Control.Monad.Variables

Monads with variables.

Documentation

data Variable m a

The type of variables. In contrast with other monads-with-variables packages, this is not done using type families.

Constructors

Variable

Fields

readVar :: m a

writeVar :: a -> m ()

class Monad m => MonadVar m where

Monads which have general variables.

Methods

newVar :: a -> m (Variable m a)

Create a variable from an initial value.

Instances

MonadVar IO

MonadVar STM

MonadVar (ST s)

MonadVar m => MonadVar (ContT r m)

(MonadVar m, Error e) => MonadVar (ErrorT e m)

MonadVar m => MonadVar (ReaderT r m)

MonadVar m => MonadVar (StateT s m)

MonadVar m => MonadVar (StateT s m)

(MonadVar m, Monoid w) => MonadVar (WriterT w m)

(MonadVar m, Monoid w) => MonadVar (WriterT w m)

(MonadVar m, Monoid w) => MonadVar (RWST r w s m)

(MonadVar m, Monoid w) => MonadVar (RWST r w s m)

stateVar :: MonadState s m => Variable m s

Access a variable representing the state of a state monad.