      static double mp_permutations(_cimg_math_parser& mp) {
        return cimg::permutations((int)_mp_arg(2),(int)_mp_arg(3),(bool)_mp_arg(4));
      }
      static double mp_permutations(_cimg_math_parser& mp) {
        return cimg::permutations((int)_mp_arg(2),(int)_mp_arg(3),(bool)_mp_arg(4));
      }