{cabal}:

cabal.mkDerivation (self : {
  pname = "mtl";
  version = "1.1.1.1"; # version of mtl1 compatible with ghc7
  sha256 = "157gbrgrg0l9r72nq45dkach53yncysif4qglsaql28g37djc4x6";
  meta = {
    description = "Monad transformer library";
  };
})