Copyright	(C) 2016 Aaron Levin
License	BSD-style (see the file LICENSE)
Maintainer	Aaron Levin <aaron.michael.benjamin.levin@gmail.com>
Stability	provisional
Portability	non-portable (rank-2 polymorphism)
Safe Haskell	Safe
Language	Haskell2010

Control.Monad.Free.VanLaarhovenE

Description

"van Laarhoven encoded Free Monad with extensible effects"

Synopsis

(.:.) :: effect m -> Effects effects m -> Effects (effect ': effects) m
data Effects a (m :: * -> *) where
- EmptyE :: Effects '[] m
- ConsE :: effect m -> Effects effects m -> Effects (effect ': effects) m
newtype Free effects a = Free {
- runFree :: forall m. Monad m => Effects effects m -> m a
}
class HasEffect (effects :: [(* -> *) -> *]) (effect :: (* -> *) -> *) where
iterM :: Monad m => Effects effects m -> Free effects a -> m a
liftF :: HasEffect effects effect => (forall m. Monad m => effect m -> m a) -> Free effects a

Documentation

(.:.) :: effect m -> Effects effects m -> Effects (effect ': effects) m infixr 4 #

Helper combinator for creating values of 'Effects effects m'

data Effects a (m :: * -> *) where #

a customized HList of effects. We need to carry the m param around for type inference.

Constructors

EmptyE :: Effects '[] m
ConsE :: effect m -> Effects effects m -> Effects (effect ': effects) m

newtype Free effects a #

The van Laarhoven-encoded Free Monad with Extensible effects

Constructors

Free
Fields runFree :: forall m. Monad m => Effects effects m -> m a

Instances

Monad (Free effect) #
Instance details Defined in Control.Monad.Free.VanLaarhovenE Methods (>>=) :: Free effect a -> (a -> Free effect b) -> Free effect b # (>>) :: Free effect a -> Free effect b -> Free effect b # return :: a -> Free effect a # fail :: String -> Free effect a #
Functor (Free effect) #
Instance details Defined in Control.Monad.Free.VanLaarhovenE Methods fmap :: (a -> b) -> Free effect a -> Free effect b # (<$) :: a -> Free effect b -> Free effect a #
Applicative (Free effect) #
Instance details Defined in Control.Monad.Free.VanLaarhovenE Methods pure :: a -> Free effect a # (<>) :: Free effect (a -> b) -> Free effect a -> Free effect b # liftA2 :: (a -> b -> c) -> Free effect a -> Free effect b -> Free effect c # (>) :: Free effect a -> Free effect b -> Free effect b # (<*) :: Free effect a -> Free effect b -> Free effect a #

class HasEffect (effects :: [(* -> *) -> *]) (effect :: (* -> *) -> *) where #

A class to help us fetch effects from our effect stack.

Minimal complete definition

Methods

getEffect :: Effects effects m -> effect m #

Instances

HasEffect (effect ': effects) effect #	An instance of `HasEffect` that handles the case where our desired effect type matches the head of the list. We then return that effect.
Instance details Defined in Control.Monad.Free.VanLaarhovenE Methods getEffect :: Effects (effect ': effects) m -> effect m #
HasEffect effects effect => HasEffect (notIt ': effects) effect #	An instance of `HasEffect` that handles the case where our desired effect type doesn't match the head of the HList.
Instance details Defined in Control.Monad.Free.VanLaarhovenE Methods getEffect :: Effects (notIt ': effects) m -> effect m #

iterM :: Monad m => Effects effects m -> Free effects a -> m a #

Tear down a Free Monad using the supplied effects value.

liftF :: HasEffect effects effect => (forall m. Monad m => effect m -> m a) -> Free effects a #

A version of lift that can be used with an effect stack.