n input iterator wrapping a generator (nullary function object); each
          time the iterator is dereferenced, the function object is called to get
          the value to return.
        </li>
<li class="listitem">
          <a class="link" href="iterator/specialized/function_output.html" title="Function Output Iterator"><code class="computeroutput"><span class="identifier">function_output_iterator</span></code></a>:
          an output iterator wrapping a unary function object; each time an element
   