[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 99ba4a1..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
@@ -123,6 +125,7 @@ import qualified List
 -}
 
 #if __GLASGOW_HASKELL__
+import Text.Read
 import Data.Generics.Basics
 import Data.Generics.Instances
 #endif
@@ -145,6 +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__
 
 {--------------------------------------------------------------------
@@ -512,7 +524,8 @@ instance Ord a => Ord (Set a) where
   Show
 --------------------------------------------------------------------}
 instance Show a => Show (Set a) where
-  showsPrec d s  = showSet (toAscList s)
+  showsPrec p xs = showParen (p > 10) $
+    showString "fromList " . shows (toList xs)
 
 showSet :: (Show a) => [a] -> ShowS
 showSet []     
@@ -527,15 +540,20 @@ showSet (x:xs)
   Read
 --------------------------------------------------------------------}
 instance (Read a, Ord a) => Read (Set a) where
-  readsPrec i r = [ (fromList xs, t) | ("{",s) <- lex r,  (xs,t) <- readl s ]
-      where readl s  = [([],t)   | ("}",t) <- lex s] ++
-                       [(x:xs,u) | (x,t)   <- readsPrec i s
-                                 , (xs,u)  <- readl' t]
-            readl' s = [([],t)   | ("}",t) <- lex s] ++
-                       [(x:xs,v) | (",",t) <- lex s
-                                 , (x,u)   <- readsPrec i t
-                                 , (xs,v)  <- readl' u]
-    
+#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/Data
 --------------------------------------------------------------------}