Copyright	Bas van Dijk, Anders Kaseorg
License	BSD-style
Maintainer	Bas van Dijk <v.dijk.bas@gmail.com>
Stability	experimental
Portability	non-portable (extended exceptions)
Safe Haskell	Trustworthy
Language	Haskell98

Control.Exception.Lifted

Contents

Throwing exceptions
Catching exceptions
Asynchronous Exceptions
- Asynchronous exception control
Brackets
Utilities

Description

This is a wrapped version of Control.Exception with types generalized from IO to all monads in either MonadBase or MonadBaseControl.

Synopsis

Documentation

module Control.Exception

Throwing exceptions

throwIO :: (MonadBase IO m, Exception e) => e -> m a Source

Generalized version of throwIO.

ioError :: MonadBase IO m => IOError -> m a Source

Generalized version of ioError.

throwTo :: (MonadBase IO m, Exception e) => ThreadId -> e -> m () Source

Generalized version of throwTo.

Catching exceptions

The `catch` functions

catch Source

Arguments

:: (MonadBaseControl IO m, Exception e)
=> m a	The computation to run
-> (e -> m a)	Handler to invoke if an exception is raised
-> m a

Generalized version of catch.

Note, when the given computation throws an exception any monadic side effects in m will be discarded.

catches :: MonadBaseControl IO m => m a -> [Handler m a] -> m a Source

Generalized version of catches.

Note, when the given computation throws an exception any monadic side effects in m will be discarded.

data Handler m a Source

Generalized version of Handler.

Constructors

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

catchJust Source

Arguments

:: (MonadBaseControl IO m, Exception e)
=> (e -> Maybe b)	Predicate to select exceptions
-> m a	Computation to run
-> (b -> m a)	Handler
-> m a

Generalized version of catchJust.

Note, when the given computation throws an exception any monadic side effects in m will be discarded.

The `handle` functions

handle :: (MonadBaseControl IO m, Exception e) => (e -> m a) -> m a -> m a Source

Generalized version of handle.

Note, when the given computation throws an exception any monadic side effects in m will be discarded.

handleJust :: (MonadBaseControl IO m, Exception e) => (e -> Maybe b) -> (b -> m a) -> m a -> m a Source

Generalized version of handleJust.

Note, when the given computation throws an exception any monadic side effects in m will be discarded.

The `try` functions

try :: (MonadBaseControl IO m, Exception e) => m a -> m (Either e a) Source

Generalized version of try.

Note, when the given computation throws an exception any monadic side effects in m will be discarded.

tryJust :: (MonadBaseControl IO m, Exception e) => (e -> Maybe b) -> m a -> m (Either b a) Source

Generalized version of tryJust.

Note, when the given computation throws an exception any monadic side effects in m will be discarded.

The `evaluate` function

evaluate :: MonadBase IO m => a -> m a Source

Generalized version of evaluate.

Asynchronous Exceptions

Asynchronous exception control

The following functions allow a thread to control delivery of asynchronous exceptions during a critical region.

mask :: MonadBaseControl IO m => ((forall a. m a -> m a) -> m b) -> m b Source

Generalized version of mask.

mask_ :: MonadBaseControl IO m => m a -> m a Source

Generalized version of mask_.

uninterruptibleMask :: MonadBaseControl IO m => ((forall a. m a -> m a) -> m b) -> m b Source

Generalized version of uninterruptibleMask.

uninterruptibleMask_ :: MonadBaseControl IO m => m a -> m a Source

Generalized version of uninterruptibleMask_.

getMaskingState :: MonadBase IO m => m MaskingState Source

Generalized version of getMaskingState.

allowInterrupt :: MonadBase IO m => m () Source

Generalized version of allowInterrupt.

Brackets

bracket Source

Arguments

:: MonadBaseControl IO m
=> m a	computation to run first ("acquire resource")
-> (a -> m b)	computation to run last ("release resource")
-> (a -> m c)	computation to run in-between
-> m c

Generalized version of bracket.

Note:

When the "acquire" or "release" computations throw exceptions any monadic side effects in m will be discarded.
When the "in-between" computation throws an exception any monadic side effects in m produced by that computation will be discarded but the side effects of the "acquire" or "release" computations will be retained.
Also, any monadic side effects in m of the "release" computation will be discarded; it is run only for its side effects in IO.

Note that when your acquire and release computations are of type IO it will be more efficient to write:

liftBaseOp (bracket acquire release)

bracket_ Source

Arguments

:: MonadBaseControl IO m
=> m a	computation to run first ("acquire resource")
-> m b	computation to run last ("release resource")
-> m c	computation to run in-between
-> m c

Generalized version of bracket_.

Note any monadic side effects in m of both the "acquire" and "release" computations will be discarded. To keep the monadic side effects of the "acquire" computation, use bracket with constant functions instead.

Note that when your acquire and release computations are of type IO it will be more efficient to write:

liftBaseOp_ (bracket_ acquire release)

bracketOnError Source

Arguments

:: MonadBaseControl IO m
=> m a	computation to run first ("acquire resource")
-> (a -> m b)	computation to run last ("release resource")
-> (a -> m c)	computation to run in-between
-> m c

Generalized version of bracketOnError.

Note:

When the "acquire" or "release" computations throw exceptions any monadic side effects in m will be discarded.
When the "in-between" computation throws an exception any monadic side effects in m produced by that computation will be discarded but the side effects of the "acquire" computation will be retained.
Also, any monadic side effects in m of the "release" computation will be discarded; it is run only for its side effects in IO.

Note that when your acquire and release computations are of type IO it will be more efficient to write:

liftBaseOp (bracketOnError acquire release)

Utilities

finally Source

Arguments

:: MonadBaseControl IO m
=> m a	computation to run first
-> m b	computation to run afterward (even if an exception was raised)
-> m a

Generalized version of finally.

Note, any monadic side effects in m of the "afterward" computation will be discarded.

onException :: MonadBaseControl IO m => m a -> m b -> m a Source

Generalized version of onException.

Note, any monadic side effects in m of the "afterward" computation will be discarded.

Documentation

Throwing exceptions

Catching exceptions

The catch functions

The handle functions

The try functions

The evaluate function

Asynchronous Exceptions

Asynchronous exception control

Brackets

Utilities

The `catch` functions

The `handle` functions

The `try` functions

The `evaluate` function