n><span class="identifier">T</span> <span class="identifier">radius</span><span class="special">,</span> <span class="identifier">T</span> <span class="identifier">arc</span><span class="special">)</span>
<span class="special">{</span>
   <span class="keyword">using</span> <span class="keyword">namespace</span> <span class="identifier">std</span><span class="special">;</span>  <span class="comment">// Help ADL of std functions.</span>
   <span class="keyword">using</span> <span class="keyword">namespace</sp