Safe Haskell	Safe
Language	Haskell2010

UnexceptionalIO

Contents

Unsafe entry points
Pseudo exceptions
Pseudo exception helpers

Description

When you've caught all the exceptions that can be handled safely, this is what you're left with.

runEitherIO . fromIO ≡ id

It is intended that you use qualified imports with this library.

import UnexceptionalIO (UIO)
import qualified UnexceptionalIO as UIO

Synopsis

data UIO a
class Monad m => Unexceptional m where
- lift :: UIO a -> m a
fromIO :: Unexceptional m => IO a -> m (Either SomeNonPseudoException a)
fromIO' :: (Exception e, Unexceptional m) => (SomeNonPseudoException -> e) -> IO a -> m (Either e a)
run :: UIO a -> IO a
runEitherIO :: Exception e => UIO (Either e a) -> IO a
unsafeFromIO :: Unexceptional m => IO a -> m a
data SomeNonPseudoException
data PseudoException
- = ProgrammerError ProgrammerError
- | ExternalError ExternalError
- | Exit ExitCode
data ProgrammerError
- = TypeError TypeError
- | ArithException ArithException
- | ArrayException ArrayException
- | AssertionFailed AssertionFailed
- | ErrorCall ErrorCall
- | NestedAtomically NestedAtomically
- | NoMethodError NoMethodError
- | PatternMatchFail PatternMatchFail
- | RecConError RecConError
- | RecSelError RecSelError
- | RecUpdError RecSelError
data ExternalError
- = CompactionFailed CompactionFailed
- | FixIOException FixIOException
- | AsyncException SomeAsyncException
- | BlockedIndefinitelyOnSTM BlockedIndefinitelyOnSTM
- | BlockedIndefinitelyOnMVar BlockedIndefinitelyOnMVar
- | Deadlock Deadlock
- | NonTermination NonTermination
bracket :: Unexceptional m => UIO a -> (a -> UIO ()) -> (a -> UIO c) -> m c
forkFinally :: Unexceptional m => UIO a -> (Either PseudoException a -> UIO ()) -> m ThreadId
fork :: Unexceptional m => UIO () -> m ThreadId
newtype ChildThreadError = ChildThreadError PseudoException

Documentation

data UIO a Source #

Like IO, but throws only PseudoException

Instances

Instances details

Monad UIO Source #
Instance details Defined in UnexceptionalIO Methods (>>=) :: UIO a -> (a -> UIO b) -> UIO b (>>) :: UIO a -> UIO b -> UIO b return :: a -> UIO a
Functor UIO Source #
Instance details Defined in UnexceptionalIO Methods fmap :: (a -> b) -> UIO a -> UIO b (<$) :: a -> UIO b -> UIO a
MonadFix UIO Source #
Instance details Defined in UnexceptionalIO Methods mfix :: (a -> UIO a) -> UIO a
Applicative UIO Source #
Instance details Defined in UnexceptionalIO Methods pure :: a -> UIO a (<>) :: UIO (a -> b) -> UIO a -> UIO b liftA2 :: (a -> b -> c) -> UIO a -> UIO b -> UIO c (>) :: UIO a -> UIO b -> UIO b (<*) :: UIO a -> UIO b -> UIO a
Unexceptional UIO Source #
Instance details Defined in UnexceptionalIO Methods lift :: UIO a -> UIO a Source #

class Monad m => Unexceptional m where Source #

Monads in which UIO computations may be embedded

Methods

lift :: UIO a -> m a Source #

Instances

Instances details

Unexceptional IO Source #
Instance details Defined in UnexceptionalIO Methods lift :: UIO a -> IO a Source #
Unexceptional UIO Source #
Instance details Defined in UnexceptionalIO Methods lift :: UIO a -> UIO a Source #

fromIO :: Unexceptional m => IO a -> m (Either SomeNonPseudoException a) Source #

Catch any exception but PseudoException in an IO action

fromIO' Source #

Arguments

:: (Exception e, Unexceptional m)
=> (SomeNonPseudoException -> e)	Default if an unexpected exception occurs
-> IO a
-> m (Either e a)

Catch any e in an IO action, with a default mapping for unexpected cases

run :: UIO a -> IO a Source #

Re-embed UIO into IO

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

Re-embed UIO and possible exception back into IO

Unsafe entry points

unsafeFromIO :: Unexceptional m => IO a -> m a Source #

You promise there are no exceptions but PseudoException thrown by this IO action

Pseudo exceptions

data SomeNonPseudoException Source #

Every SomeException but PseudoException

Instances

Instances details

Show SomeNonPseudoException Source #
Instance details Defined in UnexceptionalIO Methods showsPrec :: Int -> SomeNonPseudoException -> ShowS show :: SomeNonPseudoException -> String showList :: [SomeNonPseudoException] -> ShowS
Exception SomeNonPseudoException Source #
Instance details Defined in UnexceptionalIO Methods toException :: SomeNonPseudoException -> SomeException fromException :: SomeException -> Maybe SomeNonPseudoException displayException :: SomeNonPseudoException -> String

data PseudoException Source #

Not everything handled by the exception system is a run-time error you can handle. This is the class of unrecoverable pseudo-exceptions.

Additionally, except for ExitCode any of these pseudo-exceptions you could never guarantee to have caught. Since they can come from anywhere at any time, we could never guarentee that UIO does not contain them.

Constructors

ProgrammerError ProgrammerError	Mistakes programmers make
ExternalError ExternalError	Errors thrown by the runtime
Exit ExitCode	Process exit requests

Instances

Instances details

Show PseudoException Source #
Instance details Defined in UnexceptionalIO Methods showsPrec :: Int -> PseudoException -> ShowS show :: PseudoException -> String showList :: [PseudoException] -> ShowS
Exception PseudoException Source #
Instance details Defined in UnexceptionalIO Methods toException :: PseudoException -> SomeException fromException :: SomeException -> Maybe PseudoException displayException :: PseudoException -> String

data ProgrammerError Source #

Pseudo-exceptions caused by a programming error

Partial functions, error, undefined, etc

Constructors

TypeError TypeError
ArithException ArithException
ArrayException ArrayException
AssertionFailed AssertionFailed
ErrorCall ErrorCall
NestedAtomically NestedAtomically
NoMethodError NoMethodError
PatternMatchFail PatternMatchFail
RecConError RecConError
RecSelError RecSelError
RecUpdError RecSelError

Instances

Instances details

Show ProgrammerError Source #
Instance details Defined in UnexceptionalIO Methods showsPrec :: Int -> ProgrammerError -> ShowS show :: ProgrammerError -> String showList :: [ProgrammerError] -> ShowS
Exception ProgrammerError Source #
Instance details Defined in UnexceptionalIO Methods toException :: ProgrammerError -> SomeException fromException :: SomeException -> Maybe ProgrammerError displayException :: ProgrammerError -> String

data ExternalError Source #

Pseudo-exceptions thrown by the runtime environment

Constructors

CompactionFailed CompactionFailed
FixIOException FixIOException
AsyncException SomeAsyncException
BlockedIndefinitelyOnSTM BlockedIndefinitelyOnSTM
BlockedIndefinitelyOnMVar BlockedIndefinitelyOnMVar
Deadlock Deadlock
NonTermination NonTermination

Instances

Instances details

Show ExternalError Source #
Instance details Defined in UnexceptionalIO Methods showsPrec :: Int -> ExternalError -> ShowS show :: ExternalError -> String showList :: [ExternalError] -> ShowS
Exception ExternalError Source #
Instance details Defined in UnexceptionalIO Methods toException :: ExternalError -> SomeException fromException :: SomeException -> Maybe ExternalError displayException :: ExternalError -> String

Pseudo exception helpers

bracket :: Unexceptional m => UIO a -> (a -> UIO ()) -> (a -> UIO c) -> m c Source #

When you're doing resource handling, PseudoException matters. You still need to use the bracket pattern to handle cleanup.

forkFinally :: Unexceptional m => UIO a -> (Either PseudoException a -> UIO ()) -> m ThreadId Source #

Mirrors forkFinally, but since the body is UIO, the thread must terminate successfully or because of PseudoException

fork :: Unexceptional m => UIO () -> m ThreadId Source #

Mirrors forkIO, but re-throws errors to the parent thread

Ignores manual thread kills, since those are on purpose.
Re-throws async exceptions (SomeAsyncException) as is.
Re-throws ExitCode as is in an attempt to exit with the requested code.
Wraps synchronous PseudoException in async ChildThreadError.

newtype ChildThreadError Source #

Async signal that a child thread ended due to non-async PseudoException

Constructors

ChildThreadError PseudoException

Instances

Instances details

Show ChildThreadError Source #
Instance details Defined in UnexceptionalIO Methods showsPrec :: Int -> ChildThreadError -> ShowS show :: ChildThreadError -> String showList :: [ChildThreadError] -> ShowS
Exception ChildThreadError Source #
Instance details Defined in UnexceptionalIO Methods toException :: ChildThreadError -> SomeException fromException :: SomeException -> Maybe ChildThreadError displayException :: ChildThreadError -> String