elements of <code>Iterator1</code>  
where all except the first element of the elements comparing equal  
have been deleted.</td></tr>
<tr><td valign="top"><a href="#usort-2">usort/2</a></td><td>
  Returns a iterator containing the sorted elements of <code>Iterator1</code> where all
  except the first element of the elements comparing equal according
  to the ordering function <code>Fun</code> have been deleted.</td></tr>
<tr><td valign="top"><a href="#zip-2">zip/2</a></td><td>
  "Zips" two iterators of equ