Module

Data.Validation.Semiring

Package: validation
Repository: purescript/purescript-validation

This module defines a variant of applicative validation with an Alt instance, for validators which support errors with multiple alternatives.

#V Source

newtype V err result

The V functor, used for alternative validation

The Alternative instance collects multiple failures in an arbitrary Semiring.

For example:

import Data.Semiring.Free

validate r :: Person -> V (Free Error) Person
validate person = { first: _, last: _, contact: _}
  <$> validateName person.first
  <*> validateName person.last
  <*> (validateEmail person.contact <|> validatePhone person.contact)

Constructors

V (Either err result)

Instances

Newtype (V err result) _
(Eq err, Eq result) => Eq (V err result)
(Eq err) => Eq1 (V err)
(Ord err, Ord result) => Ord (V err result)
(Ord err) => Ord1 (V err)
(Show err, Show result) => Show (V err result)
Functor (V err)
Bifunctor V
(Semiring err) => Apply (V err)
(Semiring err) => Applicative (V err)
(Semiring err, Semigroup a) => Semigroup (V err a)
(Semiring err, Monoid a) => Monoid (V err a)
(Semiring err) => Alt (V err)
(Semiring err) => Plus (V err)
Foldable (V err)
Traversable (V err)

#validation Source

validation :: forall err result r. (err -> r) -> (result -> r) -> V err result -> r

Takes two functions an a V value, if the validation failed the error is applied to the first function, if the validation succeeded the inner value is applied to the second function.

#unV Source

unV :: forall err result r. Warn (Text "\'unV\' is deprecated, use \'validation\' instead") => (err -> r) -> (result -> r) -> V err result -> r

Deprecated previous name of validation.

#invalid Source

invalid :: forall err result. err -> V err result

Fail with a validation error.

#isValid Source

isValid :: forall err result. V err result -> Boolean

Test whether validation was successful or not.

#toEither Source

toEither :: forall err result. V err result -> Either err result

#andThen Source

andThen :: forall err a b. V err a -> (a -> V err b) -> V err b

Apply a function if successful, to enable chaining of validation.

Similar to a monadic bind, except it is inconsistent with Apply - that is, where as apply (V err a) (V err a) accumulates failures, (V err a) ``andThen`` (\a -> V err a) has fail-fast semantics (>>= would be expected to be consistent).

Modules: Data.Validation.Semigroup; Data.Validation.Semiring