><span class="special">(</span><span class="identifier">sink1</span><span class="special">);</span>

    <span class="comment">// One can construct backend separately and pass it to the frontend</span>
    <span class="identifier">boost</span><span class="special">::</span><span class="identifier">shared_ptr</span><span class="special">&lt;</span> <span class="identifier">my_backend</span> <span class="special">&gt;</span> <span class="identifier">backend</span><span class="special">(</span><span class="key