-{-# OPTIONS_GHC -fno-implicit-prelude -funbox-strict-fields #-}
+{-# OPTIONS_GHC -fno-warn-orphans #-}
+{-# OPTIONS_GHC -XNoImplicitPrelude -funbox-strict-fields -XBangPatterns #-}
{-# OPTIONS_HADDOCK hide #-}
-----------------------------------------------------------------------------
-- |
-- #hide
module GHC.IO (
- IO(..), unIO, failIO, liftIO, bindIO, thenIO, returnIO,
+ IO(..), unIO, failIO, liftIO,
unsafePerformIO, unsafeInterleaveIO,
unsafeDupablePerformIO, unsafeDupableInterleaveIO,
noDuplicate,
--SDM
-}
-{-|
-A value of type @'IO' a@ is a computation which, when performed,
-does some I\/O before returning a value of type @a@.
-
-There is really only one way to \"perform\" an I\/O action: bind it to
-@Main.main@ in your program. When your program is run, the I\/O will
-be performed. It isn't possible to perform I\/O from an arbitrary
-function, unless that function is itself in the 'IO' monad and called
-at some point, directly or indirectly, from @Main.main@.
-
-'IO' is a monad, so 'IO' actions can be combined using either the do-notation
-or the '>>' and '>>=' operations from the 'Monad' class.
--}
-newtype IO a = IO (State# RealWorld -> (# State# RealWorld, a #))
-
-unIO :: IO a -> (State# RealWorld -> (# State# RealWorld, a #))
-unIO (IO a) = a
-
-instance Functor IO where
- fmap f x = x >>= (return . f)
-
-instance Monad IO where
- {-# INLINE return #-}
- {-# INLINE (>>) #-}
- {-# INLINE (>>=) #-}
- m >> k = m >>= \ _ -> k
- return x = returnIO x
-
- m >>= k = bindIO m k
- fail s = failIO s
-
liftIO :: IO a -> State# RealWorld -> STret RealWorld a
liftIO (IO m) = \s -> case m s of (# s', r #) -> STret s' r
-bindIO :: IO a -> (a -> IO b) -> IO b
-bindIO (IO m) k = IO ( \ s ->
- case m s of
- (# new_s, a #) -> unIO (k a) new_s
- )
-
-thenIO :: IO a -> IO b -> IO b
-thenIO (IO m) k = IO ( \ s ->
- case m s of
- (# new_s, _ #) -> unIO k new_s
- )
-
-returnIO :: a -> IO a
-returnIO x = IO (\ s -> (# s, x #))
-
failIO :: String -> IO a
failIO s = IO (raiseIO# (toException (userError s)))
(# s', i #) -> (# s', i /=# 0# #)
onException :: IO a -> IO b -> IO a
-onException io what = io `catchException` \e -> do what
+onException io what = io `catchException` \e -> do _ <- what
throw (e :: SomeException)
finally :: IO a -- ^ computation to run first
a `finally` sequel =
block (do
r <- unblock a `onException` sequel
- sequel
+ _ <- sequel
return r
)
-- > evaluate x = (return $! x) >>= return
--
evaluate :: a -> IO a
-evaluate a = IO $ \s -> case a `seq` () of () -> (# s, a #)
- -- NB. can't write
- -- a `seq` (# s, a #)
- -- because we can't have an unboxed tuple as a function argument
+evaluate a = IO $ \s -> let !va = a in (# s, va #) -- NB. see #2273