            </code>boost::optional&lt;boost::optional&lt;int&gt; &gt;<code class="computeroutput"> <span class="identifier">will</span> <span class="identifier">be</span>
            <span class="identifier">collapsed</span> <span class="identifier">to</span>
            </code>boost::optional&lt;int&gt;`. Thanks to Peter Schueller for reporting
            that problem.
          </li>
<li class="listitem">
            Actions attached to binary parsers now properly propagate the parser's
            attri