proposition: Lemma nth_error_In {A} (n : nat) (x : A) (ls : list A) : nth_error ls n = Some x -> List.In x ls.
proof: Proof. revert n; induction ls; intros [|n]; simpl in *; intros; try discriminate; unfold value in *. { left; congruence. } { right; eauto. } Qed.
imports: Fiat.Common.Coq__8_4__8_5__Compat Coq.ZArith.ZArith Coq.Lists.List Coq.Lists.SetoidList Coq.Bool.Bool Fiat.Common Fiat.Common.List.Operations Fiat.Common.Equality Fiat.Common.List.FlattenList Fiat.Common.LogicFacts