Safe Haskell	Safe
Language	Haskell98

Control.Exceptional

Synopsis

data Exceptional x
- = Failure String
- | Success x
runExceptional :: Monad m => Exceptional x -> m x
fromMaybe :: String -> Maybe a -> Exceptional a
toMaybe :: Exceptional a -> Maybe a
fromEither :: Either String a -> Exceptional a
toEither :: Exceptional a -> Either String a
exceptIO :: IO a -> IO (Exceptional a)
exceptional :: MonadCatch m => m a -> m (Exceptional a)
failures :: Foldable t => t (Exceptional x) -> [String]
successes :: Foldable t => t (Exceptional x) -> [x]
foldExceptional :: Foldable t => t (Exceptional x) -> Either [String] [x]

Documentation

data Exceptional x #

This is basically specialized 'Either String', or Maybe with error messages.

Constructors

Failure String
Success x

Instances

Monad Exceptional #	This is `fail`-safe, so to speak. That is, fail = Failure
Instance details Defined in Control.Exceptional Methods (>>=) :: Exceptional a -> (a -> Exceptional b) -> Exceptional b # (>>) :: Exceptional a -> Exceptional b -> Exceptional b # return :: a -> Exceptional a # fail :: String -> Exceptional a #
Functor Exceptional #
Instance details Defined in Control.Exceptional Methods fmap :: (a -> b) -> Exceptional a -> Exceptional b # (<$) :: a -> Exceptional b -> Exceptional a #
Applicative Exceptional #
Instance details Defined in Control.Exceptional Methods pure :: a -> Exceptional a # (<>) :: Exceptional (a -> b) -> Exceptional a -> Exceptional b # liftA2 :: (a -> b -> c) -> Exceptional a -> Exceptional b -> Exceptional c # (>) :: Exceptional a -> Exceptional b -> Exceptional b # (<*) :: Exceptional a -> Exceptional b -> Exceptional a #
Alternative Exceptional #
Instance details Defined in Control.Exceptional Methods empty :: Exceptional a # (<\|>) :: Exceptional a -> Exceptional a -> Exceptional a # some :: Exceptional a -> Exceptional [a] # many :: Exceptional a -> Exceptional [a] #
Eq x => Eq (Exceptional x) #
Instance details Defined in Control.Exceptional Methods (==) :: Exceptional x -> Exceptional x -> Bool # (/=) :: Exceptional x -> Exceptional x -> Bool #
Read x => Read (Exceptional x) #
Instance details Defined in Control.Exceptional Methods readsPrec :: Int -> ReadS (Exceptional x) # readList :: ReadS [Exceptional x] # readPrec :: ReadPrec (Exceptional x) # readListPrec :: ReadPrec [Exceptional x] #
Show x => Show (Exceptional x) #
Instance details Defined in Control.Exceptional Methods showsPrec :: Int -> Exceptional x -> ShowS # show :: Exceptional x -> String # showList :: [Exceptional x] -> ShowS #

runExceptional :: Monad m => Exceptional x -> m x #

Convert Exceptional into another Monad. If you don't have proper exception handling in your monad, this can throw errors.

runExceptional (Failure s) = fail s
runExceptional (Success s) = pure s

fromMaybe :: String -> Maybe a -> Exceptional a #

Convert a Maybe to an Exceptional

fromMaybe s Nothing = fail s
fromMaybe s (Just x) = pure x

toMaybe :: Exceptional a -> Maybe a #

Convert an Exceptional into a Maybe. This function disregards the error message.

toMaybe (Success x) = Just x
toMaybe (Failure _) = Nothing

fromEither :: Either String a -> Exceptional a #

Convert an Either String to an Exceptional

fromEither (Left s) = fail s
fromEither (Right x) = pure x

toEither :: Exceptional a -> Either String a #

Convert an Exceptional to an Either String

toEither (Failure s) = Left s
toEither (Success x) = Right x

exceptIO :: IO a -> IO (Exceptional a) #

A wrapper around tryIOError. Encapsulates I/O exceptions in the Exceptional monad.

exceptional :: MonadCatch m => m a -> m (Exceptional a) #

Run an exception-prone action in another monad, catch the errors in Exceptional.

failures :: Foldable t => t (Exceptional x) -> [String] #

Get all of the Failures from a bunch of Exceptionals

successes :: Foldable t => t (Exceptional x) -> [x] #

Get all of the Successes from a bunch of Exceptionals

foldExceptional :: Foldable t => t (Exceptional x) -> Either [String] [x] #

Given a number of Exceptional values:

If all are Successful, then return Right with the sucesses * If there is at least one Failure, then return Left the list of error messages