Control.Monad.State.Class · rerebase-1.21.2

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

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

valuemodify :: 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.

valuemodify' :: MonadState s m => (s -> s) -> m ()

#

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

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

#

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

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.

Instances26MonadState, …

MonadState s m => MonadState s (CatchT m)Defined in exceptions-0.10.9 · Control.Monad.Catch.Pure
MonadState s m => MonadState s (Free m)Defined in free-5.2 · Control.Monad.Free
MonadState s m => MonadState s (Free m)Defined in free-5.2 · Control.Monad.Free.Ap
MonadState s m => MonadState s (F m)Defined in free-5.2 · Control.Monad.Free.Church
MonadState s m => MonadState s (IterT m)Defined in free-5.2 · Control.Monad.Trans.Iter
MonadState s m => MonadState s (MaybeT m)Defined in mtl-2.3.1 · Control.Monad.State.Class
Monad m => MonadState s (StateT s m)Defined in mtl-2.3.1 · Control.Monad.State.Class
Monad m => MonadState s (StateT s m)Defined in mtl-2.3.1 · Control.Monad.State.Class
MonadState s m => MonadState s (FT f m)Defined in free-5.2 · Control.Monad.Trans.Free.Church
MonadState s m => MonadState s (ExceptT e m)Defined in mtl-2.3.1 · Control.Monad.State.Class
MonadState s m => MonadState s (IdentityT m)Defined in mtl-2.3.1 · Control.Monad.State.Class
MonadState s m => MonadState s (ReaderT r m)Defined in mtl-2.3.1 · Control.Monad.State.Class
MonadState s m => MonadState s (SelectT r m)Defined in mtl-2.3.1 · Control.Monad.State.Class
(Representable g, Monad m, Rep g ~ s) => MonadState s (StateT g m)Defined in adjunctions-4.4.3 · Control.Monad.Representable.State
(Applicative f, MonadState s m) => MonadState s (FreeT f m)Defined in free-5.2 · Control.Monad.Trans.Free.Ap
(Functor f, MonadState s m) => MonadState s (FreeT f m)Defined in free-5.2 · Control.Monad.Trans.Free
(Monoid w, MonadState s m) => MonadState s (AccumT w m)Defined in mtl-2.3.1 · Control.Monad.State.Class
(Monoid w, MonadState s m) => MonadState s (WriterT w m)Defined in mtl-2.3.1 · Control.Monad.State.Class
(Monoid w, MonadState s m) => MonadState s (WriterT w m)Defined in mtl-2.3.1 · Control.Monad.State.Class
(Monoid w, MonadState s m) => MonadState s (WriterT w m)Defined in mtl-2.3.1 · Control.Monad.State.Class
MonadState s m => MonadState s (ContT r m)Defined in mtl-2.3.1 · Control.Monad.State.Class
(Comonad w, MonadState s m) => MonadState s (CoT w m)Defined in kan-extensions-5.2.7 · Control.Monad.Co
(m ~~ m', MonadReader r m') => MonadState r (Codensity m)Defined in kan-extensions-5.2.7 · Control.Monad.Codensity
(Monad m, Monoid w) => MonadState s (RWST r w s m)Defined in mtl-2.3.1 · Control.Monad.State.Class
(Monad m, Monoid w) => MonadState s (RWST r w s m)Defined in mtl-2.3.1 · Control.Monad.State.Class
(Monad m, Monoid w) => MonadState s (RWST r w s m)Defined in mtl-2.3.1 · Control.Monad.State.Class