proposition: Lemma NoDup_map_inj : forall A B (f : A -> B), (forall x y, f x = f y -> x = y) -> forall ls, NoDup ls -> NoDup (map f ls).
proof: Proof. induction 2; simpl; eauto. constructor; eauto. intro. apply in_map_iff in H2; firstorder. apply H in H2. congruence. Qed.
imports: Coq(FunctionalExtensionality Arith Lia) Coq(Arith.Peano_dec Arith.Compare_dec) Coq(Relations.Relation_Operators) Coq(List) Chapar(Predefs)