lisdigit
lua_assert(lisdigit(ls->current));
for (i = 0; i < 3 && lisdigit(ls->current); i++) { /* read up to 3 digits */
if (!lisdigit(ls->current))
else if (!lisdigit(ls->current)) return '.';
if (!lisdigit(cast_uchar(*s)))
while (lisdigit(cast_uchar(*s))) /* read exponent */
if (lisdigit(c)) return c - '0';