eter to copier - declaring this here as a constant
is really just a convenience - the value could be passed directly
to class <font size="2" face="Courier New">copier</font>. The
value of <i>can_opt</i> is computed by verifying that all of the
following are true:</p>

<ul>
    <li>first that the two iterators point to the same type by
        using a type-traits class <i>is_same</i>.</li>
    <li>Then that both iterators are real pointers - using the
        class <i>is_pointer</i> described above.</li>
   