Safe Haskell	None
Language	Haskell2010
Extensions	Cpp DeriveFunctor DeriveTraversable DeriveFoldable DeriveGeneric DerivingStrategies GeneralizedNewtypeDeriving ExplicitNamespaces PatternSynonyms

Data.Either.Result

Description

Result a is a wrapper of Either String a, but Result is an instance of MonadFail. A discussion about MonadFail of Either is https://gitlab.haskell.org/ghc/ghc/-/issues/12160.

Synopsis

newtype Result a = Result {
- runResult :: Either String a
}
pattern Error :: String -> Result a
pattern Success :: a -> Result a
result :: (String -> b) -> (a -> b) -> Result a -> b
fromEither :: Either String a -> Result a
toEither :: Result a -> Either String a
fromSuccess :: a -> Result a -> a
toMonadFail :: MonadFail m => Result a -> m a

Documentation

newtype Result a Source #

Result a is a wrapper of Either String a.

Constructors

Result
Fields runResult :: Either String a

Instances

Monad Result Source #
Instance details Defined in Data.Either.Result Methods (>>=) :: Result a -> (a -> Result b) -> Result b # (>>) :: Result a -> Result b -> Result b # return :: a -> Result a # fail :: String -> Result a #
Functor Result Source #
Instance details Defined in Data.Either.Result Methods fmap :: (a -> b) -> Result a -> Result b # (<$) :: a -> Result b -> Result a #
MonadFail Result Source #
Instance details Defined in Data.Either.Result Methods fail :: String -> Result a #
Applicative Result Source #
Instance details Defined in Data.Either.Result Methods pure :: a -> Result a # (<>) :: Result (a -> b) -> Result a -> Result b # liftA2 :: (a -> b -> c) -> Result a -> Result b -> Result c # (>) :: Result a -> Result b -> Result b # (<*) :: Result a -> Result b -> Result a #
Foldable Result Source #
Instance details Defined in Data.Either.Result Methods fold :: Monoid m => Result m -> m # foldMap :: Monoid m => (a -> m) -> Result a -> m # foldr :: (a -> b -> b) -> b -> Result a -> b # foldr' :: (a -> b -> b) -> b -> Result a -> b # foldl :: (b -> a -> b) -> b -> Result a -> b # foldl' :: (b -> a -> b) -> b -> Result a -> b # foldr1 :: (a -> a -> a) -> Result a -> a # foldl1 :: (a -> a -> a) -> Result a -> a # toList :: Result a -> [a] # null :: Result a -> Bool # length :: Result a -> Int # elem :: Eq a => a -> Result a -> Bool # maximum :: Ord a => Result a -> a # minimum :: Ord a => Result a -> a # sum :: Num a => Result a -> a # product :: Num a => Result a -> a #
Traversable Result Source #
Instance details Defined in Data.Either.Result Methods traverse :: Applicative f => (a -> f b) -> Result a -> f (Result b) # sequenceA :: Applicative f => Result (f a) -> f (Result a) # mapM :: Monad m => (a -> m b) -> Result a -> m (Result b) # sequence :: Monad m => Result (m a) -> m (Result a) #
Alternative Result Source #
Instance details Defined in Data.Either.Result Methods empty :: Result a # (<\|>) :: Result a -> Result a -> Result a # some :: Result a -> Result [a] # many :: Result a -> Result [a] #
MonadPlus Result Source #
Instance details Defined in Data.Either.Result Methods mzero :: Result a # mplus :: Result a -> Result a -> Result a #
Eq a => Eq (Result a) Source #
Instance details Defined in Data.Either.Result Methods (==) :: Result a -> Result a -> Bool # (/=) :: Result a -> Result a -> Bool #
Ord a => Ord (Result a) Source #
Instance details Defined in Data.Either.Result Methods compare :: Result a -> Result a -> Ordering # (<) :: Result a -> Result a -> Bool # (<=) :: Result a -> Result a -> Bool # (>) :: Result a -> Result a -> Bool # (>=) :: Result a -> Result a -> Bool # max :: Result a -> Result a -> Result a # min :: Result a -> Result a -> Result a #
Read a => Read (Result a) Source #
Instance details Defined in Data.Either.Result Methods readsPrec :: Int -> ReadS (Result a) # readList :: ReadS [Result a] # readPrec :: ReadPrec (Result a) # readListPrec :: ReadPrec [Result a] #
Show a => Show (Result a) Source #
Instance details Defined in Data.Either.Result Methods showsPrec :: Int -> Result a -> ShowS # show :: Result a -> String # showList :: [Result a] -> ShowS #
Generic (Result a) Source #
Instance details Defined in Data.Either.Result Associated Types type Rep (Result a) :: Type -> Type # Methods from :: Result a -> Rep (Result a) x # to :: Rep (Result a) x -> Result a #
Semigroup (Result a) Source #
Instance details Defined in Data.Either.Result Methods (<>) :: Result a -> Result a -> Result a # sconcat :: NonEmpty (Result a) -> Result a # stimes :: Integral b => b -> Result a -> Result a #
Monoid (Result a) Source #
Instance details Defined in Data.Either.Result Methods mempty :: Result a # mappend :: Result a -> Result a -> Result a # mconcat :: [Result a] -> Result a #
type Rep (Result a) Source #
Instance details Defined in Data.Either.Result type Rep (Result a) = D1 (MetaData "Result" "Data.Either.Result" "either-result-0.1.2.0-3ob5e3Ippz9HyZyCTCt59F" True) (C1 (MetaCons "Result" PrefixI True) (S1 (MetaSel (Just "runResult") NoSourceUnpackedness NoSourceStrictness DecidedLazy) (Rec0 (Either String a))))

pattern Error :: String -> Result a Source #

Error means errors and failures etc.

pattern Success :: a -> Result a Source #

Success means successes and OKs etc.

result :: (String -> b) -> (a -> b) -> Result a -> b Source #

Case analysis for the Result type.

Examples

Expand

>>> let s = Success 0
>>> let e = Error "critical"
>>> result ("Bad: " ++) (("OK: " ++) . show) s
"OK: 0"
>>> result ("Bad: " ++) (("OK: " ++) . show) e
"Bad: critical"

fromEither :: Either String a -> Result a Source #

Convert Either String a to Result a.

toEither :: Result a -> Either String a Source #

Convert Result a to Either String a.

fromSuccess :: a -> Result a -> a Source #

Convert Result a to a with a default value.

toMonadFail :: MonadFail m => Result a -> m a Source #

Convert Result a to MonadFail m => m a.