wing:
      </p>
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
            The left expression is passed to evaluator (with the current context,
            that contains our invert_actions)
          </li>
<li class="listitem">
            The right expression is passed to evaluator (with the current context,
            that contains our invert_actions)
          </li>
<li class="listitem">
            The result of these two <a href="http://www.