anchor.diff:  
   { pkgs ?
       (import (fetchTarball {
  -      url = "https://github.com/NixOS/nixpkgs/archive/060a98e9f4ad879492e48d63e887b0b6db26299e.tar.gz";
  -      sha256 = "1lzvp3md0hf6kp2bvc6dbzh40navlyd51qlns9wbkz6lqk3lgf6j";
  +      url = "https://github.com/NixOS/nixpkgs/archive/4477cf04b6779a537cdb5f0bd3dd30e75aeb4a3b.tar.gz";
  +      sha256 = "1i39wsfwkvj9yryj8di3jibpdg3b3j86ych7s9rb6z79k08yaaxc";
       }) {})
   , ocamlPackages ? pkgs.ocaml-ng.ocamlPackages_4_06
   , buildIde ? true
  
positive.code:     else
        with builtins; filterSource
          (path: _:
             !elem (baseNameOf path) [".git" "result" "bin" "_build_ci"]) ./.;
  
    prefixKey = "-prefix ";
  
  
negative.code:   buildInputs = [
      hostname
      python2 time # coq-makefile timing tools
      jbuilder
    ]
    ++ (with ocamlPackages; [ ocaml findlib camlp5_strict num ])
    ++ optional buildIde ocamlPackages.lablgtk
  