Control.Monad.Freer

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

Documentation

data Freer f a where

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 :: a -> Freer f a

A pure computation.

Do :: 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

Applicative (Freer f)

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)

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)

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

Lift an effect into the freer monad.

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

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