_lvalue.html"><img src="../../../images/next.png" alt="Next"></a></div><div id="content">
  <div class="titlepage"><div><div><h1 style="clear: both"><code>const value_type &amp;&amp;assume_value() const &amp;&amp; noexcept</code></h1></div></div></div>
  <p>Narrow contract const rvalue reference observer of any value present. <code>NoValuePolicy::narrow_value_check()</code> is first invoked, then the reference to the value is returned. The convention is that hard undefined behaviour occurs if no value is ac