    const_iterator operator++(int) {
      const_iterator tmp(charPtr_, char16Ptr_);
      if (charPtr_) {
        ++charPtr_;
      } else {
        ++char16Ptr_;
      }
      return tmp;
    }
    const_iterator operator++(int) {
      const_iterator tmp(charPtr_, char16Ptr_);
      if (charPtr_) {
        ++charPtr_;
      } else {
        ++char16Ptr_;
      }
      return tmp;
    }