Control.Effects.Reader

The regular old MonadReader effect with some differences. First, there's no functional dependency limiting your stack to a single environment type. This means less type inference so it might not be enough to just write readEnv. Write 'readEnv @MyEnvType' instead using TypeApplications.

Second, the function has a less generic name and is called readEnv.

Third, since it's a part of this effect framework, you get a implementReadEnv function with which you can provide a different environment implementation _at runtime_.

Documentation

data ReadEnv e

Instances

Effect (ReadEnv e)

Associated Types

data EffMethods (ReadEnv e) (m :: * -> *) :: *

type CanLift (ReadEnv e) (t :: (* -> *) -> * -> *) :: Constraint

Methods

liftThrough :: (CanLift (ReadEnv e) t, Monad m, Monad (t m)) => EffMethods (ReadEnv e) m -> EffMethods (ReadEnv e) (t m)

mergeContext :: Monad m => m (EffMethods (ReadEnv e) m) -> EffMethods (ReadEnv e) m

Generic (EffMethods (ReadEnv e) m)

Associated Types

type Rep (EffMethods (ReadEnv e) m) :: * -> *

Methods

from :: EffMethods (ReadEnv e) m -> Rep (EffMethods (ReadEnv e) m) x

to :: Rep (EffMethods (ReadEnv e) m) x -> EffMethods (ReadEnv e) m

data EffMethods (ReadEnv e)

data EffMethods (ReadEnv e) = ReadEnvMethods {

• _readEnv :: m e

}

type CanLift (ReadEnv e) t

type CanLift (ReadEnv e) t = MonadTrans t

type Rep (EffMethods (ReadEnv e) m)

type Rep (EffMethods (ReadEnv e) m) = D1 * (MetaData "EffMethods" "Control.Effects.Reader" "simple-effects-0.10.0.0-JYzNQJPZcR6HRHgMmvCghQ" False) (C1 * (MetaCons "ReadEnvMethods" PrefixI True) (S1 * (MetaSel (Just Symbol "_readEnv") NoSourceUnpackedness NoSourceStrictness DecidedLazy) (Rec0 * (m e))))

readEnv :: forall e m. MonadEffect (ReadEnv e) m => m e

Read a value of type e. Use with the TypeApplications extension to help with type inference readEnv @Int

implementReadEnv :: Functor m => m e -> RuntimeImplemented (ReadEnv e) m a -> m a

Use the given action in the underlying monad to provide environment values. You can think of implementReadEnv x m as replacing all readEnv calls in m with x.

module Control.Effects