[project @ 2005-10-25 09:29:16 by ross]

[haskell-directory.git] / Data / IntSet.hs

diff --git a/Data/IntSet.hs b/Data/IntSet.hs
index 6220827..a47244f 100644 (file)
--- a/Data/IntSet.hs
+++ b/Data/IntSet.hs
@@ -94,6 +94,7 @@ import Data.Bits
 import Data.Int
 
 import qualified Data.List as List
+import Data.Monoid (Monoid(..))
 import Data.Typeable
 
 {-
@@ -159,6 +160,11 @@ data IntSet = Nil
 type Prefix = Int
 type Mask   = Int
 
+instance Monoid IntSet where
+    mempty  = empty
+    mappend = union
+    mconcat = unions
+
 #if __GLASGOW_HASKELL__
 
 {--------------------------------------------------------------------