Subset_s _an_element_

[trevorkarn]

Currently the Subset_s.an_element() method returns a different result from the Subset_s._an_element_() method. The proposed fix is to move the current implementation of an_element to _an_element_ and let the parent framework take care of the rest.

sage: from sage.combinat.subset import Subsets_s
sage: Subsets_s([1,2,3])._an_element_()
{}
sage: Subsets_s([1,2,3]).an_element()
{1, 2}

CC: @tscrim

Component: combinatorics

Keywords: gsoc2022 subsets elements

Author: Trevor K. Karn

Branch/Commit: 922c40a

Reviewer: Travis Scrimshaw

Issue created by migration from https://trac.sagemath.org/ticket/33990

[trevorkarn]

New commits:

922c40a

Change an_element to _an_element_

[trevorkarn]

Commit: 922c40a

[trevorkarn]

Branch: u/tkarn/33990-an_element

[tscrim]

Reviewer: Travis Scrimshaw

[tscrim]

comment:4

Strictly speaking, this is not a bug: we provide a default implementation of an_element() that caches the result of _an_element_() (which has its own generic implementation). However, we have no requirement that they both need to be implemented non-generically and return the same result. However, I do find that by using the caching mechanism this becomes an improvement. Once the patchbot comes around and is green, then this is a positive review.

[trevorkarn]

comment:5

It looks like a plugin failed, but I am not sure how to read the message. Do you have any advice?

[tscrim]

comment:6

That one can be ignored.

[vbraun]

Changed branch from u/tkarn/33990-an_element to 922c40a