(Emacs24.3, MacOSX10.8)
install ghc
The Glorious Glasgow Haskell Compilation System
sudo port install ghc sudo port install hs-cabal-install
zshrc or bashrc
PATH=$HOME/.cabal/bin:$PATH
Install package in Emacs
init.el
;; Haskell (add-hook 'haskell-mode-hook (lambda () (flymake-haskell-multi-load) (turn-on-haskell-indentation) ))