Hi all
<div><br></div><div>I have a class tree as the following</div><div><br></div><div><div>template&lt;typename T&gt;</div><div>struct base{</div><div>  bool operator()(int i)const {</div><div>    return static_cast&lt; const T&amp;&gt;(*this)(i);</div>
<div>  }</div><div>};</div><div>struct F1:public base&lt;F1&gt;{</div><div>  bool operator()(int i) const{</div><div>    return true;</div><div>  }</div><div>};</div><div>struct F2:public base&lt;F2&gt;{</div><div>  bool operator()(int i) const{</div>
<div>    return true;</div><div>  }</div><div>};</div><div>struct F3 :public base&lt;F3&gt;{</div><div>  std::string junk_;</div><div>  F3(std::string junk):junk_(junk){}</div><div>  bool operator()(int i) const{</div><div>
    std::cout &lt;&lt; junk_ &lt;&lt; std::endl;</div><div>    return false;</div><div>  }</div><div>};</div></div><div><br></div><div>==================================================================</div><div><br></div>
<div>I am trying to use proto to derive the following systax </div><div><br></div><div><div>Predicate&lt;F1&gt; f1;</div><div>Predicate&lt;F2&gt; f2;</div><div>Predicate&lt;F3&gt; f3(&quot;hodqhoqw&quot;);</div><div><br></div>
<div>cout &lt;&lt; ((f1||f2)&amp;&amp;f3)(1) &lt;&lt; endl;</div></div><div><br></div><div>==================================================================</div><div><br></div><div>When proto get to the point of invoking the F3::operator(), the junk_ attribute got sliced away. I thought I am passing everything by constant reference but the exception tells me otherwise. The full sample code is attached, can someone tell me what I have missed? I am testing my code on vc9 and vc10, and I am not using virtual function for performance issue.</div>
<div><br></div><div>Ultimately, I want to have the following syntax in the client code</div><div><br></div><div><div><div>F1 f1;</div><div>F2 f2;</div><div>F3 f3(&quot;hodqhoqw&quot;);</div><div><br></div><div>cout &lt;&lt; ((f1||f2)&amp;&amp;f3)(1) &lt;&lt; endl;</div>
</div></div><div><br></div><div><br></div><div><br></div><div>Thanks</div><div><br></div>