an><span class="identifier">RealType</span> <span class="identifier">i</span><span class="special">);</span>

   <span class="comment">// Accessor to parameter:</span>
   <span class="identifier">RealType</span> <span class="identifier">degrees_of_freedom</span><span class="special">()</span><span class="keyword">const</span><span class="special">;</span>

   <span class="comment">// Parameter estimation:</span>
   <span class="keyword">static</span> <span class="identifier">RealType</span> <span class="ide