[C++-sig] call policies

[Ricardo Kirkner]

Thank you for the info... I will look further into it to see if I can
use it to solve my problems..

Unfortunately I cannot avoid using pointers, since I am trying to
write a wrapper for a library (which wasn't written by me) which uses
them....

I will have to manage to get around them somehow...

Thanks for the suggestions, though...

Regards,

Ricardo Kirkner

On 11/8/05, Ralf W. Grosse-Kunstleve <rwgk at yahoo.com> wrote:
> --- Ricardo Kirkner <ricardokirkner at gmail.com> wrote:
> > real mData[3];
> >
> > and having these methods as member functions of a class
> >
> >               inline real * getData()
> >               {
> >                       return mData;
> >               }
> >
> >               inline const real * getData()const
> >               {
> >                       return mData;
> >               }
> >
> > How should I wrap them? I was thinking of defining a wrapper that
> > would return a list built from the elements of mData, but... how would
> > using a wrapper cope with this overloaded function? Should I only
> > define it once, and ignore the second override? (for example the one
> > with const?)
>
> You can keep your C++ interface if you want. C++ const-ness doesn't map
> directly to Python, but it isn't in the way.
>
> Your idea with the wrapper returning a new list seems reasonable:
>
>   boost::python::list
>   getData_as_list(T const& self)
>   {
>     //...
>   }
>
> then
>
>   .def("getData", getData_as_list)
>
> This will use the "const" overload.
>
> The Python interface cannot map directly to the C++ interface when it comes
> to resetting data. I'd try this:
>
>   void
>   setData_from_list(T& self, boost::python::list const& new_data)
>   {
>      double* d = self.getData(); // will use the non-const overload
>      //... loop over new_data, d[i] =
> boost::python::extract<double>(new_data[i])();
>   }
>
> I am not sure about the exact details; I hope you can work it out.
> Finally:
>
>   def("setData", setData_from_list)
>
> BTW: your problems remind me of my early days with Boost.Python. I moved away
> from using raw pointers entirely. Instead I wrote a library with a family of
> useful array types, including types with and without dynamic memory allocation.
> A general purpose "container_conversions.h" header provides mappings from C++
> arrays to Python tuples and vice versa. The mappings for a C++ type can be
> defined with just one line. See the Boost.Python FAQ for some pointers. If you
> want to use Boost.Python at a larger scale you may want to know about this
> approach. Sadly I never found the time to document my libraries, but I think
> the code you'll find is still useful as a source of ideas, and I'll answer
> questions here.
>
> Cheers,
>         Ralf
>
>
>
>
>
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