der must be manually included
              if multi visitors are meant for use.</li>
<li class="listitem">The overloads accepting only a visitor return a
              <code class="computeroutput"><a class="link" href="apply_visitor_delayed_t.html" title="Class template apply_visitor_delayed_t">C++03 compatible generic function object</a></code>
              or
                <code class="computeroutput"><a class="link" href="apply_visit_1_3_46_5_7_1_2.html" title="Class template apply_visitor_delayed_cp