ecial>() </span><span class=keyword>const
    </span><span class=special>{
        </span><span class=keyword>return </span><span class=identifier>data_</span><span class=special>.</span><span class=identifier>size</span><span class=special>();
    </span><span class=special>}
    
    </span><span class=keyword>const </span><span class=identifier>T</span><span class=special>&amp; </span><span class=keyword>operator</span><span class=special>[]( </span><span class=identifier>size_type </span><span class=ide