at aren't defined as part of the class.
For example, if you had code like this
</p>

<div class="code">
<pre>
class Complex {
...
friend Complex operator+(double, const Complex &amp;c);
...
};
</pre>
</div>

<p>
then SWIG doesn't know what to do with the friend function--in fact,
it simply ignores it and issues a warning.   You can still wrap the operator,
but you may have to encapsulate it in a special function.  For example:
</p>

<div class="code">
<pre>
%rename(Complex_add_dc) operator+(double, const Co