ial">(</span><span class="identifier">k</span><span class="special">)</span> <span class="special">-</span> <span class="identifier">m_arc</span><span class="special">;</span>
   <span class="special">}</span>
<span class="keyword">private</span><span class="special">:</span>
   <span class="identifier">T</span> <span class="identifier">m_arc</span><span class="special">;</span>     <span class="comment">// length of arc.</span>
   <span class="identifier">T</span> <span class="identifier">m_radius</span><s