Copyright	(c) Gregory Crosswhite
License	BSD-style
Maintainer	gcross@haskell.org
Stability	provisional
Portability	portable
Safe Haskell	Safe
Language	Haskell98

Data.Either.Unwrap

Description

Functions for probing and unwrapping values inside of Either.

Synopsis

Documentation

isLeft :: Either a b -> Bool #

The isLeft function returns True iff its argument is of the form Left _.

isRight :: Either a b -> Bool #

The isRight function returns True iff its argument is of the form Right _.

fromLeft :: Either a b -> a #

The fromLeft function extracts the element out of a Left and throws an error if its argument take the form Right _.

fromRight :: Either a b -> b #

The fromRight function extracts the element out of a Right and throws an error if its argument take the form Left _.

mapBoth :: (a -> c) -> (b -> d) -> Either a b -> Either c d #

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 _'.

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

The mapLeft function takes a function and applies it to an Either value iff the value takes the form 'Left _'.

mapRight :: (b -> c) -> Either a b -> Either a c #

The mapLeft function takes a function and applies it to an Either value iff the value takes the form 'Left _'.

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

The eitherM function takes an Either value and two functions which return monads. If the argument takes the form Left _ then the element within is passed to the first function, otherwise the element within is passed to the second function.

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

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.

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

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 Right _, otherwise it does nothing.

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

A synonym of whenRight.

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

A synonym of whenLeft.