[project @ 2005-10-22 00:28:21 by ross]

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

diff --git a/Data/Map.hs b/Data/Map.hs
index f916606..37a9695 100644 (file)
--- a/Data/Map.hs
+++ b/Data/Map.hs
@@ -28,7 +28,7 @@
 
 module Data.Map  ( 
             -- * Map type
-              Map          -- instance Eq,Show
+              Map          -- instance Eq,Show,Read
 
             -- * Operators
             , (!), (\\)
@@ -161,6 +161,7 @@ import List(nub,sort)
 -}
 
 #if __GLASGOW_HASKELL__
+import Text.Read
 import Data.Generics.Basics
 import Data.Generics.Instances
 #endif
@@ -1305,10 +1306,36 @@ instance Functor (Map k) where
   fmap f m  = map f m
 
 {--------------------------------------------------------------------
+  Read
+--------------------------------------------------------------------}
+instance (Ord k, Read k, Read e) => Read (Map k 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
+
+-- parses a pair of things with the syntax a:=b
+readPair :: (Read a, Read b) => ReadS (a,b)
+readPair s = do (a, ct1)    <- reads s
+                (":=", ct2) <- lex ct1
+                (b, ct3)    <- reads ct2
+                return ((a,b), ct3)
+
+{--------------------------------------------------------------------
   Show
 --------------------------------------------------------------------}
 instance (Show k, Show a) => Show (Map k a) where
-  showsPrec d m  = showMap (toAscList m)
+  showsPrec d m  = showParen (d > 10) $
+    showString "fromList " . shows (toList m)
 
 showMap :: (Show k,Show a) => [(k,a)] -> ShowS
 showMap []     
@@ -1317,9 +1344,9 @@ showMap (x:xs)
   = showChar '{' . showElem x . showTail xs
   where
     showTail []     = showChar '}'
-    showTail (x:xs) = showChar ',' . showElem x . showTail xs
+    showTail (x:xs) = showString ", " . showElem x . showTail xs
     
-    showElem (k,x)  = shows k . showString ":=" . shows x
+    showElem (k,x)  = shows k . showString " := " . shows x
   
 
 -- | /O(n)/. Show the tree that implements the map. The tree is shown