orresponding
          operations are considered to be not supported by the attribute value. But
          before we define the filter factory we have to improve our <code class="computeroutput"><span class="identifier">point</span></code> class slightly:
        </p>
<p>
</p>
<pre class="programlisting"><span class="keyword">struct</span> <span class="identifier">point</span>
<span class="special">{</span>
    <span class="keyword">float</span> <span class="identifier">m_x</span><span class="special">,</sp