boost::python, returning new PyObject references

[Arnaldur Gylfason]

Dave,

It would be great if you could give an example (maybe something that can
solve object<sequence,mapping>) so I can see the way.
I have only taken a brief look at 2 files in boost::mpl but am interested
in exploring this kind of programming.

Regarding virtual/non-virtual, I guess I agree that ovirriding non-virtual
functions is ok as long as the semantics are the same, i.e. no
side-effects.
(When using the object through a base class &/* the effects are the same
even though a different method is called since there is no polymorphism).

I am beginning to form the design in my head but using mpl wil mean a steep
learning curve in the beginning.

Cheers

Arnaldur


----- Original Message -----
From: "Arnaldur Gylfason" <arnaldur at decode.is>

> I came up with a similar idea some weeks ago (i.e.
> object<number,sequence,mapping,...> ).

Silly me for not seeing the wisdom of your idea :(

> You mentioned the Andrei's GenScatterHierarchy .
>
> I've looked into this and I don't think GenScatterHierarchy is the way to
> go. Maybe something similar.

Hmm. It's hard to say. Something like GenScatterHierarchy could be useful
for generating all of the appropriate interface elements (e.g. operator[],
operator+=, ...)

> We can use the same design as in boost::function to have variable number
of
> parameters.

Yes, or in mpl::type_list.

> Problem is some interfaces intersect (e.g. += for number and sequence
> etc.).

That's why the concept tags should only be high-level objects. At a lower
level

> I was wondering if it was possible to define a INTERSECT macro that can
> handle this but am way out of my league here.
> It is possible to pull this off using template specialization but the
> number of specializations would be high
> (exponential explosion).

That's easy with mpl. You can use copy_if to build a type_list that
consists
of all elements of A that are also in B.

I can help with some of the metaprogramming infrastructure.

-Dave