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Polyhedron.restricted_automorphism_group(): allow returning an actual affine group #21228

Open mkoeppe opened 8 years ago

mkoeppe commented 8 years ago

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.

CC: @jdemeyer @vbraun

Component: geometry

Issue created by migration from https://trac.sagemath.org/ticket/21228

jdemeyer commented 8 years ago

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.

jdemeyer commented 8 years ago
comment:2

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).

mkoeppe commented 8 years ago
comment:3

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).

jdemeyer commented 8 years ago
comment:4

Shouldn't we just close this ticket for now?

mkoeppe commented 8 years ago
comment:5

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