For GHC, implement the Typeable.hs macros using standalone deriving

[ghc-base.git] / System / Timeout.hs

diff --git a/System/Timeout.hs b/System/Timeout.hs
index dbf9209..df33625 100644 (file)
--- a/System/Timeout.hs
+++ b/System/Timeout.hs
@@ -1,4 +1,8 @@
-{-# OPTIONS -fglasgow-exts #-}
+{-# LANGUAGE CPP #-}
+#ifdef __GLASGOW_HASKELL__
+{-# LANGUAGE DeriveDataTypeable, StandaloneDeriving #-}
+#endif
+
 -------------------------------------------------------------------------------
 -- |
 -- Module      :  System.Timeout
@@ -13,26 +17,34 @@
 --
 -------------------------------------------------------------------------------
 
-module System.Timeout ( timeout ) where
+#ifdef __GLASGOW_HASKELL__
+#include "Typeable.h"
+#endif
 
-#if __NHC__
-timeout :: Int -> IO a -> IO (Maybe a)
-timeout n f = fmap Just f
-#else
+module System.Timeout ( timeout ) where
 
-import Prelude             (IO, Ord((<)), Eq((==)), Int, (.), otherwise, fmap)
+#ifdef __GLASGOW_HASKELL__
+import Prelude             (Show(show), IO, Ord((<)), Eq((==)), Int,
+                            otherwise, fmap)
 import Data.Maybe          (Maybe(..))
-import Control.Monad       (Monad(..), guard)
+import Control.Monad       (Monad(..))
 import Control.Concurrent  (forkIO, threadDelay, myThreadId, killThread)
-import Control.Exception   (handleJust, throwDynTo, dynExceptions, bracket)
-import Data.Dynamic        (Typeable, fromDynamic)
+import Control.Exception   (Exception, handleJust, throwTo, bracket)
+import Data.Typeable
 import Data.Unique         (Unique, newUnique)
 
 -- An internal type that is thrown as a dynamic exception to
 -- interrupt the running IO computation when the timeout has
 -- expired.
 
-data Timeout = Timeout Unique deriving (Eq, Typeable)
+newtype Timeout = Timeout Unique deriving Eq
+INSTANCE_TYPEABLE0(Timeout,timeoutTc,"Timeout")
+
+instance Show Timeout where
+    show _ = "<<timeout>>"
+
+instance Exception Timeout
+#endif /* !__GLASGOW_HASKELL__ */
 
 -- |Wrap an 'IO' computation to time out and return @Nothing@ in case no result
 -- is available within @n@ microseconds (@1\/10^6@ seconds). In case a result
@@ -64,15 +76,18 @@ data Timeout = Timeout Unique deriving (Eq, Typeable)
 -- I\/O or file I\/O using this combinator.
 
 timeout :: Int -> IO a -> IO (Maybe a)
+#ifdef __GLASGOW_HASKELL__
 timeout n f
     | n <  0    = fmap Just f
     | n == 0    = return Nothing
     | otherwise = do
         pid <- myThreadId
         ex  <- fmap Timeout newUnique
-        handleJust (\e -> dynExceptions e >>= fromDynamic >>= guard . (ex ==))
+        handleJust (\e -> if e == ex then Just () else Nothing)
                    (\_ -> return Nothing)
-                   (bracket (forkIO (threadDelay n >> throwDynTo pid ex))
+                   (bracket (forkIO (threadDelay n >> throwTo pid ex))
                             (killThread)
                             (\_ -> fmap Just f))
-#endif
+#else
+timeout n f = fmap Just f
+#endif /* !__GLASGOW_HASKELL__ */