>struct</span> <a class="link" href="add_t_1_3_44_10_2_36_1_1_4.html" title="Struct template add_typeof_helper&lt;quantity&lt; unit&lt; Dim, System &gt;, X &gt;, quantity&lt; unit&lt; Dim, System &gt;, Y &gt;&gt;">add_typeof_helper</a><span class="special">&lt;</span><span class="identifier">quantity</span><span class="special">&lt;</span> <span class="identifier">unit</span><span class="special">&lt;</span> <span class="identifier">Dim</span><span class="special">,</span> <span class="identifier">System</s