proposition: Lemma permJ s t x : (s ^ t) (t x) = t (s x).
proof: Proof. by rewrite !permM permK. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq path) mathcomp(choice fintype tuple finfun bigop finset binomial) mathcomp(fingroup morphism)