Xref: utzoo comp.lang.c:11426 comp.arch:5604
Path: utzoo!attcan!uunet!yale!mfci!colwell
From: colwell@mfci.UUCP (Robert Colwell)
Newsgroups: comp.lang.c,comp.arch
Subject: Re: Self-modifying code
Message-ID: <472@m3.mfci.UUCP>
Date: 20 Jul 88 17:08:49 GMT
References: <5262@june.cs.washington.edu> <260@thor.wright.EDU> <759@cernvax.UUCP>
Sender: root@mfci.UUCP
Reply-To: colwell@mfci.UUCP (Robert Colwell)
Organization: Multiflow Computer Inc., Branford Ct. 06405
Lines: 39

In article <759@cernvax.UUCP> hjm@cernvax.UUCP () writes:
>
>Programmers have become quite accustomed to the destructive assignment of
>data ( x := y + 2 ), so why should the destructive changing of code be any
>different?  If the practice were more common, then it wouldn't seem quite so
>bad, surely.  After all, a Turing machine with a finite length tape is not
>*that* difficult ...

Hubert, I was going to let this whole SMC discussion slide on by, but
your post finally convinced me otherwise.

First, you meant "y" := y + 2, not "x", right?

Second, it seems like only yesterday when we (the royal we) CPU
architects were so concerned with trying to narrow the semantic gap
between what a programmer was trying to express and what the
machine/language was coercing her into.  Languages like Ada and
machine architectures like capability machines were intended to
address this perceived need.  The basic idea is that (oversimplifying
drastically) in a small programming environment (you at your
standalone workstation) anything goes in terms of protection and
language type checking, etc.  

The interesting domain is that of programming-in-the-large, with
large teams of programmers producing hundreds of thousands of lines
of code (SDI/Shuttle).  There, extracting the last nano-mip of
performance is of far less interest than in avoiding bugs and
producing maintainable code, and I still believe that supporting that
environment is a far more important challenge to architects than
worrying about SMC could ever be.  And I don't think (heavy sarcasm
here) that UNIX/C is the ultimate answer to that environment.




Bob Colwell            mfci!colwell@uunet.uucp
Multiflow Computer
175 N. Main St.
Branford, CT 06405     203-488-6090