Safe Haskell	None
Language	Haskell2010

Effectful.Labeled.Reader

Contents

Description

Convenience functions for the Labeled Reader effect.

Since: 2.4.0.0

Synopsis

data Reader r (a :: Type -> Type) b where
- Ask :: forall r (a :: Type -> Type). Reader r a r
- Local :: forall r (a :: Type -> Type) b. (r -> r) -> a b -> Reader r a b
runReader :: forall {k} (label :: k) r (es :: [(Type -> Type) -> Type -> Type]) a. HasCallStack => r -> Eff (Labeled label (Reader r) ': es) a -> Eff es a
ask :: forall {k} (label :: k) r (es :: [Effect]). (HasCallStack, Labeled label (Reader r) :> es) => Eff es r
asks :: forall {k} (label :: k) r (es :: [Effect]) a. (HasCallStack, Labeled label (Reader r) :> es) => (r -> a) -> Eff es a
local :: forall {k} (label :: k) r (es :: [Effect]) a. (HasCallStack, Labeled label (Reader r) :> es) => (r -> r) -> Eff es a -> Eff es a

Effect

data Reader r (a :: Type -> Type) b where Source #

Constructors

Ask :: forall r (a :: Type -> Type). Reader r a r
Local :: forall r (a :: Type -> Type) b. (r -> r) -> a b -> Reader r a b

Instances details

type DispatchOf (Reader r) Source #
Instance details Defined in Effectful.Reader.Dynamic type DispatchOf (Reader r) = 'Dynamic

Handlers

Arguments

:: forall {k} (label :: k) r (es :: [(Type -> Type) -> Type -> Type]) a. HasCallStack
=> r	The initial environment.
-> Eff (Labeled label (Reader r) ': es) a
-> Eff es a

Run the Reader effect with the given initial environment (via Effectful.Reader.Static).

ask :: forall {k} (label :: k) r (es :: [Effect]). (HasCallStack, Labeled label (Reader r) :> es) => Eff es r Source #

Fetch the value of the environment.

Arguments

:: forall {k} (label :: k) r (es :: [Effect]) a. (HasCallStack, Labeled label (Reader r) :> es)
=> (r -> a)	The function to apply to the environment.
-> Eff es a

Retrieve a function of the current environment.

asks f ≡ f <$> ask

Arguments

:: forall {k} (label :: k) r (es :: [Effect]) a. (HasCallStack, Labeled label (Reader r) :> es)
=> (r -> r)	The function to modify the environment.
-> Eff es a
-> Eff es a

Execute a computation in a modified environment.

runReader r (local f m) ≡ runReader (f r) m