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From: uucibg@swbatl.UUCP (3929)
Newsgroups: comp.sys.mac.programmer
Subject: C++ interface to Object Pascal, whyfor?
Keywords: C++, Object Pascal, interface, uses
Message-ID: <934@swbatl.UUCP>
Date: 13 Nov 89 02:36:43 GMT
Organization: Southwestern Bell Tele. Co. - Advanced Technology Lab - St. Louis
Lines: 47


I'm not trying to flame, I just want to make sure I understand the nature of
the C++/Object-Pascal relationship.  Please correct my misunderstandings:


+ Object Pascal uses objects a la Smalltalk (methods and dynamic dispatch).
    (Side note: does this mean that objects in Object Pascal are weakly
     typed?)

+ Apple has extended the Cfront translator so that you can work with
  Object Pascal style objects.

+ While it's possible (apparently) to mix-and-match Object Pascal Objects
  and C++ objects in the same program, trying to do so within a class or
  class heirarchy is going to have significant limitations (which are
  essentially unavoidable due to the differing semantics of "object"
  in the two languages).
  NOTE: I only said "apparently" above because I've not spent the time to
  figure out how to do it yet... :-)

+ It's not possible to involve Object Pascal classes in a multiple inheritance
  heirarchy.

If this is correct, then it would seem that you can't use C++ to extend the
Object Pascal heirarchies in a fashion that takes advantage of weak typing of
objects (assuming that Object Pascal has weakly typed objects) or of the
Multiple Inheritance of C++ (which would make sense given the nature of the
dynamic-dispatch problem for mult. inheritance).

This would seem to indicate that the interfaces are primarily for providing
access to the power of MacApp.  This is certainly a worthwhile objective and
is valuable in and of itself.  However, I'm wondering: what other advantages
might this interface provide?

DISCLAIMER:
I wouldn't be at all surprised if much of the above is totally off kilter :-)

Thanks,
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Brian R. Gilstrap    ...!{ texbell, uunet }!swbatl!uucibg OR uucibg@swbatl.UUCP
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Disclaimer:
Me, speak for my company?  You must be joking.  I'm just speaking my mind.