Copyright	(c) Owen Shepherd 2021
License	MIT
Maintainer	owen@owen.cafe
Stability	stable
Portability	portable
Safe Haskell	Safe-Inferred
Language	Haskell2010

Control.Applicative.MultiExcept

Description

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)

Synopsis

data MultiExcept err a
fromEither :: Either err a -> MultiExcept err a
fromEitherPoly :: Either (NonEmpty err) a -> MultiExcept err a
join :: MultiExcept err (MultiExcept err a) -> MultiExcept err a
or :: MultiExcept err a -> MultiExcept err a -> MultiExcept err a
runMultiExcept :: MultiExcept err a -> Either (NonEmpty err) a
succeed :: forall err a. a -> MultiExcept err a
throwError :: forall a err. err -> MultiExcept err a
throwErrors :: forall a err. NonEmpty err -> MultiExcept err a
mapMultiExcept :: (err -> err') -> (a -> a') -> MultiExcept err a -> MultiExcept err' a'

Documentation

data MultiExcept err a Source #

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

Instances

Instances details

Bifunctor MultiExcept Source #	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.
Instance details 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) Source #
Instance details 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) Source #
Instance details 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) Source #
Instance details 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) Source #
Instance details 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) Source #
Instance details 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) Source #
Instance details 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) Source #
Instance details 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 Source #

Convert an Either to a MultiExcept.

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

Convert a multi-error Either to a MultiExcept.

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

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 Source #

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

Examples

Expand

>>> 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 Source #

Run the computation.

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

Embeds a value into a MultiExcept context.

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

Throw a single error.

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

Throw one or more errors.

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

A non-overloaded bimap