anchor.diff:  
   stdenv.mkDerivation rec {
     name = "singular-${version}";
  -  version="3-1-2";
  +  version="3-1-7";
   
     src = fetchurl {
  -    url = "http://www.mathematik.uni-kl.de/ftp/pub/Math/Singular/SOURCES/${version}/${name}.tar.gz";
  -    sha256 = "04f9i1xar0r7qrrbfki1h9rrmx5y2xg4w7rrvlbx05v2dy6s8djv";
  +    url = "http://www.mathematik.uni-kl.de/ftp/pub/Math/Singular/SOURCES/${version}/Singular-${version}.tar.gz";
  +    sha256 = "1j4mcpnwzdp3h4qspk6ww0m67rmx4s11cy17pvzbpf70lm0jzzh2";
     };
   
     buildInputs = [ gmp bison perl autoconf ncurses readline coreutils ];
  
positive.code: 
    postInstall = ''
      rm -rf "$out/LIB"
      cp -r Singular/LIB "$out"
      mkdir -p "$out/bin"
      ln -s "$out/"*/Singular "$out/bin"
    '';
  
negative.code:     platforms = platforms.linux;
      license = licenses.gpl3; # Or GPLv2 at your option - but not GPLv4
      homepage = "http://www.singular.uni-kl.de/index.php";
      downloadPage = "http://www.mathematik.uni-kl.de/ftp/pub/Math/Singular/SOURCES/";
    };
  }
  