Safe Haskell	None
Language	Haskell2010

Accuerr

Description

Provides Accuerr, a type similar to Either but where the Applicative instance accumulates error values. This module is based on work in the validation package, which is available at

https://hackage.haskell.org/package/validation

The main differences between the validation package and this one:

validation has more data types, many of which overlap with those available in other packages. This package sticks with the Accuerr type only.
This package works with GHC 8; as of 2016-06-11, validation does not.
Accuerr has fewer typeclass instances than its corresponding type in validation.

Synopsis

data Accuerr e a
- = AccFailure e
- | AccSuccess a
_AccSuccess :: forall e a a. Prism (Accuerr e a) (Accuerr e a) a a
_AccFailure :: forall e a e. Prism (Accuerr e a) (Accuerr e a) e e
accuerr :: (a -> c) -> (b -> c) -> Accuerr a b -> c
accuerrToEither :: Accuerr e a -> Either e a
eitherToAccuerr :: Either e a -> Accuerr e a
isoAccuerrEither :: Iso' (Accuerr e a) (Either e a)
isoEitherAccuerr :: Iso' (Either e a) (Accuerr e a)

Documentation

data Accuerr e a #

A type similar to Either but the Applicative instance accumulates error values. Unlike Either, there is no Monad instance, because there is no >>= such that ap equals <*>.

For the Applicative instance to work, your error type must be a Semigroup, such as a list or a NonEmpty.

Examples

Expand

>>> import Text.Read
>>> :{
       let readInt x = case readMaybe x of
             Nothing -> AccFailure [x]
             Just a -> AccSuccess a
               where _types = a :: Int
    :}

>>> (+) <$> readInt "3" <*> readInt "4"
AccSuccess 7
>>> (+) <$> readInt "x3" <*> readInt "4"
AccFailure ["x3"]
>>> (+) <$> readInt "x3" <*> readInt "x4"
AccFailure ["x3","x4"]
>>> (,,) <$> readInt "3" <*> readInt "4" <*> readInt "x5"
AccFailure ["x5"]
>>> sequenceA [AccSuccess 3, AccSuccess 4]
AccSuccess [3,4]
>>> sequenceA [AccSuccess 3, AccSuccess 4, AccFailure ['c'], AccFailure ['a']]
AccFailure "ca"

Constructors

AccFailure e
AccSuccess a

Instances

Bitraversable Accuerr #
Instance details Defined in Accuerr Methods bitraverse :: Applicative f => (a -> f c) -> (b -> f d) -> Accuerr a b -> f (Accuerr c d) #
Bifoldable Accuerr #
Instance details Defined in Accuerr Methods bifold :: Monoid m => Accuerr m m -> m # bifoldMap :: Monoid m => (a -> m) -> (b -> m) -> Accuerr a b -> m # bifoldr :: (a -> c -> c) -> (b -> c -> c) -> c -> Accuerr a b -> c # bifoldl :: (c -> a -> c) -> (c -> b -> c) -> c -> Accuerr a b -> c #
Bifunctor Accuerr #
Instance details Defined in Accuerr Methods bimap :: (a -> b) -> (c -> d) -> Accuerr a c -> Accuerr b d # first :: (a -> b) -> Accuerr a c -> Accuerr b c # second :: (b -> c) -> Accuerr a b -> Accuerr a c #
Swapped Accuerr #
Instance details Defined in Accuerr Methods swapped :: (Profunctor p, Functor f) => p (Accuerr b a) (f (Accuerr d c)) -> p (Accuerr a b) (f (Accuerr c d)) #
Functor (Accuerr e) #
Instance details Defined in Accuerr Methods fmap :: (a -> b) -> Accuerr e a -> Accuerr e b # (<$) :: a -> Accuerr e b -> Accuerr e a #
Semigroup e => Applicative (Accuerr e) #
Instance details Defined in Accuerr Methods pure :: a -> Accuerr e a # (<>) :: Accuerr e (a -> b) -> Accuerr e a -> Accuerr e b # liftA2 :: (a -> b -> c) -> Accuerr e a -> Accuerr e b -> Accuerr e c # (>) :: Accuerr e a -> Accuerr e b -> Accuerr e b # (<*) :: Accuerr e a -> Accuerr e b -> Accuerr e a #
Foldable (Accuerr e) #
Instance details Defined in Accuerr Methods fold :: Monoid m => Accuerr e m -> m # foldMap :: Monoid m => (a -> m) -> Accuerr e a -> m # foldr :: (a -> b -> b) -> b -> Accuerr e a -> b # foldr' :: (a -> b -> b) -> b -> Accuerr e a -> b # foldl :: (b -> a -> b) -> b -> Accuerr e a -> b # foldl' :: (b -> a -> b) -> b -> Accuerr e a -> b # foldr1 :: (a -> a -> a) -> Accuerr e a -> a # foldl1 :: (a -> a -> a) -> Accuerr e a -> a # toList :: Accuerr e a -> [a] # null :: Accuerr e a -> Bool # length :: Accuerr e a -> Int # elem :: Eq a => a -> Accuerr e a -> Bool # maximum :: Ord a => Accuerr e a -> a # minimum :: Ord a => Accuerr e a -> a # sum :: Num a => Accuerr e a -> a # product :: Num a => Accuerr e a -> a #
Traversable (Accuerr e) #
Instance details Defined in Accuerr Methods traverse :: Applicative f => (a -> f b) -> Accuerr e a -> f (Accuerr e b) # sequenceA :: Applicative f => Accuerr e (f a) -> f (Accuerr e a) # mapM :: Monad m => (a -> m b) -> Accuerr e a -> m (Accuerr e b) # sequence :: Monad m => Accuerr e (m a) -> m (Accuerr e a) #
(Eq e, Eq a) => Eq (Accuerr e a) #
Instance details Defined in Accuerr Methods (==) :: Accuerr e a -> Accuerr e a -> Bool # (/=) :: Accuerr e a -> Accuerr e a -> Bool #
(Ord e, Ord a) => Ord (Accuerr e a) #
Instance details Defined in Accuerr Methods compare :: Accuerr e a -> Accuerr e a -> Ordering # (<) :: Accuerr e a -> Accuerr e a -> Bool # (<=) :: Accuerr e a -> Accuerr e a -> Bool # (>) :: Accuerr e a -> Accuerr e a -> Bool # (>=) :: Accuerr e a -> Accuerr e a -> Bool # max :: Accuerr e a -> Accuerr e a -> Accuerr e a # min :: Accuerr e a -> Accuerr e a -> Accuerr e a #
(Show e, Show a) => Show (Accuerr e a) #
Instance details Defined in Accuerr Methods showsPrec :: Int -> Accuerr e a -> ShowS # show :: Accuerr e a -> String # showList :: [Accuerr e a] -> ShowS #

_AccSuccess :: forall e a a. Prism (Accuerr e a) (Accuerr e a) a a #

_AccFailure :: forall e a e. Prism (Accuerr e a) (Accuerr e a) e e #

accuerr :: (a -> c) -> (b -> c) -> Accuerr a b -> c #

Case analysis for the Accuerr type. Like either.

accuerrToEither :: Accuerr e a -> Either e a #

eitherToAccuerr :: Either e a -> Accuerr e a #

isoAccuerrEither :: Iso' (Accuerr e a) (Either e a) #

isoEitherAccuerr :: Iso' (Either e a) (Accuerr e a) #