s="special">&amp;</span> <span class="identifier">x</span><span class="special">)</span> <span class="keyword">const</span>
    <span class="special">{</span>
        <span class="special">*</span><span class="identifier">m_str</span> <span class="special">+=</span> <span class="identifier">x</span><span class="special">;</span>
    <span class="special">}</span>

    <span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span><span class="special">*</span> <span 