Control.Monad.Levels.Cont

This module allows inclusion of ContT into your monad stack so as to represent continuation-passing style (CPS) computations.

Note that the behaviour of some monad transformers and how they deal with continuations differs from how mtl handles them. For example, with a lazy state transformer, using this module results in liftCallCC, whereas mtl uses liftCallCC'.

Documentation

callCC :: forall m a b. HasCont m a b => ((a -> m b) -> m a) -> m a

callCC (call-with-current-continuation) calls a function with the current continuation as its argument.

newtype ContT r m a :: * -> (* -> *) -> * -> *

The continuation monad transformer. Can be used to add continuation handling to other monads.

Constructors

ContT

Fields

runContT :: (a -> m r) -> m r

Instances

MonadTrans (ContT r)

MonadLevel m => ConstraintPassThrough (IsTransformer (ContT r)) (ListT m) True

MonadLevel m => ConstraintPassThrough (IsTransformer (StateT s)) (ContT r m) True

MonadLevel m => ConstraintPassThrough (IsTransformer (StateT s)) (ContT r m) True

MonadLevel m => ConstraintPassThrough (IsTransformer (ReaderT r)) (ContT c m) True

MonadTower m => ConstraintPassThrough (IsReader r) (ContT c m) True

MonadTower m => ConstraintPassThrough (IsState s) (ContT r m) True

Monad (ContT r m)

Functor (ContT r m)

Applicative (ContT r m)

MonadIO m => MonadIO (ContT r m)

MonadTower m => MonadLevel_ (ContT r m)

MonadTower m => MonadTower_ (ContT r m)

MonadTower m => IsCont (ContT r m)

type LowerMonad (ContT r m) = m

type WithLower_ (ContT r m) = AddIM

type AllowOtherValues (ContT r m) = False

type DefaultAllowConstraints (ContT r m) = False

type BaseMonad (ContT r m) = BaseMonad m

type InnerValue (ContT r m) a = r

type HasCont m a b = SatisfyConstraintF IsCont m a (ContFn b)

Represents monad stacks that can successfully pass callCC down to a ContT transformer.

class MonadLevel m => IsCont m

A simple class just to match up with the ContT monad transformer.

Instances

ValidConstraint IsCont

MonadTower m => ConstraintPassThrough IsCont (ListT m) True

MonadTower m => IsCont (ContT r m)

type ConstraintSatisfied IsCont m

type ContFn b = MkVarFn (Func (Func ValueOnly (MonadicOther b)) MonadicValue)

This corresponds to CallCC in transformers.