[COFF] [simh] [TUHS] Regex archaeology

[Tim Shoppa via COFF]

You mention MAD which is great!

I actually got to use MAD a few times in the 1980s in a moonlighting job where i was further extending a special purpose RUNOFF variant that drove Calcomp plotters to make transparency decks for a geology department. I specifically extended it to talk to HP pen plotters and added a preview for Tek4014. I had a lot of fun, much more fun than anything else I ever did on the university’s IBM mainframes.

Even today the favorite part of my job is hacking code that generates SVG.

Tim N3QE

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From: simh at groups.io <simh at groups.io> on behalf of Clement T Cole via groups.io <clemc=ccc.com at groups.io>
Sent: Tuesday, 01 September 2026 22:44:49
To: Will Senn <will.senn at gmail.com>
Cc: Computer Old Farts Followers <coff at tuhs.org>; simh at groups.io <simh at groups.io>
Subject: Re: [simh] [TUHS] Regex archaeology

Will, CCing COFF and SIMH which is really where this question belongs and BCC: TUHS.org

On Tue, Sep 1, 2026 at 9:21 PM Will Senn via TUHS <tuhs at tuhs.org<mailto:tuhs at tuhs.org>> wrote:
All,

I've been doing some experimentation to test my language, aiki, a small
interpreted language. Most of my pressure tests have begun to move
toward emulation because emulating machines is challenging in an
interpreter (can you say sllllloooooowwwww?). Anyhow, when I had the
regex implemented by my outsourced team (claude & chatgpt), I lacked any
comprehension of how it actually worked beyond textbook level (which is
to say, names of things that I didn't truly comprehend). So, I went
looking to primary sources, as I usually do and I came across a sweet
little regex implementation by none other than Ken Thompson, in his well
known article, Regular Expression Search Algorithm, CACM v. 11, No. 6,
June 1968. I found a decent copy and transcribed it so I could use it's
examples more directly. It's a piece of work - an Algol 60 three stage
program that emits IBM 7094 machine code that processes a string and
produces signals.

What I really appreciate is that the code "works", it's not a fragment,
not partial implementation, but serious work, the core third stage.
Anyhow, I wrote a small 7094 processor (only enough instructions to
execute thompson's search) in aiki, and tried it out and it's glorious
(to me) running the machine code it generates and producing expected
results (as provided in this exceptional article).

This like all shiny objects took me down a rabbit trail. My language is
interpreted remember? I have been thinking about compilers - didn't
think I wanted one originally, but man slow is so not me, but not just
any implementation. My language is grammar bound, I already have an IR
in the AST output, it's closed and therefore, I can prolly just emit it
or better yet, follow Thompson with a bytecode emit (something for a go
vm, for example). Anyhow, I started wondering, what about algol 60, it's
always popping up in any serious language discussion and that took to
Randell & Russell's 1964 Algol 60 implementation where translation is
discussed, confirming my suspicion on how I might do the compiler for
Aiki and preserve it's exact semantic representation and profiling
capabilities dtrace style. Then I came back to Thompson, and that's
hopefully where y'all come in... Do any of you know what implementation
of algol-60 he might have used on the 7094? BC Algol is out in the wild
and could be right, but I'm really jazzing to implement the search on an
emulated 7094 using an actual algol and preferably the one he was using.

As I understand it, there are at least three:

  *   IBM ALGOL 60 (System Monitor Compiler) for the IBSYS operating system
  *   SHARE ALGOL 60 Translator  targeting the IBM 709/7090/7094 hardware and I thought could run on CTSS
  *   ALCOR ALGOL 60 European-American consortium dedicated to standardized ALGOL deployment for the for the 7090/7094

You might ask Ken what he remembers.   I haven't read the paper inm a few years, did he say which OS he was using that might help you track it down.  Google tells me that ALCOR-Illinois 7090/7094 compiler project has some influence in CTSS.   But it also says:
"While standard ALGOL 60 dialects like ALCOR existed on the hardware, they were not the primary way people wrote algorithmic code on CTSS day-to-day. CTSS users heavily favored two deeply related "ALGOL-cousin" systems. ... MAD (Michigan Algorithm Decoder - ALGOL 58, and compiled unbelievably fast): was one of the most popular high-level languages on CTSS ...  AED (Algol Extended for Design): created at MIT, AED was an explicit, major extension of ALGOL 60 designed specifically to run under CTSS."

I know, on topic? maybe a little stretch for folks only interested in
bandying about in the userland/kernel, but regex and it's implementation
in ed and elsewhere were surely influenced by this exact work.

Thanks!

Will

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