span><span class="special">;</span>
    <span class="keyword">typedef</span> <span class="comment">/* see below */</span> <span class="identifier">iterator_category</span><span class="special">;</span>

    <span class="identifier">filter_iterator</span><span class="special">();</span>
    <span class="identifier">filter_iterator</span><span class="special">(</span><span class="identifier">Predicate</span> <span class="identifier">f</span><span class="special">,</span> <span class="identifier">Iterator</spa