+#if __GLASGOW_HASKELL__
+
+{--------------------------------------------------------------------
+ A Data instance
+--------------------------------------------------------------------}
+
+-- This instance preserves data abstraction at the cost of inefficiency.
+-- We omit reflection services for the sake of data abstraction.
+
+instance (Data k, Data a, Ord k) => Data (Map k a) where
+ gfoldl f z map = z fromList `f` (toList map)
+ toConstr _ = error "toConstr"
+ gunfold _ _ = error "gunfold"
+ dataTypeOf _ = mkNorepType "Data.Map.Map"
+
+#endif
+