validation
A data-type like Either but with an accumulating Applicative
https://github.com/qfpl/validation
| LTS Haskell 24.16: | 1.1.3@rev:1 |
| Stackage Nightly 2025-10-24: | 1.1.3@rev:1 |
| Latest on Hackage: | 1.1.3@rev:1 |
Maintained by Tony Morris <ʇǝu˙sıɹɹoɯʇ@ןןǝʞsɐɥ> <dibblego>, Nick Partridge <nkpart>, Queensland Functional Programming Lab <oᴉ˙ldɟb@llǝʞsɐɥ>
This version can be pinned in stack with:
validation-1.1.3@sha256:3fdc553ee28ec1c954e5658cf0476b4c0b0fcff408c79343a2e580953dd2b952,3699Module documentation for 1.1.3
- Data
Depends on 7 packages(full list with versions):
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.
Validation
The Validation 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. Validation is an example of, "An applicative
functor that is not a monad."