Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!usc!apple!lsr
From: lsr@Apple.COM (Larry Rosenstein)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Objective-C compiler?
Message-ID: <47336@apple.Apple.COM>
Date: 13 Dec 90 03:04:51 GMT
References: <#%F^8W_@rpi.edu> <1990Dec12.161329.12831@cbnewsk.att.com>
Organization: Future Stuff, Apple Computer, Inc.
Lines: 36

In article <1990Dec12.161329.12831@cbnewsk.att.com> ech@cbnewsk.att.com (ned.horvath) writes:
>
>By contrast, Objective-C is, to a first approximation, SmallTalk-80
>embedded in C.  (I don't claim the approximation is exact, flames to
>comp.object.)  While every object still has a definite type, object
>references are essentially typeless, and it's always valid to send any
>message to any object, with a default behavior that the system stops

This is true, except that I think Objective-C also supports typed object
references, which use a faster dispatching mechanism.  (I'm not Objective-C
expert, so perhaps someone else can verify this.)

>The plus side of my posting is that, while I wouldn't expect MacApp
>to be supported by Objective-C, MacApp is not the only generic
>application imaginable, or even the only one presently shipping
>(the Think Class Library comes immediately to mind).

To support MacApp or TCL in Objective-C there are 2 alternatives: (1)
support the exact same runtime implementation so that you can link the
existing class library with Objective-C code, or (2) translate the class
library into Objective-C.

MPW C++ takes the first approach to supporting MacApp, while THINK Pascal
takes the second.  (Although it's easy since the langugages are the same
except for minor differences.)

(2) would be difficult for Objective-C, and I don't know enough about the
Objective-C runtime to know if (1) is possible.  If Objective-C does support
typed object references, then it might not be as difficult as it first seems.


-- 
Larry Rosenstein,  Object Specialist
Apple Computer, Inc.  20525 Mariani Ave, MS 77-A  Cupertino, CA 95014
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