ng this function. When two tuples compare
  equal, the tuple from <code>TupleIterator1</code> is picked and the one from
  <code>TupleIterator2</code> is deleted.</p>
 
  The first element of each iterator will be evaluated.</p>

<h3 class="function"><a name="ukeysort-2">ukeysort/2</a></h3>
<div class="spec">
<p><tt>ukeysort(N, TupleIterator1) -&gt; TupleIterator2</tt>
<ul class="definitions"><li><tt>N = pos_integer()</tt></li><li><tt>TupleIterator1 = <a href="#type-iterator">iterator</a>(Elem)</tt></li><li