entifier">fan</span><span class="special">&lt;</span><span class="number">6</span><span class="special">&gt;</span>
<span class="special">{</span>
    <span class="comment">// Helper typedef's</span>
    <span class="keyword">typedef</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">base_from_member</span><span class="special">&lt;</span><span class="identifier">an_int</span><span class="special">&gt;</span>       <span class="identifier">pbase0_type</span><