A Haskell editing modehttp://www.iro.umontreal.ca/~lapalme/layout/index.html
M-x package-install [RET] haskell-mode [RET]
A major mode for editing Haskell (the functional programming language, see URL `http://www.haskell.org') in Emacs. Some of its major features include: - syntax highlighting (font lock), - automatic indentation, - on-the-fly documentation, - interaction with inferior GHCi/Hugs instance, - scans declarations and places them in a menu. See URL `https://github.com/haskell/haskell-mode' and/or Info node `(haskell-mode)Introduction' for more information. Use `M-x haskell-mode-view-news` (after Haskell Mode is installed) to show information on recent changes in Haskell Mode.