Safe Haskell	None
Language	GHC2021

Control.Monad.Freer

Description

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

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 a1. f a1 -> m a1) -> 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 a1. f a1 -> m a1) -> Freer f a -> m a Source #

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