de>i2</code>-iterator <code>it2</code>
are <i>equivalent</i> if:
<ul>
  <li> <code>it1==i1.end()</code> AND <code>it2==i2.end()</code>,</li>
  <li> OR <code>it1</code> and <code>it2</code> point to the
    same element.</li>
</ul>
</p>

<code>template&lt;int N,typename IteratorType><br>
typename nth_index&lt;N>::type::iterator project(IteratorType it);</code>

<blockquote>
<b>Requires:</b> <code>0 &lt;= N &lt; I</code>. <code>IteratorType</code>
belongs to <code>iterator_type_list</code>. <code>it</code> is