[project @ 2005-12-05 11:42:47 by simonmar]

Add IO versions of the STM primitives that allocate new transactional variables:

  newTVarIO :: a -> IO (TVar a)
  newTChanIO :: IO (TChan a)
  newTMVarIO :: a -> IO (TMVar a)

These can be used inside unsafePerformIO, unlike the STM versions.

diff --git a/GHC/Conc.lhs b/GHC/Conc.lhs
index 6c21cf4..d83a2c3 100644 (file)
--- a/GHC/Conc.lhs
+++ b/GHC/Conc.lhs
@@ -59,6 +59,7 @@ module GHC.Conc
         , catchSTM      -- :: STM a -> (Exception -> STM a) -> STM a
        , TVar          -- abstract
        , newTVar       -- :: a -> STM (TVar a)
+       , newTVarIO     -- :: a -> STM (TVar a)
        , readTVar      -- :: TVar a -> STM a
        , writeTVar     -- :: a -> TVar a -> STM ()
        , unsafeIOToSTM -- :: IO a -> STM a
@@ -321,6 +322,15 @@ newTVar val = STM $ \s1# ->
     case newTVar# val s1# of
         (# s2#, tvar# #) -> (# s2#, TVar tvar# #)
 
+-- |@IO@ version of 'newTVar'.  This is useful for creating top-level
+-- 'TVar's using 'System.IO.Unsafe.unsafePerformIO', because using
+-- 'atomically' inside 'System.IO.Unsafe.unsafePerformIO' isn't
+-- possible.
+newTVarIO :: a -> IO (TVar a)
+newTVarIO val = IO $ \s1# ->
+    case newTVar# val s1# of
+        (# s2#, tvar# #) -> (# s2#, TVar tvar# #)
+
 -- |Return the current value stored in a TVar
 readTVar :: TVar a -> STM a
 readTVar (TVar tvar#) = STM $ \s# -> readTVar# tvar# s#