er</span><span class="special">=</span><span class="number">1</span><span class="special">&gt;</span>
    <span class="keyword">class</span> <span class="identifier">discrete_lanczos_derivative</span> <span class="special">{</span>
    <span class="keyword">public</span><span class="special">:</span>
        <span class="identifier">discrete_lanczos_derivative</span><span class="special">(</span><span class="identifier">Real</span> <span class="identifier">spacing</span><span class="special">,</span>
      