Control.Carrier.State.IORef

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.

Strict state carrier

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

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

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

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

Since: 1.0.0.0

Constructors

StateC

Fields

• runStateC :: ReaderC (IORef s) m a

Instances

Monad m => Monad (StateC s m)

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

Functor m => Functor (StateC s m)

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)

Defined in Control.Carrier.State.IORef

Methods

mfix :: (a -> StateC s m a) -> StateC s m a

MonadFail m => MonadFail (StateC s m)

Defined in Control.Carrier.State.IORef

Methods

fail :: String -> StateC s m a

Applicative m => Applicative (StateC s m)

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)

Defined in Control.Carrier.State.IORef

Methods

liftIO :: IO a -> StateC s m a

Alternative m => Alternative (StateC s m)

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)

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) => Algebra (State s :+: sig) (StateC s m)

Defined in Control.Carrier.State.IORef

Methods

alg :: forall ctx (n :: Type -> Type) a. Functor ctx => Handler ctx n (StateC s m) -> (State s :+: sig) n a -> ctx () -> StateC s m (ctx a)

State effect