ral"><span class="pre">Iterator</span></tt> models Bidirectional Traversal Iterator, then
<tt class="docutils literal"><span class="pre">iterator_category</span></tt> is convertible to
<tt class="docutils literal"><span class="pre">bidirectional_iterator_tag</span></tt>.  Otherwise <tt class="docutils literal"><span class="pre">iterator_category</span></tt> is
convertible to <tt class="docutils literal"><span class="pre">forward_iterator_tag</span></tt>. If <tt class="docutils literal"><span class="pre">Ite