failing doctests with optional package coxeter 3

[videlec]

With coxeter3 installed

sage: W = CoxeterGroup(['B', 3], implementation='coxeter3')
Traceback (most recent call last):
...
.../coxeter3/coxeter.pyx in sage.libs.coxeter3.coxeter.CoxGroup.__cinit__ (.../cythonized/sage/libs/coxeter3/coxeter.cpp:3329)()
    266
    267         if len(cartan_type) == 2:
--> 268             type, rank = cartan_type
    269         else:
    270             type, rank, affine = cartan_type
ValueError: too many values to unpack (expected 2)

And indeed

sage: c = CartanType('B3')
sage: len(c)
2
sage: len(list(c))
3

This causes many doctest failures.

CC: @tscrim @fchapoton @anneschilling @AndrewAtLarge @nthiery

Component: packages: optional

Author: Travis Scrimshaw

Branch/Commit: 312462a

Reviewer: Vincent Delecroix

Issue created by migration from https://trac.sagemath.org/ticket/21077

[tscrim]

Author: Travis Scrimshaw

[tscrim]

comment:2

This is caused by #20973 and is independent of coxeter3. I will post a fix shortly.

[tscrim]

comment:3

The problem is that there is an affine method for finite Cartan types that returns the corresponding affine type, whereas for affine types, the twist number is in the attribute affine. We already override __getitem__ for affine Cartan types, so we just default to 2 valid indices for the general __getitem__.

---

New commits:

312462a

Fixing `__getitem__` for non-affine Cartan types.

[tscrim]

Branch: public/combinat/root_system/fix_cartan_type-20177

[tscrim]

Commit: 312462a

[videlec]

comment:4

At least the optional doctest now pass ;-)

[videlec]

Reviewer: Vincent Delecroix

[vbraun]

Changed branch from public/combinat/root_system/fix_cartan_type-20177 to 312462a