X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=Control%2FException.hs;h=3fc1139ff89f693c52b773f1ea09ea914f8dcbae;hb=9c05ec8933459aed098ed65f929f748107f5b8b8;hp=e52f674725efcb47d4cd03b323b79bff0316523a;hpb=26d2805a6e58822d246cf9601fb226b0861e7f65;p=ghc-base.git diff --git a/Control/Exception.hs b/Control/Exception.hs index e52f674..3fc1139 100644 --- a/Control/Exception.hs +++ b/Control/Exception.hs @@ -27,155 +27,155 @@ module Control.Exception ( - -- * The Exception type - Exception(..), -- instance Eq, Ord, Show, Typeable - IOException, -- instance Eq, Ord, Show, Typeable - ArithException(..), -- instance Eq, Ord, Show, Typeable - ArrayException(..), -- instance Eq, Ord, Show, Typeable - AsyncException(..), -- instance Eq, Ord, Show, Typeable - - -- * Throwing exceptions - throwIO, -- :: Exception -> IO a - throw, -- :: Exception -> a - ioError, -- :: IOError -> IO a + -- * The Exception type + Exception(..), -- instance Eq, Ord, Show, Typeable + IOException, -- instance Eq, Ord, Show, Typeable + ArithException(..), -- instance Eq, Ord, Show, Typeable + ArrayException(..), -- instance Eq, Ord, Show, Typeable + AsyncException(..), -- instance Eq, Ord, Show, Typeable + + -- * Throwing exceptions + throwIO, -- :: Exception -> IO a + throw, -- :: Exception -> a + ioError, -- :: IOError -> IO a #ifdef __GLASGOW_HASKELL__ - throwTo, -- :: ThreadId -> Exception -> a + throwTo, -- :: ThreadId -> Exception -> a #endif - -- * Catching Exceptions + -- * Catching Exceptions - -- |There are several functions for catching and examining - -- exceptions; all of them may only be used from within the - -- 'IO' monad. + -- |There are several functions for catching and examining + -- exceptions; all of them may only be used from within the + -- 'IO' monad. - -- ** The @catch@ functions - catch, -- :: IO a -> (Exception -> IO a) -> IO a - catchJust, -- :: (Exception -> Maybe b) -> IO a -> (b -> IO a) -> IO a + -- ** The @catch@ functions + catch, -- :: IO a -> (Exception -> IO a) -> IO a + catchJust, -- :: (Exception -> Maybe b) -> IO a -> (b -> IO a) -> IO a - -- ** The @handle@ functions - handle, -- :: (Exception -> IO a) -> IO a -> IO a - handleJust,-- :: (Exception -> Maybe b) -> (b -> IO a) -> IO a -> IO a + -- ** The @handle@ functions + handle, -- :: (Exception -> IO a) -> IO a -> IO a + handleJust,-- :: (Exception -> Maybe b) -> (b -> IO a) -> IO a -> IO a - -- ** The @try@ functions - try, -- :: IO a -> IO (Either Exception a) - tryJust, -- :: (Exception -> Maybe b) -> a -> IO (Either b a) + -- ** The @try@ functions + try, -- :: IO a -> IO (Either Exception a) + tryJust, -- :: (Exception -> Maybe b) -> a -> IO (Either b a) - -- ** The @evaluate@ function - evaluate, -- :: a -> IO a + -- ** The @evaluate@ function + evaluate, -- :: a -> IO a - -- ** The @mapException@ function - mapException, -- :: (Exception -> Exception) -> a -> a + -- ** The @mapException@ function + mapException, -- :: (Exception -> Exception) -> a -> a - -- ** Exception predicates - - -- $preds + -- ** Exception predicates + + -- $preds - ioErrors, -- :: Exception -> Maybe IOError - arithExceptions, -- :: Exception -> Maybe ArithException - errorCalls, -- :: Exception -> Maybe String - dynExceptions, -- :: Exception -> Maybe Dynamic - assertions, -- :: Exception -> Maybe String - asyncExceptions, -- :: Exception -> Maybe AsyncException - userErrors, -- :: Exception -> Maybe String + ioErrors, -- :: Exception -> Maybe IOError + arithExceptions, -- :: Exception -> Maybe ArithException + errorCalls, -- :: Exception -> Maybe String + dynExceptions, -- :: Exception -> Maybe Dynamic + assertions, -- :: Exception -> Maybe String + asyncExceptions, -- :: Exception -> Maybe AsyncException + userErrors, -- :: Exception -> Maybe String - -- * Dynamic exceptions + -- * Dynamic exceptions - -- $dynamic - throwDyn, -- :: Typeable ex => ex -> b + -- $dynamic + throwDyn, -- :: Typeable ex => ex -> b #ifdef __GLASGOW_HASKELL__ - throwDynTo, -- :: Typeable ex => ThreadId -> ex -> b + throwDynTo, -- :: Typeable ex => ThreadId -> ex -> b #endif - catchDyn, -- :: Typeable ex => IO a -> (ex -> IO a) -> IO a - - -- * Asynchronous Exceptions + catchDyn, -- :: Typeable ex => IO a -> (ex -> IO a) -> IO a + + -- * Asynchronous Exceptions - -- $async + -- $async - -- ** Asynchronous exception control + -- ** Asynchronous exception control - -- |The following two functions allow a thread to control delivery of - -- asynchronous exceptions during a critical region. + -- |The following two functions allow a thread to control delivery of + -- asynchronous exceptions during a critical region. block, -- :: IO a -> IO a unblock, -- :: IO a -> IO a - -- *** Applying @block@ to an exception handler + -- *** Applying @block@ to an exception handler - -- $block_handler + -- $block_handler - -- *** Interruptible operations + -- *** Interruptible operations - -- $interruptible + -- $interruptible - -- * Assertions + -- * Assertions - assert, -- :: Bool -> a -> a + assert, -- :: Bool -> a -> a - -- * Utilities + -- * Utilities - bracket, -- :: IO a -> (a -> IO b) -> (a -> IO c) -> IO () - bracket_, -- :: IO a -> IO b -> IO c -> IO () - bracketOnError, + bracket, -- :: IO a -> (a -> IO b) -> (a -> IO c) -> IO () + bracket_, -- :: IO a -> IO b -> IO c -> IO () + bracketOnError, - finally, -- :: IO a -> IO b -> IO a - + finally, -- :: IO a -> IO b -> IO a + #ifdef __GLASGOW_HASKELL__ - setUncaughtExceptionHandler, -- :: (Exception -> IO ()) -> IO () - getUncaughtExceptionHandler -- :: IO (Exception -> IO ()) + setUncaughtExceptionHandler, -- :: (Exception -> IO ()) -> IO () + getUncaughtExceptionHandler -- :: IO (Exception -> IO ()) #endif ) where #ifdef __GLASGOW_HASKELL__ -import GHC.Base ( assert ) -import GHC.Exception as ExceptionBase hiding (catch) -import GHC.Conc ( throwTo, ThreadId ) -import Data.IORef ( IORef, newIORef, readIORef, writeIORef ) +import GHC.Base ( assert ) +import GHC.Exception as ExceptionBase hiding (catch) +import GHC.Conc ( throwTo, ThreadId ) +import Data.IORef ( IORef, newIORef, readIORef, writeIORef ) import Foreign.C.String ( CString, withCString ) -import System.IO ( stdout, hFlush ) +import System.IO ( stdout, hFlush ) #endif #ifdef __HUGS__ -import Hugs.Exception as ExceptionBase +import Hugs.Exception as ExceptionBase #endif -import Prelude hiding ( catch ) -import System.IO.Error hiding ( catch, try ) +import Prelude hiding ( catch ) +import System.IO.Error hiding ( catch, try ) import System.IO.Unsafe (unsafePerformIO) import Data.Dynamic #ifdef __NHC__ import System.IO.Error (catch, ioError) import IO (bracket) -import DIOError -- defn of IOError type +import DIOError -- defn of IOError type -- minimum needed for nhc98 to pretend it has Exceptions -type Exception = IOError +type Exception = IOError type IOException = IOError data ArithException data ArrayException data AsyncException -throwIO :: Exception -> IO a +throwIO :: Exception -> IO a throwIO = ioError -throw :: Exception -> a +throw :: Exception -> a throw = unsafePerformIO . throwIO evaluate :: a -> IO a evaluate x = x `seq` return x -ioErrors :: Exception -> Maybe IOError +ioErrors :: Exception -> Maybe IOError ioErrors e = Just e arithExceptions :: Exception -> Maybe ArithException arithExceptions = const Nothing -errorCalls :: Exception -> Maybe String +errorCalls :: Exception -> Maybe String errorCalls = const Nothing -dynExceptions :: Exception -> Maybe Dynamic +dynExceptions :: Exception -> Maybe Dynamic dynExceptions = const Nothing -assertions :: Exception -> Maybe String +assertions :: Exception -> Maybe String assertions = const Nothing asyncExceptions :: Exception -> Maybe AsyncException asyncExceptions = const Nothing -userErrors :: Exception -> Maybe String +userErrors :: Exception -> Maybe String userErrors (UserError _ s) = Just s userErrors _ = Nothing @@ -238,9 +238,9 @@ assert False _ = throw (UserError "" "Assertion failed") -- and then using @C.catch@ -- #ifndef __NHC__ -catch :: IO a -- ^ The computation to run - -> (Exception -> IO a) -- ^ Handler to invoke if an exception is raised - -> IO a +catch :: IO a -- ^ The computation to run + -> (Exception -> IO a) -- ^ Handler to invoke if an exception is raised + -> IO a catch = ExceptionBase.catchException #endif -- | The function 'catchJust' is like 'catch', but it takes an extra @@ -256,21 +256,21 @@ catch = ExceptionBase.catchException -- are re-raised, and may be caught by an enclosing -- 'catch' or 'catchJust'. catchJust - :: (Exception -> Maybe b) -- ^ Predicate to select exceptions - -> IO a -- ^ Computation to run - -> (b -> IO a) -- ^ Handler - -> IO a + :: (Exception -> Maybe b) -- ^ Predicate to select exceptions + -> IO a -- ^ Computation to run + -> (b -> IO a) -- ^ Handler + -> IO a catchJust p a handler = catch a handler' where handler' e = case p e of - Nothing -> throw e - Just b -> handler b + Nothing -> throw e + Just b -> handler b -- | A version of 'catch' with the arguments swapped around; useful in -- situations where the code for the handler is shorter. For example: -- -- > do handle (\e -> exitWith (ExitFailure 1)) $ --- > ... -handle :: (Exception -> IO a) -> IO a -> IO a +-- > ... +handle :: (Exception -> IO a) -> IO a -> IO a handle = flip catch -- | A version of 'catchJust' with the arguments swapped around (see @@ -318,10 +318,10 @@ tryJust :: (Exception -> Maybe b) -> IO a -> IO (Either b a) tryJust p a = do r <- try a case r of - Right v -> return (Right v) - Left e -> case p e of - Nothing -> throw e - Just b -> return (Left b) + Right v -> return (Right v) + Left e -> case p e of + Nothing -> throw e + Just b -> return (Left b) ----------------------------------------------------------------------------- -- Dynamic exceptions @@ -358,15 +358,15 @@ throwDynTo t exception = throwTo t (DynException (toDyn exception)) -- catchDyn :: Typeable exception => IO a -> (exception -> IO a) -> IO a #ifdef __NHC__ -catchDyn m k = m -- can't catch dyn exceptions in nhc98 +catchDyn m k = m -- can't catch dyn exceptions in nhc98 #else catchDyn m k = catchException m handle where handle ex = case ex of - (DynException dyn) -> - case fromDynamic dyn of - Just exception -> k exception - Nothing -> throw ex - _ -> throw ex + (DynException dyn) -> + case fromDynamic dyn of + Just exception -> k exception + Nothing -> throw ex + _ -> throw ex #endif ----------------------------------------------------------------------------- @@ -377,13 +377,13 @@ catchDyn m k = catchException m handle -- 'catchJust', 'tryJust', or 'handleJust' to select certain common -- classes of exceptions. #ifndef __NHC__ -ioErrors :: Exception -> Maybe IOError -arithExceptions :: Exception -> Maybe ArithException -errorCalls :: Exception -> Maybe String -assertions :: Exception -> Maybe String -dynExceptions :: Exception -> Maybe Dynamic -asyncExceptions :: Exception -> Maybe AsyncException -userErrors :: Exception -> Maybe String +ioErrors :: Exception -> Maybe IOError +arithExceptions :: Exception -> Maybe ArithException +errorCalls :: Exception -> Maybe String +assertions :: Exception -> Maybe String +dynExceptions :: Exception -> Maybe Dynamic +asyncExceptions :: Exception -> Maybe AsyncException +userErrors :: Exception -> Maybe String ioErrors (IOException e) = Just e ioErrors _ = Nothing @@ -430,16 +430,16 @@ userErrors _ = Nothing -- #ifndef __NHC__ bracket - :: IO a -- ^ computation to run first (\"acquire resource\") - -> (a -> IO b) -- ^ computation to run last (\"release resource\") - -> (a -> IO c) -- ^ computation to run in-between - -> IO c -- returns the value from the in-between computation + :: IO a -- ^ computation to run first (\"acquire resource\") + -> (a -> IO b) -- ^ computation to run last (\"release resource\") + -> (a -> IO c) -- ^ computation to run in-between + -> IO c -- returns the value from the in-between computation bracket before after thing = block (do a <- before r <- catch - (unblock (thing a)) - (\e -> do { after a; throw e }) + (unblock (thing a)) + (\e -> do { after a; throw e }) after a return r ) @@ -448,15 +448,15 @@ bracket before after thing = -- | A specialised variant of 'bracket' with just a computation to run -- afterward. -- -finally :: IO a -- ^ computation to run first - -> IO b -- ^ computation to run afterward (even if an exception - -- was raised) - -> IO a -- returns the value from the first computation +finally :: IO a -- ^ computation to run first + -> IO b -- ^ computation to run afterward (even if an exception + -- was raised) + -> IO a -- returns the value from the first computation a `finally` sequel = block (do r <- catch - (unblock a) - (\e -> do { sequel; throw e }) + (unblock a) + (\e -> do { sequel; throw e }) sequel return r ) @@ -469,16 +469,16 @@ bracket_ before after thing = bracket before (const after) (const thing) -- | Like bracket, but only performs the final action if there was an -- exception raised by the in-between computation. bracketOnError - :: IO a -- ^ computation to run first (\"acquire resource\") - -> (a -> IO b) -- ^ computation to run last (\"release resource\") - -> (a -> IO c) -- ^ computation to run in-between - -> IO c -- returns the value from the in-between computation + :: IO a -- ^ computation to run first (\"acquire resource\") + -> (a -> IO b) -- ^ computation to run last (\"release resource\") + -> (a -> IO c) -- ^ computation to run in-between + -> IO c -- returns the value from the in-between computation bracketOnError before after thing = block (do a <- before catch - (unblock (thing a)) - (\e -> do { after a; throw e }) + (unblock (thing a)) + (\e -> do { after a; throw e }) ) -- ----------------------------------------------------------------------------- @@ -576,7 +576,7 @@ uncaughtExceptionHandler = unsafePerformIO (newIORef defaultHandler) let msg = case ex of Deadlock -> "no threads to run: infinite loop or deadlock?" ErrorCall s -> s - other -> showsPrec 0 other "\n" + other -> showsPrec 0 other "" withCString "%s" $ \cfmt -> withCString msg $ \cmsg -> errorBelch cfmt cmsg