Moduleeffectful-core-2.7.1.2GHC2021

Effectful.Reader.Dynamic

The dynamically dispatched variant of the Reader effect.

Note: unless you plan to change interpretations at runtime or you need the Control.Monad.Reader.MonadReader instance for compatibility with existing code, it's recommended to use the statically dispatched variant, i.e. Effectful.Reader.Static.

1 type
5 values

Packageeffectful-core-2.7.1.2
Exports6
LanguageGHC2021
LicenceBSD-3-Clause
SourceDynamic.hs

Effect

1 declaration

datadata Reader r (a :: Type -> Type) b where

Constructors

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

Instances1DispatchOf

type DispatchOf (Reader r) = 'DynamicDefined in effectful-core-2.7.1.2 · Effectful.Internal.Effect.Dynamic

Handlers

valuerunReader

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

Run the Reader effect with the given initial environment.

valuewithReader

:: 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

Deprecated. withReader doesn't work correctly for all potential interpreters

Execute a computation in a modified environment.

Operations

valueask :: (HasCallStack, Reader r :> es) => Eff es r

Fetch the value of the environment.

valueasks

:: (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

valuelocal

:: (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