Safe Haskell	None
Language	Haskell2010

Effectful.Reader.Dynamic

Contents

Effect
- Handlers
- Operations

Description

The dynamically dispatched variant of the Reader effect.

Note: unless you plan to change interpretations at runtime, it's recommended to use the statically dispatched variant, i.e. Effectful.Reader.Static.

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 r (es :: [(Type -> Type) -> Type -> Type]) a. HasCallStack => r -> Eff (Reader r ': es) a -> Eff es a
withReader :: forall r1 r2 (es :: [(Type -> Type) -> Type -> Type]) a. HasCallStack => (r1 -> r2) -> Eff (Reader r2 ': es) a -> Eff (Reader r1 ': es) a
ask :: forall r (es :: [Effect]). (HasCallStack, Reader r :> es) => Eff es r
asks :: forall r (es :: [Effect]) a. (HasCallStack, Reader r :> es) => (r -> a) -> Eff es a
local :: forall r (es :: [Effect]) a. (HasCallStack, 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

Instances details

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

Handlers

runReader Source #

Arguments

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

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

withReader Source #

Arguments

:: forall r1 r2 (es :: [(Type -> Type) -> Type -> Type]) a. HasCallStack
=> (r1 -> r2)	The function to modify the environment.
-> Eff (Reader r2 ': es) a	Computation to run in the modified environment.
-> Eff (Reader r1 ': es) a

Execute a computation in a modified environment.

Since: 1.1.0.0

Operations

ask :: forall r (es :: [Effect]). (HasCallStack, Reader r :> es) => Eff es r Source #

Fetch the value of the environment.

asks Source #

Arguments

:: forall r (es :: [Effect]) a. (HasCallStack, 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

local Source #

Arguments

:: forall r (es :: [Effect]) a. (HasCallStack, 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