Fourmolu is a formatter for Haskell source code. It is a fork of Ormolu,
with the intention to continue to merge upstream improvements.

We share all bar one of Ormolu's goals:

* Using GHC's own parser to avoid parsing problems caused by
  haskell-src-exts.
* Let some whitespace be programmable. The layout of the input influences
  the layout choices in the output. This means that the choices between
  single-line/multi-line layouts in certain situations are made by the
  user, not by an algorithm. This makes the implementation simpler and
  leaves some control to the user while still guaranteeing that the
  formatted code is stylistically consistent.
* Writing code in such a way so it's easy to modify and maintain.
* That formatting style aims to result in minimal diffs.
* Choose a style compatible with modern dialects of Haskell. As new Haskell
  extensions enter broad use, we may change the style to accommodate them.
* Idempotence: formatting already formatted code doesn't change it.
* Be well-tested and robust so that the formatter can be used in large
  projects.
* We allow configuration of various parameters, via CLI options or config
  files. We encourage any contributions which add further flexibility.

Homepage:
http://hackage.haskell.org/package/fourmolu
