s="keyword">void</span> <span class="keyword">operator</span><span class="special">()(</span> <span class="keyword">const</span> <span class="identifier">StateIn</span> <span class="special">&amp;</span><span class="identifier">x</span> <span class="special">,</span> <span class="identifier">StateOut</span> <span class="special">&amp;</span><span class="identifier">dxdt</span> <span class="special">,</span> <span class="identifier">Value</span> <span class="identifier">t</span> <span class="special">)</span