anchor.diff:    outputs = [ "bin" "dev" "out" "man" "doc" ] ++ stdenv.lib.optional pythonSupport "py";
   
     buildInputs = [ libxml2.dev ]
  +    ++ stdenv.lib.optional stdenv.isDarwin gettext
       ++ stdenv.lib.optionals pythonSupport [ libxml2.py python ]
       ++ stdenv.lib.optionals cryptoSupport [ libgcrypt ];
   
  
positive.code:     "--without-debug"
      "--without-mem-debug"
      "--without-debugger"
    ] ++ optional pythonSupport "--with-python=${python}"
      ++ optional (!cryptoSupport) "--without-crypto";
  
    postFixup = ''
      moveToOutput bin/xslt-config "$dev"
      moveToOutput lib/xsltConf.sh "$dev"
      moveToOutput share/man/man1 "$bin"
    '' + optionalString pythonSupport ''
      mkdir -p $py/nix-support
      echo ${libxml2.py} >> $py/nix-support/propagated-build-inputs
      moveToOutput ${python.libPrefix} "$py"
  
negative.code: { stdenv, fetchurl, fetchpatch, libxml2, findXMLCatalogs, gettext, python, libgcrypt
  , cryptoSupport ? false
  , pythonSupport ? stdenv.buildPlatform == stdenv.hostPlatform
  }:
  
  stdenv.mkDerivation rec {
    pname = "libxslt";
  