From: Simon Marlow <marlowsd@gmail.com>
Date: Fri, 10 Oct 2008 11:38:35 +0000 (+0000)
Subject: add readTVarIO :: TVar a -> IO a
X-Git-Tag: 2009-06-25~107
X-Git-Url: http://git.megacz.com/?a=commitdiff_plain;h=6567f258a7a9e8ec0f5167f87ee6a104f83582b3;p=ghc-base.git

add readTVarIO :: TVar a -> IO a
---

diff --git a/GHC/Conc.lhs b/GHC/Conc.lhs
index b19f520..9e0969d 100644
--- a/GHC/Conc.lhs
+++ b/GHC/Conc.lhs
@@ -72,6 +72,7 @@ module GHC.Conc
         , newTVar       -- :: a -> STM (TVar a)
         , newTVarIO     -- :: a -> STM (TVar a)
         , readTVar      -- :: TVar a -> STM a
+        , readTVarIO    -- :: TVar a -> IO a
         , writeTVar     -- :: a -> TVar a -> STM ()
         , unsafeIOToSTM -- :: IO a -> STM a
 
@@ -550,6 +551,16 @@ newTVarIO val = IO $ \s1# ->
     case newTVar# val s1# of
          (# s2#, tvar# #) -> (# s2#, TVar tvar# #)
 
+-- |Return the current value stored in a TVar.
+-- This is equivalent to
+--
+-- >  readTVarIO = atomically . readTVar
+--
+-- but works much faster, because it doesn't perform a complete
+-- transaction, it just reads the current value of the 'TVar'.
+readTVarIO :: TVar a -> IO a
+readTVarIO (TVar tvar#) = IO $ \s# -> readTVarIO# tvar# s#
+
 -- |Return the current value stored in a TVar
 readTVar :: TVar a -> STM a
 readTVar (TVar tvar#) = STM $ \s# -> readTVar# tvar# s#