      A semantic action function with a signature: <code class="computeroutput"><span class="keyword">void</span>
                <span class="identifier">f</span><span class="special">(</span><span class="identifier">Iterator</span><span class="special">&amp;,</span>
                <span class="identifier">Iterator</span><span class="special">&amp;,</span>
                <span class="identifier">pass_flag</span><span class="special">&amp;,</span>
                <span class="identifier">Idtype</span><spa