Control.Applicative.MultiExcept

Errors are accumulated through Applicative sequencing. The recommended way to use MultiExcept is with ApplicativeDo:

{-# LANGUAGE ApplicativeDo #-}

import Control.Applicative.MultiExcept

errors :: MultiExcept String (Int, Int, Int)
errors = do
  a <- throwError "no monad instance"
  b <- pure 12
  c <- throwError "i am scared"
  pure (a, b, c)

Documentation

data MultiExcept err a

A MultiExcept is a success value, or one or more errors.

Instances

Bifunctor MultiExcept

WARNING: O(n) space and time in the length of the amount of errors this could be fixed by changing the difference list Functor instance.

Defined in Control.Applicative.MultiExcept

Methods

bimap :: (a -> b) -> (c -> d) -> MultiExcept a c -> MultiExcept b d

first :: (a -> b) -> MultiExcept a c -> MultiExcept b c

second :: (b -> c) -> MultiExcept a b -> MultiExcept a c

Foldable (MultiExcept err)

Defined in Control.Applicative.MultiExcept

Methods

fold :: Monoid m => MultiExcept err m -> m

foldMap :: Monoid m => (a -> m) -> MultiExcept err a -> m

foldMap' :: Monoid m => (a -> m) -> MultiExcept err a -> m

foldr :: (a -> b -> b) -> b -> MultiExcept err a -> b

foldr' :: (a -> b -> b) -> b -> MultiExcept err a -> b

foldl :: (b -> a -> b) -> b -> MultiExcept err a -> b

foldl' :: (b -> a -> b) -> b -> MultiExcept err a -> b

foldr1 :: (a -> a -> a) -> MultiExcept err a -> a

foldl1 :: (a -> a -> a) -> MultiExcept err a -> a

toList :: MultiExcept err a -> [a]

null :: MultiExcept err a -> Bool

length :: MultiExcept err a -> Int

elem :: Eq a => a -> MultiExcept err a -> Bool

maximum :: Ord a => MultiExcept err a -> a

minimum :: Ord a => MultiExcept err a -> a

sum :: Num a => MultiExcept err a -> a

product :: Num a => MultiExcept err a -> a

Traversable (MultiExcept err)

Defined in Control.Applicative.MultiExcept

Methods

traverse :: Applicative f => (a -> f b) -> MultiExcept err a -> f (MultiExcept err b)

sequenceA :: Applicative f => MultiExcept err (f a) -> f (MultiExcept err a)

mapM :: Monad m => (a -> m b) -> MultiExcept err a -> m (MultiExcept err b)

sequence :: Monad m => MultiExcept err (m a) -> m (MultiExcept err a)

Applicative (MultiExcept err)

Defined in Control.Applicative.MultiExcept

Methods

pure :: a -> MultiExcept err a

(<*>) :: MultiExcept err (a -> b) -> MultiExcept err a -> MultiExcept err b

liftA2 :: (a -> b -> c) -> MultiExcept err a -> MultiExcept err b -> MultiExcept err c

(*>) :: MultiExcept err a -> MultiExcept err b -> MultiExcept err b

(<*) :: MultiExcept err a -> MultiExcept err b -> MultiExcept err a

Functor (MultiExcept err)

Defined in Control.Applicative.MultiExcept

Methods

fmap :: (a -> b) -> MultiExcept err a -> MultiExcept err b

(<$) :: a -> MultiExcept err b -> MultiExcept err a

(Show a, Show err) => Show (MultiExcept err a)

Defined in Control.Applicative.MultiExcept

Methods

showsPrec :: Int -> MultiExcept err a -> ShowS

show :: MultiExcept err a -> String

showList :: [MultiExcept err a] -> ShowS

(Eq a, Eq err) => Eq (MultiExcept err a)

Defined in Control.Applicative.MultiExcept

Methods

(==) :: MultiExcept err a -> MultiExcept err a -> Bool

(/=) :: MultiExcept err a -> MultiExcept err a -> Bool

(Ord a, Ord err) => Ord (MultiExcept err a)

Defined in Control.Applicative.MultiExcept

Methods

compare :: MultiExcept err a -> MultiExcept err a -> Ordering

(<) :: MultiExcept err a -> MultiExcept err a -> Bool

(<=) :: MultiExcept err a -> MultiExcept err a -> Bool

(>) :: MultiExcept err a -> MultiExcept err a -> Bool

(>=) :: MultiExcept err a -> MultiExcept err a -> Bool

max :: MultiExcept err a -> MultiExcept err a -> MultiExcept err a

min :: MultiExcept err a -> MultiExcept err a -> MultiExcept err a

fromEither :: Either err a -> MultiExcept err a

Convert an Either to a MultiExcept.

fromEitherPoly :: Either (NonEmpty err) a -> MultiExcept err a

Convert a multi-error Either to a MultiExcept.

join :: MultiExcept err (MultiExcept err a) -> MultiExcept err a

Join nested MultiExcepts with the same error type. Note that this doesn't imply a useful Monad instance. The instance defined in terms of join discards errors on the RHS of >>=, when the LHS is an error value.

or :: MultiExcept err a -> MultiExcept err a -> MultiExcept err a

Return the first success, or all of the combined errors.

Examples

>>> pure 1 `or` throwError 3
Success 1

>>> throwError 2 `or` pure 1
Success 1

>>> throwError 2 `or` throwError 3
Errors [2, 3]

runMultiExcept :: MultiExcept err a -> Either (NonEmpty err) a

Run the computation.

succeed :: forall err a. a -> MultiExcept err a

Embeds a value into a MultiExcept context.

throwError :: forall a err. err -> MultiExcept err a

Throw a single error.

throwErrors :: forall a err. NonEmpty err -> MultiExcept err a

Throw one or more errors.

mapMultiExcept :: (err -> err') -> (a -> a') -> MultiExcept err a -> MultiExcept err' a'

A non-overloaded bimap