al>{
        </span><span class=keyword>template </span><span class=special>&lt;</span><span class=keyword>typename </span><span class=identifier>CharT</span><span class=special>&gt;
        </span><span class=identifier>CharT filter</span><span class=special>(</span><span class=identifier>CharT ch</span><span class=special>) </span><span class=keyword>const
        </span><span class=special>{ 
            </span><span class=keyword>return </span>std::<span class=identifier>tolower</span><span class=specia