proposition: Lemma dom_map : dom (map f1 f2 E) [=] dom E.
proof: Proof. clear. induction E as [ | a ]; simpl; try (destruct a); fsetdec. Qed.
imports: Coq.FSets.FSets Coq.Lists.List Coq.Logic.Decidable Metalib.CoqFSetDecide Metalib.CoqListFacts Metalib.LibTactics Metalib.MetatheoryAtom Metalib.LibTactics