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
Validation data type is isomorphic to
Either, but has an instance
Applicative that accumulates on the error side. That is to say, if two
(or more) errors are encountered, they are appended using a
As a consequence of this
Applicative instance, there is no corresponding
Validation is an example of, "An applicative
functor that is not a monad."
* Generalise types of `validate` and `ensure` functions to use `Maybe` instead of `Bool`
* Rename `AccValidation` to `Validation`
* Add `Generic` and `NFData` instances
* Make AccValidation Apply and Applicative lazier
* Add `bindValidation` and `validationed`
* Add validate, validationnel, fromEither, liftError, validation, toEither, orElse, valueOr, ensure, codiagonal, revalidate
* Delete `Validation`, `ValidationB`, `ValidationT`, `Validation'`
* Remove `_Validation` member from `Validate` class
* Raise upper bounds on base.
* Include nix build.
* remove redundant constraints.
* add instance `Validate` for `ValidationB Identity`.
* Update `transformers` dependency to work with GHC8.
* Remove LANGUAGE Safe because won't build against lens-4.13 or higher otherwise.
* Update documentation
* Export the `ValidationB` (formerly `ValidationTB`) data type.
* Renamed `ValidationTB` to `ValidationB`.
* Add upper-bounds on some dependencies.
* Move repository to https://github.com/NICTA/validation.
* Add README.
* Update copyright notice for 2015.
* Rename `ValidationT` to `ValidationTB`
* Introduce `ValidationT` with `MonadTrans` instance
* Export constructors on `AccValidation` and `Validation`.
* Remove `Alternative` instances. They are obscene.
* INLINE pragmas
* Change the premise of the `Validate` type-class to more strongly reflect the isomorphism to Either.
* The `_Failure` and `_Success` prisms are now derived.
* Lots more examples
A restructuring of 0.2.x where:
* Tests updated to use doctest
* Update API to use Prism and Iso (Control.Lens)
* Rename package Validation (deprecated) to validation
Use Safe Haskell pragma
Implement Validate on Either
Provide Isos between (ValidationT Identity) and other data types.
Loosen the type of the Isos for polymorphic update.