-- Hoogle documentation, generated by Haddock
-- See Hoogle, http://www.haskell.org/hoogle/
-- | A data-type like Either but with an accumulating Applicative
--
--
-- A data-type like Either but with differing properties and type-class
-- instances.
--
-- Library support is provided for this different representation, include
-- lens-related functions for converting between each and
-- abstracting over their similarities.
--
--
--
-- The AccValidation data type is isomorphic to Either, but
-- has an instance of Applicative that accumulates on the error
-- side. That is to say, if two (or more) errors are encountered, they
-- are appended using a Semigroup operation.
--
-- As a consequence of this Applicative instance, there is no
-- corresponding Bind or Monad instance.
-- AccValidation is an example of, "An applicative functor that is
-- not a monad."
@package validation
@version 0.6.1
-- | A data type similar to Data.Either that accumulates failures.
module Data.Validation
-- | An AccValidation is either a value of the type err
-- or a, similar to Either. However, the
-- Applicative instance for AccValidation
-- accumulates errors using a Semigroup on err. In
-- contrast, the Applicative for Either returns only
-- the first error.
--
-- A consequence of this is that AccValidation has no
-- Bind or Monad instance. This is because such an instance
-- would violate the law that a Monad's ap must equal the
-- Applicative's <*>
--
-- An example of typical usage can be found here.
data AccValidation err a
AccFailure :: err -> AccValidation err a
AccSuccess :: a -> AccValidation err a
-- | validates the a with the given predicate, returning
-- e if the predicate does not hold.
--
-- This can be thought of as having the less general type:
--
--
-- validate :: e -> (a -> Bool) -> a -> AccValidation e a
--
validate :: Validate v => e -> (a -> Bool) -> a -> v e a
-- | validationNel is liftError specialised to
-- NonEmpty lists, since they are a common semigroup to use.
validationNel :: Either e a -> AccValidation (NonEmpty e) a
-- | Converts from Either to AccValidation.
fromEither :: Either e a -> AccValidation e a
-- | liftError is useful for converting an Either to an
-- AccValidation when the Left of the Either needs
-- to be lifted into a Semigroup.
liftError :: (b -> e) -> Either b a -> AccValidation e a
-- | validation is the catamorphism for AccValidation.
validation :: (e -> c) -> (a -> c) -> AccValidation e a -> c
-- | Converts from AccValidation to Either.
toEither :: AccValidation e a -> Either e a
-- | v orElse a returns a when v is
-- AccFailure, and the a in AccSuccess a.
--
-- This can be thought of as having the less general type:
--
--
-- orElse :: AccValidation e a -> a -> a
--
orElse :: Validate v => v e a -> a -> a
-- | Return the a or run the given function over the e.
--
-- This can be thought of as having the less general type:
--
--
-- valueOr :: (e -> a) -> AccValidation e a -> a
--
valueOr :: Validate v => (e -> a) -> v e a -> a
-- | ensure leaves the validation unchanged when the predicate
-- holds, or fails with e otherwise.
--
-- This can be thought of as having the less general type:
--
--
-- ensure :: e -> (a -> Bool) -> AccValidation e a -> AccValidation e a
--
ensure :: Validate v => e -> (a -> Bool) -> v e a -> v e a
-- | codiagonal gets the value out of either side.
codiagonal :: AccValidation a a -> a
-- | This prism generalises _Left. It targets the failure case of
-- either Either or AccValidation.
_Failure :: Validate f => Prism (f e1 a) (f e2 a) e1 e2
-- | This prism generalises _Right. It targets the success case of
-- either Either or AccValidation.
_Success :: Validate f => Prism (f e a) (f e b) a b
-- | The Validate class carries around witnesses that the type
-- f is isomorphic to AccValidation, and hence isomorphic to
-- Either.
class Validate f where _Either = _EitherV
_AccValidation :: Validate f => Iso (f e a) (f g b) (AccValidation e a) (AccValidation g b)
_Either :: Validate f => Iso (f e a) (f g b) (Either e a) (Either g b)
-- | revalidate converts between any two instances of
-- Validate.
revalidate :: (Validate f, Validate g) => Iso (f e1 s) (f e2 t) (g e1 s) (g e2 t)
instance (Data.Data.Data a, Data.Data.Data err) => Data.Data.Data (Data.Validation.AccValidation err a)
instance (GHC.Show.Show a, GHC.Show.Show err) => GHC.Show.Show (Data.Validation.AccValidation err a)
instance (GHC.Classes.Ord a, GHC.Classes.Ord err) => GHC.Classes.Ord (Data.Validation.AccValidation err a)
instance (GHC.Classes.Eq a, GHC.Classes.Eq err) => GHC.Classes.Eq (Data.Validation.AccValidation err a)
instance GHC.Base.Functor (Data.Validation.AccValidation err)
instance Data.Semigroup.Semigroup err => Data.Functor.Bind.Class.Apply (Data.Validation.AccValidation err)
instance Data.Semigroup.Semigroup err => GHC.Base.Applicative (Data.Validation.AccValidation err)
instance Data.Functor.Alt.Alt (Data.Validation.AccValidation err)
instance Data.Foldable.Foldable (Data.Validation.AccValidation err)
instance Data.Traversable.Traversable (Data.Validation.AccValidation err)
instance Data.Bifunctor.Bifunctor Data.Validation.AccValidation
instance Data.Bifoldable.Bifoldable Data.Validation.AccValidation
instance Data.Bitraversable.Bitraversable Data.Validation.AccValidation
instance Data.Semigroup.Semigroup e => Data.Semigroup.Semigroup (Data.Validation.AccValidation e a)
instance GHC.Base.Monoid e => GHC.Base.Monoid (Data.Validation.AccValidation e a)
instance Control.Lens.Iso.Swapped Data.Validation.AccValidation
instance Data.Validation.Validate Data.Validation.AccValidation
instance Data.Validation.Validate Data.Either.Either