pan><span class="identifier">filter_factory</span><span class="special">&lt;</span> <span class="keyword">char</span> <span class="special">&gt;</span>
<span class="special">{</span>
<span class="keyword">public</span><span class="special">:</span>
    <span class="identifier">logging</span><span class="special">::</span><span class="identifier">filter</span> <span class="identifier">on_exists_test</span><span class="special">(</span><span class="identifier">logging</span><span class="special">::</span><spa