Safe Haskell	None
Language	Haskell2010

Control.Effect.Resource

Synopsis

data Resource m k
- = Resource (m resource) (resource -> m any) (resource -> m output) (output -> k)
- | OnError (m resource) (resource -> m any) (resource -> m output) (output -> k)
bracket :: (Member Resource sig, Carrier sig m) => m resource -> (resource -> m any) -> (resource -> m a) -> m a
bracketOnError :: (Member Resource sig, Carrier sig m) => m resource -> (resource -> m any) -> (resource -> m a) -> m a
finally :: (Member Resource sig, Carrier sig m) => m a -> m b -> m a
onException :: (Member Resource sig, Carrier sig m) => m a -> m b -> m a
runResource :: (forall x. m x -> IO x) -> ResourceC m a -> m a
withResource :: MonadUnliftIO m => ResourceC m a -> m a
newtype ResourceC m a = ResourceC {
- runResourceC :: ReaderC (Handler m) m a
}

Documentation

data Resource m k Source #

Constructors

Resource (m resource) (resource -> m any) (resource -> m output) (output -> k)
OnError (m resource) (resource -> m any) (resource -> m output) (output -> k)

Instances

Effect Resource Source #
Instance details Defined in Control.Effect.Resource Methods handle :: Functor f => f () -> (forall x. f (m x) -> n (f x)) -> Resource m (m a) -> Resource n (n (f a)) Source #
HFunctor Resource Source #
Instance details Defined in Control.Effect.Resource Methods fmap' :: (a -> b) -> Resource m a -> Resource m b Source # hmap :: (forall x. m x -> n x) -> Resource m a -> Resource n a Source #
Functor (Resource m) Source #
Instance details Defined in Control.Effect.Resource Methods fmap :: (a -> b) -> Resource m a -> Resource m b # (<$) :: a -> Resource m b -> Resource m a #
(Carrier sig m, MonadIO m) => Carrier (Resource :+: sig) (ResourceC m) Source #
Instance details Defined in Control.Effect.Resource Methods eff :: (Resource :+: sig) (ResourceC m) (ResourceC m a) -> ResourceC m a Source #

bracket Source #

Arguments

:: (Member Resource sig, Carrier sig m)
=> m resource	computation to run first ("acquire resource")
-> (resource -> m any)	computation to run last ("release resource")
-> (resource -> m a)	computation to run in-between
-> m a

Provides a safe idiom to acquire and release resources safely.

When acquiring and operating on a resource (such as opening and reading file handle with openFile or writing to a blob of memory with malloc), any exception thrown during the operation may mean that the resource is not properly released. bracket acquire release op ensures that release is run on the value returned from acquire even if op throws an exception.

bracket is safe in the presence of asynchronous exceptions.

bracketOnError Source #

Arguments

:: (Member Resource sig, Carrier sig m)
=> m resource	computation to run first ("acquire resource")
-> (resource -> m any)	computation to run last ("release resource")
-> (resource -> m a)	computation to run in-between
-> m a

Like bracket, but only performs the final action if there was an exception raised by the in-between computation.

finally Source #

Arguments

:: (Member Resource sig, Carrier sig m)
=> m a	computation to run first
-> m b	computation to run afterward (even if an exception was raised)
-> m a

Like bracket, but for the simple case of one computation to run afterward.

onException Source #

Arguments

:: (Member Resource sig, Carrier sig m)
=> m a	computation to run first
-> m b	computation to run afterward if an exception was raised
-> m a

Like bracketOnError, but for the simple case of one computation to run afterward.

runResource Source #

Arguments

:: (forall x. m x -> IO x)	"unlifting" function to run the carrier in `IO`
-> ResourceC m a
-> m a

withResource :: MonadUnliftIO m => ResourceC m a -> m a Source #

A helper for runResource that uses withRunInIO to automatically select a correct unlifting function.

newtype ResourceC m a Source #

Constructors

ResourceC
Fields runResourceC :: ReaderC (Handler m) m a

Instances

MonadTrans ResourceC Source #
Instance details Defined in Control.Effect.Resource Methods lift :: Monad m => m a -> ResourceC m a #
Monad m => Monad (ResourceC m) Source #
Instance details Defined in Control.Effect.Resource Methods (>>=) :: ResourceC m a -> (a -> ResourceC m b) -> ResourceC m b # (>>) :: ResourceC m a -> ResourceC m b -> ResourceC m b # return :: a -> ResourceC m a # fail :: String -> ResourceC m a #
Functor m => Functor (ResourceC m) Source #
Instance details Defined in Control.Effect.Resource Methods fmap :: (a -> b) -> ResourceC m a -> ResourceC m b # (<$) :: a -> ResourceC m b -> ResourceC m a #
MonadFail m => MonadFail (ResourceC m) Source #
Instance details Defined in Control.Effect.Resource Methods fail :: String -> ResourceC m a #
Applicative m => Applicative (ResourceC m) Source #
Instance details Defined in Control.Effect.Resource Methods pure :: a -> ResourceC m a # (<>) :: ResourceC m (a -> b) -> ResourceC m a -> ResourceC m b # liftA2 :: (a -> b -> c) -> ResourceC m a -> ResourceC m b -> ResourceC m c # (>) :: ResourceC m a -> ResourceC m b -> ResourceC m b # (<*) :: ResourceC m a -> ResourceC m b -> ResourceC m a #
MonadIO m => MonadIO (ResourceC m) Source #
Instance details Defined in Control.Effect.Resource Methods liftIO :: IO a -> ResourceC m a #
Alternative m => Alternative (ResourceC m) Source #
Instance details Defined in Control.Effect.Resource Methods empty :: ResourceC m a # (<\|>) :: ResourceC m a -> ResourceC m a -> ResourceC m a # some :: ResourceC m a -> ResourceC m [a] # many :: ResourceC m a -> ResourceC m [a] #
(Alternative m, Monad m) => MonadPlus (ResourceC m) Source #
Instance details Defined in Control.Effect.Resource Methods mzero :: ResourceC m a # mplus :: ResourceC m a -> ResourceC m a -> ResourceC m a #
MonadUnliftIO m => MonadUnliftIO (ResourceC m) Source #
Instance details Defined in Control.Effect.Resource Methods askUnliftIO :: ResourceC m (UnliftIO (ResourceC m)) withRunInIO :: ((forall a. ResourceC m a -> IO a) -> IO b) -> ResourceC m b
(Carrier sig m, MonadIO m) => Carrier (Resource :+: sig) (ResourceC m) Source #
Instance details Defined in Control.Effect.Resource Methods eff :: (Resource :+: sig) (ResourceC m) (ResourceC m a) -> ResourceC m a Source #