#17798: Create a class for Coxeter matrices and types
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Reporter: tscrim | Owner: sage-combinat
Type: enhancement | Status: needs_review
Priority: major | Milestone: sage-6.9
Component: group theory | Resolution:
Keywords: Coxeter groups, | Merged in:
matrices, types, days64 | Reviewers: Jean-Philippe Labbé,
Authors: Travis Scrimshaw, | Travis Scrimshaw
Jean-Philippe Labbé | Work issues:
Report Upstream: N/A | Commit:
Branch: | e659186e20bbb4b4a942008dff32901659e42503
public/combinat/coxeter_matrices-17798| Stopgaps:
Dependencies: #17990, #18152, |
#18743 |
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Comment (by jipilab):
Replying to [comment:74 tscrim]:
> The fix was that the cluster seed code was assuming the indexing set of
a Cartan matrix constructed from a matrix that was of finite type had the
standard finite type indexing set of `[1, 2, ..., n]`. I fixed this by
explicitly specifying this to be the index set of the Cartan matrix.
Is my last edition to make test pass consistent with this change?
>
> This brings up a point that might need a discussion: Should the index
set of a matrix representing a finite type Cartan matrix be by default
1-based or 0-based? The argument for being 1-based is above, a natural
assumption on index sets of finite type. Why we should have 0-based is
consistency with the rest for default labellings and it agrees with the
indexing set of the given matrix (and everything in python is 0-based).
Thoughts?
I would say 1-based for finite type since they probably have a labeling
hardcoded when dealing with them through Cartan matrices and Coxeter
Types.
I would say 0-based whenever there is no labels specified and it comes
through a CoxeterMatrix type, eventhough the type is finite.
But this probably causes trouble?
In a sense, having a "relabel" method somehow means that we have a
canonical way of doing and then whenever it is not that one, it means that
it was relabeled.
Does that make sense?
--
Ticket URL: <http://trac.sagemath.org/ticket/17798#comment:77>
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