anchor.diff:      ++ network-tools
       ++ dev-tools;
   
  -in
  -  rec {
  +  in rec {
       allowUnfree = true;
   
       firefox = {
  
positive.code: with pkgs;
  
  let
    is-osx = builtins.currentSystem == "x86_64-darwin";
    is-linux = builtins.currentSystem != "x86_64-darwin";
  
    pkg-set = {
      all ? [],
      osx ? [],
      linux ? []
    }: (
      all
      ++ (if is-osx then osx else [])
      ++ (if is-linux then linux else [])
    );
  
    nvim = pkgs.callPackage ./nvim {};
    eslint = pkgs.callPackage ./node/eslint.nix {};
    prettier = pkgs.callPackage ./node/prettier.nix {};
  
negative.code:     dep
    ];
  
    python2-env = with python27Packages; [
      (python27Full.withPackages (ps: [
        ps.setuptools
      ]))
      ipython
      flake8
      virtualenv
      Fabric
      pylint
    ];
  
    base-tools =
  