% -----------------------------------------------------------------------------
-% $Id: PrelConc.lhs,v 1.20 2000/07/07 11:03:58 simonmar Exp $
+% $Id: PrelConc.lhs,v 1.24 2001/05/18 16:54:05 simonmar Exp $
%
% (c) The University of Glasgow, 1994-2000
%
, newEmptyMVar -- :: IO (MVar a)
, takeMVar -- :: MVar a -> IO a
, putMVar -- :: MVar a -> a -> IO ()
- , readMVar -- :: MVar a -> IO a
- , swapMVar -- :: MVar a -> a -> IO a
, tryTakeMVar -- :: MVar a -> IO (Maybe a)
+ , tryPutMVar -- :: MVar a -> a -> IO Bool
, isEmptyMVar -- :: MVar a -> IO Bool
+ , addMVarFinalizer -- :: MVar a -> IO () -> IO ()
) where
import PrelBase
import PrelMaybe
-import PrelErr ( parError, seqError )
+import PrelErr ( parError, seqError )
import PrelIOBase ( IO(..), MVar(..) )
import PrelBase ( Int(..) )
import PrelException ( Exception(..), AsyncException(..) )
yield = IO $ \s ->
case (yield# s) of s1 -> (# s1, () #)
--- "seq" is defined a bit wierdly (see below)
+-- "seq" is defined a bit weirdly (see below)
--
-- The reason for the strange "0# -> parError" case is that
-- it fools the compiler into thinking that seq is non-strict in
case putMVar# mvar# x s# of
s2# -> (# s2#, () #)
+tryPutMVar :: MVar a -> a -> IO Bool
+tryPutMVar (MVar mvar#) x = IO $ \ s# ->
+ case tryPutMVar# mvar# x s# of
+ (# s, 0# #) -> (# s, False #)
+ (# s, _ #) -> (# s, True #)
+
newMVar :: a -> IO (MVar a)
newMVar value =
newEmptyMVar >>= \ mvar ->
putMVar mvar value >>
return mvar
-readMVar :: MVar a -> IO a
-readMVar mvar =
- takeMVar mvar >>= \ value ->
- putMVar mvar value >>
- return value
-
-swapMVar :: MVar a -> a -> IO a
-swapMVar mvar new =
- takeMVar mvar >>= \ old ->
- putMVar mvar new >>
- return old
-
-- tryTakeMVar is a non-blocking takeMVar
tryTakeMVar :: MVar a -> IO (Maybe a)
tryTakeMVar (MVar m) = IO $ \ s ->
isEmptyMVar (MVar mv#) = IO $ \ s# ->
case isEmptyMVar# mv# s# of
(# s2#, flg #) -> (# s2#, not (flg ==# 0#) #)
+
+-- Like addForeignPtrFinalizer, but for MVars
+addMVarFinalizer :: MVar a -> IO () -> IO ()
+addMVarFinalizer (MVar m) finalizer =
+ IO $ \s -> case mkWeak# m () finalizer s of { (# s1, w #) -> (# s1, () #) }
\end{code}