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


-- | Computational Effects
--   
--   An alternative to Monad Transformers.
@package effects
@version 0.1

module Control.Effects

-- | <tt>with</tt> takes a handler and creates a new <tt>Proxy</tt> (effect
--   identifier). The <tt>Proxy</tt> is passed on to a function which can
--   use it to do operations with it.
with :: Monad m => Handler e r m a -> (Proxy (ContT e m) -> ContT e m a) -> m r

-- | Unwrap the result of the top-level effect.
run :: Identity a -> a

-- | A <tt>Handler e r m a</tt> is a handler of effects with type
--   <tt>e</tt>. The <tt>ret</tt> field provides a function to lift pure
--   values into the effect. The <tt>fin</tt> field provides a function to
--   extract a final value of type <tt>r</tt> from the effect. The
--   parameter <tt>m</tt> should narmally be left polymorphic, it's the
--   monad that handles the other effects.
data Handler e r m a
Handler :: (a -> m e) -> (e -> m r) -> Handler e r m a
ret :: Handler e r m a -> a -> m e
fin :: Handler e r m a -> e -> m r

-- | Define an operation, which is autolifted so it can be used inside
--   other effects.
operation :: (c ~ (ContT e m), AutoLift c n) => Proxy c -> ((a -> m e) -> m e) -> n a

-- | Variant of <a>run</a> that allows I/O effects. (Just the identity
--   function, but it helps the type checker.)
runIO :: IO () -> IO ()

-- | Convert an <a>IO</a> action to an I/O effect operation.
io :: AutoLift IO n => IO a -> n a

-- | The continuation monad transformer. Can be used to add continuation
--   handling to other monads.
data ContT r m :: (* -> *) a :: * -> (* -> *) -> * -> *
data Proxy m :: (* -> *)
class AutoLift m1 m2
instance AutoLift' m1 m2 m1 m2 => AutoLift m1 m2
instance AutoLift' m1 m2 n1 n2 => AutoLift' m1 m2 (ContT r1 n1) (ContT r2 n2)
instance (AutoLift' m1 m2 Identity n, Monad m2) => AutoLift' m1 (ContT r m2) Identity (ContT s n)
instance (AutoLift' m1 m2 IO n, Monad m2) => AutoLift' m1 (ContT r m2) IO (ContT s n)
instance m1 ~ m2 => AutoLift' m1 m2 Identity Identity
instance m1 ~ m2 => AutoLift' m1 m2 IO IO

module Control.Effects.Cont
shift :: (c ~ (ContT r m), AutoLift c n, Monad m) => Proxy c -> ((m a -> m r) -> m r) -> n a
reset :: Monad m => Handler a a m a

module Control.Effects.Either
throwEither :: (c ~ (ContT (Either e r) m), AutoLift c n, Monad m) => Proxy c -> e -> n Void
catchEither :: Monad m => (e -> m a) -> Handler (Either e a) a m a

module Control.Effects.Error
throwError :: (c ~ (ContT ((e -> m r) -> m r) m), AutoLift c n, Monad m) => Proxy c -> e -> n Void
catchError :: Monad m => (e -> m a) -> Handler ((e -> m a) -> m a) a m a

module Control.Effects.Set
choose :: (c ~ (ContT (Set r) m), AutoLift c n, Monad m, Ord r) => Proxy c -> [a] -> n a
set :: (Monad m, Ord a) => Handler (Set a) (Set a) m a

module Control.Effects.State
get :: (c ~ (ContT (s -> m r) m), AutoLift c n, Monad m) => Proxy c -> n s
put :: (c ~ (ContT (s -> m r) m), AutoLift c n, Monad m) => Proxy c -> s -> n ()
ref :: Monad m => s -> Handler (s -> m a) a m a

module Control.Effects.Writer
tell :: (c ~ (ContT (w, r) m), AutoLift c n, Monad m, Monoid w) => Proxy c -> w -> n ()
writer :: (Monad m, Monoid w) => Handler (w, a) (w, a) m a