X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=GHC%2FIO.hs;h=ad98a5ebf5460392c3e8523d65cffe74388a6f50;hb=7e0984fb4e3bf25e6050ab6fecc98211ad9f3ecd;hp=7295a2cd3e7b38563ffecdab606ee82cda0fe271;hpb=333e764afeb1c08b239caf9510e5e18a6c81ae31;p=ghc-base.git

diff --git a/GHC/IO.hs b/GHC/IO.hs
index 7295a2c..ad98a5e 100644
--- a/GHC/IO.hs
+++ b/GHC/IO.hs
@@ -36,7 +36,7 @@ module GHC.IO (
     mask, mask_, uninterruptibleMask, uninterruptibleMask_, 
     MaskingState(..), getMaskingState,
     block, unblock, blocked, unsafeUnmask,
-    onException, finally, evaluate
+    onException, bracket, finally, evaluate
   ) where
 
 import GHC.Base
@@ -432,6 +432,18 @@ uninterruptibleMask io = do
     MaskedInterruptible   -> blockUninterruptible $ io block
     MaskedUninterruptible -> io id
 
+bracket
+        :: IO a         -- ^ computation to run first (\"acquire resource\")
+        -> (a -> IO b)  -- ^ computation to run last (\"release resource\")
+        -> (a -> IO c)  -- ^ computation to run in-between
+        -> IO c         -- returns the value from the in-between computation
+bracket before after thing =
+  mask $ \restore -> do
+    a <- before
+    r <- restore (thing a) `onException` after a
+    _ <- after a
+    return r
+
 finally :: IO a         -- ^ computation to run first
         -> IO b         -- ^ computation to run afterward (even if an exception
                         -- was raised)