Re: [sigc] Generic member functors

[klaus triendl <klaus triendl eu>]

JinXXXX Kili Billl schrieb:
> Hello,
>
> I have been trying to use sigc++ library to make a kind of a generic 
> member functor, but I didn't succeed.
>
> Basically, I would like to create a functor, to which I would be able 
> assign arbitrary member functions of any class derived from a previously 
> chosen base class. I tried this, but with not much luck. I am attaching 
> a simple example where I would like to show what exactly I mean.
>
> I hope that something like this is possible with sigc++.
>
> I have also come across several ambiguities with sigc++, which are 
> commented in the source file. I don't understand the behavior of sigc++ 
> there, and I marked these spots, so you can look at them.

There are no ambiguities with sigc++. There are templates involved, so 
you can't e.g. assign a mem_functor typed for a child to a mem_functor 
typed for a Parent. And I think you are mixing slots and functors...

A slot represents a callable entity, no matter what functor is behind. 
So, a slot is the generic functor you want to have (only knowing about 
the return type and parameters, but loosing compile-time information 
about the original functor).
What you want to do is the following:

<code>
Parent p;
Child c;

sigc::slot<int, Parent*, int, double, char> myclosure;

myclosure = sigc::mem_fun(&Parent::f);
const int ret1 = myclosure(&p, 0, 1.0, 'c');

myclosure = sigc::mem_fun(&Child::g);
const int ret2 = myclosure(&c, 0, 1.0, 'c');
</code>


Klaus Triendl