an>
   <span class="comment">//</span>
   <span class="comment">// Whew.  Now we can make the actual call to the implementation.</span>
   <span class="comment">// Arguments are explicitly cast to the evaluation type, and the result</span>
   <span class="comment">// passed through checked_narrowing_cast which handles things like overflow</span>
   <span class="comment">// according to the policy passed:</span>
   <span class="comment">//</span>
   <span class="keyword">return</span> <span class="identifier