lass="computeroutput"><span class="keyword">operator</span><span class="special">()</span></code>
        and <code class="computeroutput"><span class="identifier">func</span><span class="special">()</span></code>
        member functions callable with the specified signature:
      </p>
<p>
</p>
<pre class="programlisting"><span class="keyword">namespace</span> <span class="special">{</span> <span class="keyword">namespace</span> <span class="identifier">callable</span>
<span class="special">{</span>
    <