[project @ 2005-01-19 22:33:32 by ralf]

[ghc-base.git] / Data / Set.hs

diff --git a/Data/Set.hs b/Data/Set.hs
index 8376f25..b357f96 100644 (file)
--- a/Data/Set.hs
+++ b/Data/Set.hs
@@ -123,6 +123,11 @@ import List (nub,sort)
 import qualified List
 -}
 
+#if __GLASGOW_HASKELL__
+import Data.Generics.Basics
+import Data.Generics.Instances
+#endif
+
 {--------------------------------------------------------------------
   Operators
 --------------------------------------------------------------------}
@@ -142,6 +147,23 @@ data Set a    = Tip
 type Size     = Int
 
 {--------------------------------------------------------------------
+  A Data instance  
+--------------------------------------------------------------------}
+
+#if __GLASGOW_HASKELL__
+
+-- This instance preserves data abstraction at the cost of inefficiency.
+-- We omit reflection services for the sake of data abstraction.
+
+instance (Data a, Ord a) => Data (Set a) where
+  gfoldl f z set = z fromList `f` (toList set)
+  toConstr _     = error "toConstr"
+  gunfold _ _    = error "gunfold"
+  dataTypeOf _   = mkNorepType "Data.Set.Set"
+
+#endif
+
+{--------------------------------------------------------------------
   Query
 --------------------------------------------------------------------}
 -- | /O(1)/. Is this the empty set?