[ForType "Global" Nothing,ForFunction "global"
,ForFunction "prim_readGlobal"
,ForFunction "prim_writeGlobal"
]

import System.IO.Unsafe
import qualified Data.IORef as Ref

type C_Global t0 = Prim (Ref.IORef t0)

global :: (Curry t0) => t0 -> C_GlobalSpec -> Result (C_Global t0)
global x spec = ref `seq` (\ _ -> PrimValue ref)
  where ref = unsafePerformIO (Ref.newIORef x) 

prim_readGlobal :: (Curry t0) => C_Global t0 -> Result (C_IO t0)
prim_readGlobal  = prim_readIORef

prim_writeGlobal :: (Curry t0) => C_Global t0 -> t0 -> Result (C_IO T0)
prim_writeGlobal  = prim_writeIORef

----------------------
-- preparing io ref
----------------------

type C_IORef a = Prim (Ref.IORef a)

instance Show (Ref.IORef a) where
  show _ = "IOREF"

instance Read (Ref.IORef a) where
  readsPrec = error "reading IOREF"

instance Generate (Ref.IORef a) where
  genFree    = error "free variable of type IOExts.IORef"
  maxArity _ = error "free variable of type IOExts.IORef"

newIORef :: Curry t0 => t0 -> Result (C_IO (C_IORef t0))
newIORef x = ioFunc0 (Ref.newIORef x) 

prim_readIORef :: Curry t0 => C_IORef t0 -> Result (C_IO t0)
prim_readIORef (PrimValue ref) _ = 
   C_IO (\ _ -> do 
           v <- Ref.readIORef ref 
           Prelude.return (IOVal v))

prim_writeIORef :: Curry t0 => C_IORef t0 -> t0 -> Result (C_IO T0)
prim_writeIORef (PrimValue ref) x = ioFunc0 (Ref.writeIORef ref x)