Excerpt from configuration.nix

configuration.nix

  nixpkgs.config.packageOverrides = pkgs: rec {
    #haskellPackages = pkgs.haskellPackages;
    haskellPackages = pkgs.haskell.packages.ghc7103;
    myHaskellEnv = haskellPackages.ghcWithHoogle (
      haskellPackages: with haskellPackages; [
        cabal-install
        ghc-mod
        HaTeX
        hlint
        ipprint
        pandoc
        pandoc-citeproc
        stylish-haskell
      ]
    );
    # ...
  };
  
  environment.systemPackages = with pkgs; [
    myHaskellEnv
    # ...
  ];