Mini.Transformers.MaybeT

Extend a monad with the ability to terminate a computation without a value

Type

newtype MaybeT m a

A terminable transformer with inner monad m, return a

Constructors

MaybeT (m (Maybe a))

Instances

MonadTrans MaybeT

Defined in Mini.Transformers.MaybeT

Methods

lift :: Monad m => m a -> MaybeT m a

Monad m => MonadFail (MaybeT m)

Defined in Mini.Transformers.MaybeT

Methods

fail :: String -> MaybeT m a

MonadIO m => MonadIO (MaybeT m)

Defined in Mini.Transformers.MaybeT

Methods

liftIO :: IO a -> MaybeT m a

Monad m => Alternative (MaybeT m)

Defined in Mini.Transformers.MaybeT

Methods

empty :: MaybeT m a

(<|>) :: MaybeT m a -> MaybeT m a -> MaybeT m a

some :: MaybeT m a -> MaybeT m [a]

many :: MaybeT m a -> MaybeT m [a]

Monad m => Applicative (MaybeT m)

Defined in Mini.Transformers.MaybeT

Methods

pure :: a -> MaybeT m a

(<*>) :: MaybeT m (a -> b) -> MaybeT m a -> MaybeT m b

liftA2 :: (a -> b -> c) -> MaybeT m a -> MaybeT m b -> MaybeT m c

(*>) :: MaybeT m a -> MaybeT m b -> MaybeT m b

(<*) :: MaybeT m a -> MaybeT m b -> MaybeT m a

Monad m => Functor (MaybeT m)

Defined in Mini.Transformers.MaybeT

Methods

fmap :: (a -> b) -> MaybeT m a -> MaybeT m b

(<$) :: a -> MaybeT m b -> MaybeT m a

Monad m => Monad (MaybeT m)

Defined in Mini.Transformers.MaybeT

Methods

(>>=) :: MaybeT m a -> (a -> MaybeT m b) -> MaybeT m b

(>>) :: MaybeT m a -> MaybeT m b -> MaybeT m b

return :: a -> MaybeT m a

Runner

runMaybeT :: MaybeT m a -> m (Maybe a)

Unwrap a MaybeT computation

Operations

nothing :: Monad m => MaybeT m a

Terminate the computation without a value

anticipate :: Monad m => MaybeT m a -> MaybeT m (Maybe a)

Run a computation and get its result