>Grep</span><span class="special">(</span><span class="identifier">GrepCallback</span> <span class="identifier">cb</span><span class="special">,</span> <span class="keyword">const</span>
                    <span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span><span class="special">&amp;</span>
                    <span class="identifier">s</span><span class="special">,</span>
                    <span class="identifier">boost</span><span class="special">::<