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From: diamond@tkou02.enet.dec.com (diamond@tkovoa)
Newsgroups: comp.lang.c++
Subject: Re: Borland Turbo C++ performance issue and tutorial errors
Message-ID: <1894@tkou02.enet.dec.com>
Date: 6 Aug 90 08:37:34 GMT
References: <7921@tekgvs.LABS.TEK.COM> <380@taumet.com>
Reply-To: diamond@tkou02.enet.dec.com (diamond@tkovoa)
Organization: Digital Equipment Corporation Japan , Tokyo
Lines: 28

In article <380@taumet.com> steve@taumet.com (Stephen Clamage) writes:

>There can be no validity to a claim that two programs written in two
>different programming languages are the "same".  It is a well-known
>theorem in the theory of computation that one cannot *in general*
>determine whether two programs have the same behavior.

False and true, respectively.  No machine (or no program, if you prefer)
can correctly check all possible pairs of programs.  Every machine will
fail (loop forever) for at least some cases.

However, some machines can check SOME programs.  Some humans can too.
I am sure that you can verify, and you can write a program to verify,
that the following two programs (executed by processors conforming to
their respective standards; and using the ASCII standard character set
or, if you prefer, similar ISO version) are the same:

int main(int argc, char **argv) {      PROGRAM junk(OUTPUT);
  printf("Hello, world.\n");           BEGIN
  return 0;                              WRITELN('Hello, world.');
}                                      END.

(In fact I thought of giving an example with null programs, but didn't
because it might mislead as to the amount of generality that this
case has.)
-- 
Norman Diamond, Nihon DEC     diamond@tkou02.enet.dec.com
This is me speaking.  If you want to hear the company speak, you need DECtalk.