Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!asuvax!ncar!boulder!gore!jacob
From: jacob@gore.com (Jacob Gore)
Newsgroups: comp.object
Subject: Re: True OOP using plain C
Message-ID: <1130008@gore.com>
Date: 7 Feb 90 05:43:26 GMT
References: <406@wmt.UUCP>
Reply-To: jacob@gore.com (Jacob Gore)
Organization: Gore Enterprises
Lines: 49

/ comp.object / mist@wmt.UUCP (Michiel Steltman) / Feb  5, 1990 /

CO2 looks interesting, but I don't see any major differences between it and
Objective C.  For example:

> Objective C solves some of the problems but has the drawback
> that it is not available on all computers and needs special
> pre-processing.

I suppose "special pre-processing" means compiling those parts of a
program that are in the Objective C language but not in the C language into
C code.  For instance, converting
	[rectangle moveBy:1.0 :2.0]
into something like
	_msg(rectangle, "moveBy::", 1.0, 2.0)
and so on.

If that's what was meant, that's certainly true---Objective C is a
different language than C, you can't just run an Objective C program
through a C compiler.  But:

> How is this CO2 used?  It is very easy to use Co2, it is just
> like normal C and it consists of standard libraries with
> methods and a program called SYNTOR.

Doesn't Syntor also perform "special pre-processing" on a CO2 program?

> This results in the fact that all messages 'new' end up in the
> same procedure.  Syntor generates a C file that contains all
> these procedures and dispatches the message to the correct
> method.  A method is very easy to write, the only speciality
> is that an instance method should start with om_ and a
> factory method with of_, followed by the class and message
> name.  The dictionary implementation of atPut is thus:
> om_Dictionary_atPut.

If I understand this correctly, both the message calls and method
declarations require conversion by Syntor into C.  Message calls may look
like C function calls, but they have to be replaced with a call to
something very similar to Objective C's _msg routine.  Similarly, Syntor
handles method declarations differently than a C compiler handles function
declarations (otherwise I don't understand why you need the naming
convention).  Is this not "special preprocessing"?

So, what exactly are the fundamental differences between CO2 and Objective C?

Jacob
--
Jacob Gore		Jacob@Gore.Com			boulder!gore!jacob