Safe Haskell	Safe-Inferred
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 :: Effect where
- Ask :: Reader r m r
- Local :: (r -> r) -> m a -> Reader r m a
runReader :: r -> Eff (Reader r ': es) a -> Eff es a
ask :: (HasCallStack, Reader r :> es) => Eff es r
asks :: (HasCallStack, Reader r :> es) => (r -> a) -> Eff es a
local :: (HasCallStack, Reader r :> es) => (r -> r) -> Eff es a -> Eff es a

Effect

data Reader r :: Effect where Source #

Constructors

Ask :: Reader r m r
Local :: (r -> r) -> m a -> Reader r m a

Instances

Instances details

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

Handlers

runReader Source #

Arguments

:: 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).

Operations

ask :: (HasCallStack, Reader r :> es) => Eff es r Source #

Fetch the value of the environment.

asks Source #

Arguments

:: (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

:: (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