Safe Haskell | Safe |
---|---|

Language | Haskell2010 |

Utilities for the `Either`

type.

## Synopsis

- whileLeft :: Monad m => (a -> Either b c) -> (a -> b -> m a) -> (a -> c -> m d) -> a -> m d
- caseEitherM :: Monad m => m (Either a b) -> (a -> m c) -> (b -> m c) -> m c
- mapEither :: (a -> c) -> (b -> d) -> Either a b -> Either c d
- mapLeft :: (a -> c) -> Either a b -> Either c b
- mapRight :: (b -> d) -> Either a b -> Either a d
- traverseEither :: Functor f => (a -> f c) -> (b -> f d) -> Either a b -> f (Either c d)
- isRight :: Either a b -> Bool
- isLeft :: Either a b -> Bool
- fromLeft :: (b -> a) -> Either a b -> a
- fromRight :: (a -> b) -> Either a b -> b
- fromLeftM :: Monad m => (b -> m a) -> m (Either a b) -> m a
- fromRightM :: Monad m => (a -> m b) -> m (Either a b) -> m b
- maybeLeft :: Either a b -> Maybe a
- maybeRight :: Either a b -> Maybe b
- allLeft :: [Either a b] -> Maybe [a]
- allRight :: [Either a b] -> Maybe [b]
- maybeToEither :: Maybe a -> Either () a

# Documentation

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

Loop while we have an exception.

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

Monadic version of `either`

with a different argument ordering.

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

`Either`

is bitraversable.

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

Analogue of `fromMaybeM`

.

maybeLeft :: Either a b -> Maybe a Source #

Safe projection from `Left`

.

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

maybeRight :: Either a b -> Maybe b Source #

Safe projection from `Right`

.

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