Control.Monad.State.Class · monads-tf-0.3.0.1

classclass Monad m => MonadState (m :: Type -> Type) where

get returns the state from the internals of the monad.

put replaces the state inside the monad.

Instances11MonadState, …

MonadState m => MonadState (MaybeT m)Defined in monads-tf-0.3.0.1 · Control.Monad.State.Class
Monad m => MonadState (StateT s m)Defined in monads-tf-0.3.0.1 · Control.Monad.State.Class
Monad m => MonadState (StateT s m)Defined in monads-tf-0.3.0.1 · Control.Monad.State.Class
MonadState m => MonadState (ExceptT e m)Defined in monads-tf-0.3.0.1 · Control.Monad.State.Class
MonadState m => MonadState (IdentityT m)Defined in monads-tf-0.3.0.1 · Control.Monad.State.Class
MonadState m => MonadState (ReaderT r m)Defined in monads-tf-0.3.0.1 · Control.Monad.State.Class
(Monoid w, MonadState m) => MonadState (WriterT w m)Defined in monads-tf-0.3.0.1 · Control.Monad.State.Class
(Monoid w, MonadState m) => MonadState (WriterT w m)Defined in monads-tf-0.3.0.1 · Control.Monad.State.Class
MonadState m => MonadState (ContT r m)Defined in monads-tf-0.3.0.1 · Control.Monad.State.Class
(Monad m, Monoid w) => MonadState (RWST r w s m)Defined in monads-tf-0.3.0.1 · Control.Monad.State.Class
(Monad m, Monoid w) => MonadState (RWST r w s m)Defined in monads-tf-0.3.0.1 · Control.Monad.State.Class

valuemodify :: MonadState m => (StateType m -> StateType m) -> 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.

valuegets :: MonadState m => (StateType m -> a) -> m a

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