anchor.diff:  { stdenv, fetchurl, libX11, libXpm, libXext, xextproto, byacc }:
   
   stdenv.mkDerivation {
  -  name = "micropolis";
  +  name = "micropolis-2010-12-18"; # version from the patch timestamp
   
     src = fetchurl {
       url = http://www.donhopkins.com/home/micropolis/micropolis-activity-source.tgz;
  
positive.code:   patches =
      [ (fetchurl {
          url = http://rmdir.de/~michael/micropolis_git.patch;
          sha256 = "13419a4394242cd11d5cabd8b1b50787282ea16b55fdcfbeadf8505af46b0592";
        })
      ];
  
  
negative.code:       chmod 755 $out/bin/micropolis
      '';
  
    meta = {
      description = "GPL'ed version of S*m C*ty";
      homepage = http://www.donhopkins.com/home/micropolis/;
      license = "GPL";
  