utput">underflow</code> are mutually exclusive. </p>
<pre class="synopsis"><span class="keyword">namespace</span> <span class="identifier">boost</span> <span class="special">{</span>
  <span class="keyword">namespace</span> <span class="identifier">histogram</span> <span class="special">{</span>
    <span class="keyword">namespace</span> <span class="identifier">axis</span> <span class="special">{</span>
      <span class="keyword">namespace</span> <span class="identifier">option</span> <span class="special