-- Hoogle documentation, generated by Haddock -- See Hoogle, http://www.haskell.org/hoogle/ -- | Combinators for working with sums -- -- Combinators for working with sums. @package either @version 5 -- | Functions for probing and unwrapping values inside of Either. -- -- Most of these combinators are provided for pedagogical purposes and -- exist in more general forms in other libraries. To that end -- alternative definitions are supplied below. module Data.Either.Combinators -- | The isLeft function returns True iff its argument is of -- the form Left _. -- -- Using Control.Lens: -- --

--   isLeft ≡ has _Left
--

-- --

--   >>> isLeft (Left 12)
--   True
--

-- --

--   >>> isLeft (Right 12)
--   False
--

isLeft :: Either a b -> Bool -- | The isRight function returns True iff its argument is of -- the form Right _. -- -- Using Control.Lens: -- --

--   isRight ≡ has _Right
--

-- --

--   >>> isRight (Left 12)
--   False
--

-- --

--   >>> isRight (Right 12)
--   True
--

isRight :: Either a b -> Bool -- | Extract the left value or a default. -- --

--   fromLeft b ≡ either id (const b)
--

-- --

--   >>> fromLeft "hello" (Right 42)
--   "hello"
--

-- --

--   >>> fromLeft "hello" (Left "world")
--   "world"
--

fromLeft :: a -> Either a b -> a -- | Extract the right value or a default. -- --

--   fromRight b ≡ either (const b) id
--

-- --

--   >>> fromRight "hello" (Right "world")
--   "world"
--

-- --

--   >>> fromRight "hello" (Left 42)
--   "hello"
--

fromRight :: b -> Either a b -> b -- | Extracts the element out of a Left and throws an error if its -- argument take the form Right _. -- -- Using Control.Lens: -- --

--   fromLeft' x ≡ x^?!_Left
--

-- --

--   >>> fromLeft' (Left 12)
--   12
--

fromLeft' :: Either a b -> a -- | Extracts the element out of a Right and throws an error if its -- argument take the form Left _. -- -- Using Control.Lens: -- --

--   fromRight' x ≡ x^?!_Right
--

-- --

--   >>> fromRight' (Right 12)
--   12
--

fromRight' :: Either a b -> b -- | The mapBoth function takes two functions and applies the first -- if iff the value takes the form Left _ and the second -- if the value takes the form Right _. -- -- Using Data.Bifunctor: -- --

--   mapBoth = bimap
--

-- -- Using Control.Arrow: -- --

--   mapBoth = (+++)
--

-- --

--   >>> mapBoth (*2) (*3) (Left 4)
--   Left 8
--

-- --

--   >>> mapBoth (*2) (*3) (Right 4)
--   Right 12
--

mapBoth :: (a -> c) -> (b -> d) -> Either a b -> Either c d -- | The mapLeft function takes a function and applies it to an -- Either value iff the value takes the form Left _. -- -- Using Data.Bifunctor: -- --

--   mapLeft = first
--

-- -- Using Control.Arrow: -- --

--   mapLeft = (left)
--

-- -- Using Control.Lens: -- --

--   mapLeft = over _Left
--

-- --

--   >>> mapLeft (*2) (Left 4)
--   Left 8
--

-- --

--   >>> mapLeft (*2) (Right "hello")
--   Right "hello"
--

mapLeft :: (a -> c) -> Either a b -> Either c b -- | The mapRight function takes a function and applies it to an -- Either value iff the value takes the form Right _. -- -- Using Data.Bifunctor: -- --

--   mapRight = second
--

-- -- Using Control.Arrow: -- --

--   mapRight = (right)
--

-- -- Using Control.Lens: -- --

--   mapRight = over _Right
--

-- --

--   >>> mapRight (*2) (Left "hello")
--   Left "hello"
--

-- --

--   >>> mapRight (*2) (Right 4)
--   Right 8
--

mapRight :: (b -> c) -> Either a b -> Either a c -- | The whenLeft function takes an Either value and a -- function which returns a monad. The monad is only executed when the -- given argument takes the form Left _, otherwise it -- does nothing. -- -- Using Control.Lens: -- --

--   whenLeft ≡ forOf_ _Left
--

-- --

--   >>> whenLeft (Left 12) print
--   12
--

whenLeft :: Applicative m => Either a b -> (a -> m ()) -> m () -- | The whenRight function takes an Either value and a -- function which returns a monad. The monad is only executed when the -- given argument takes the form Right _, otherwise it -- does nothing. -- -- Using Data.Foldable: -- --

--   whenRight ≡ forM_
--

-- -- Using Control.Lens: -- --

--   whenRight ≡ forOf_ _Right
--

-- --

--   >>> whenRight (Right 12) print
--   12
--

whenRight :: Applicative m => Either a b -> (b -> m ()) -> m () -- | A synonym of whenRight. unlessLeft :: Applicative m => Either a b -> (b -> m ()) -> m () -- | A synonym of whenLeft. unlessRight :: Applicative m => Either a b -> (a -> m ()) -> m () -- | Maybe get the Left side of an Either. -- --

--   leftToMaybe ≡ either Just (const Nothing)
--

-- -- Using Control.Lens: -- --

--   leftToMaybe ≡ preview _Left
--   leftToMaybe x ≡ x^?_Left
--

-- --

--   >>> leftToMaybe (Left 12)
--   Just 12
--

-- --

--   >>> leftToMaybe (Right 12)
--   Nothing
--

leftToMaybe :: Either a b -> Maybe a -- | Maybe get the Right side of an Either. -- --

--   rightToMaybe ≡ either (const Nothing) Just
--

-- -- Using Control.Lens: -- --

--   rightToMaybe ≡ preview _Right
--   rightToMaybe x ≡ x^?_Right
--

-- --

--   >>> rightToMaybe (Left 12)
--   Nothing
--

-- --

--   >>> rightToMaybe (Right 12)
--   Just 12
--

rightToMaybe :: Either a b -> Maybe b -- | Maybe produce a Left, otherwise produce a Right. -- --

--   >>> maybeToRight "default" (Just 12)
--   Left 12
--

-- --

--   >>> maybeToRight "default" Nothing
--   Right "default"
--

maybeToLeft :: b -> Maybe a -> Either a b -- | Maybe produce a Right, otherwise produce a Left. -- --

--   >>> maybeToRight "default" (Just 12)
--   Right 12
--

-- --

--   >>> maybeToRight "default" Nothing
--   Left "default"
--

maybeToRight :: b -> Maybe a -> Either b a -- | Generalize Either e as MonadError e m. -- -- If the argument has form Left e, an error is produced in the -- monad via throwError. Otherwise, the Right a part is -- forwarded. eitherToError :: (MonadError e m) => Either e a -> m a -- | Swap the Left and Right sides of an Either. -- --

--   >>> swapEither (Right 3)
--   Left 3
--   
--   >>> swapEither (Left "error")
--   Right "error"
--

swapEither :: Either e a -> Either a e -- | Monoidal Validation sibling to Either. module Data.Either.Validation -- | Validation is Either with a Left that is a Monoid data Validation e a Failure :: e -> Validation e a Success :: a -> Validation e a _Success :: Prism (Validation c a) (Validation c b) a b _Failure :: Prism (Validation a c) (Validation b c) a b eitherToValidation :: Either e a -> Validation e a validationToEither :: Validation e a -> Either e a -- | Validation is isomorphic to Either _Validation :: Iso (Validation e a) (Validation g b) (Either e a) (Either g b) vap :: Semigroup m => Either m (a -> b) -> Either m a -> Either m b ealt :: Validation e a -> Validation e a -> Validation e a instance (GHC.Show.Show a, GHC.Show.Show e) => GHC.Show.Show (Data.Either.Validation.Validation e a) instance (GHC.Classes.Ord a, GHC.Classes.Ord e) => GHC.Classes.Ord (Data.Either.Validation.Validation e a) instance (GHC.Classes.Eq a, GHC.Classes.Eq e) => GHC.Classes.Eq (Data.Either.Validation.Validation e a) instance GHC.Base.Functor (Data.Either.Validation.Validation e) instance Data.Semigroup.Semigroup e => Data.Functor.Bind.Class.Apply (Data.Either.Validation.Validation e) instance Data.Semigroup.Semigroup e => GHC.Base.Applicative (Data.Either.Validation.Validation e) instance Data.Semigroup.Semigroup e => Data.Functor.Alt.Alt (Data.Either.Validation.Validation e) instance (Data.Semigroup.Semigroup e, GHC.Base.Monoid e) => GHC.Base.Alternative (Data.Either.Validation.Validation e) instance Data.Foldable.Foldable (Data.Either.Validation.Validation e) instance Data.Traversable.Traversable (Data.Either.Validation.Validation e) instance Data.Bifunctor.Bifunctor Data.Either.Validation.Validation instance Data.Bifoldable.Bifoldable Data.Either.Validation.Validation instance Data.Bitraversable.Bitraversable Data.Either.Validation.Validation instance Data.Semigroup.Semigroup e => Data.Semigroup.Semigroup (Data.Either.Validation.Validation e a) instance GHC.Base.Monoid e => GHC.Base.Monoid (Data.Either.Validation.Validation e a)