n it. This function object must be:
    </p>
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
          Lightweight to copy.
        </li>
<li class="listitem">
          Default constructible (when the container constructor overload requires
          it).
        </li>
<li class="listitem">
          It shall define:
          <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
                