Control.Monad.Eff.Internal

Documentation

type Arr r a b = a -> Eff r b

Effectful arrow type: a function from a to b that also does effects denoted by r

type Arrs r a b = FTCQueue (Eff r) a b

An effectful function from a to b that is a composition of several effectful functions. The paremeter r describes the overall effect. The composition members are accumulated in a type-aligned queue

data Eff r a where

The Eff monad (not a transformer!) It is a fairly standard coroutine monad It is NOT a Free monad! There are no Functor constraints Status of a coroutine (client): done with the value of type w, or sending a request of type Union r with the continuation Arrs r b a. Potentially, inline Union into Impure

Constructors

Pure :: a -> Eff r a

Impure :: Union r x -> Arrs r x a -> Eff r a

Instances

Monad (Eff r)

Methods

(>>=) :: Eff r a -> (a -> Eff r b) -> Eff r b

(>>) :: Eff r a -> Eff r b -> Eff r b

return :: a -> Eff r a

fail :: String -> Eff r a

Functor (Eff r)

Methods

fmap :: (a -> b) -> Eff r a -> Eff r b

(<$) :: a -> Eff r b -> Eff r a

Applicative (Eff r)

Methods

pure :: a -> Eff r a

(<*>) :: Eff r (a -> b) -> Eff r a -> Eff r b

(*>) :: Eff r a -> Eff r b -> Eff r b

(<*) :: Eff r a -> Eff r b -> Eff r a

qApp :: Arrs r b w -> b -> Eff r w

Application to the `generalized effectful function' Arrs r b w

qComp :: Arrs r a b -> (Eff r b -> Eff r' c) -> Arr r' a c

Compose effectful arrows (and possibly change the effect!)

qComps :: Arrs r a b -> (Eff r b -> Eff r' c) -> Arrs r' a c

send :: Member t r => t v -> Eff r v

send a request and wait for a reply

run :: Eff '[] w -> w

type Handler t r w = forall v. t v -> Arr r v w -> Eff r w

Handler type

type HandlerS s t r w = forall v. s -> t v -> (s -> Arr r v w) -> Eff r w

Parameterized Handler type

handleRelay :: (a -> Eff r w) -> Handler t r w -> Eff (t ': r) a -> Eff r w

A convenient pattern: given a request (open union), either handle it or relay it.

handleRelayS :: s -> (s -> a -> Eff r w) -> HandlerS s t r w -> Eff (t ': r) a -> Eff r w

Parameterized handleRelay

interpose :: Member t r => (a -> Eff r w) -> (forall v. t v -> Arr r v w -> Eff r w) -> Eff r a -> Eff r w

Intercept the request and possibly reply to it, but leave it unhandled (that's why we use the same r all throuout)