Safe Haskell	None
Language	Haskell2010

Control.Carrier.State.Lazy

Contents

Lazy state carrier
State effect

Description

A carrier for the State effect that refrains from evaluating its state until necessary. This is less efficient than Control.Carrier.State.Strict but allows some cyclic computations to terminate that would loop infinitely in a strict state carrier.

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.

Since: 1.0.0.0

Synopsis

runState :: s -> StateC s m a -> m (s, a)
evalState :: forall s m a. Functor m => s -> StateC s m a -> m a
execState :: forall s m a. Functor m => s -> StateC s m a -> m s
newtype StateC s m a = StateC (s -> m (s, a))
module Control.Effect.State

Lazy state carrier

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

Run a lazy State effect, yielding the result value and the final state. More programs terminate with lazy state than strict state, but injudicious use of lazy state may lead to thunk buildup.

runState s (pure a) = pure (s, a)

runState s get = pure (s, s)

runState s (put t) = pure (t, ())

Since: 1.0.0.0

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

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

evalState s m = fmap snd (runState s m)

Since: 1.0.0.0

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

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

execState s m = fmap fst (runState s m)

Since: 1.0.0.0

newtype StateC s m a Source #

Since: 1.0.0.0

Constructors

StateC (s -> m (s, a))

Instances

Instances details

MonadTrans (StateC s) Source #
Instance details Defined in Control.Carrier.State.Lazy Methods lift :: Monad m => m a -> StateC s m a #
Monad m => Monad (StateC s m) Source #
Instance details Defined in Control.Carrier.State.Lazy 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) Source #
Instance details Defined in Control.Carrier.State.Lazy 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.Lazy 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.Lazy Methods fail :: String -> StateC s m a #
Monad m => Applicative (StateC s m) Source #
Instance details Defined in Control.Carrier.State.Lazy 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.Lazy Methods liftIO :: IO a -> StateC s m a #
(Alternative m, Monad m) => Alternative (StateC s m) Source #
Instance details Defined in Control.Carrier.State.Lazy 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.Lazy Methods mzero :: StateC s m a # mplus :: StateC s m a -> StateC s m a -> StateC s m a #
Algebra sig m => Algebra (State s :+: sig) (StateC s m) Source #
Instance details Defined in Control.Carrier.State.Lazy 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) Source #

State effect

module Control.Effect.State