#20555: descents for Permutations : cleanup
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Reporter: | Owner:
chapoton | Status: needs_review
Type: | Milestone: sage-7.2
enhancement | Resolution:
Priority: major | Merged in:
Component: | Reviewers:
combinatorics | Work issues:
Keywords: | Commit:
permutation | e6393ab4a5bc9917a95a7e472452548eeed33ddd
Authors: | Stopgaps:
Frédéric Chapoton |
Report Upstream: N/A |
Branch: |
u/chapoton/20555 |
Dependencies: |
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Comment (by tscrim):
There is a (very) good reason for descents of permutations to be 0-based
indices: they correspond to the positions in the list, which are also
0-based, where there is a descent. This is also a perfectly valid
definition and almost certainly corresponds to the initial definition of a
descent. Personally I am for switching the descents convention, but this
is a major backwards incompatible change that is highly likely to break
personal code. Also there will not be deprecation period. Much care must
be taken here.
A possible way to introduce a deprecation would be to have an optional
argument to `descents` for being 0-based, which is `True` by default. If
this argument is `True`, then we print a deprecation warning. At the very
least, this requires a posting of sage(-combinat)-devel notifying of the
behavior change.
--
Ticket URL: <http://trac.sagemath.org/ticket/20555#comment:6>
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