#19737: SetPartition.to_permutation().cycle_tuples() is not the identity
-------------------------------------+-------------------------------------
Reporter: mantepse | Owner:
Type: defect | Status: needs_review
Priority: major | Milestone: sage-7.0
Component: combinatorics | Resolution:
Keywords: set partitions, | Merged in:
permutations | Reviewers:
Authors: Martin Rubey | Work issues:
Report Upstream: N/A | Commit:
Branch: | 26169d76d77d69d32ef5b7dc75d7f5faad8ee909
u/mantepse/setpartition_to_permutation___cycle_tuples___is_not_the_identity|
Stopgaps:
Dependencies: |
-------------------------------------+-------------------------------------
Comment (by ncohen):
> Oh, I missed that, I thought that Permutation would handle bijections,
not just Permutations of `{1,...,n}`. That's really strange, I must say.
>
> Hm, now I'm not sure what should be done. I guess, the only reasonable
thing then is to fail when the ground set is not of this form. Well, that
might make sense anyway.
On the sage-devel thread I opened (se [comment:6]) I proposed to rename
the class (or to create a new one) which checks from the start that its
ground set is 1...n. This way, one could write methods like
`to_permutation` without having to check it manually, each time.
There is a usage from a `SetPartition` class with arbitrary ground set (I
do have examples in mind) and usage for a specific `IntegerSetPartition`
class restricted to those 1...n integers, which is the only case many seem
to be interested in.
Mixing the two, as it is done in this class, is a bad idea.
Nathann
--
Ticket URL: <http://trac.sagemath.org/ticket/19737#comment:15>
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.
