Control.Monad.Trans.Ether.State.Lazy

See Control.Monad.Trans.State.Lazy.

The State monad

type State tag r = StateT tag r Identity

The parametrizable state monad.

Computations have access to a mutable state.

The return function leaves the state unchanged, while >>= uses the final state of the first computation as the initial state of the second.

state :: Monad m => proxy tag -> (s -> (a, s)) -> StateT tag s m a

Constructor for computations in the state monad (the inverse of runState).

runState :: proxy tag -> State tag s a -> s -> (a, s)

Runs a State with the given initial state and returns both the final value and the final state.

evalState :: proxy tag -> State tag s a -> s -> a

Runs a State with the given initial state and returns the final value, discarding the final state.

execState :: proxy tag -> State tag s a -> s -> s

Runs a State with the given initial state and returns the final state, discarding the final value.

The StateT monad transformer

data StateT tag s m a

The state monad transformer.

The return function leaves the state unchanged, while >>= uses the final state of the first computation as the initial state of the second.

Instances

Monad m => MonadState tag s (StateT tag s m)

MonadBase b m => MonadBase b (StateT tag s m)

MonadBaseControl b m => MonadBaseControl b (StateT tag s m)

MonadError e m => MonadError e (StateT tag s m)

MonadReader r m => MonadReader r (StateT tag s m)

MonadState s' m => MonadState s' (StateT tag s m)

MonadWriter w m => MonadWriter w (StateT tag s m)

MFunctor (StateT tag s)

MonadTrans (StateT tag s)

MonadTransControl (StateT tag s)

LiftLocal (StateT tag s)

LiftCallCC (StateT tag s)

LiftPass (StateT tag s)

LiftListen (StateT tag s)

LiftCatch (StateT tag s)

Monad m => Monad (StateT tag s m)

Functor m => Functor (StateT tag s m)

MonadFix m => MonadFix (StateT tag s m)

Monad m => Applicative (StateT tag s m)

MonadPlus m => Alternative (StateT tag s m)

MonadPlus m => MonadPlus (StateT tag s m)

MonadIO m => MonadIO (StateT tag s m)

MonadCont m => MonadCont (StateT tag s m)

Taggable (StateT tag s m)

Tagged (StateT tag s m) tag

Generic (StateT tag s m a)

Newtype (StateT tag s m a)

type StT (StateT tag s) a = StT (StateT s) a

type StT (StateT tag s) a = StT (StateT tag s) a

type Untagged (StateT tag s m) = StateT s m

type Tag (StateT tag s m) = Just * tag

type Inner (StateT tag s m) = Just (* -> *) m

type StM (StateT tag s m) a = ComposeSt (StateT tag s) m a

type Rep (StateT tag s m a)

type O (StateT tag s m a) = GO (Rep (StateT tag s m a))

stateT :: proxy tag -> (s -> m (a, s)) -> StateT tag s m a

Constructor for computations in the state monad transformer.

runStateT :: proxy tag -> StateT tag s m a -> s -> m (a, s)

Runs a StateT with the given initial state and returns both the final value and the final state.

evalStateT :: Monad m => proxy tag -> StateT tag s m a -> s -> m a

Runs a StateT with the given initial state and returns the final value, discarding the final state.

execStateT :: Monad m => proxy tag -> StateT tag s m a -> s -> m s

Runs a StateT with the given initial state and returns the final state, discarding the final value.

State operations

get :: Monad m => proxy tag -> StateT tag s m s

Fetch the current value of the state within the monad.

put :: Monad m => proxy tag -> s -> StateT tag s m ()

Set the value of the state within the monad.