# Pastebin EpNnlkFH
```
let
config = {
  packageOverrides = pkgs: rec {
    haskellPackages = pkgs.haskellPackages.override {
      overrides = haskellPackagesNew: haskellPackagesOld: rec {
        project1 =
          haskellPackagesNew.callPackage ./default.nix { };
        # QuickCheck =
        #   haskellPackagesNew.callPackage ./QuickCheck.nix { };
        hmatrix =
          haskellPackagesNew.callPackage ./hmatrix.nix { };
      };
    };
  };
};

pkgs = import <nixpkgs> { inherit config; };

in
{ project1 = pkgs.haskellPackages.project1;
}
```