywords: Iwahori Hecke | Merged in:
algebra | Reviewers: Andrew Mathas, Brant
Authors: Brant Jones, | Jones, Travis Scrimshaw
Travis Scrimshaw | Work issues:
Report Upstream: N/A | Commit:
Branch: | Stopgaps:
Dependencies: #13735 #14014 |
#14678 #14516 |
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Comment (by tscrim):
Replying to [comment:49 andrew.mathas]:
> It was my bug rather than one in `BindableClass`. The problem was that I
hadn't defined the shortcuts in the generic Hecke algebra class. As a
result the non-generic shortcuts were being inherited and used instead of
their generic replacements.
Ah, I see.
> I have to try and finish a paper today, but hopefully I will manage to
finalise this by the end of the week. Apologies for the delay.
No worries. Thanks for doing the refactoring with the generic algebras.
> Btw, I just noticed failing doc-test in the original patch (and in my
"review"). The following is supposed to work but doesn't:
> {{{
> sage: G = CoxeterGroup("B2")
> sage: T[G.simple_reflection(1)]
> }}}
> The problem is that `CoxeterGroup` and `WeylGroup` return different
groups:
> {{{
> sage: CoxeterGroup("B2")
> Permutation Group with generators [(1,3)(2,6)(5,7), (1,5)(2,4)(6,8)]
> sage: WeylGroup("B2")
> Weyl Group of type ['B', 2] (as a matrix group acting on the ambient
space)
> }}}
> Does anyone know if this is fixed in some patch or reported as a bug
somewhere?
>
> We can fudge the failing doc-test by using `WeylGroup` instead of
`CoxeterGroup`.
I wouldn't necessarily call that the output is different a bug since the
class of Coxeter groups is larger than the class of Weyl groups and they
are constructed from different underlying spaces, and by using a different
API, it's okay to expect a different output. However that the output from
`CoxeterGroup` and `WeylGroup` behave differently is a bug. I'd guess that
the permutation group from `CoxeterGroup` is not in the `CoxeterGroups`
category is the root of the problem. I'll look into this.
--
Ticket URL: <http://trac.sagemath.org/ticket/14261#comment:50>
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