proposition: Lemma hd_error_In: forall {A:Type} (l: list A) a, hd_error l = Some a -> In a l.
proof: Proof. intros. destruct l; simpl in H; inversion H. left; auto. Qed.
imports: Coq.Lists.List Coq.micromega.Lia Coq.Sorting.Permutation Coq.ZArith.ZArith_base Coq.ZArith.Zcomplements Coq.Logic.FunctionalExtensionality CertiGraph.lib.Coqlib CertiGraph.lib.EquivDec_ext VST.zlist.sublist VST.zlist.list_solver