 <code>Iterator1</code> is a suffix of <code>Iterator2</code>, otherwise
  <code>false</code>.</td></tr>
<tr><td valign="top"><a href="#sum-1">sum/1</a></td><td>
  Returns the sum of the elements in <code>Iterator</code>.</td></tr>
<tr><td valign="top"><a href="#takewhile-2">takewhile/2</a></td><td>
  Takes elements <code>Elem</code> from <code>Iterator1</code> while <code>Pred(Elem)</code> returns
  true, that is, the function returns the longest prefix of the
  iterator for which all elements satisfy the 