#15456: fix bug in has_right/left_descents in Weyl group code
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Reporter: | Owner:
zabrocki | Status: needs_review
Type: | Milestone: sage-6.2
defect | Resolution:
Priority: major | Merged in:
Component: | Reviewers:
combinatorics | Work issues:
Keywords: | Commit:
coxeter | c1deaa5708d0f9e08e02d24c8cb5a0a39328453b
Authors: | Stopgaps:
Frédéric Chapoton |
Report Upstream: N/A |
Branch: |
u/chapoton/15456 |
Dependencies: |
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Comment (by zabrocki):
I am comfortable with accepting Frédéric's changes. From Nicolas'
comments I think that the original implementation meant to have
`has_descent` should call either `has_left` or `has_right` and at least
one of those needs to be implemented.
I checked that at least the `_test_has_descent` will fail when one of
these is not implemented by going into a Coxeter group implementation,
deleting the `has_right_descent` method, and then checking that
`G._test_has_descent()` raises an error. The problem is that all tests
will pass in the implementation of a Coxeter group unless the
`_test_has_descent` method is called (which was probably always the case
and the source of the original problem). Is there a way of ensuring that
a test of the left and right functions will be made for future
implementations? We can just leave it up to the warning which is already
in the documentation.
--
Ticket URL: <http://trac.sagemath.org/ticket/15456#comment:25>
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