From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <n8gray@gmail.com>
Received: from nez-perce.inria.fr (nez-perce.inria.fr [192.93.2.78])
	by yquem.inria.fr (Postfix) with ESMTP id E0B0DBD73
	for <caml-list@yquem.inria.fr>; Wed, 17 Aug 2005 00:04:31 +0200 (CEST)
Received: from zproxy.gmail.com (zproxy.gmail.com [64.233.162.194])
	by nez-perce.inria.fr (8.13.0/8.13.0) with ESMTP id j7GM4Uoj014300
	for <caml-list@yquem.inria.fr>; Wed, 17 Aug 2005 00:04:31 +0200
Received: by zproxy.gmail.com with SMTP id 8so30018nzo
        for <caml-list@yquem.inria.fr>; Tue, 16 Aug 2005 15:04:30 -0700 (PDT)
DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws;
        s=beta; d=gmail.com;
        h=received:message-id:date:from:to:subject:mime-version:content-type:content-transfer-encoding:content-disposition;
        b=lDTcgW+5gOL3OsAjJVIkD/AF8IdARLYBFcWlnfBxpJqAx69gqFhhwrDMRRrBW+qkrCjG4hih2fIz4mkiHw/uvofUwJtB2YMoqvIlYYCfDvL7uz0WozeMh9COJbq8wHj+/O8cN0niCLHzDsUYfX6HnLAwkzpf3fHvl9mG5H1eC8w=
Received: by 10.36.7.6 with SMTP id 6mr92672nzg;
        Tue, 16 Aug 2005 15:04:30 -0700 (PDT)
Received: by 10.36.17.2 with HTTP; Tue, 16 Aug 2005 15:04:30 -0700 (PDT)
Message-ID: <aee06c9e050816150491c35f9@mail.gmail.com>
Date: Tue, 16 Aug 2005 15:04:30 -0700
From: Nathaniel Gray <n8gray@gmail.com>
To: caml-list@yquem.inria.fr
Subject: Representation of objects
Mime-Version: 1.0
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: quoted-printable
Content-Disposition: inline
X-Miltered: at nez-perce with ID 430262EF.000 by Joe's j-chkmail (http://j-chkmail.ensmp.fr)!
X-Spam: no; 0.00; ocaml:01 asmrun:01 stdlib:01 invocations:01 superclass:01 bytecode:01 hash:01 cheers:01 closures:01 functions:01 essentially:01 caltech:02 caltech:02 caml:02 confused:02 
X-Spam-Checker-Version: SpamAssassin 3.0.3 (2005-04-27) on yquem.inria.fr
X-Spam-Level: 
X-Spam-Status: No, score=0.0 required=5.0 tests=RCVD_BY_IP autolearn=disabled 
	version=3.0.3

I've been poking around a bit into the representation of objects in
OCaml and I'm a bit confused.  Based on caml_get_public_method in
asmrun/obj.c and various bits of stdlib/camlinternalOO.ml I see that
the method table is an "array" where the even entries are closures and
the odd entries "tags" -- hashed method names.  (The first two entries
are special.)  The table is stored sorted in order of increasing tag
value.  Please correct me if I've misunderstood something here.

I've got two questions:

1.  Does this mean that essentially all method invocations need to
search the method table?  The method table of a superclass is no
longer a prefix of that of a subclass.  There's a GETMETHOD(i,obj)
bytecode, but I'm struggling to figure out when you could use it.

2.  What about hash collisions?  There's no collision resolution code
in the method lookup functions.

Cheers,
-n8

--=20
>>>-- Nathaniel Gray -- Caltech Computer Science ------>
>>>-- Mojave Project -- http://mojave.cs.caltech.edu -->