anchor.diff:        , libyaml, yamlSupport ? true
         , libffi, fiddleSupport ? true
         , autoreconfHook, bison, autoconf
  -      , darwin ? null
         }:
         stdenv.mkDerivation rec {
           inherit version;
  
positive.code: { stdenv, lib, fetchurl, fetchFromSavannah, fetchFromGitHub
  , zlib, openssl, gdbm, ncurses, readline, groff, libyaml, libffi, autoreconfHook, bison
  , autoconf, darwin ? null
  } @ args:
  
  let
  
negative.code:         '';
  
          configureFlags = ["--enable-shared" "--enable-pthread"]
            ++ op useRailsExpress "--with-baseruby=${baseruby}/bin/ruby";
  
          installFlags = stdenv.lib.optionalString docSupport "install-doc";
          # Bundler tries to create this directory
  