io-classes-1.2.0.0: Type classes for concurrency with STM, ST and timing
Safe HaskellSafe-Inferred
LanguageHaskell2010

Control.Monad.Class.MonadThrow

Synopsis

Documentation

class Monad m => MonadThrow m where Source #

Throwing exceptions, and resource handling in the presence of exceptions.

Does not include the ability to respond to exceptions.

Minimal complete definition

throwIO

Methods

throwIO :: Exception e => e -> m a Source #

bracket :: m a -> (a -> m b) -> (a -> m c) -> m c Source #

default bracket :: MonadCatch m => m a -> (a -> m b) -> (a -> m c) -> m c Source #

bracket_ :: m a -> m b -> m c -> m c Source #

finally :: m a -> m b -> m a Source #

Instances

Instances details
MonadThrow STM Source # 
Instance details

Defined in Control.Monad.Class.MonadThrow

Methods

throwIO :: Exception e => e -> STM a Source #

bracket :: STM a -> (a -> STM b) -> (a -> STM c) -> STM c Source #

bracket_ :: STM a -> STM b -> STM c -> STM c Source #

finally :: STM a -> STM b -> STM a Source #

MonadThrow IO Source # 
Instance details

Defined in Control.Monad.Class.MonadThrow

Methods

throwIO :: Exception e => e -> IO a Source #

bracket :: IO a -> (a -> IO b) -> (a -> IO c) -> IO c Source #

bracket_ :: IO a -> IO b -> IO c -> IO c Source #

finally :: IO a -> IO b -> IO a Source #

MonadThrow m => MonadThrow (ReaderT r m) Source # 
Instance details

Defined in Control.Monad.Class.MonadThrow

Methods

throwIO :: Exception e => e -> ReaderT r m a Source #

bracket :: ReaderT r m a -> (a -> ReaderT r m b) -> (a -> ReaderT r m c) -> ReaderT r m c Source #

bracket_ :: ReaderT r m a -> ReaderT r m b -> ReaderT r m c -> ReaderT r m c Source #

finally :: ReaderT r m a -> ReaderT r m b -> ReaderT r m a Source #

class MonadThrow m => MonadCatch m where Source #

Catching exceptions.

Covers standard utilities to respond to exceptions.

Minimal complete definition

catch

Methods

catch :: Exception e => m a -> (e -> m a) -> m a Source #

catchJust :: Exception e => (e -> Maybe b) -> m a -> (b -> m a) -> m a Source #

try :: Exception e => m a -> m (Either e a) Source #

tryJust :: Exception e => (e -> Maybe b) -> m a -> m (Either b a) Source #

handle :: Exception e => (e -> m a) -> m a -> m a Source #

handleJust :: Exception e => (e -> Maybe b) -> (b -> m a) -> m a -> m a Source #

onException :: m a -> m b -> m a Source #

bracketOnError :: m a -> (a -> m b) -> (a -> m c) -> m c Source #

generalBracket :: m a -> (a -> ExitCase b -> m c) -> (a -> m b) -> m (b, c) Source #

default generalBracket :: MonadMask m => m a -> (a -> ExitCase b -> m c) -> (a -> m b) -> m (b, c) Source #

Instances

Instances details
MonadCatch STM Source # 
Instance details

Defined in Control.Monad.Class.MonadThrow

Methods

catch :: Exception e => STM a -> (e -> STM a) -> STM a Source #

catchJust :: Exception e => (e -> Maybe b) -> STM a -> (b -> STM a) -> STM a Source #

try :: Exception e => STM a -> STM (Either e a) Source #

tryJust :: Exception e => (e -> Maybe b) -> STM a -> STM (Either b a) Source #

handle :: Exception e => (e -> STM a) -> STM a -> STM a Source #

handleJust :: Exception e => (e -> Maybe b) -> (b -> STM a) -> STM a -> STM a Source #

onException :: STM a -> STM b -> STM a Source #

bracketOnError :: STM a -> (a -> STM b) -> (a -> STM c) -> STM c Source #

generalBracket :: STM a -> (a -> ExitCase b -> STM c) -> (a -> STM b) -> STM (b, c) Source #

MonadCatch IO Source # 
Instance details

Defined in Control.Monad.Class.MonadThrow

Methods

catch :: Exception e => IO a -> (e -> IO a) -> IO a Source #

catchJust :: Exception e => (e -> Maybe b) -> IO a -> (b -> IO a) -> IO a Source #

try :: Exception e => IO a -> IO (Either e a) Source #

tryJust :: Exception e => (e -> Maybe b) -> IO a -> IO (Either b a) Source #

handle :: Exception e => (e -> IO a) -> IO a -> IO a Source #

handleJust :: Exception e => (e -> Maybe b) -> (b -> IO a) -> IO a -> IO a Source #

onException :: IO a -> IO b -> IO a Source #

bracketOnError :: IO a -> (a -> IO b) -> (a -> IO c) -> IO c Source #

generalBracket :: IO a -> (a -> ExitCase b -> IO c) -> (a -> IO b) -> IO (b, c) Source #

MonadCatch m => MonadCatch (ReaderT r m) Source # 
Instance details

Defined in Control.Monad.Class.MonadThrow

Methods

catch :: Exception e => ReaderT r m a -> (e -> ReaderT r m a) -> ReaderT r m a Source #

catchJust :: Exception e => (e -> Maybe b) -> ReaderT r m a -> (b -> ReaderT r m a) -> ReaderT r m a Source #

try :: Exception e => ReaderT r m a -> ReaderT r m (Either e a) Source #

tryJust :: Exception e => (e -> Maybe b) -> ReaderT r m a -> ReaderT r m (Either b a) Source #

handle :: Exception e => (e -> ReaderT r m a) -> ReaderT r m a -> ReaderT r m a Source #

handleJust :: Exception e => (e -> Maybe b) -> (b -> ReaderT r m a) -> ReaderT r m a -> ReaderT r m a Source #

onException :: ReaderT r m a -> ReaderT r m b -> ReaderT r m a Source #

bracketOnError :: ReaderT r m a -> (a -> ReaderT r m b) -> (a -> ReaderT r m c) -> ReaderT r m c Source #

generalBracket :: ReaderT r m a -> (a -> ExitCase b -> ReaderT r m c) -> (a -> ReaderT r m b) -> ReaderT r m (b, c) Source #

class MonadCatch m => MonadMask m where Source #

Support for safely working in the presence of asynchronous exceptions.

This is typically not needed directly as the utilities in MonadThrow and MonadCatch cover most use cases.

Minimal complete definition

mask, uninterruptibleMask

Methods

mask :: ((forall a. m a -> m a) -> m b) -> m b Source #

uninterruptibleMask :: ((forall a. m a -> m a) -> m b) -> m b Source #

mask_ :: m a -> m a Source #

uninterruptibleMask_ :: m a -> m a Source #

Instances

Instances details
MonadMask IO Source # 
Instance details

Defined in Control.Monad.Class.MonadThrow

Methods

mask :: ((forall a. IO a -> IO a) -> IO b) -> IO b Source #

uninterruptibleMask :: ((forall a. IO a -> IO a) -> IO b) -> IO b Source #

mask_ :: IO a -> IO a Source #

uninterruptibleMask_ :: IO a -> IO a Source #

MonadMask m => MonadMask (ReaderT r m) Source # 
Instance details

Defined in Control.Monad.Class.MonadThrow

Methods

mask :: ((forall a. ReaderT r m a -> ReaderT r m a) -> ReaderT r m b) -> ReaderT r m b Source #

uninterruptibleMask :: ((forall a. ReaderT r m a -> ReaderT r m a) -> ReaderT r m b) -> ReaderT r m b Source #

mask_ :: ReaderT r m a -> ReaderT r m a Source #

uninterruptibleMask_ :: ReaderT r m a -> ReaderT r m a Source #

class MonadMask m => MonadMaskingState m where Source #

Minimal complete definition

getMaskingState, interruptible

Instances

Instances details
MonadMaskingState IO Source # 
Instance details

Defined in Control.Monad.Class.MonadThrow

class MonadThrow m => MonadEvaluate m where Source #

Monads which can evaluate.

Methods

evaluate :: a -> m a Source #

Instances

Instances details
MonadEvaluate IO Source # 
Instance details

Defined in Control.Monad.Class.MonadThrow

Methods

evaluate :: a -> IO a Source #

MonadEvaluate m => MonadEvaluate (ReaderT r m) Source # 
Instance details

Defined in Control.Monad.Class.MonadThrow

Methods

evaluate :: a -> ReaderT r m a Source #

data MaskingState #

Describes the behaviour of a thread when an asynchronous exception is received.

Constructors

Unmasked

asynchronous exceptions are unmasked (the normal state)

MaskedInterruptible

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

Instances

Instances details
Show MaskingState

Since: base-4.3.0.0

Instance details

Defined in GHC.IO

Eq MaskingState

Since: base-4.3.0.0

Instance details

Defined in GHC.IO

class (Typeable e, Show e) => Exception e where #

Any type that you wish to throw or catch as an exception must be an instance of the Exception class. The simplest case is a new exception type directly below the root:

data MyException = ThisException | ThatException
    deriving Show

instance Exception MyException

The default method definitions in the Exception class do what we need in this case. You can now throw and catch ThisException and ThatException as exceptions:

*Main> throw ThisException `catch` \e -> putStrLn ("Caught " ++ show (e :: MyException))
Caught ThisException

In more complicated examples, you may wish to define a whole hierarchy of exceptions:

---------------------------------------------------------------------
-- Make the root exception type for all the exceptions in a compiler

data SomeCompilerException = forall e . Exception e => SomeCompilerException e

instance Show SomeCompilerException where
    show (SomeCompilerException e) = show e

instance Exception SomeCompilerException

compilerExceptionToException :: Exception e => e -> SomeException
compilerExceptionToException = toException . SomeCompilerException

compilerExceptionFromException :: Exception e => SomeException -> Maybe e
compilerExceptionFromException x = do
    SomeCompilerException a <- fromException x
    cast a

---------------------------------------------------------------------
-- Make a subhierarchy for exceptions in the frontend of the compiler

data SomeFrontendException = forall e . Exception e => SomeFrontendException e

instance Show SomeFrontendException where
    show (SomeFrontendException e) = show e

instance Exception SomeFrontendException where
    toException = compilerExceptionToException
    fromException = compilerExceptionFromException

frontendExceptionToException :: Exception e => e -> SomeException
frontendExceptionToException = toException . SomeFrontendException

frontendExceptionFromException :: Exception e => SomeException -> Maybe e
frontendExceptionFromException x = do
    SomeFrontendException a <- fromException x
    cast a

---------------------------------------------------------------------
-- Make an exception type for a particular frontend compiler exception

data MismatchedParentheses = MismatchedParentheses
    deriving Show

instance Exception MismatchedParentheses where
    toException   = frontendExceptionToException
    fromException = frontendExceptionFromException

We can now catch a MismatchedParentheses exception as MismatchedParentheses, SomeFrontendException or SomeCompilerException, but not other types, e.g. IOException:

*Main> throw MismatchedParentheses `catch` \e -> putStrLn ("Caught " ++ show (e :: MismatchedParentheses))
Caught MismatchedParentheses
*Main> throw MismatchedParentheses `catch` \e -> putStrLn ("Caught " ++ show (e :: SomeFrontendException))
Caught MismatchedParentheses
*Main> throw MismatchedParentheses `catch` \e -> putStrLn ("Caught " ++ show (e :: SomeCompilerException))
Caught MismatchedParentheses
*Main> throw MismatchedParentheses `catch` \e -> putStrLn ("Caught " ++ show (e :: IOException))
*** Exception: MismatchedParentheses

Minimal complete definition

Nothing

Methods

toException :: e -> SomeException #

fromException :: SomeException -> Maybe e #

displayException :: e -> String #

Render this exception value in a human-friendly manner.

Default implementation: show.

Since: base-4.8.0.0

Instances

Instances details
Exception AsyncCancelled 
Instance details

Defined in Control.Concurrent.Async

Exception ExceptionInLinkedThread 
Instance details

Defined in Control.Concurrent.Async

Exception NestedAtomically

Since: base-4.0

Instance details

Defined in Control.Exception.Base

Exception NoMethodError

Since: base-4.0

Instance details

Defined in Control.Exception.Base

Exception NonTermination

Since: base-4.0

Instance details

Defined in Control.Exception.Base

Exception PatternMatchFail

Since: base-4.0

Instance details

Defined in Control.Exception.Base

Exception RecConError

Since: base-4.0

Instance details

Defined in Control.Exception.Base

Exception RecSelError

Since: base-4.0

Instance details

Defined in Control.Exception.Base

Exception RecUpdError

Since: base-4.0

Instance details

Defined in Control.Exception.Base

Exception TypeError

Since: base-4.9.0.0

Instance details

Defined in Control.Exception.Base

Exception Void

Since: base-4.8.0.0

Instance details

Defined in Data.Void

Exception ErrorCall

Since: base-4.0.0.0

Instance details

Defined in GHC.Exception

Exception ArithException

Since: base-4.0.0.0

Instance details

Defined in GHC.Exception.Type

Exception SomeException

Since: base-3.0

Instance details

Defined in GHC.Exception.Type

Exception AllocationLimitExceeded

Since: base-4.8.0.0

Instance details

Defined in GHC.IO.Exception

Exception ArrayException

Since: base-4.1.0.0

Instance details

Defined in GHC.IO.Exception

Exception AssertionFailed

Since: base-4.1.0.0

Instance details

Defined in GHC.IO.Exception

Exception AsyncException

Since: base-4.7.0.0

Instance details

Defined in GHC.IO.Exception

Exception BlockedIndefinitelyOnMVar

Since: base-4.1.0.0

Instance details

Defined in GHC.IO.Exception

Exception BlockedIndefinitelyOnSTM

Since: base-4.1.0.0

Instance details

Defined in GHC.IO.Exception

Exception CompactionFailed

Since: base-4.10.0.0

Instance details

Defined in GHC.IO.Exception

Exception Deadlock

Since: base-4.1.0.0

Instance details

Defined in GHC.IO.Exception

Exception ExitCode

Since: base-4.1.0.0

Instance details

Defined in GHC.IO.Exception

Exception FixIOException

Since: base-4.11.0.0

Instance details

Defined in GHC.IO.Exception

Exception IOException

Since: base-4.1.0.0

Instance details

Defined in GHC.IO.Exception

Exception SomeAsyncException

Since: base-4.7.0.0

Instance details

Defined in GHC.IO.Exception

Exception Timeout

Since: base-4.7.0.0

Instance details

Defined in System.Timeout

Exception ExceptionInLinkedThread Source # 
Instance details

Defined in Control.Monad.Class.MonadAsync

data SomeException #

The SomeException type is the root of the exception type hierarchy. When an exception of type e is thrown, behind the scenes it is encapsulated in a SomeException.

Instances

Instances details
Exception SomeException

Since: base-3.0

Instance details

Defined in GHC.Exception.Type

Show SomeException

Since: base-3.0

Instance details

Defined in GHC.Exception.Type

data ExitCase a Source #

Used in generalBracket

See exceptions package for discussion and motivation.

Instances

Instances details
Functor ExitCase Source # 
Instance details

Defined in Control.Monad.Class.MonadThrow

Methods

fmap :: (a -> b) -> ExitCase a -> ExitCase b #

(<$) :: a -> ExitCase b -> ExitCase a #

Show a => Show (ExitCase a) Source # 
Instance details

Defined in Control.Monad.Class.MonadThrow

Methods

showsPrec :: Int -> ExitCase a -> ShowS #

show :: ExitCase a -> String #

showList :: [ExitCase a] -> ShowS #

data Handler m a Source #

The default handler type for catches, whcih is a generalisation of Handler.

Constructors

forall e.Exception e => Handler (e -> m a) 

Instances

Instances details
Functor m => Functor (Handler m) Source # 
Instance details

Defined in Control.Monad.Class.MonadThrow

Methods

fmap :: (a -> b) -> Handler m a -> Handler m b #

(<$) :: a -> Handler m b -> Handler m a #

catches :: forall m a. MonadCatch m => m a -> [Handler m a] -> m a Source #

Like catches but for MonadCatch rather than only IO.