      static double mp_round(_cimg_math_parser& mp) {
        return cimg::round(_mp_arg(2),_mp_arg(3),(int)_mp_arg(4));
      }
      static double mp_round(_cimg_math_parser& mp) {
        return cimg::round(_mp_arg(2),_mp_arg(3),(int)_mp_arg(4));
      }