Control.MaybeEitherMonad

A collection of utility functions to mediate between Maybe, Either, other Monads, and exceptions.

Documentation

maybeFail :: Monad m => Maybe a -> m a

Return the Just value, or fail on Nothing

eitherFailS :: Monad m => Either String a -> m a

Return the Right value, or fail with the Left error message.

eitherFail :: (Show s, Monad m) => Either s a -> m a

Return the Right value, or fail with the Left error value.

data NothingException

Thrown when maybeFail runs into a Nothing

Constructors

NothingException

Instances

Show NothingException

Defined in Control.MaybeEitherMonad

Methods

showsPrec :: Int -> NothingException -> ShowS

show :: NothingException -> String

showList :: [NothingException] -> ShowS

Exception NothingException

Defined in Control.MaybeEitherMonad

Methods

toException :: NothingException -> SomeException

fromException :: SomeException -> Maybe NothingException

displayException :: NothingException -> String

data LeftException

Thrown when eitherFail or eitherFailS runs into a Left

Constructors

LeftException String

Instances

Show LeftException

Defined in Control.MaybeEitherMonad

Methods

showsPrec :: Int -> LeftException -> ShowS

show :: LeftException -> String

showList :: [LeftException] -> ShowS

Exception LeftException

Defined in Control.MaybeEitherMonad

Methods

toException :: LeftException -> SomeException

fromException :: SomeException -> Maybe LeftException

displayException :: LeftException -> String

maybeThrow :: Maybe a -> a

Get Just the value, or throw a NothingException

eitherThrowS :: Either String a -> a

Get the Right value, or throw a LeftException

eitherThrow :: Exception err => Either err a -> a

Get the Right value, or throw a LeftException

eitherThrowWith :: Exception err => (x -> err) -> Either x a -> a

optionally :: Monad m => (a -> m ()) -> Maybe a -> m ()

optionally f v executes the f action on Just the value of v, or does nothing if v is Nothing.