="special">;</span>
    <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> A1<span class="special">,</span> <span class="keyword">typename</span> S1<span class="special">,</span> <span class="keyword">typename</span> A2<span class="special">,</span> <span class="keyword">typename</span> S2<span class="special">&gt;</span> 
      <span class="keyword">auto</span> <a name="boost.histogram.operator_idm45105994383600"></a><span class="keyword">operator</s