+
+INSTANCE_TYPEABLE1(Bag,bagTc,"Bag")
+
+instance Data a => Data (Bag a) where
+ gfoldl k z b = z listToBag `k` bagToList b -- traverse abstract type abstractly
+ toConstr _ = abstractConstr $ "Bag("++show (typeOf (undefined::a))++")"
+ gunfold _ _ = error "gunfold"
+ dataTypeOf _ = mkNoRepType "Bag"