proposition: Lemma gactR : {in D, forall a, {in R &, {morph to^~ a : x y / [~ x, y]}}}.
proof: Proof. by move=> a Da /= x Rx y Ry; rewrite -!actmE // morphR. Qed.
imports: mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat div seq) mathcomp(fintype bigop finset fingroup morphism perm) mathcomp(automorphism quotient)