Data.Acquire.Internal

Documentation

newtype Acquire a

A method for acquiring a scarce resource, providing the means of freeing it when no longer needed. This data type provides FunctorApplicativeMonad instances for composing different resources together. You can allocate these resources using either the bracket pattern (via with) or using ResourceT (via allocateAcquire).

This concept was originally introduced by Gabriel Gonzalez and described at: http://www.haskellforall.com/2013/06/the-resource-applicative.html. The implementation in this package is slightly different, due to taking a different approach to async exception safety.

Since 1.1.0

Constructors

Acquire ((forall b. IO b -> IO b) -> IO (Allocated a))

Instances

Monad Acquire

Functor Acquire

Applicative Acquire

MonadIO Acquire

MonadBase IO Acquire

data Allocated a

Constructors

Allocated !a !(ReleaseType -> IO ())

with :: MonadBaseControl IO m => Acquire a -> (a -> m b) -> m b

Allocate the given resource and provide it to the provided function. The resource will be freed as soon as the inner block is exited, whether normally or via an exception. This function is similar in function to bracket.

Since 1.1.0

withEx :: (MonadMask m, MonadIO m) => Acquire a -> (a -> m b) -> m b

Same as with, but uses the MonadMask typeclass from exceptions instead of MonadBaseControl from exceptions.

Since 1.1.3

mkAcquire

Arguments

:: IO a

acquire the resource

-> (a -> IO ())

free the resource

-> Acquire a

Create an Acquire value using the given allocate and free functions.

Since 1.1.0

data ReleaseType

The way in which a release is called.

Since 1.1.2

Constructors

ReleaseEarly

ReleaseNormal

ReleaseException

Instances

Bounded ReleaseType

Enum ReleaseType

Eq ReleaseType

Ord ReleaseType

Read ReleaseType

Show ReleaseType

mkAcquireType

Arguments

:: IO a

acquire the resource

-> (a -> ReleaseType -> IO ())

free the resource

-> Acquire a

Same as mkAcquire, but the cleanup function will be informed of how cleanup was initiated. This allows you to distinguish, for example, between normal and exceptional exits.

Since 1.1.2