ss</span> <span class="identifier">Real</span><span class="special">&gt;</span>
    <span class="identifier">Real</span> <span class="identifier">complex_step_derivative</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">F</span> <span class="identifier">f</span><span class="special">,</span> <span class="identifier">Real</span> <span class="identifier">x</span><span class="special">);</span>

    <span class="keyword">template</span> <span class="special">&lt;</