span><span class="special">()</span>
            <span class="special">)</span>
        <span class="special">);</span>
<span class="special">}</span>
</pre>
<p>
        Run some tests to see if it is working:
      </p>
<pre class="programlisting"><span class="identifier">invert</span><span class="special">(</span><span class="identifier">_1</span><span class="special">);</span>                    <span class="comment">// --&gt; _1</span>
<span class="identifier">invert</span><span class="special">(</span>