scalaz/scalaz — pull request #93 by YoEight (2012-05-22 21:22:34+00:00)
Title: MonadWriter typeclass

Partially a port from Haskell MonadWriter.

It pemits to use Writer Monad Transformer computation without type annotations nightmare

This comes with two implementations: WriterT and ValidationT

Here an example https://gist.github.com/2771406