module Graphics.Rendering.OpenGL.GL.IOState (
IOState(..), getIOState, peekIOState, evalIOState, nTimes
) where
import Foreign.Ptr ( Ptr, plusPtr )
import Foreign.Storable ( Storable(sizeOf,peek) )
newtype IOState s a = IOState { runIOState :: Ptr s -> IO (a, Ptr s) }
instance Functor (IOState s) where
fmap f m = IOState $ \s -> do (x, s') <- runIOState m s ; return (f x, s')
instance Monad (IOState s) where
return a = IOState $ \s -> return (a, s)
m >>= k = IOState $ \s -> do (a, s') <- runIOState m s ; runIOState (k a) s'
fail str = IOState $ \_ -> fail str
getIOState :: IOState s (Ptr s)
getIOState = IOState $ \s -> return (s, s)
putIOState :: Ptr s -> IOState s ()
putIOState s = IOState $ \_ -> return ((), s)
peekIOState :: Storable a => IOState a a
peekIOState = do
ptr <- getIOState
x <- liftIOState $ peek ptr
putIOState (ptr `plusPtr` sizeOf x)
return x
liftIOState :: IO a -> IOState s a
liftIOState m = IOState $ \s -> do a <- m ; return (a, s)
evalIOState :: IOState s a -> Ptr s -> IO a
evalIOState m s = do (a, _) <- runIOState m s ; return a
nTimes :: Integral a => a -> IOState b c -> IOState b [c]
nTimes n = sequence . replicate (fromIntegral n)