n>
    <span class="identifier">FilterIter</span><span class="special">;</span>

  <span class="identifier">is_positive_number</span> <span class="identifier">predicate</span><span class="special">;</span>
  <span class="identifier">FilterIter</span> <span class="identifier">filter_iter_first</span><span class="special">(</span><span class="identifier">predicate</span><span class="special">,</span> <span class="identifier">numbers</span><span class="special">,</span> <span class="identifier">numbers</span> 