CGAL users discussion list

[Andreas Fabri <>]

Matthijs Sypkens Smit wrote:
> On Thursday 11 October 2007 12:59, Andreas Fabri wrote:
>
>
> > Hello,
> >
> > Shouldn't  adding
> >
> > operator()( const Box &box_a, const Box &box_b )
> >
> > to the class CallbackAid do it ?
> >
> > I should add a precision. The callback is not passed as a reference, but
> > as a copy, so if your callback is not lightweight enough you need a
> > handle.
>
> Thank you, Andreas. The operator indeed works. I'm not really familiar with 
> the use of operators in c++. That's why I never considered using the 
> function call-operator. I tried passing a class-method and its address, 
> but all without success.
>
> I note that it is indeed slower. Is there a reason why the callback is 
> passed as a copy instead of a reference?
>
> Can you clarify what you mean with 'if [...] you need a handle'? How would 
> that work? I cannot just pass a handle to a function as a callback, since 
> that isn't accepted, right?


First of all, we didn't invent this design, but picked it up in the
good old STL and the BGL.


You need this

class CallbackAidHandle {
  CallbackAid * ptr;

public:
  CallbackAidHandle(CallbackAid* aid)
    : ptr(aid)
   {}

   void operator()( const Box &box_a, const Box &box_b )
   {
      (*ptr)(box_a, box_b);
   }

};

andreas