rns pointer to const T in variant or null pointer if type does not match. </span>
      <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> T<span class="special">,</span> <span class="keyword">class</span><span class="special">...</span> Us<span class="special">&gt;</span> 
        <span class="keyword">const</span> <span class="identifier">T</span> <span class="special">*</span> <a name="boost.histogram.axis.get_if_idm45105994578944"></a><span class=