Safe Haskell	None
Language	GHC2021

Control.Monad.Freer

Description

This module defines the freer monad Freer, which allows manipulating effectful computations algebraically.

It is unlikely you need this, except maybe to define your own backends or something. We may hide/remove it in future versions.

Synopsis

data Freer (f :: Type -> Type) a where
- Return :: forall a (f :: Type -> Type). a -> Freer f a
- Do :: forall (f :: Type -> Type) b a. f b -> (b -> Freer f a) -> Freer f a
toFreer :: f a -> Freer f a
interpFreer :: Monad m => (forall b. f b -> m b) -> Freer f a -> m a

Documentation

data Freer (f :: Type -> Type) a where Source #

Freer monads.

A freer monad Freer f a represents an effectful computation that returns a value of type a. The parameter f :: * -> * is a effect signature that defines the effectful operations allowed in the computation. Freer f a is called a freer monad in that it's a Monad given any f.

Constructors

Return :: forall a (f :: Type -> Type). a -> Freer f a	A pure computation.
Do :: forall (f :: Type -> Type) b a. f b -> (b -> Freer f a) -> Freer f a	An effectful computation where the first argument `f b` is the effect to perform and returns a result of type `b`; the second argument `b -> Freer f a` is a continuation that specifies the rest of the computation given the result of the performed effect.

Instances

Instances details

Applicative (Freer f) Source #
Instance details Defined in Control.Monad.Freer Methods pure :: a -> Freer f a # (<>) :: Freer f (a -> b) -> Freer f a -> Freer f b # liftA2 :: (a -> b -> c) -> Freer f a -> Freer f b -> Freer f c # (>) :: Freer f a -> Freer f b -> Freer f b # (<*) :: Freer f a -> Freer f b -> Freer f a #
Functor (Freer f) Source #
Instance details Defined in Control.Monad.Freer Methods fmap :: (a -> b) -> Freer f a -> Freer f b # (<$) :: a -> Freer f b -> Freer f a #
Monad (Freer f) Source #
Instance details Defined in Control.Monad.Freer Methods (>>=) :: Freer f a -> (a -> Freer f b) -> Freer f b # (>>) :: Freer f a -> Freer f b -> Freer f b # return :: a -> Freer f a #

toFreer :: f a -> Freer f a Source #

Lift an effect into the freer monad.

interpFreer :: Monad m => (forall b. f b -> m b) -> Freer f a -> m a Source #

Interpret the effects in a freer monad in terms of another monad.