Data.Either.Result

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.

Documentation

data Result a

Result a is a wrapper of Either String a.

Instances

Monad Result

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

Defined in Data.Either.Result

Methods

fmap :: (a -> b) -> Result a -> Result b

(<$) :: a -> Result b -> Result a

MonadFail Result

Defined in Data.Either.Result

Methods

fail :: String -> Result a

Applicative Result

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

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

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

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

Defined in Data.Either.Result

Methods

mzero :: Result a

mplus :: Result a -> Result a -> Result a

Eq a => Eq (Result a)

Defined in Data.Either.Result

Methods

(==) :: Result a -> Result a -> Bool

(/=) :: Result a -> Result a -> Bool

Ord a => Ord (Result a)

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)

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)

Defined in Data.Either.Result

Methods

showsPrec :: Int -> Result a -> ShowS

show :: Result a -> String

showList :: [Result a] -> ShowS

Generic (Result a)

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)

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)

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)

Defined in Data.Either.Result

type Rep (Result a) = D1 (MetaData "Result" "Data.Either.Result" "either-result-0.1.0.0-3d133Bvk9dRBobYUljJ4mm" True) (C1 (MetaCons "Result" PrefixI True) (S1 (MetaSel (Just "either") NoSourceUnpackedness NoSourceStrictness DecidedLazy) (Rec0 (Either String a))))

pattern Error :: String -> Result a

Error means errors and failures etc.

pattern Success :: a -> Result a

Success means successes and OKs etc.

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

Case analysis for the Result type.

Examples

>>> 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

Convert Either String a to Result a.

toEither :: Result a -> Either String a

Convert Either String a from Result a.

fromSuccess :: a -> Result a -> a

Convert Result a to a with a default value.