<span class="keyword">const</span> <span class="identifier">T</span> <span class="special">&amp;</span> in_value<span class="special">,</span> <span class="identifier">T</span> <span class="special">&amp;</span> out_value<span class="special">,</span> 
            <span class="identifier">Op</span> op<span class="special">)</span><span class="special">;</span>
<span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> T<span class="special">,</span> <span cla