module Control.Monad.Eff.Reader (
Reader(..),
ask, asks, reader, local,
runReader
) where
import Control.Monad.Eff
data Reader e a where
Get :: Reader e e
ask :: Member (Reader e) r => Eff r e
ask = send Get
asks, reader :: Member (Reader e) r => (e -> a) -> Eff r a
asks f = fmap f ask
reader = asks
runReader :: e -> Eff (Reader e ': r) a -> Eff r a
runReader e = handleRelay ret (handle e)
local :: forall e r a. Member (Reader e) r => (e -> e) -> Eff r a -> Eff r a
local f m = do
e <- ask
interpose ret (handle (f e)) m
ret :: a -> Eff r a
ret = return
handle :: e -> Handler (Reader e) r a
handle e Get k = k e