UnexceptionalIO

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

Documentation

data UIO a

Like IO, but throws only PseudoException

Instances

Monad UIO

Defined in UnexceptionalIO

Methods

(>>=) :: UIO a -> (a -> UIO b) -> UIO b

(>>) :: UIO a -> UIO b -> UIO b

return :: a -> UIO a

fail :: String -> UIO a

Functor UIO

Defined in UnexceptionalIO

Methods

fmap :: (a -> b) -> UIO a -> UIO b

(<$) :: a -> UIO b -> UIO a

MonadFix UIO

Defined in UnexceptionalIO

Methods

mfix :: (a -> UIO a) -> UIO a

Applicative UIO

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

Defined in UnexceptionalIO

Methods

lift :: UIO a -> UIO a

class Monad m => Unexceptional m where

Monads in which UIO computations may be embedded

Methods

lift :: UIO a -> m a

Instances

Unexceptional IO

Defined in UnexceptionalIO

Methods

lift :: UIO a -> IO a

Unexceptional UIO

Defined in UnexceptionalIO

Methods

lift :: UIO a -> UIO a

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

Catch any exception but PseudoException in an IO action

fromIO'

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

Re-embed UIO into IO

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

Re-embed UIO and possible exception back into IO

Unsafe entry points

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

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

Pseudo exceptions

data SomeNonPseudoException

Every SomeException but PseudoException

Instances

Show SomeNonPseudoException

Defined in UnexceptionalIO

Methods

showsPrec :: Int -> SomeNonPseudoException -> ShowS

show :: SomeNonPseudoException -> String

showList :: [SomeNonPseudoException] -> ShowS

Exception SomeNonPseudoException

Defined in UnexceptionalIO

Methods

toException :: SomeNonPseudoException -> SomeException

fromException :: SomeException -> Maybe SomeNonPseudoException

displayException :: SomeNonPseudoException -> String

data PseudoException

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

Show PseudoException

Defined in UnexceptionalIO

Methods

showsPrec :: Int -> PseudoException -> ShowS

show :: PseudoException -> String

showList :: [PseudoException] -> ShowS

Exception PseudoException

Defined in UnexceptionalIO

Methods

toException :: PseudoException -> SomeException

fromException :: SomeException -> Maybe PseudoException

displayException :: PseudoException -> String

data ProgrammerError

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

Show ProgrammerError

Defined in UnexceptionalIO

Methods

showsPrec :: Int -> ProgrammerError -> ShowS

show :: ProgrammerError -> String

showList :: [ProgrammerError] -> ShowS

Exception ProgrammerError

Defined in UnexceptionalIO

Methods

toException :: ProgrammerError -> SomeException

fromException :: SomeException -> Maybe ProgrammerError

displayException :: ProgrammerError -> String

data ExternalError

Pseudo-exceptions thrown by the runtime environment

Constructors

CompactionFailed CompactionFailed

FixIOException FixIOException

AsyncException SomeAsyncException

BlockedIndefinitelyOnSTM BlockedIndefinitelyOnSTM

BlockedIndefinitelyOnMVar BlockedIndefinitelyOnMVar

Deadlock Deadlock

NonTermination NonTermination

Instances

Show ExternalError

Defined in UnexceptionalIO

Methods

showsPrec :: Int -> ExternalError -> ShowS

show :: ExternalError -> String

showList :: [ExternalError] -> ShowS

Exception ExternalError

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

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

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

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

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

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

Constructors

ChildThreadError PseudoException

Instances

Show ChildThreadError

Defined in UnexceptionalIO

Methods

showsPrec :: Int -> ChildThreadError -> ShowS

show :: ChildThreadError -> String

showList :: [ChildThreadError] -> ShowS

Exception ChildThreadError

Defined in UnexceptionalIO

Methods

toException :: ChildThreadError -> SomeException

fromException :: SomeException -> Maybe ChildThreadError

displayException :: ChildThreadError -> String