anchor.diff:  { stdenv, fetchurl, zlib ? null, zlibSupport ? true, bzip2, pkgconfig, libffi
  -, sqlite, openssl, ncurses, pythonFull }:
  +, sqlite, openssl, ncurses, pythonFull, expat }:
   
   assert zlibSupport -> zlib != null;
   
  
positive.code:   majorVersion = "2.0";
    version = "${majorVersion}.2";
  
    src = fetchurl {
      url = "https://bitbucket.org/pypy/pypy/downloads/pypy-${version}-src.tar.bz2";
      sha256 = "0g2cajs6m3yf0lak5f18ccs6j77cf5xvbm4h6y5l1qlqdc6wk48r";
    };
  
    #patches =
    #  [ # Look in C_INCLUDE_PATH and LIBRARY_PATH for stuff.
    #    ./search-path.patch
  
        # Python recompiles a Python if the mtime stored *in* the
        # pyc/pyo file differs from the mtime of the source file.  This
        # doesn't work in Nix because Nix changes the mtime of files in
        # the Nix store to 1.  So treat that as a special case.
    #    ./nix-store-mtime.patch
  
        # patch python to put zero timestamp into pyc
        # if DETERMINISTIC_BUILD env var is set
    #    ./deterministic-build.patch
    #  ];
    #'';
  
    install = ''
      cd ./pypy/pypy/tool/release/
      ${pythonFull}/bin/python package.py ../../.. pypy-my-own-package-name
    '';
  
    buildInputs =
      stdenv.lib.optional (stdenv ? gcc && stdenv.gcc.libc != null) stdenv.gcc.libc ++
      [ bzip2 openssl pkgconfig pythonFull libffi ncurses ]
      ++ stdenv.lib.optional zlibSupport zlib;
  
    pypy = stdenv.mkDerivation rec {
      name = "pypy-${version}";
  
      inherit majorVersion version src buildInputs;
  
      preConfigure = ''
        substituteInPlace Makefile \
          --replace "-Ojit" "-Ojit --batch" \
          --replace "pypy/goal/targetpypystandalone.py" "pypy/goal/targetpypystandalone.py --withmod-_minimal_curses"
  
        # we are using cpython and not pypy to do translation
        substituteInPlace rpython/bin/rpython \
  
negative.code:       #  --replace "return library_dirs" "return tuple(\"{expat}\", *library_dirs)"
      '';
  
      TERMINFO = "${ncurses}/share/terminfo/";
  
      doCheck = true;
      checkPhase = ''
         export HOME="$TMPDIR"
        ./pypy-c ./pypy/test_all.py --pypy=./pypy-c -k "not shutil" lib-python
      '';
  
      installPhase = ''
         mkdir -p $out/bin
         cp -R {include,lib_pypy,lib-python,pypy-c} $out/
         ln -s $out/pypy-c $out/bin/pypy
         chmod +x $out/bin/pypy
         # TODO: compile python files?
      '';
  
      passthru = {
        inherit zlibSupport;
        libPrefix = "pypy${majorVersion}";
  