Acquire

IO

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

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

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

Use

newtype Use env err res

Resource handler, which has a notion of pure errors.

Constructors

Use (ReaderT env (ExceptT err IO) res)

Instances

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.