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From: tombre@crin.crin.fr (Karl Tombre)
Newsgroups: comp.lang.misc,comp.lang.smalltalk,comp.lang.c++
Subject: Re: C++ vs Objective-C
Message-ID: <338@crin.crin.fr>
Date: Tue, 22-Sep-87 04:42:21 EDT
Article-I.D.: crin.338
Posted: Tue Sep 22 04:42:21 1987
Date-Received: Sat, 26-Sep-87 04:17:53 EDT
References: <3405@ece-csc.UUCP> <638@its63b.ed.ac.uk> <1811@watcgl.waterloo.edu>
Reply-To: tombre@crin.crin.fr (Karl Tombre)
Organization: CRIN - INRIA Lorraine, Nancy, France
Lines: 52
Xref: mnetor comp.lang.misc:681 comp.lang.smalltalk:332 comp.lang.c++:450

I don't think it's so easy to say which language is "better". Neither do I
think that one is more "unified" than the other. What was said about
Objective-C (dealing with 2 universes) may be true, but

1) it depends on the way you program. If it is important for you to use
strings as objects, use the Smalltalk-80 like class for strings. If you
occasionnaly want to printf() something, use a C string. In fact, you can
consider it as two layers. You are not compelled to use the C constructs,
but they may be useful for efficiency.

2) the same can be said of C++. It is not more "unified" than Objective-C.
You also retain full compatibility with C, you can use structs instead of
classes, the privacy mechanism is sometimes a bit confusing because of the C
layer, ...

In fact, C++ and Objective-C are good examples for two main directions in
Object-Oriented Programming : the "norwegian" school and the Smalltalk
school.

C++ is in the "norwegian" family, that is a successor of Simula-67, the
first object-oriented language. As Simula, it has static typing and
restricted dynamic binding by ways of virtual functions. As Bjarne
Stroustrup points out in a paper (What is Object-Oriented Programming), a
C++ (or Simula-67) class is an exact specification, whereas a Smalltalk
class is a minimal specification.

C++ adds some new features to Simula-67 : private data, friend functions
(which are not necessary in Simula-67 where the data are not private),
operator overloading, constructors and destructors... But basically it
remains in the same family. Among other things, the main entity is the
class, not the object. Inside a class, there is no privacy : two instances
of the same class have access two each other's private fields.

Objective-C is a child of Smalltalk-80. It implements dynamic typing and
binding by means of run-time message transmission. The individual object is
completely private : you are only allowed to access it's fields through
access methods, and hence a message. There are clear analogies between the
factory methods and the metaclass methods in Smalltalk. At run-time, the
factory is a special object which implements the class in a way. But you can
also use at any moment the C layer, for instance when writing a method for a
class. Thus, you have direct access to the private data of the current
object, and hence you can write efficient methods.

My feeling : it is interesting to compare the two languages, but difficult
to say which is "better", as both of them implement well the principles of
one of the OOP "schools". The comparison is more between those schools than
between the 2 languages.

--- Karl Tombre @ CRIN (Centre de Recherche en Informatique de Nancy)
EMAIL : tombre@crin.crin.fr  --   tombre@crin.UUCP
POST  : Karl Tombre, CRIN, B.P. 239, 54506 VANDOEUVRE CEDEX, France
PHONE : +33  83e the ce t