[C++-sig] Retrieving lvalues using custom converters (numpy 1-D converters attached)

[Ravi]

On Thursday 02 October 2008 20:03:58 Neal Becker wrote:
> ublas::vector<double> create (int size, double init) {
>    return ublas::vector<double> (size, init);
> }
>
> With default return value policy, this fails.    We used:
>   register_vector_to_python_converters< false, contiguous_vector_to_py,
>     default_ublas_array_traits>();
>
> Which does _not_ copy the data and uses PyArray_SimpleNewFromData.  The
> data is immediately destroyed and the array returned to python is garbage.

You are right; I was wrong in my previous reply. I need the help of a 
boost.python expert to tell me what to do in this case. For the default return 
value policy, we end up in registry_to_python_value<T>::operator(), but the 
last line of that function is never called. Why this is, I have been unable to 
figure out.

> It would be nice if the function could return a shared_ptr, which python
> would manage.  This doesn't seem to work:
>
> boost::shared_ptr<ublas::vector<double> > create (int size, double init) {
>   boost::shared_ptr<ublas::vector<double> > u (new ublas::vector<double>
> (size, init)); return u;
> }

This, too, remains a puzzle to me. Do shared_ptr conversions not work for 
objects with custom to_python converters?

Regards,
Ravi