[C++-sig] Re: Methods returning & taking pointers to functions

[David Abrahams]

"Niall Douglas" <s_sourceforge at nedprod.com> writes:

> I /think/ these don't compile properly ie; lots of compiler warnings. 
> Unfortunately a mechanism of specifying a sort function is 
> commonplace in my library and ultimately I'll really need it.
>
> I see a two pronged approach: (i) make a pointer to a function an 
> opaque type and (ii) write a thunk which invokes an arbitrary python 
> function. The latter, through some small alterations to the base 
> library, could be entirely driven by parameters (all I need is a 
> pointer to the thing calling the sort function).
>
> Has anyone else tried this? Is it even possible? 

I think what you're asking for is an automatic conversion from a
Python callable object to a C++ function pointer.

Well, no, it isn't possible, at least not in a reliable way.  That's
because a C++ function pointer can't have any associated data, and
you'd need some way to bind the callable Python object to it.

If you can change your interface to use, say, 

        boost::function2<bool, T, T>

I think we can come up with a solution.

> If BP can't wrap methods taking or receiving pointers to functions,
> then it's a non- starter.

It may be that.  This isn't a Boost.Python issue.  Search back in the
archives for posts about FLTK if you want more details.

-- 
Dave Abrahams
Boost Consulting
www.boost-consulting.com