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_seq {m l n: nat} :
n < l -> nth_error (seq m l) n = Some (m+n).