either

An either monad transformer

http://github.com/ekmett/either/

Version on this page:4.4.1
LTS Haskell 22.39:5.0.2@rev:2
Stackage Nightly 2024-10-31:5.0.2@rev:2
Latest on Hackage:5.0.2@rev:2

See all snapshots either appears in

BSD-3-Clause licensed by Edward A. Kmett
Maintained by Edward A. Kmett
This version can be pinned in stack with:either-4.4.1@sha256:85a6e87bb53f52b2bfb6ef4be7a4e6e1abcb703726f09c1c2a1c7e95d6f95982,1468

Module documentation for 4.4.1

either

Build Status

This provides an Either monad transformer that unlike ErrorT is unencumbered by a constraint on its Left hand argument. This is needed for a number of applications of this monad transformer, notably in recursion-schemes.

Contact Information

Contributions and bug reports are welcome!

Please feel free to contact me through github or on the #haskell IRC channel on irc.freenode.net.

-Edward Kmett

Changes

4.4

  • Support mmorph

4.3.4.1

  • Support MonadRandom 0.4

4.3.4

  • Support bifunctors 5, profunctors 5, and semigroupoids 5.

4.3.3.3

  • Fixed and enhanced documentation for eitherToError.

4.3.3.2

  • Support exceptions 0.8

4.3.3.1

  • Support exceptions 0.7

4.3.3

  • Added eitherToError.

4.3.2.1

  • Support monad-control 1.0

4.3.2

  • Added Validation.

4.3.0.2

  • Updated MonadRandom support.

4.3.0.1

  • Fixed import of MonadCatch to support versions of base before 4.6

4.3

  • Inverted dependency between free and either.

4.2

  • Added instances for MonadThrow, MonadCatch.

4.1

  • Added instances for MonadBase, MonadBaseControl, and MonadTransControl.

4.0

  • Updated dependencies.

3.4.2

  • Added ‘Data.Either.Combinators’.

3.4.1

  • Trustworthy despite UndecidableInstances

3.4

  • Delegate fail to the underlying Monad, rather than error.

3.3

  • Inverted roles between Semigroup and Alt. This let us write Alternative and MonadPlus instances that are compatible.
  • Removed the Functor constraint on most instances in exchange for incurring a Monad constraint on Traversable. EitherT is after all, a Monad transformer first and foremost.

3.2

  • Changed the Semigroup to use a Semigroup to combine Left branches. Left Alt untouched, so you can mix and match.

3.1

  • Added instances for mtl classes and MonadRandom.
  • The meaning of mapEitherT has changed to match mapErrorT in the mtl. The old mapEitherT is now bimapEitherT.

3.0.3

  • Started CHANGELOG