Newsgroups: perl.perl6.internals
Path: archiver1.google.com!news2.google.com!news.maxwell.syr.edu!newsfeed.stanford.edu!nntp.perl.org
Return-Path: <d...@sidhe.org>
Mailing-List: contact perl6-internals-h...@perl.org; run by ezmlm
Delivered-To: mailing list perl6-intern...@perl.org
Delivered-To: perl6-intern...@perl.org
X-Scanned-By: AMaViS-ng at sidhe.org
Mime-Version: 1.0
X-Sender: dan@localhost
Message-ID: <a06010216bbf259ac617f@[10.0.1.2]>
Date: Tue, 2 Dec 2003 10:52:18 -0500
To: perl6-intern...@perl.org
Subject: Objects!
Content-Type: text/plain; charset="us-ascii" ; format="flowed"
X-Spam-Check-By: one.develooper.com
X-Spam-Status: No, hits=0.8 required=7.0 tests=CARRIAGE_RETURNS,SPAM_PHRASE_01_02 version=2.44
X-SMTPD: qpsmtpd/0.26, http://develooper.com/code/qpsmtpd/
Approved: n...@nntp.perl.org
From: d...@sidhe.org (Dan Sugalski)
Lines: 53

Well, objects-ish, at least.

Single-inheritance objects seem to be done. The code can use a lot of 
abuse and cleanup, and we need actual tests to make sure that it 
functions as it should, but they're in.

Here's the technical scoop.

When you create a ParrotClass-based class (which is to say, you use 
the class creation ops that we provide) you get a class PMC that's 
got all the class information hanging off it. This stuff's documented 
at the top of classes/parrotclass.pmc though better docs are 
definitely in order.

Since creating the class is handled by the code in objects.c rather 
than in the class vtable, we get to play a number of games:

Games we play:
==============
*) The class code knows its dealing with parrot classes (there's a 
flag to tell us) and it cheats. Not too badly, but some. Probably 
should cheat more, but I'm up for getting it working before doing 
Horribly Evil Things.
*) Creating new objects involves calling the ->init vtable entry *on 
the class*. Because of this each class gets a custom vtable where the 
init method has been swapped out for one (from objects.c) that 
creates a new object instead.

But it seems to work out. Slowly (no method cache definitely hurts) 
but still, works is good. The PMC that the class ->init method hands 
back is a ParrotObject, rather than a ParrotClass, which is good as 
it's an object and all. The vtable on the object is currently the 
base ParrotObject vtable which, as you can probably see, doesn't do a 
whole lot besides method calls.

Still to do:
============
*) Multiple inheritance
*) Runtime inheritance changes
*) Runtime attribute changes
*) Metadata support for class creation
*) Tests to make sure it actually, y'know, works.
*) Delegation of vtable methods to methods in the class
*) fallback method finding

Happy "Abuse the Objects" day, everyone. :)
-- 
                                         Dan

--------------------------------------"it's like this"-------------------
Dan Sugalski                          even samurai
d...@sidhe.org                         have teddy bears and even
                                       teddy bears get drunk