Data.Validation

This module defines the Validation data type.

Most functionality is the same as in the validation library, but the module doesn't provide certain typeclass instances that require a dependency on the lens library.

Documentation

data Validation err a

A Validation is very similar to Either in that it contains a value of type e or a. In contrast to Either however, Validation accumulates all errors it comes across in it's Applicative instance.

A complete example where Validation is used can be found here.

Constructors

Failure !err

Success !a

Instances

Bitraversable Validation

Defined in Data.Validation

Methods

bitraverse :: Applicative f => (a -> f c) -> (b -> f d) -> Validation a b -> f (Validation c d)

Bifoldable Validation

Defined in Data.Validation

Methods

bifold :: Monoid m => Validation m m -> m

bifoldMap :: Monoid m => (a -> m) -> (b -> m) -> Validation a b -> m

bifoldr :: (a -> c -> c) -> (b -> c -> c) -> c -> Validation a b -> c

bifoldl :: (c -> a -> c) -> (c -> b -> c) -> c -> Validation a b -> c

Bifunctor Validation

Defined in Data.Validation

Methods

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

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

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

Functor (Validation err)

Defined in Data.Validation

Methods

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

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

Semigroup err => Applicative (Validation err)

Defined in Data.Validation

Methods

pure :: a -> Validation err a

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

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

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

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

Foldable (Validation err)

Defined in Data.Validation

Methods

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

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

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

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

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

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

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

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

toList :: Validation err a -> [a]

null :: Validation err a -> Bool

length :: Validation err a -> Int

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

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

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

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

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

Traversable (Validation err)

Defined in Data.Validation

Methods

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

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

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

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

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

Defined in Data.Validation

Methods

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

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

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

Defined in Data.Validation

Methods

compare :: Validation err a -> Validation err a -> Ordering

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

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

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

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

max :: Validation err a -> Validation err a -> Validation err a

min :: Validation err a -> Validation err a -> Validation err a

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

Defined in Data.Validation

Methods

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

show :: Validation err a -> String

showList :: [Validation err a] -> ShowS

toEither :: Validation err a -> Either err a

Conversion function from Validation to Either.

>>> toEither (Failure 1)
Left 1
>>> toEither (Success True)
Right True

fromEither :: Either err a -> Validation err a

Conversion function from Either to Validation.

>>> fromEither (Left 1)
Failure 1
>>> fromEither (Right True)
Success True