{ pkgs ? (import <nixpkgs> {})
, haskellPackages ? pkgs.haskellPackages
}:

let
  ghc = haskellPackages.ghcWithPackages (ps: with ps; [ mtl ]);
in
pkgs.stdenv.mkDerivation rec {
  name = "gausshs-env";
  buildInputs = [ ghc ];
  shellHook = ''
    eval $(egrep ^export ${ghc}/bin/ghc)
    export PROMPT_INFO="${name}"
  '';
}