--- This relies on IO and ST having the same representation modulo the
--- constraint on the type of the state
---
-unsafeIOToST :: IO a -> ST s a
-unsafeIOToST (IO io) = ST $ \ s -> (unsafeCoerce# io) s
+#ifdef __HUGS__
+import Data.Typeable
+import Hugs.ST
+import qualified Hugs.LazyST as LazyST
+
+INSTANCE_TYPEABLE2(ST,sTTc,"ST")
+INSTANCE_TYPEABLE0(RealWorld,realWorldTc,"RealWorld")
+
+fixST :: (a -> ST s a) -> ST s a
+fixST f = LazyST.lazyToStrictST (LazyST.fixST (LazyST.strictToLazyST . f))
+
+unsafeInterleaveST :: ST s a -> ST s a
+unsafeInterleaveST =
+ LazyST.lazyToStrictST . LazyST.unsafeInterleaveST . LazyST.strictToLazyST
+#endif
+
+#ifdef __GLASGOW_HASKELL__
+import GHC.ST ( ST, runST, fixST, unsafeInterleaveST )
+import GHC.Base ( RealWorld )
+import GHC.IOBase ( stToIO, unsafeIOToST )