For Kenny Tilton: Why do I need macros revisited.
mis6 at pitt.edu
Sun Aug 24 11:31:32 CEST 2003
Kenny Tilton <ktilton at nyc.rr.com> wrote in message news:<3F47BDCA.3070001 at nyc.rr.com>...
> A few months back I started on a PyCells project, and of course was
> having great fun down at the metaclass level. It was a little daunting
> compared to the Lisp MOP, which just takes the same concepts of calls
> and instance and does a conceptual-shift-up (new machine language
> instruction?) so a class is now an instance (of a metaclass, which is
> just another class really--the "meta" is only to keep one's head
> straight). Python might be viewed as easier because it jumps over to
> using internals such as that __dict__ thing (sorry if that is wrong, it
> has been a while and I only played for a few weeks), so it there is none
> of that class-being-an-instance confusion. Fun stuff, either way.
I don't follow you. In Python it is just the same, a class is just an
instance of a metaclass, a metaclass is just an instance of a meta-meta
class, etc. Metaclasses are classes, their simply have a different
type.__new__ method than object.__new__ so the instantiation syntax
looks a bit different.
> The CLOS MOP is a better playground, but Python has
> a clear win in that there is only one Python. If I really need the MOP
> for a project, I just pick a CL which exposes it. If I want to deliver a
> package any lispnik can use, I better not use the MOP.
Hear, hear, people who say CL is more standard than Python!
> (How do you like that?
> Multiple inheritance of metaclasses! <g>)
I need more multiple inheritance for metaclasses than for classes.
You maybe interested in this recipe of mine:
> Even if CLOS metaclasses were standard, kind of in the spirit of some of
> this thread, I think I would like to avoid doing Cells by tinkering with
> the object model. A hack that kinda disappears at run time (the macros
> expand into vanilla CL) is probably going to play better with other
> hacks, including not breaking optimizations. ANd it may be a Message
> From God(tm) that Cells internals got simpler when I ripped out the
> metaclass thing.
As always, the most abstract solution is not necessarely the best
Michele Simionato, Ph. D.
MicheleSimionato at libero.it
--- Currently looking for a job ---
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