r</a></code>;
              otherwise, let <span class="emphasis"><em>E</em></span> be
              <code class="computeroutput"><a class="link" href="../expr.html" title="Struct template expr">proto::expr</a></code>.
              Given an lvalue <code class="computeroutput">t</code> of type
              <code class="computeroutput">T</code>:
              </p>
<div class="itemizedlist"><ul class="itemizedlist" type="disc">
<li class="listitem">
                  If <code class="computeroutput">T</code> 