ably produced using the changesign function
          <code class="computeroutput"><span class="special">(</span><span class="identifier">changesign</span><span class="special">)(</span><span class="keyword">static_cast</span><span class="special">&lt;</span><span class="identifier">ValType</span><span class="special">&gt;(</span><span class="number">0</span><span class="special">))</span></code>
          where <code class="computeroutput"><span class="identifier">ValType</span></code> is <code class="comp