      static bool is_varname(const char *const str, const unsigned int length=~0U) {
        if (*str>='0' && *str<='9') return false;
        for (unsigned int l = 0; l<length && str[l]; ++l)
          if (!is_varchar(str[l])) return false;
        return true;
      }
      static bool is_varname(const char *const str, const unsigned int length=~0U) {
        if (*str>='0' && *str<='9') return false;
        for (unsigned int l = 0; l<length && str[l]; ++l)
          if (!is_varchar(str[l])) return false;
        return true;
      }