 to the tip provided above, this example could be rewritten
            using <span class="emphasis"><em>Spirit's</em></span> multi-attribute API function:
</p>
<pre class="programlisting"><span class="keyword">double</span> <span class="identifier">d1</span> <span class="special">=</span> <span class="number">0.0</span><span class="special">,</span> <span class="identifier">d2</span> <span class="special">=</span> <span class="number">0.0</span><span class="special">;</span>
<span class="identifier">qi</sp