the iterators, this time we will
use the <a href="../../tuple/doc/tuple_users_guide.html#tiers"><tt>boost::tie()</tt></a> helper function.
This handy function can be used to assign the parts of a <tt>std::pair</tt> into
two separate variables, in this case <tt>ei</tt> and <tt>ei_end</tt>. This is
usually more convenient than creating a <tt>std::pair</tt> and is our method of
choice for the BGL.
<p>&nbsp;
<pre>
  // ...
  int main(int,char*[])
  {
    // ...
    std::cout &lt;&lt; &quot;edges(g) = &quot;;
  