"identifier">n</span> <span class="special">=</span> <span class="number">12</span><span class="special">;</span>
<span class="identifier">size_t</span> <span class="identifier">p</span> <span class="special">=</span> <span class="number">2</span><span class="special">;</span>
<span class="keyword">auto</span> <span class="identifier">lanczos</span> <span class="special">=</span> <span class="identifier">lanczos_derivative</span><span class="special">(</span><span class="identifier">spacing</span><span clas