// Instance of <code class="computeroutput">underflow_t</code>. </span>
        <span class="keyword">constexpr</span> <span class="identifier">overflow_t</span> <a class="link" href="../boost/histogram/axis/option/overflow.html" title="Global overflow">overflow</a><span class="special">;</span>        <span class="comment">// Instance of <code class="computeroutput">overflow_t</code>. </span>
        <span class="keyword">constexpr</span> <span class="identifier">circular_t</span> <a class="link" href="../