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Control.Monad.State.Class

Copyright (c) Andy Gill 2001
(c) Oregon Graduate Institute of Science and Technology 2001
License BSD-style (see the file LICENSE)
Maintainer [email protected]
Stability experimental
Portability non-portable (multi-param classes, functional dependencies)
Safe Haskell Safe
Language Haskell2010

Description

MonadState class.

This module is inspired by the paper Functional Programming with Overloading and Higher-Order Polymorphism, Mark P Jones (http://web.cecs.pdx.edu/~mpj/) Advanced School of Functional Programming, 1995.

class Monad m => MonadState s m | m -> s where Source

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

Minimal complete definition

state | get, put

Methods

get :: m s Source

Return the state from the internals of the monad.

put :: s -> m () Source

Replace the state inside the monad.

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

Embed a simple state action into the monad.

Instances
MonadState s m => MonadState s (MaybeT m)
Instance details

Defined in Control.Monad.State.Class

Methods

get :: MaybeT m s Source

put :: s -> MaybeT m () Source

state :: (s -> (a, s)) -> MaybeT m a Source

MonadState s m => MonadState s (ListT m)
Instance details

Defined in Control.Monad.State.Class

Methods

get :: ListT m s Source

put :: s -> ListT m () Source

state :: (s -> (a, s)) -> ListT m a Source

(Monoid w, MonadState s m) => MonadState s (WriterT w m)
Instance details

Defined in Control.Monad.State.Class

Methods

get :: WriterT w m s Source

put :: s -> WriterT w m () Source

state :: (s -> (a, s)) -> WriterT w m a Source

(Monoid w, MonadState s m) => MonadState s (WriterT w m)
Instance details

Defined in Control.Monad.State.Class

Methods

get :: WriterT w m s Source

put :: s -> WriterT w m () Source

state :: (s -> (a, s)) -> WriterT w m a Source

MonadState s m => MonadState s (IdentityT m)
Instance details

Defined in Control.Monad.State.Class

Methods

get :: IdentityT m s Source

put :: s -> IdentityT m () Source

state :: (s -> (a, s)) -> IdentityT m a Source

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 Source

put :: s -> ExceptT e m () Source

state :: (s -> (a, s)) -> ExceptT e m a Source

(Error e, MonadState s m) => MonadState s (ErrorT e m)
Instance details

Defined in Control.Monad.State.Class

Methods

get :: ErrorT e m s Source

put :: s -> ErrorT e m () Source

state :: (s -> (a, s)) -> ErrorT e m a Source

Monad m => MonadState s (StateT s m)
Instance details

Defined in Control.Monad.State.Class

Methods

get :: StateT s m s Source

put :: s -> StateT s m () Source

state :: (s -> (a, s)) -> StateT s m a Source

Monad m => MonadState s (StateT s m)
Instance details

Defined in Control.Monad.State.Class

Methods

get :: StateT s m s Source

put :: s -> StateT s m () Source

state :: (s -> (a, s)) -> StateT s m a Source

MonadState s m => MonadState s (ReaderT r m)
Instance details

Defined in Control.Monad.State.Class

Methods

get :: ReaderT r m s Source

put :: s -> ReaderT r m () Source

state :: (s -> (a, s)) -> ReaderT r m a Source

MonadState s m => MonadState s (ContT r m)
Instance details

Defined in Control.Monad.State.Class

Methods

get :: ContT r m s Source

put :: s -> ContT r m () Source

state :: (s -> (a, s)) -> ContT r m a Source

(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 Source

put :: s -> RWST r w s m () Source

state :: (s -> (a, s)) -> RWST r w s m a Source

(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 Source

put :: s -> RWST r w s m () Source

state :: (s -> (a, s)) -> RWST r w s m a Source

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

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 () Source

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

Since: mtl-2.2

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

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

© The University of Glasgow and others
Licensed under a BSD-style license (see top of the page).
https://downloads.haskell.org/~ghc/8.6.1/docs/html/libraries/mtl-2.2.2/Control-Monad-State-Class.html