Agda.Utils.Either

Utilities for the Either type.

Documentation

whileLeft :: Monad m => (a -> Either b c) -> (a -> b -> m a) -> (a -> c -> m d) -> a -> m d

Loop while we have an exception.

caseEitherM :: Monad m => m (Either a b) -> (a -> m c) -> (b -> m c) -> m c

Monadic version of either with a different argument ordering.

mapLeft :: (a -> c) -> Either a b -> Either c b

'Either _ b' is a functor.

mapRight :: (b -> d) -> Either a b -> Either a d

'Either a' is a functor.

traverseEither :: Functor f => (a -> f c) -> (b -> f d) -> Either a b -> f (Either c d)

Either is bitraversable. Note: From base >= 4.10.0.0 already present in Bitraversable.

isLeft :: Either a b -> Bool

isRight :: Either a b -> Bool

fromLeft :: (b -> a) -> Either a b -> a

Analogue of fromMaybe.

fromRight :: (a -> b) -> Either a b -> b

Analogue of fromMaybe.

fromLeftM :: Monad m => (b -> m a) -> m (Either a b) -> m a

Analogue of fromMaybeM.

fromRightM :: Monad m => (a -> m b) -> m (Either a b) -> m b

Analogue of fromMaybeM.

maybeLeft :: Either a b -> Maybe a

Safe projection from Left.

maybeLeft (Left a) = Just a
maybeLeft Right{}  = Nothing

maybeRight :: Either a b -> Maybe b

Safe projection from Right.

maybeRight (Right b) = Just b
maybeRight Left{}    = Nothing

allLeft :: [Either a b] -> Maybe [a]

Returns Just input_with_tags_stripped if all elements are to the Left, and otherwise Nothing.

allRight :: [Either a b] -> Maybe [b]

Returns Just input_with_tags_stripped if all elements are to the right, and otherwise Nothing.

 allRight xs ==
   if all isRight xs then
     Just (map ((Right x) -> x) xs)
    else
     Nothing

groupByEither :: forall a b. [Either a b] -> [Either (List1 a) (List1 b)]

Groups a list into alternating chunks of Left and Right values

maybeToEither :: e -> Maybe a -> Either e a

Convert Maybe to Either e, given an error e for the Nothing case.

swapEither :: Either a b -> Either b a

Swap tags Left and Right.