Section ForallNorm.
Variable T : Type.
Variable P : T -> Prop.
(* use: rewrite ? Forall_norm *)
Definition Forall_norm := (@Forall_appP, @Forall_singletonP, @Forall_consP, @Forall_nilP).
End ForallNorm.
(* nth_error facts *)

Lemma nth_error_map {X Y: Type} {f: X -> Y} {l: list X} {n: nat} :
nth_error (map f l) n = omap f (nth_error l n).