er">T</span> <span class="special">=</span> <span class="keyword">double</span><span class="special">&gt;</span>
<span class="keyword">struct</span> <span class="identifier">elliptic_root_functor_noderiv</span>
<span class="special">{</span> <span class="comment">//  Nth root of x using only function - no derivatives.</span>
   <span class="identifier">elliptic_root_functor_noderiv</span><span class="special">(</span><span class="identifier">T</span> <span class="keyword">const</span><span class="special">&