-- Hoogle documentation, generated by Haddock
-- See Hoogle, http://www.haskell.org/hoogle/


-- | Monads with variables, without deep magic
--   
--   Monads with variables, without deep magic
@package variables
@version 0.1.1


-- | Monads with variables.
module Control.Monad.Variables

-- | The type of variables. In contrast with other
--   <a>monads-with-variables</a> packages, this is not done using type
--   families.
data Variable m a
Variable :: m a -> (a -> m ()) -> Variable m a
readVar :: Variable m a -> m a
writeVar :: Variable m a -> a -> m ()

-- | Monads which have general variables.
class Monad m => MonadVar m
newVar :: MonadVar m => a -> m (Variable m a)

-- | Access a variable representing the state of a state monad.
stateVar :: MonadState s m => Variable m s
instance MonadVar m => MonadVar (ContT r m)
instance (MonadVar m, Error e) => MonadVar (ErrorT e m)
instance (MonadVar m, Monoid w) => MonadVar (RWST r w s m)
instance (MonadVar m, Monoid w) => MonadVar (RWST r w s m)
instance MonadVar m => MonadVar (StateT s m)
instance MonadVar m => MonadVar (StateT s m)
instance (MonadVar m, Monoid w) => MonadVar (WriterT w m)
instance (MonadVar m, Monoid w) => MonadVar (WriterT w m)
instance MonadVar m => MonadVar (ReaderT r m)
instance MonadVar STM
instance MonadVar (ST s)
instance MonadVar IO