Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!uunet!mcsun!goya!esink@turia.dit.upm.es
From: esink@turia.dit.upm.es (Eric W. Sink)
Newsgroups: comp.lang.c++
Subject: C < X < C++,  worthwhile(X), solve for X
Keywords: implementation, object oriented, sanity
Message-ID: <1991May23.115050.5755@dit.upm.es>
Date: 23 May 91 11:50:50 GMT
Sender: @dit.upm.es
Reply-To: esink@turia.dit.upm.es (Eric W. Sink)
Followup-To: comp.lang.c++
Organization: Dept. Ingenieria de Sistemas Telematicos, dit, upm, Madrid, Spain
Lines: 54
Nntp-Posting-Host: turia.dit.upm.es


I've been thinking about augmenting a C compiler with some object oriented
features.  Several months ago, I posting a question to the net, asking
how difficult it would be to modify a C compiler into a C++ compiler.
I'm fairly familiar with both languages, but have only a little understanding
of how C++ is traditionally implemented.  Steve Clamage responded to my
question by email, I assume he doesn't mind my paraphrasing his response (I
lost the original note from Steve) :

   Hard.  Really hard.  Most people don't realize just how difficult
   is to parse C++.  Any quantitative estimate of the effort would
   no doubt be ruinously low.  All known attempts at making a C++ compiler
   out of a C compiler have failed.

[Steve, feel free to post and correct my paraphrase if necessary, but
I think I got the gist of it]

Well, I dropped the idea for quite a while, and have just picked it
back up again.  In light of Steve's prophesy, I have lowered my aim
a bit.

Q:  Given a working ANSI compliant C compiler, suppose that you want
    to modify it to compile an object oriented superset of C.  This
    language must be a subset of C++.  Handling all of C++ is deemed
    to be not worth the effort for your project.  What features of C++
    would you implement ?  Is there a subset of C++ which can be
    implemented with reasonable effort, which would be useful ?

I am speculating that features like operator overloading, exceptions,
templates, multiple inheritance are out of the question.  The features
I would *like* to try to implement are :

  member functions, virtual and otherwise
  inheritance
  anything else that would not be too hard
    (how about simply the ability to intermix declarations
     with statements within a block)

Feel free to change my list, that's the point of the question.

Any responses appreciated.  Those who want to tell me that the
creation of non-standard object oriented C like languages is
a waste of time should keep in mind that I do not attend to
win the world over with my language, merely to learn from its
implementation and gain the ability to use it myself.

Thanks in advance,

Eric

Eric W. Sink                     | "If no one is criticizing |Opinions
Departamento de Telematica       | your work, it is possible |mine -
Universidad Politecnica de Madrid| that you are not doing    |all of
esink@turia.dit.upm.es           | anything." -George Verwer |them.