span class="special">;</span>
        <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span><span class="special">...</span> Ts<span class="special">,</span> <span class="keyword">typename</span> U<span class="special">&gt;</span> 
          <span class="keyword">auto</span> <a class="link" href="../boost/histogram/axis/traits/index_idm45105994761696.html" title="Function template index"><span class="identifier">index</span></a><span class="special">(</span>