Data.Validation

Data types similar to Data.Either that are explicit about failure and success.

Documentation

data AccValidation err a

A value of the type err or a, however, the Applicative instance accumulates values. This is witnessed by the Semigroup context on the instance. Note that there is no @Monad@ such that @ap = (<*>).

• success (+1) * success 7 == AccSuccess 8

• failure [f1] * success 7 == AccFailure [f1]

• success (+1) * failure [f2] == AccFailure [f2]

• failure [f1] * failure [f2] == AccFailure [f1,f2]

Instances

Typeable2 AccValidation

Bitraversable AccValidation

Bifunctor AccValidation

Bifoldable AccValidation

Validate AccValidation

Functor (AccValidation err)

Semigroup err => Applicative (AccValidation err)

Foldable (AccValidation err)

Traversable (AccValidation err)

(Semigroup err, Monoid err) => Alternative (AccValidation err)

Semigroup err => Alt (AccValidation err)

Semigroup err => Apply (AccValidation err)

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

(Data err, Data a) => Data (AccValidation err a)

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

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

Monoid e => Monoid (AccValidation e a)

Semigroup e => Semigroup (AccValidation e a)

data Validation err a

A value of the type err or a and isomorphic to Data.Either.

Instances

Typeable2 Validation

Bitraversable Validation

Bifunctor Validation

Bifoldable Validation

Validate Validation

Monad (Validation err)

Functor (Validation err)

Applicative (Validation err)

Foldable (Validation err)

Traversable (Validation err)

Monoid err => Alternative (Validation err)

Alt (Validation err)

Apply (Validation err)

Bind (Validation err)

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

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

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

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

data ValidationT m err a

The transformer version of Validation.

Constructors

ValidationT

Fields

runValidationT :: m (Validation err a)

Instances

Traversable m => Bitraversable (ValidationT m)

Functor m => Bifunctor (ValidationT m)

Foldable m => Bifoldable (ValidationT m)

Applicative m => Validate (ValidationT m)

Monad m => Monad (ValidationT m err)

Functor m => Functor (ValidationT m err)

Applicative m => Applicative (ValidationT m err)

Foldable m => Foldable (ValidationT m err)

Traversable m => Traversable (ValidationT m err)

(Applicative m, Monad m, Monoid err) => Alternative (ValidationT m err)

(Functor m, Monad m) => Alt (ValidationT m err)

Apply m => Apply (ValidationT m err)

(Apply m, Monad m) => Bind (ValidationT m err)

class Validate v where

Construction for validation values.

Methods

success :: a -> v err a

Construct a success validation value.

failure :: err -> v err a

Construct a failure validation value.

Instances

Validate Validation

Validate AccValidation

Applicative m => Validate (ValidationT m)