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