Acquire

IO

acquire :: Acquire a -> IO a

Acquire resources and use them by lifting IO into acquire.

acquireAndUse :: Acquire env -> Use env err res -> IO (Either err res)

Execute an action, which uses a resource, having a resource provider.

useAcquired :: env -> Use env err res -> IO (Either err res)

Run use on an acquired environment.

Acquire

newtype Acquire env

Resource provider. Abstracts over resource acquisition and releasing.

Composes well, allowing you to merge multiple providers into one.

Implementation of http://www.haskellforall.com/2013/06/the-resource-applicative.html

Constructors

Acquire (IO (env, IO ()))

Instances

MonadIO Acquire

Defined in Acquire

Methods

liftIO :: IO a -> Acquire a

Applicative Acquire

Defined in Acquire

Methods

pure :: a -> Acquire a

(<*>) :: Acquire (a -> b) -> Acquire a -> Acquire b

liftA2 :: (a -> b -> c) -> Acquire a -> Acquire b -> Acquire c

(*>) :: Acquire a -> Acquire b -> Acquire b

(<*) :: Acquire a -> Acquire b -> Acquire a

Functor Acquire

Defined in Acquire

Methods

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

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

Monad Acquire

Defined in Acquire

Methods

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

(>>) :: Acquire a -> Acquire b -> Acquire b

return :: a -> Acquire a

startAndStop

Arguments

:: IO a

Start the service.

-> (a -> IO ())

Stop the service.

-> Acquire a

Construct Acquire by specifying a resource initializer and finalizer actions.

Use

newtype Use env err res

Resource handler, which has a notion of pure errors.

Constructors

Use (ReaderT env (ExceptT err IO) res)

Instances

MonadError err (Use env err)

Defined in Acquire

Methods

throwError :: err -> Use env err a

catchError :: Use env err a -> (err -> Use env err a) -> Use env err a

MonadReader env (Use env err)

Defined in Acquire

Methods

ask :: Use env err env

local :: (env -> env) -> Use env err a -> Use env err a

reader :: (env -> a) -> Use env err a

Bifunctor (Use env)

Defined in Acquire

Methods

bimap :: (a -> b) -> (c -> d) -> Use env a c -> Use env b d

first :: (a -> b) -> Use env a c -> Use env b c

second :: (b -> c) -> Use env a b -> Use env a c

MonadIO (Use env err)

Defined in Acquire

Methods

liftIO :: IO a -> Use env err a

Monoid err => Alternative (Use env err)

Defined in Acquire

Methods

empty :: Use env err a

(<|>) :: Use env err a -> Use env err a -> Use env err a

some :: Use env err a -> Use env err [a]

many :: Use env err a -> Use env err [a]

Applicative (Use env err)

Defined in Acquire

Methods

pure :: a -> Use env err a

(<*>) :: Use env err (a -> b) -> Use env err a -> Use env err b

liftA2 :: (a -> b -> c) -> Use env err a -> Use env err b -> Use env err c

(*>) :: Use env err a -> Use env err b -> Use env err b

(<*) :: Use env err a -> Use env err b -> Use env err a

Functor (Use env err)

Defined in Acquire

Methods

fmap :: (a -> b) -> Use env err a -> Use env err b

(<$) :: a -> Use env err b -> Use env err a

Monad (Use env err)

Defined in Acquire

Methods

(>>=) :: Use env err a -> (a -> Use env err b) -> Use env err b

(>>) :: Use env err a -> Use env err b -> Use env err b

return :: a -> Use env err a

Monoid err => MonadPlus (Use env err)

Defined in Acquire

Methods

mzero :: Use env err a

mplus :: Use env err a -> Use env err a -> Use env err a

mapEnv :: (b -> a) -> Use a err res -> Use b err res

Map the environment of a resource handler.

mapErr :: (a -> b) -> Use env a res -> Use env b res

Map the error of a resource handler.

mapEnvAndErr :: (envB -> envA) -> (errA -> errB) -> Use envA errA res -> Use envB errB res

Map both the environment and the error of a resource handler.