Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Posting-Version: version B 2.10.3 4.3bsd-beta 6/6/85; site ucbjade.BERKELEY.EDU
Path: utzoo!watmath!clyde!burl!ulysses!ucbvax!ucbjade!network
From: network@ucbjade.BERKELEY.EDU (Berkeley Network)
Newsgroups: net.arch
Subject: Re: self-modifying code, conditionals
Message-ID: <381@ucbjade.BERKELEY.EDU>
Date: Wed, 26-Feb-86 20:10:49 EST
Article-I.D.: ucbjade.381
Posted: Wed Feb 26 20:10:49 1986
Date-Received: Fri, 28-Feb-86 21:59:19 EST
References: <546@tekcrl.UUCP> <426@utastro.UUCP>
Reply-To: oster@ucblapis.UUCP (David Phillip Oster)
Distribution: net
Organization: University of California, Berkeley
Lines: 26

In article <426@utastro.UUCP> nather@utastro.UUCP (Ed Nather) writes
about self-modifying code:
>It will return; it's too neat an idea to stay dead.  What we lack is the
>needed formal discipline to use it carefully.  Spaghetti code has given

1) The language I use (built in forth) has an executable struct -
viewed as an execution object it is a procedure.  Vieweed as a data object
it is a struct.  What this means is, I can store the appropriate typed
objects into fields in the structure (instructions, addresses, etc.) and
then execute it.  It is useful for just the purpose Ed describes -
cranking every last iota of speed out of a piece of code that the machine
is really too slow to do.  And having a decent type structure for this
kind of thing sure cuts down on errors.

2) Living without branches is not a new idea - The Aiken/IBM Mark 1
computer, an amazinearly computer built at Harvard, kept its data in RAM,
but its program on siz paper tape readers.  To program a loop, you got out
the gummed paper and literally looped the tape! instead of a branch
instruction (which advances the program counter) you executed an
instruction that transferred to a different tape reader.  (The teaching
assistants used to challenge us to save room on the machine by coming up
with a useful loop that used Mobius encoding.
---David Philip Oster
---------------------  ``What do you look like when you aren't visualizing?''
Arpa: oster@lapis.berkeley.edu
Uucp: ucbvax!ucblapis!oster