anchor.diff:  
     version = "1.6.54";
   in
  -
  -assert xorg != null ->
  -  xorg.libXext != null
  -  && xorg.libXcursor != null
  -  && xorg.libXft != null
  -  && xorg.libXrandr != null
  -  && xorg.libXrender != null
  -  && xorg.renderproto != null
  -  && xorg.xproto != null;
  -
   stdenv.mkDerivation rec {
     name = "fox-${version}";
   
  
positive.code: , libsm
  , libtiff
  , libx11
  , opengl-dummy
  , xorg
  , zlib
  }:
  
  
negative.code:     libsm
      libtiff
      libx11
      libxext
      libxcursor
      libxft
      libxrandr
      libxrender
      opengl-dummy
      xorgproto
      zlib
    ];
  
  