Beginner tickets and GSoC 2020

[Sagnik Dey]

I was hoping to contribute towards the Sage community in the coming summer ad thus in preparation, I was going through a few beginner tickets. I first tried #13649 but in the current code, the implementation seems to be done already as calling domain on an element works as intended. Also, codomain is not really defined for the symmetric group. 

Then, I sent a review request on the ticket #28882. I would really appreciate some feedback on whether I sent the request properly since this is my first time contributing to sage.

[Michael Orlitzky]

On 2/26/20 4:56 AM, Sagnik Dey wrote:
> I was hoping to contribute towards the Sage community in the coming
> summer ad thus in preparation, I was going through a few beginner
> tickets. I first tried #13649 but in the current code, the
> implementation seems to be done already as calling domain on an element
> works as intended. Also, codomain is not really defined for the
> symmetric group.

This is partly done but the ticket was never updated. If you think of a
permutation as a function, its codomain should be the same as its
domain, because a permutation (bijectively) rearranges the elements of
its domain. For "image" I'm not so sure though. The last proposed patch
does something I didn't expect, and defines the image of a permutation
to be the set of elements that it does not fix. I would have expected
the image to be equal to the codomain, since permutations are surjective.

If someone who works with symmetric groups can comment on what "image"
should do, adding codomain() and image() should be straightforward.