ddresses for equality.
        </p>
<pre class="programlisting"><span class="keyword">friend</span> <span class="keyword">bool</span> <span class="keyword">operator</span><span class="special">==(</span>
    <span class="keyword">const</span> <span class="identifier">address</span> <span class="special">&amp;</span> <span class="identifier">a1</span><span class="special">,</span>
    <span class="keyword">const</span> <span class="identifier">address</span> <span class="special">&amp;</span> <span class="id