[commit: packages/random] master: Support base < 4.6 / GHC 7.4. (e6a0a92)

[git at git.haskell.org]

Repository : ssh://git@git.haskell.org/random

On branch  : master
Link       : http://git.haskell.org/packages/random.git/commitdiff/e6a0a92594d4c90cebc5806febd01d1c5ab23b18

>---------------------------------------------------------------

commit e6a0a92594d4c90cebc5806febd01d1c5ab23b18
Author: Mikhail Glushenkov <mikhail.glushenkov at gmail.com>
Date:   Sat Aug 23 20:55:31 2014 +0200

    Support base < 4.6 / GHC 7.4.
    
    Fixes #10.


>---------------------------------------------------------------

e6a0a92594d4c90cebc5806febd01d1c5ab23b18
 System/Random.hs | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/System/Random.hs b/System/Random.hs
index 97e98a5..4efcad6 100644
--- a/System/Random.hs
+++ b/System/Random.hs
@@ -93,7 +93,11 @@ import Data.Ratio       ( numerator, denominator )
 #endif
 import Data.Char	( isSpace, chr, ord )
 import System.IO.Unsafe ( unsafePerformIO )
-import Data.IORef
+import Data.IORef       ( IORef, atomicModifyIORef, newIORef, readIORef
+                        , writeIORef )
+#if MIN_VERSION_base (4,6,0)
+import Data.IORef       ( atomicModifyIORef' )
+#endif
 import Numeric		( readDec )
 
 #ifdef __GLASGOW_HASKELL__
@@ -105,6 +109,15 @@ build :: ((a -> [a] -> [a]) -> [a] -> [a]) -> [a]
 build g = g (:) []
 #endif
 
+#if !MIN_VERSION_base (4,6,0)
+atomicModifyIORef' :: IORef a -> (a -> (a,b)) -> IO b
+atomicModifyIORef' ref f = do
+    b <- atomicModifyIORef ref
+            (\x -> let (a, b) = f x
+                    in (a, a `seq` b))
+    b `seq` return b
+#endif
+
 -- The standard nhc98 implementation of Time.ClockTime does not match
 -- the extended one expected in this module, so we lash-up a quick
 -- replacement here.