#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-6.10
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 nthiery):
For whatever it's worth, the strategy I followed in the root system
code was to never make any assumption on the indexing set `I`.
For Cartan matrices, the situation is similar with that of matrices of
module morphisms. Ideally they would be indexed by I; however we don't
really have yet a good matrix class supporting arbitrary indexing (or
do we? Panda's DataFrame class [1] could be an interesting starting
point!). That's in particular why I avoided using the Cartan matrix as
much as possible in computations, preferring instead the Dynkin
diagram.
Until we have a class for matrices with arbitrary indexing, I believe
we should stick to what has been done so far: index the matrix by
`0,...,|I|-1` with row/column i corresponding to the i-th element of
the indexing set `I` (following Python's convention: i=0 gives the
first element).
Cheers,
Nicolas
[1] http://www.gregreda.com/2013/10/26/working-with-pandas-dataframes/
--
Ticket URL: <http://trac.sagemath.org/ticket/17798#comment:79>
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