Safe Haskell	None
Language	Haskell2010

Control.Effect.Interpose

Description

This module provides an InterposeC carrier capable of "eavesdropping" on requests made to other carriers. This is a useful capability for dynamism in deeply-nested effect stacks, but can lead to complicated control flow. Be careful.

Synopsis

newtype InterposeC eff m a = InterposeC {
- runInterposeC :: ReaderC (Handler eff m) m a
}
runInterpose :: (forall x. eff m (m x) -> m x) -> InterposeC eff m a -> m a

Documentation

newtype InterposeC eff m a Source #

Constructors

InterposeC
Fields runInterposeC :: ReaderC (Handler eff m) m a

Instances

(HFunctor eff, Carrier sig m, Member eff sig) => Carrier sig (InterposeC eff m) Source #
Instance details Defined in Control.Effect.Interpose Methods eff :: sig (InterposeC eff m) (InterposeC eff m a) -> InterposeC eff m a Source #
MonadTrans (InterposeC eff) Source #
Instance details Defined in Control.Effect.Interpose Methods lift :: Monad m => m a -> InterposeC eff m a #
Monad m => Monad (InterposeC eff m) Source #
Instance details Defined in Control.Effect.Interpose Methods (>>=) :: InterposeC eff m a -> (a -> InterposeC eff m b) -> InterposeC eff m b # (>>) :: InterposeC eff m a -> InterposeC eff m b -> InterposeC eff m b # return :: a -> InterposeC eff m a # fail :: String -> InterposeC eff m a #
Functor m => Functor (InterposeC eff m) Source #
Instance details Defined in Control.Effect.Interpose Methods fmap :: (a -> b) -> InterposeC eff m a -> InterposeC eff m b # (<$) :: a -> InterposeC eff m b -> InterposeC eff m a #
Applicative m => Applicative (InterposeC eff m) Source #
Instance details Defined in Control.Effect.Interpose Methods pure :: a -> InterposeC eff m a # (<>) :: InterposeC eff m (a -> b) -> InterposeC eff m a -> InterposeC eff m b # liftA2 :: (a -> b -> c) -> InterposeC eff m a -> InterposeC eff m b -> InterposeC eff m c # (>) :: InterposeC eff m a -> InterposeC eff m b -> InterposeC eff m b # (<*) :: InterposeC eff m a -> InterposeC eff m b -> InterposeC eff m a #

runInterpose :: (forall x. eff m (m x) -> m x) -> InterposeC eff m a -> m a Source #

runInterpose takes a handler for a given effect (such as State or Reader) and runs that handler whenever an effect of that type is encountered. Within a handler you can use all the capabilities of the underlying monad stack, including the intercepted effect, and you can pass the effect on to the original handler using send.

run . evalState @Int a . runInterpose @(State Int) (\op -> modify @Int (+b) *> send op) $ modify @Int (+b) == a + b + b