t;</span> 
          <span class="keyword">auto</span> <a class="link" href="../boost/histogram/axis/traits/index_idm45105994767696.html" title="Function template index"><span class="identifier">index</span></a><span class="special">(</span><span class="keyword">const</span> <span class="identifier">Axis</span> <span class="special">&amp;</span><span class="special">,</span> <span class="keyword">const</span> <span class="identifier">U</span> <span class="special">&amp;</span><span class="special">)</span><