From 4f72c9cd9f46ff4f42ba1c48f7847190c41542c4 Mon Sep 17 00:00:00 2001
From: Simon Marlow <simonmar@microsoft.com>
Date: Wed, 15 Mar 2006 16:02:32 +0000
Subject: [PATCH] Add unsafeSTToIO :: ST s a -> IO a Implementation for Hugs
 is missing, but should be easy.  We need this for the
 forthcoming nested data parallelism implementation.

---
 Control/Monad/ST.hs |    5 +++--
 GHC/IOBase.lhs      |    5 ++++-
 2 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/Control/Monad/ST.hs b/Control/Monad/ST.hs
index 0a40720..d736eb6 100644
--- a/Control/Monad/ST.hs
+++ b/Control/Monad/ST.hs
@@ -27,7 +27,8 @@ module Control.Monad.ST
 
 	-- * Unsafe operations
 	unsafeInterleaveST,  	-- :: ST s a -> ST s a
-	unsafeIOToST		-- :: IO a -> ST s a
+	unsafeIOToST,		-- :: IO a -> ST s a
+	unsafeSTToIO		-- :: ST s a -> IO a
       ) where
 
 import Prelude
@@ -55,7 +56,7 @@ unsafeInterleaveST =
 #ifdef __GLASGOW_HASKELL__
 import GHC.ST		( ST, runST, fixST, unsafeInterleaveST )
 import GHC.Base		( RealWorld )
-import GHC.IOBase 	( stToIO, unsafeIOToST )
+import GHC.IOBase 	( stToIO, unsafeIOToST, unsafeSTToIO )
 #endif
 
 instance MonadFix (ST s) where
diff --git a/GHC/IOBase.lhs b/GHC/IOBase.lhs
index 112268e..78a334d 100644
--- a/GHC/IOBase.lhs
+++ b/GHC/IOBase.lhs
@@ -20,7 +20,7 @@ module GHC.IOBase(
     unsafePerformIO, unsafeInterleaveIO,
   
 	-- To and from from ST
-    stToIO, ioToST, unsafeIOToST,
+    stToIO, ioToST, unsafeIOToST, unsafeSTToIO,
 
 	-- References
     IORef(..), newIORef, readIORef, writeIORef, 
@@ -155,6 +155,9 @@ ioToST (IO m) = (ST m)
 unsafeIOToST        :: IO a -> ST s a
 unsafeIOToST (IO io) = ST $ \ s -> (unsafeCoerce# io) s
 
+unsafeSTToIO :: ST s a -> IO a
+unsafeSTToIO (ST m) = IO (unsafeCoerce# m)
+
 -- ---------------------------------------------------------------------------
 -- Unsafe IO operations
 
-- 
1.7.10.4