 root-finding code is now almost the same as before, but we'll make use
        of Newton-iteration to get the result:
      </p>
<pre class="programlisting"><span class="keyword">template</span> <span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">T</span> <span class="special">=</span> <span class="keyword">double</span><span class="special">&gt;</span>
<span class="identifier">T</span> <span class="identifier">elliptic_root_1deriv</span><span class="special">(</spa