:</span><span class="identifier">string</span><span class="special">(</span><span class="identifier">x</span><span class="special">.</span><span class="identifier">first</span><span class="special">,</span> <span class="identifier">x</span><span class="special">.</span><span class="identifier">last</span><span class="special">)</span> <span class="special">&lt;&lt;</span> <span class="char">'"'</span> <span class="special">&lt;&lt;</span> <span class="identifier">std</span><span class="special">::</span><sp