{-# LANGUAGE AllowAmbiguousTypes #-} {-# LANGUAGE FlexibleContexts #-} {-# LANGUAGE ScopedTypeVariables #-} {-# LANGUAGE PolyKinds #-} {-# LANGUAGE TypeApplications #-} -- | Labelled 'Reader' operations. -- -- @since 1.0.2.0 module Control.Effect.Reader.Labelled ( -- * Reader effect Reader , ask , asks , local -- * Re-exports , Algebra , Effect , Has , run ) where import Control.Effect.Labelled import qualified Control.Effect.Reader as R import Control.Effect.Reader.Internal -- | Retrieve the environment value. -- -- @ -- runReader a ('runLabelled' @label ('ask' @label) '>>=' k) = runReader a (k a) -- @ -- -- @since 1.0.2.0 ask :: forall label r m sig . HasLabelled label (Reader r) sig m => m r ask = runUnderLabel @label R.ask {-# INLINE ask #-} -- | Project a function out of the current environment value. -- -- @ -- 'asks' @label f = 'fmap' f ('ask' @label) -- @ -- -- @since 1.0.2.0 asks :: forall label r m a sig . HasLabelled label (Reader r) sig m => (r -> a) -> m a asks f = runUnderLabel @label (R.asks f) {-# INLINE asks #-} -- | Run a computation with an environment value locally modified by the passed function. -- -- @ -- runReader a ('runLabelled' @label ('local' @label f m)) = runReader (f a) m -- @ -- -- @since 1.0.2.0 local :: forall label r m a sig . HasLabelled label (Reader r) sig m => (r -> r) -> m a -> m a local f m = runUnderLabel @label (R.local f (UnderLabel m)) {-# INLINE local #-}