Safe Haskell	None
Language	Haskell2010

Control.Carrier.State.IORef

Contents

Strict state carrier
State effect

Description

A carrier for the State effect. It uses an IORef internally to handle its state, and thus is safe to use with Control.Carrier.Resource. Underlying IORef operations are performed with readIORef and writeIORef.

Note that the parameter order in runState, evalState, and execState is reversed compared the equivalent functions provided by transformers. This is an intentional decision made to enable the composition of effect handlers with . without invoking flip.

Synopsis

runState :: MonadIO m => s -> StateC s m a -> m (s, a)
evalState :: forall s m a. MonadIO m => s -> StateC s m a -> m a
execState :: forall s m a. MonadIO m => s -> StateC s m a -> m s
newtype StateC s m a = StateC {
- runStateC :: ReaderC (IORef s) m a
}
module Control.Effect.State

Strict state carrier

runState :: MonadIO m => s -> StateC s m a -> m (s, a) Source #

Run a State effect starting from the passed value.

run (runState a (pure b)) === (a, b)

Since: 1.0.0.0

evalState :: forall s m a. MonadIO m => s -> StateC s m a -> m a Source #

Run a State effect, yielding the result value and discarding the final state.

run (evalState a (pure b)) === b

Since: 1.0.0.0

execState :: forall s m a. MonadIO m => s -> StateC s m a -> m s Source #

Run a State effect, yielding the final state and discarding the return value.

run (execState a (pure b)) === a

Since: 1.0.0.0

newtype StateC s m a Source #

Since: 1.0.0.0

Constructors

StateC
Fields runStateC :: ReaderC (IORef s) m a

Instances

Monad m => Monad (StateC s m) Source #
Instance details Defined in Control.Carrier.State.IORef Methods (>>=) :: StateC s m a -> (a -> StateC s m b) -> StateC s m b # (>>) :: StateC s m a -> StateC s m b -> StateC s m b # return :: a -> StateC s m a # fail :: String -> StateC s m a #
Functor m => Functor (StateC s m) Source #
Instance details Defined in Control.Carrier.State.IORef Methods fmap :: (a -> b) -> StateC s m a -> StateC s m b # (<$) :: a -> StateC s m b -> StateC s m a #
MonadFix m => MonadFix (StateC s m) Source #
Instance details Defined in Control.Carrier.State.IORef Methods mfix :: (a -> StateC s m a) -> StateC s m a #
MonadFail m => MonadFail (StateC s m) Source #
Instance details Defined in Control.Carrier.State.IORef Methods fail :: String -> StateC s m a #
Applicative m => Applicative (StateC s m) Source #
Instance details Defined in Control.Carrier.State.IORef Methods pure :: a -> StateC s m a # (<>) :: StateC s m (a -> b) -> StateC s m a -> StateC s m b # liftA2 :: (a -> b -> c) -> StateC s m a -> StateC s m b -> StateC s m c # (>) :: StateC s m a -> StateC s m b -> StateC s m b # (<*) :: StateC s m a -> StateC s m b -> StateC s m a #
MonadIO m => MonadIO (StateC s m) Source #
Instance details Defined in Control.Carrier.State.IORef Methods liftIO :: IO a -> StateC s m a #
Alternative m => Alternative (StateC s m) Source #
Instance details Defined in Control.Carrier.State.IORef Methods empty :: StateC s m a # (<\|>) :: StateC s m a -> StateC s m a -> StateC s m a # some :: StateC s m a -> StateC s m [a] # many :: StateC s m a -> StateC s m [a] #
(Alternative m, Monad m) => MonadPlus (StateC s m) Source #
Instance details Defined in Control.Carrier.State.IORef Methods mzero :: StateC s m a # mplus :: StateC s m a -> StateC s m a -> StateC s m a #
(MonadIO m, Algebra sig m, Effect sig) => Algebra (State s :+: sig) (StateC s m) Source #
Instance details Defined in Control.Carrier.State.IORef Methods alg :: (State s :+: sig) (StateC s m) a -> StateC s m a #

State effect

module Control.Effect.State