[use IsEmpty class
John Meacham <john@repetae.net>**20060409080418] hunk ./E/Subst.hs 173
-typeSubst' termSub typeSub e | S.null termSub && S.null typeSub = e
+typeSubst' termSub typeSub e | isEmpty termSub && isEmpty typeSub = e
hunk ./E/Subst.hs 192
-typeSubst termSubst typeSubst e | S.null termSubst && S.null typeSubst = e
+typeSubst termSubst typeSubst e | isEmpty termSubst && isEmpty typeSubst = e
hunk ./Name/Id.hs 36
-    deriving(Typeable,Monoid,HasSize,SetLike,BuildSet Id,ModifySet Id)
+    deriving(Typeable,Monoid,HasSize,SetLike,BuildSet Id,ModifySet Id,IsEmpty,Eq,Ord)
hunk ./Name/Id.hs 49
-    deriving(Typeable,Monoid,HasSize,SetLike,BuildSet (Id,a),MapLike Id a,Functor,FunctorM,Show)
+    deriving(Typeable,Monoid,HasSize,SetLike,BuildSet (Id,a),MapLike Id a,Functor,FunctorM,Show,IsEmpty,Eq,Ord)