proposition: Lemma NoDup_filter: forall A f (l: list A), NoDup l -> NoDup (filter f l).
proof: Proof. intros. induction l. - simpl; constructor. - inversion H; subst. simpl; destruct (f a) eqn:?; [constructor |]; auto. rewrite filter_In. tauto. 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