config.nix

{
  packageOverrides = super:
    let
      self = super.pkgs;
      ghc784Package = self.haskell.packages.ghc784.ghcWithPackages (
        haskellPackages: with haskellPackages; [
          cabal-install
          cabal2nix
        ]
      );
    in
  {
    # GHC 7.6.3
    ghc763 = self.haskell.packages.ghc763.ghcWithPackages (
      haskellPackages: with haskellPackages; [
        cabal-install
        cabal2nix
      ]
    );

    ghc784 = self.stdenv.mkDerivation {
      name = "ghc784";
      src = ./.;
      NIX_MYENV_NAME = "ghc784";
      buildInputs = [ ghc784H ];
      shellHook = "source ~/.bash_prompt";
    };

    # GHC 7.10.1
    ghc7101 = self.haskell.packages.ghc7101.ghcWithPackages (
      haskellPackages: with haskellPackages; [
        cabal-install
        cabal2nix
      ]
    );
  };
}