span class="special">(</span><span class="identifier">c</span><span class="special">)</span> <span class="special">{}</span>

    <span class="identifier">result_type</span> <span class="keyword">operator</span><span class="special">()()</span>
    <span class="special">{</span>
        <span class="keyword">if</span> <span class="special">(</span><span class="identifier">c_</span> <span class="special">==</span> <span class="char">'M'</span><span class="special">)</span>
            <span class="keyword">r