shell.nix

let

pkgs = fetchTarball "https://github.com/NixOS/nixpkgs/archive/nixos-unstable.tar.gz";

myHaskellPackageOverlay = self: super: {

  myHaskellPackages = super.haskell.packages.ghc922.override {
    overrides = hself: hsuper: rec {
      random = self.haskell.lib.addBuildDepends(
        hsuper.callHackageDirect {
          pkg = "random";
          ver = "1.2.1.1";
          sha256 = "sha256-+oDdFTsmai2E/ICr18Kd+uHVhMQvud2hBve5IJIMKMA=";
        } { }) [ ];
    };
  };
};

in

{ nixpkgs ? import pkgs { overlays = [ myHaskellPackageOverlay ]; }}:

 let

  haskellDeps = ps: with ps; [
    base random
  ];

in

  nixpkgs.stdenv.mkDerivation {
  name = "env";
  buildInputs = [
    (nixpkgs.myHaskellPackages.ghcWithPackages haskellDeps)
  ];
  }