[C++-sig] current spelling of from_python<>?

[Ralf W. Grosse-Kunstleve]

--- David Abrahams <david.abrahams at rcn.com> wrote:
> From: "Ralf W. Grosse-Kunstleve" <rwgk at yahoo.com>
> 
> 
> > Until about a week ago the code below worked as a placeholder
> > for a user-level from_python<> converter:
> > 
> >   template <typename U>
> >   struct extractor
> >   {
> >     static
> >     U
> >     get(PyObject* obj)
> >     {
> >       Py_INCREF(obj);
> >       return converter::callback_from_python<U>()(obj);
> >     }
> >   };
> > 
> > converter::callback_from_python<> is defined in the obsolete file
> > converter/callback.hpp. What should I be using instead?
> 
>     converter::return_from_python<> in converter/return_from_python.hpp

Using return_from_python<>, extractor<T> works fine. Thanks!
Is it expected that extractor<T const&> does not work for
converting the elements of a Python tuple of Python float or int?

I also need this convertible() test:

    static void* convertible(PyObject* obj)
    {
      using namespace boost::python;
      tuple t = list_or_tuple_as_tuple(obj);
      if (!ContainerAdaptor::check_size(
        type<ContainerType>(), t.size())) return 0;
      for(std::size_t i=0;i<t.size();i++) {
        arg_from_python<container_element_type const&> from_py(t[i].get());
        if (!from_py.convertible()) return 0;
      }
      return obj;
    }

Observations:

The code as shown works with Linux/gcc304, but VC6 reports
"indirect_traits.hpp(308) : error C2057: expected constant expression."
arg_from_python<container_element_type> also works with Linux/gcc304, but VC6
reports "fatal error C1001: INTERNAL COMPILER ERROR."
Should/could I use a different approach for testing convertibility that VC6
might not choke on?

Thanks,
        Ralf


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