anchor.diff:        # "v8"      -- mongo still bundles 3.12 and does not work with 3.15+
         # "stemmer" -- not nice to package yet (no versioning, no makefile, no shared libs)
         # "yaml"    -- it seems nixpkgs' yamlcpp (0.5.1) is problematic for mongo
  -    ] ++ stdenv.lib.optionals (!stdenv.isDarwin) [ "tcmalloc" ];
  -    system-lib-args = stdenv.lib.concatStringsSep " "
  -                          (map (lib: "--use-system-${lib}") system-libraries);
  +    ] ++ optionals (!stdenv.isDarwin) [ "tcmalloc" ];
  +    system-lib-args = concatStringsSep " "
  +                        (map (lib: "--use-system-${lib}") system-libraries);
   
   in stdenv.mkDerivation rec {
     name = "mongodb-${version}";
  
positive.code: { stdenv, fetchurl, scons, boost, gperftools, pcre, snappy }:
  
  let version = "2.6.4";
      system-libraries = [
  
negative.code:   meta = {
      description = "a scalable, high-performance, open source NoSQL database";
      homepage = http://www.mongodb.org;
      license = licenses.agpl3;
  
      maintainers = with maintainers; [ bluescreen303 offline ];
      platforms = platforms.unix;
    };
  }
  