anchor.diff:          url = "http://developer.download.nvidia.com/cg/Cg_${version}/Cg-${version}_${date}_x86.tgz";
           sha256 = "0hr8l0r20akbfm5j0vqv4ghl0acwjf5996pxnfxlajacl9w58nam";
         }
  -    else null;
  +    else throw "nvidia-cg-toolkit does not support platform ${stdenv.system}";
  +    
     installPhase = ''
       for b in cgc cgfxcat cginfo
       do
  
positive.code: { stdenv, fetchurl, patchelf }:
  stdenv.mkDerivation rec {
    version = "3.0";
    date = "February2011";
    name = "nvidia-cg-toolkit-${version}";
    src =
      if stdenv.system == "x86_64-linux" then
        fetchurl {
  
negative.code:     ensureDir "$out/share/doc/$name/"
      cp -v -r local/Cg/* "$out/share/doc/$name/"
    '';
    
    meta = {
      homepage = http://developer.nvidia.com/cg-toolkit;
      license = [ "nonfree-redistributable" ];
  