[pypy-dev] Builtin types

[Samuele Pedroni]

From: "Christian Tismer" <tismer at tismer.com>
> Christian Tismer wrote:
> ...
>
> A small addition:
> >> I'm not really understanding what you're proposing here.
> >
> >
> > I am trying to extend the new-style classes
> > that includes ctypes, somehow.
> >
> >> You could look at ctypes as implementing 'typed slots' with
> >> C-compatible layout.
> ...
>
> >> This is maybe also something that ctypes already does.
> >> The B *class* above knows all about this C structure
> >>
> >> struct B {
> >>     char x;
> >>     int y;
> >>     long long z;
> >> };
>
> Ok, what I was thinking of was to use ctypes
> or something similar to describe structs,
> and then to build all objects on top of this.
> This means that details like type pointer and
> reference counts go into this definiton as
> well, together with their behavior, and we
> are able to try different approaches as well.
>
> Probably this idea is trivial, and you though
> this way all the time.

maybe I'm stating the obvious, I think all of this is useful and necessary to
get a running/working Python in Python and for targetting
C-like/machine-code-level backends.

OTOH I think a higher level of abstraction is necessary to targert more general
backends. E.g. at such level what is relevant

- about an integer object is its value and that's its type is integer
- semantics of non-control-flow and binding byte codes are important e.g. :

def binary_add(o1,o2): ...

but the fact that there's a bytecode eval loop is much less so.

(From my experience) a relevant issue is how to abstract over the PyTypeObject
struct  and the interpreter internal inheritance and lookup mechanisms (which
do not correspond so directly to the language level semantics).

regards.