ve</span><span class="special">;</span>
<span class="keyword">auto</span> <span class="identifier">lanczos</span> <span class="special">=</span> <span class="identifier">discrete_lanczos_derivative</span><span class="special">(</span><span class="identifier">spacing</span><span class="special">);</span>
<span class="comment">// Compute dvdt at index 30:</span>
<span class="keyword">double</span> <span class="identifier">dvdt30</span> <span class="special">=</span> <span class="identifier">lanczos</span><spa