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

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

diff --git a/Data/IntMap.hs b/Data/IntMap.hs
index ff9d30b..0dd6bf0 100644 (file)
--- a/Data/IntMap.hs
+++ b/Data/IntMap.hs
@@ -136,6 +136,7 @@ import Prelude hiding (lookup,map,filter,foldr,foldl,null)
 import Data.Bits 
 import Data.Int
 import qualified Data.IntSet as IntSet
+import Data.Monoid (Monoid(..))
 import Data.Typeable
 
 {-
@@ -147,6 +148,7 @@ import qualified List
 -}  
 
 #if __GLASGOW_HASKELL__
+import Text.Read
 import Data.Generics.Basics
 import Data.Generics.Instances
 #endif
@@ -209,6 +211,11 @@ type Prefix = Int
 type Mask   = Int
 type Key    = Int
 
+instance Ord a => Monoid (IntMap a) where
+    mempty  = empty
+    mappend = union
+    mconcat = unions
+
 #if __GLASGOW_HASKELL__
 
 {--------------------------------------------------------------------
@@ -978,8 +985,8 @@ instance Functor IntMap where
 --------------------------------------------------------------------}
 
 instance Show a => Show (IntMap a) where
-  showsPrec d t   = showMap (toList t)
-
+  showsPrec d m   = showParen (d > 10) $
+    showString "fromList " . shows (toList m)
 
 showMap :: (Show a) => [(Key,a)] -> ShowS
 showMap []     
@@ -991,7 +998,25 @@ showMap (x:xs)
     showTail (x:xs) = showChar ',' . showElem x . showTail xs
     
     showElem (k,x)  = shows k . showString ":=" . shows x
-  
+
+{--------------------------------------------------------------------
+  Read
+--------------------------------------------------------------------}
+instance (Read e) => Read (IntMap e) where
+#ifdef __GLASGOW_HASKELL__
+  readPrec = parens $ prec 10 $ do
+    Ident "fromList" <- lexP
+    xs <- readPrec
+    return (fromList xs)
+
+  readListPrec = readListPrecDefault
+#else
+  readsPrec p = readParen (p > 10) $ \ r -> do
+    ("fromList",s) <- lex r
+    (xs,t) <- reads s
+    return (fromList xs,t)
+#endif
+
 {--------------------------------------------------------------------
   Typeable
 --------------------------------------------------------------------}