proposition: Lemma foot_last: forall A (L : list A) (a : A), foot (L +:: a) = Some a.
proof: Proof. induction L; auto; intros; destruct L; auto; rewrite <- (IHL a0); simpl; destruct (L +:: a0); simpl; 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