Safe Haskell	None
Language	Haskell2010

Control.Carrier.Empty.Maybe

Contents

Empty carrier
Empty effect

Description

A carrier for an Empty effect, indicating failure with a Nothing value. Users that need access to an error message should use the Fail effect.

Note that Empty effects can, when they are the last effect in a stack, be interpreted directly to a Maybe without a call to runEmpty.

Since: 1.0.0.0

Synopsis

runEmpty :: EmptyC m a -> m (Maybe a)
newtype EmptyC m a = EmptyC (MaybeT m a)
module Control.Effect.Empty

Empty carrier

runEmpty :: EmptyC m a -> m (Maybe a) Source #

Run an Empty effect, returning Nothing for empty computations, or Just the result otherwise.

runEmpty empty = pure Nothing

runEmpty (pure a) = Just a

Since: 1.0.0.0

newtype EmptyC m a Source #

Since: 1.0.0.0

Constructors

EmptyC (MaybeT m a)

Instances

Instances details

MonadTrans EmptyC Source #
Instance details Defined in Control.Carrier.Empty.Maybe Methods lift :: Monad m => m a -> EmptyC m a #
Monad m => Monad (EmptyC m) Source #
Instance details Defined in Control.Carrier.Empty.Maybe Methods (>>=) :: EmptyC m a -> (a -> EmptyC m b) -> EmptyC m b # (>>) :: EmptyC m a -> EmptyC m b -> EmptyC m b # return :: a -> EmptyC m a #
Functor m => Functor (EmptyC m) Source #
Instance details Defined in Control.Carrier.Empty.Maybe Methods fmap :: (a -> b) -> EmptyC m a -> EmptyC m b # (<$) :: a -> EmptyC m b -> EmptyC m a #
MonadFix m => MonadFix (EmptyC m) Source #
Instance details Defined in Control.Carrier.Empty.Maybe Methods mfix :: (a -> EmptyC m a) -> EmptyC m a #
MonadFail m => MonadFail (EmptyC m) Source #	`EmptyC` passes `MonadFail` operations along to the underlying monad `m`, rather than interpreting it as a synonym for `empty` à la `MaybeT`.
Instance details Defined in Control.Carrier.Empty.Maybe Methods fail :: String -> EmptyC m a #
Monad m => Applicative (EmptyC m) Source #
Instance details Defined in Control.Carrier.Empty.Maybe Methods pure :: a -> EmptyC m a # (<>) :: EmptyC m (a -> b) -> EmptyC m a -> EmptyC m b # liftA2 :: (a -> b -> c) -> EmptyC m a -> EmptyC m b -> EmptyC m c # (>) :: EmptyC m a -> EmptyC m b -> EmptyC m b # (<*) :: EmptyC m a -> EmptyC m b -> EmptyC m a #
MonadIO m => MonadIO (EmptyC m) Source #
Instance details Defined in Control.Carrier.Empty.Maybe Methods liftIO :: IO a -> EmptyC m a #
(Algebra sig m, Effect sig) => Algebra (Empty :+: sig) (EmptyC m) Source #
Instance details Defined in Control.Carrier.Empty.Maybe Methods alg :: (Empty :+: sig) (EmptyC m) a -> EmptyC m a Source #

Empty effect

module Control.Effect.Empty