This is a Heroku buildpack for Haskell apps. It uses GHC 7.4.1 and cabal-1.16.0.1.
A demo is online here:
http://haskell-buildpack-demo.herokuapp.com/
The demo repo is here:
https://github.com/pufuwozu/haskell-buildpack-demo
$ ls
Procfile app.cabal src
$ heroku create --stack=cedar --buildpack https://github.com/pufuwozu/heroku-buildpack-haskell.git
$ git push heroku master
...
-----> Heroku receiving push
-----> Fetching custom git buildpack... done
-----> Haskell app detected
-----> Downloading GHC
######################################################################## 100.0%
-----> Downloading Cabal
######################################################################## 100.0%
-----> Setting up ghc-pkg
...