optics-by-example.nix

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

  config = {
    packageOverrides = pkgs: {
      haskellPackages = pkgs.haskellPackages.override {
        overrides = self: super: {
        };
      };
    };
  };

  hp = p: with p; [
    base
    aeson
    containers
    lens
    lens-aeson
    mtl
    text
  ];

  ghc = pkgs.haskellPackages.ghcWithPackages hp;

  env = pkgs.stdenv.mkDerivation {
    name = "env";
    buildInputs = [ ghc ];
  };

  haskellPackages = pkgs.haskellPackages;

  tags = pkgs.callPackage ../haskell-sources-tags-nix/tag-sources.nix {
    inherit pkgs haskellPackages;
    packages = hp haskellPackages;
  };

in

  # nix-shell -A env
  # nix-build --out-link dependencies -A tags shell.nix

  { inherit env tags; }