proposition: Lemma erase_app: forall h1 h2, erase (h1 ++ h2) = (erase h1) ++ (erase h2).
proof: Proof. intros. unfold erase. apply map_app. Qed.
imports: Coq(FunctionalExtensionality Arith Lia) Coq(Arith.Peano_dec Arith.Compare_dec) Coq(Relations.Relation_Operators) Coq(List) Chapar(Predefs)