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From: ucbesvax.turner@ucbcad.UUCP
Newsgroups: net.lang
Subject: Re: Self-modifying code - (nf)
Message-ID: <1248@ucbcad.UUCP>
Date: Thu, 12-Jan-84 01:06:40 EST
Article-I.D.: ucbcad.1248
Posted: Thu Jan 12 01:06:40 1984
Date-Received: Sat, 7-Jan-84 01:58:27 EST
Sender: notes@ucbcad.UUCP
Organization: UC Berkeley CAD Group
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#R:fortune:-215700:ucbesvax:4500007:000:1642
ucbesvax!turner    Jan  5 03:13:00 1984

To mention FORTH in this newsgroup is perhaps only to invite flamage
(con-, and maybe pro-), but I think the problem of self-modifying code
for most cases could be solved by providing a support library for building
up segments of threaded code.  One could then dynamically "compile"
(dreaded FORTH re-definition of the word) and execute interpreted code
that was as much as five times slower than *real* compiled code, but
usually around five times faster than most interpreters written in high-
level languages.

The niches are everywhere: just about every termcap-style device-
description format I've seen has a BUGS entry--"Really should be
compiled."  (This is true of both BSD termcap and a local, device-
independent graphics driver that could use it even more.)  The
interactive function-plotter is another good example.  Database-
query compilers yet another.

With a threaded-code interpreter-kernel linked as a subroutine, and
some macros and routines for segment definition, exception-trapping,
etc., all that is left for many applications is an infix-to-postfix
converter.  Recursive descent or lex/yacc can be used.  Then your code
can be ported to any machine with an implementation of the library. 

Finally, since the threaded-code kernel and support routines can be
defined in a largely machine-independent way, porting the library
itself would involve a fairly small, one-time-only effort.

But there's a danger: someone might use it to bring up FORTH on your
machine.  Pretty soon, you'd have weird people all over the place,
late-night drug-deals in the office, the whole bit.
---
Michael Turner (ucbvax!ucbesvax.turner)