proposition: Lemma permX s x n : (s ^+ n) x = iter n s x.
proof: Proof. by elim: n => [|n /= <-]; rewrite ?perm1 // -permM expgSr. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq path) mathcomp(choice fintype tuple finfun bigop finset binomial) mathcomp(fingroup morphism)