      static double mp_isdir(_cimg_math_parser& mp) {
        const unsigned int siz = (unsigned int)mp.opcode[3];
        const double *ptrs = &_mp_arg(2) + (siz?1:0);
        if (!siz) { char str[2] = { 0 }; *str = *ptrs; return (double)cimg::is_directory(str); }
        CImg<charT> ss(siz + 1);
        cimg_forX(ss,i) ss[i] = (char)ptrs[i];
        ss.back() = 0;
        return (double)cimg::is_directory(ss);
      }
      static double mp_isdir(_cimg_math_parser& mp) {
        const unsigned int siz = (unsigned int)mp.opcode[3];
        const double *ptrs = &_mp_arg(2) + (siz?1:0);
        if (!siz) { char str[2] = { 0 }; *str = *ptrs; return (double)cimg::is_directory(str); }
        CImg<charT> ss(siz + 1);
        cimg_forX(ss,i) ss[i] = (char)ptrs[i];
        ss.back() = 0;
        return (double)cimg::is_directory(ss);
      }