[project @ 2005-11-29 14:31:59 by ross]

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

diff --git a/Data/Set.hs b/Data/Set.hs
index 2029faa..fe3b0b4 100644 (file)
--- a/Data/Set.hs
+++ b/Data/Set.hs
@@ -113,7 +113,9 @@ module Data.Set  (
 
 import Prelude hiding (filter,foldr,null,map)
 import qualified Data.List as List
+import Data.Monoid (Monoid(..))
 import Data.Typeable
+import Data.Foldable (Foldable(foldMap))
 
 {-
 -- just for testing
@@ -146,6 +148,15 @@ data Set a    = Tip
 
 type Size     = Int
 
+instance Ord a => Monoid (Set a) where
+    mempty  = empty
+    mappend = union
+    mconcat = unions
+
+instance Foldable Set where
+    foldMap f Tip = mempty
+    foldMap f (Bin _s k l r) = foldMap f l `mappend` f k `mappend` foldMap f r
+
 #if __GLASGOW_HASKELL__
 
 {--------------------------------------------------------------------