style-guide.md

Haskell Style Guide

There are really only 5 things you need to know:

1. Use 4 spaces.
2. Use stylish-haskell for imports.
3. Use spaces around all operators in all cases (exception: (%) from Formatting).
4. As a default, use ! to make all fields in data types strict. If strictness annotations are omitted, document why.
5. As a default, make functions lazy. If they must be strict, document why.
6. All imports should be either qualified or explicit, i.e. with enumeration of stuff that you're importing (exception: Universum).

The rest of the style guide can be found here.