span></dt>
<dd>Object of type value_type</dd>
</dl></div>
</div>
<div class="refsect1">
<a name="id-1.3.49.3.7.7"></a><h2>Type expressions</h2>
<div class="variablelist"><dl class="variablelist">
<dt><span class="term">Category tag</span></dt>
<dd><p><span class="type">category</span> must be
                  derived from <span class="type">std::forward_iterator_tag</span>.
                </p></dd>
</dl></div>
</div>
<div class="refsect1">
<a name="id-1.3.49.3.7.8"></a><h2>Valid expressions</h2>
<div clas