proposition: Lemma nth_error_Some_short {A} (n : nat) (x : A) (ls : list A) : nth_error ls n = Some x -> n < List.length ls.
proof: Proof. destruct (le_lt_dec (List.length ls) n) as [H|H]; intro H'; trivial. apply nth_error_None_long in H; congruence. 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