#20555: descents for Permutations : cleanup
-------------------------+-------------------------------------------------
Reporter: | Owner:
chapoton | Status: needs_review
Type: | Milestone: sage-7.2
enhancement | Resolution:
Priority: major | Merged in:
Component: | Reviewers: Travis Scrimshaw, Christian Stump
combinatorics | Work issues:
Keywords: | Commit:
permutation | 8dc44205ed34a559df49aa24ddd14facf47a7b0e
Authors: | Stopgaps:
Frédéric Chapoton |
Report Upstream: N/A |
Branch: |
u/chapoton/20555 |
Dependencies: |
-------------------------+-------------------------------------------------
Comment (by tscrim):
Replying to [comment:28 stumpc5]:
> Replying to [comment:26 tscrim]:
> I would consider {{{p[0]}}} an implementation detail (as this might mean
something in one-line notation, or the first cycle in cycle decomposition,
or whatever else, depending on the implementation of permutations) and not
a mathematically well-defined operation. In my eyes, the mathematical
operation is
> {{{
> sage: p(1)
> 5
> }}}
> which matches Frédéric's indexing.
If you think of the permutation as an automorphism of [n], yes, but if you
think of it as an ordering of [n] written as (p,,0,,, p,,1,,, ...,
p,,n-1,,), then `p[i]` corresponds to p,,i,,. So it is a little more than
an implementation detail. Moreover, this perspective makes the descent set
independent of the index set and/or the objects we are permuting.
Also, what is both of your opinions on removing the `from_zero` option or
just changing the default?
@chapoton Thanks for the changes.
--
Ticket URL: <http://trac.sagemath.org/ticket/20555#comment:29>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
--
You received this message because you are subscribed to the Google Groups
"sage-trac" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to [email protected].
To post to this group, send email to [email protected].
Visit this group at https://groups.google.com/group/sage-trac.
For more options, visit https://groups.google.com/d/optout.
