ss="keyword">const</span><span class="special">&amp;</span> <span class="identifier">mp</span><span class="special">);</span>

        <span class="comment">// increment is called whenever multi_pass::operator++ is invoked</span>
        <span class="comment">//</span>
        <span class="comment">//   mp:    is a reference to the whole multi_pass instance</span>
        <span class="keyword">template</span> <span class="special">&lt;</span><span class="keyword">typename</span> <span class="identifier">Mul