proposition: Lemma map_app : map f (E ++ F) = map f E ++ map f F.
proof: Proof. clear. unfold map. rewrite List.map_app. reflexivity. Qed.
imports: Coq.FSets.FSets Coq.Lists.List Coq.Logic.Decidable Coq.Strings.String String Metalib.CoqFSetDecide Metalib.CoqListFacts Metalib.LibTactics Metalib.CoqFSetInterface Coq.Classes.Equivalence Coq.Classes.EquivDec Metalib.CoqEqDec