proposition: Lemma hd_error_app {A} : forall (a : A) (l l' : list A), hd_error l = Some a -> hd_error (l ++ l') = Some a.
proof: Proof. destruct l; simpl; intros; first [ discriminate | eauto]. Qed.
imports: Fiat.Common.Coq__8_4__8_5__Compat Bedrock.Word Coq.ZArith.ZArith Coq.NArith.NArith Coq.Arith.Arith Coq.Numbers.Natural.Peano.NPeano Coq.Logic.Eqdep_dec Fiat.Narcissus.Common.Specs