Safe Haskell	Safe
Language	Haskell2010

RIO.State

Description

Provides reexports of MonadState and related helpers.

Since: 0.1.4.0

Synopsis

class Monad m => MonadState s (m :: Type -> Type) | m -> s where
- get :: m s
- put :: s -> m ()
- state :: (s -> (a, s)) -> m a
gets :: MonadState s m => (s -> a) -> m a
modify :: MonadState s m => (s -> s) -> m ()
modify' :: MonadState s m => (s -> s) -> m ()

Documentation

class Monad m => MonadState s (m :: Type -> Type) | m -> s where #

Minimal definition is either both of get and put or just state

Minimal complete definition

state | get, put

Methods

get :: m s #

Return the state from the internals of the monad.

put :: s -> m () #

Replace the state inside the monad.

state :: (s -> (a, s)) -> m a #

Embed a simple state action into the monad.

Instances

HasStateRef s env => MonadState s (RIO env) Source #
Instance details Defined in RIO.Prelude.RIO Methods get :: RIO env s # put :: s -> RIO env () # state :: (s -> (a, s)) -> RIO env a #
MonadState s m => MonadState s (MaybeT m)
Instance details Defined in Control.Monad.State.Class Methods get :: MaybeT m s # put :: s -> MaybeT m () # state :: (s -> (a, s)) -> MaybeT m a #
MonadState s m => MonadState s (ListT m)
Instance details Defined in Control.Monad.State.Class Methods get :: ListT m s # put :: s -> ListT m () # state :: (s -> (a, s)) -> ListT m a #
(Monoid w, MonadState s m) => MonadState s (WriterT w m)
Instance details Defined in Control.Monad.State.Class Methods get :: WriterT w m s # put :: s -> WriterT w m () # state :: (s -> (a, s)) -> WriterT w m a #
(Monoid w, MonadState s m) => MonadState s (WriterT w m)
Instance details Defined in Control.Monad.State.Class Methods get :: WriterT w m s # put :: s -> WriterT w m () # state :: (s -> (a, s)) -> WriterT w m a #
Monad m => MonadState s (StateT s m)
Instance details Defined in Control.Monad.State.Class Methods get :: StateT s m s # put :: s -> StateT s m () # state :: (s -> (a, s)) -> StateT s m a #
Monad m => MonadState s (StateT s m)
Instance details Defined in Control.Monad.State.Class Methods get :: StateT s m s # put :: s -> StateT s m () # state :: (s -> (a, s)) -> StateT s m a #
MonadState s m => MonadState s (IdentityT m)
Instance details Defined in Control.Monad.State.Class Methods get :: IdentityT m s # put :: s -> IdentityT m () # state :: (s -> (a, s)) -> IdentityT m a #
MonadState s m => MonadState s (ExceptT e m)	Since: mtl-2.2
Instance details Defined in Control.Monad.State.Class Methods get :: ExceptT e m s # put :: s -> ExceptT e m () # state :: (s -> (a, s)) -> ExceptT e m a #
(Error e, MonadState s m) => MonadState s (ErrorT e m)
Instance details Defined in Control.Monad.State.Class Methods get :: ErrorT e m s # put :: s -> ErrorT e m () # state :: (s -> (a, s)) -> ErrorT e m a #
MonadState s m => MonadState s (ReaderT r m)
Instance details Defined in Control.Monad.State.Class Methods get :: ReaderT r m s # put :: s -> ReaderT r m () # state :: (s -> (a, s)) -> ReaderT r m a #
MonadState s m => MonadState s (ContT r m)
Instance details Defined in Control.Monad.State.Class Methods get :: ContT r m s # put :: s -> ContT r m () # state :: (s -> (a, s)) -> ContT r m a #
(Monad m, Monoid w) => MonadState s (RWST r w s m)
Instance details Defined in Control.Monad.State.Class Methods get :: RWST r w s m s # put :: s -> RWST r w s m () # state :: (s -> (a, s)) -> RWST r w s m a #
(Monad m, Monoid w) => MonadState s (RWST r w s m)
Instance details Defined in Control.Monad.State.Class Methods get :: RWST r w s m s # put :: s -> RWST r w s m () # state :: (s -> (a, s)) -> RWST r w s m a #

gets :: MonadState s m => (s -> a) -> m a #

Gets specific component of the state, using a projection function supplied.

modify :: MonadState s m => (s -> s) -> m () #

Monadic state transformer.

Maps an old state to a new state inside a state monad. The old state is thrown away.

     Main> :t modify ((+1) :: Int -> Int)
     modify (...) :: (MonadState Int a) => a ()

This says that modify (+1) acts over any Monad that is a member of the MonadState class, with an Int state.

modify' :: MonadState s m => (s -> s) -> m () #

A variant of modify in which the computation is strict in the new state.

Since: mtl-2.2