#20027: Different behavior for reflections for matrix Coxeter group and Weyl
groups
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Reporter: tscrim | Owner: sage-combinat
Type: defect | Status: new
Priority: major | Milestone: sage-7.1
Component: | Keywords: coxeter groups, reflections
combinatorics | Authors:
Merged in: | Report Upstream: N/A
Reviewers: | Branch:
Work issues: | Dependencies:
Commit: |
Stopgaps: |
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Currently, we have the following behavior:
{{{
sage: W = CoxeterGroup(['A',1])
sage: W.reflections()
[[-1]]
sage: W = WeylGroup(['A',1])
sage: W.reflections()
Finite family {[0 1]
[1 0]: (1, -1)}
}}}
In particular, the former returns a list of elements in the group, whereas
the latter returns a family whose keys are elements in the group and whose
values are roots. This leads to different iterator behaviors between the
two. Since Weyl groups are a subcategory of Coxeter groups, we should make
this behavior consistent.
Note, this was introduced by #11010 and is specific for the matrix
implementation of `CoxeterGroup`. We can also lift this up to the category
of (finite) Coxeter groups.
--
Ticket URL: <http://trac.sagemath.org/ticket/20027>
Sage <http://www.sagemath.org>
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