Polyhedron.restricted_automorphism_group(): allow returning an actual affine group

[Matthias Köppe]

This is a follow-up on #20259, which added the output="matrix" argument to restricted_automorphism_group. It returns a MatrixGroup.

In this ticket, I propose to add output="affine" to return an AffineGroup.

[Jeroen Demeyer]

Replying to mkoeppe:

In this ticket, I propose to add output="affine" to return an AffineGroup.

I wonder why I didn't do that in #20259. Either I didn't know about AffineGroup or it was lacking in functionality.

[Jeroen Demeyer]

Answering my own question: it seems that an AffineGroup always refers to the group of all affine transformations, not a subgroup.

So, as far as I can tell, the object you want to return doesn't exist in Sage (and it would be non-trivial work to implement it).

[Matthias Köppe]

Replying to jdemeyer:

Answering my own question: it seems that an AffineGroup always refers to the group of all affine transformations, not a subgroup.

So, as far as I can tell, the object you want to return doesn't exist in Sage (and it would be non-trivial work to implement it).

Thanks! I was already wondering why there was no method to make a subgroup (though methods subsemigroup and submonoid exist).

[Jeroen Demeyer]

Shouldn't we just close this ticket for now?

[Matthias Köppe]

I've instead created a ticket for subgroups of AffineGroup - #21275