n><span class="special">,</span> <span class="identifier">std_valarray_tag</span><span class="special">,</span> <span class="identifier">std_valarray_tag</span><span class="special">&gt;</span> <span class="special">:</span> <span class="keyword">public</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">binary_function</span><span class="special">&lt;</span> <span class="identifier">Left</span><span class="special">,</span> <span class="identifier">Right</span>