>complex_step_derivative</span><span class="special">(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">exp</span><span class="special">&lt;</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">complex</span><span class="special">&lt;</span><span class="keyword">double</span><span class="special">&gt;&gt;,</span> <span class="identifier">x</span><span class="special">);</span>
</pre>
<p>
      References:
    </p>
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