iterator
      begin() _GLIBCXX_NOEXCEPT
      { return iterator(this->_M_impl._M_start); }

      /**
       *  Returns a read-only (constant) iterator that points to the
       *  first element in the %vector.  Iteration is done in ordinary
       *  element order.
       */
      const_iterator
      begin() const _GLIBCXX_NOEXCEPT
      { return const_iterator(this->_M_impl._M_start); }

      /**
       *  Returns a read/write iterator that points one past the last
       *  element in the %vector.  Iteration is done in ordinary
       *  element order.
       */
      iterator
      end() _GLIBCXX_NOEXCEPT
      { return iterator(this->_M_impl._M_finish); }