fact: Fixpoint appn {A} (f : A -> A) (n : nat) : A -> A := fun x => match n with | 0%nat => x | S n' => f (appn f n' x) end.
imports: Coq.Classes.Morphisms mathcomp.ssreflect.ssreflect mathcomp(ssrbool ssrnat) Sets Tactics Recdef List ZArith ZArith.Znat Arith Producer Generators Enumerators