diff options
Diffstat (limited to 'libraries/base/GHC/IO.hs')
| -rw-r--r-- | libraries/base/GHC/IO.hs | 20 |
1 files changed, 11 insertions, 9 deletions
diff --git a/libraries/base/GHC/IO.hs b/libraries/base/GHC/IO.hs index 118ebeaeed..6b83cca0d1 100644 --- a/libraries/base/GHC/IO.hs +++ b/libraries/base/GHC/IO.hs @@ -53,8 +53,8 @@ import {-# SOURCE #-} GHC.IO.Exception ( userError, IOError ) -- The IO Monad {- -The IO Monad is just an instance of the ST monad, where the state is -the real world. We use the exception mechanism (in GHC.Exception) to +The IO Monad is just an instance of the ST monad, where the state thread +is the real world. We use the exception mechanism (in GHC.Exception) to implement IO exceptions. NOTE: The IO representation is deeply wired in to various parts of the @@ -84,7 +84,7 @@ failIO s = IO (raiseIO# (toException (userError s))) -- --------------------------------------------------------------------------- -- Coercions between IO and ST --- | Embed a strict state transformer in an 'IO' +-- | Embed a strict state thread in an 'IO' -- action. The 'RealWorld' parameter indicates that the internal state -- used by the 'ST' computation is a special one supplied by the 'IO' -- monad, and thus distinct from those used by invocations of 'runST'. @@ -92,20 +92,20 @@ stToIO :: ST RealWorld a -> IO a stToIO (ST m) = IO m -- | Convert an 'IO' action into an 'ST' action. The type of the result --- is constrained to use a 'RealWorld' state, and therefore the result cannot --- be passed to 'runST'. +-- is constrained to use a 'RealWorld' state thread, and therefore the +-- result cannot be passed to 'runST'. ioToST :: IO a -> ST RealWorld a ioToST (IO m) = (ST m) -- | Convert an 'IO' action to an 'ST' action. -- This relies on 'IO' and 'ST' having the same representation modulo the --- constraint on the type of the state. +-- constraint on the state thread type parameter. unsafeIOToST :: IO a -> ST s a unsafeIOToST (IO io) = ST $ \ s -> (unsafeCoerce# io) s -- | Convert an 'ST' action to an 'IO' action. -- This relies on 'IO' and 'ST' having the same representation modulo the --- constraint on the type of the state. +-- constraint on the state thread type parameter. -- -- For an example demonstrating why this is unsafe, see -- https://mail.haskell.org/pipermail/haskell-cafe/2009-April/060719.html @@ -279,7 +279,9 @@ data MaskingState -- ^ the state during 'mask': asynchronous exceptions are masked, but blocking operations may still be interrupted | MaskedUninterruptible -- ^ the state during 'uninterruptibleMask': asynchronous exceptions are masked, and blocking operations may not be interrupted - deriving (Eq,Show) + deriving ( Eq -- ^ @since 4.3.0.0 + , Show -- ^ @since 4.3.0.0 + ) -- | Returns the 'MaskingState' for the current thread. getMaskingState :: IO MaskingState @@ -334,7 +336,7 @@ onException io what = io `catchException` \e -> do _ <- what -- 'MaskedInterruptible' state, -- use @mask_ $ forkIO ...@. This is particularly useful if you need -- to establish an exception handler in the forked thread before any --- asynchronous exceptions are received. To create a a new thread in +-- asynchronous exceptions are received. To create a new thread in -- an unmasked state use 'Control.Concurrent.forkIOWithUnmask'. -- mask :: ((forall a. IO a -> IO a) -> IO b) -> IO b |