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@simon_brooke@mastodon.scot
2026-05-10 07:38:29

OK, Abdulaziz Ghuloum's #Lisp compiler course, and all of the many implementations thereof, intercept the (usually x86) assembly language generated by GCC, and build from that. My next challenge: how to do the same trick for LLVM-IR...

@simon_brooke@mastodon.scot
2026-04-03 22:45:28

I've been hacking on Beowulf again, today; and I'm reminded how enchanted I am with the Beowulf logo, which sort-of designed itself.
I take no credit for it, really.
#Lisp 1.5
git.journeyman.cc/simon/beowulf

A Lisp trace of the evaluation of the function RANGE, in Beowulf. Beowulf is a recreation of Lisp 1.5, and therefore has all its prompts and error messages written in Old English. The evaluation trace naturally forms the symbol Lambda.
@simon_brooke@mastodon.scot
2026-04-05 12:17:38

#Software peeps: do you still do box diagrams to work out how your structures will sit in memory?
#Lisp

A section of a design document I am working on, comprising text surrounding a box diagram. The text is: In the beginning was the Word My intention is that memory will be considered as an array of 64 bit words. Each word may be considered as 1. a cons cell: two instances of object32, each having one mark bit, three tag bits and 28 payload bits; 2. a single object64, having one mark bit, seven tag bits, and 56 payload bits. Note that, for any word, the first four bits comprise the mark and …
@simon_brooke@mastodon.scot
2026-05-05 18:52:02

I've started my development log for May. It's really mostly about tooling -- specifically, editors and debuggers.
#PostScarcitySoftware
#Lisp

Post Scarcity state of play, May 2026
My monster, she builds! Admittedly, she doesn't yet do much, but... (also in this post, a lot of discussion of debuggers and editors).

@simon_brooke@mastodon.scot
2026-03-28 11:08:37

OK, folks, I've written yet another incomprehensible essay on the intricacies of implementing a software environment for the hardware of the deep future.
Read this only if you're incurably geeky, and, ideally, interested in #Lisp.
#PostScarcitySoftware

Nodes, threads, locks and links
Up to now, I've been building a single threaded Lisp. I haven't had to worry about who is mutating memory while I'm trying to read it. The idea that this is a mostly immutable Lisp has encouraged me to be blasé about this. But actually, it isn't entirely immutable, and that matters.

@simon_brooke@mastodon.scot
2026-04-04 09:59:39

OK, Beowulf bug. Both EVAL and APPLY in Beowulf are straight transcriptions of the mexprs on pages 70 and 71 of the #Lisp 1.5 Porgammer's Manual.
CONC is the only FEXPR I have implemented so far (and one of only three FEXPRs in the manual).
The unit test for CONC fails, because EVLIS is called on the argument list by EVAL (line 20 on page 71) before it reaches APPLY, and therefore b…

@simon_brooke@mastodon.scot
2026-04-04 10:32:41

SO!
I can fix my code so that the arguments to FEXPRs are not evaluated, by deferring the call to EVLIS into APPLY; but this is not what the code given on pages 70-71 does, and so my code will then not directly follow the specification in the #Lisp 1.5 Programmer's Manual;
OR,
I can not do this, in which case FEXPRs will not work as specified on pages 18 and 19.
(Note that…

@simon_brooke@mastodon.scot
2026-04-25 22:08:05

There's a Common #Lisp cryptography library called 'Ironclad'. I'm going to need cryptography for #PostScarcitySoftware authentication, but Post Scarcity #Lisp is going to be a lot more…

GitHub - mikera/ironclad: Ironclad: Steam Legions - A steampunk strategy game in Clojure
Ironclad: Steam Legions - A steampunk strategy game in Clojure - mikera/ironclad

@simon_brooke@mastodon.scot
2026-04-01 12:02:56

OK, so as I've decided my new #Lisp prototype should use read-tables and read-macros to read anything, I need to implement `eval` before I can implement `read`!
Still, progress is being made.

@simon_brooke@mastodon.scot
2026-04-19 10:46:15

I did ten hours on #PostScarcitySoftware yesterday, and then slept a bit, and then woke up with an intention to rapid prototype a '#Lisp structure editor in the browser' idea I've been thinking on for a while. I did about five hours on that, and it's looking promising.
I&…

The WEditor prototype, viewing a Clojure project file. The popup text at the mouse pointer shows the underlying s-expression represented by that element in the displayed document. This isn't perfect but it looks usable.
The editor displaying its own source code (in Clojure). Again, this looks usable.
The prototype editor displaying some code from the Post Scarcity 0.0.6 prototype.
The editor viewing some Lisp 1.5 code, from Beowulf (actually taken from page 66 of the Lisp 1.5 Programmer's Manual).
@simon_brooke@mastodon.scot
2026-03-18 11:26:15

Oh, Jings, my own execution traces are REALLY hard to read. It's my own fault: these are my traces in my software, there's no-one else to blame, but...
#Lisp

Screenshot from my editor. In the bottom pane, a REPL, in which I'm defining and executing the function `member?`. I'm doing this because it exercises a particular bug in `cond` (I think), which I'm struggling to understand. In the upper pane, an execution trace shows what the Lisp evaluator is doing... It's really hard to get the level of detail right when writing execution traces. There's far more detail here than I need to trace the particular but I'm working on, even though I have only ena…
@simon_brooke@mastodon.scot
2026-03-23 23:38:33

Yet another blog post on #Lisp memory management. If you are not obsessively geeky, this one isn't for you.
journeyman.cc/blog/posts-outpu

Paged space objects
Antecedents for this essay:

@simon_brooke@mastodon.scot
2026-04-25 09:59:15

RE: #Lisp! OK, it's about as sophisticated as the ed…

@simon_brooke@mastodon.scot
2026-04-24 11:30:00

In other news, I'm now posting my #PostScarcitySoftware development log on my blog, in case anyone is interested. Which, if you're sane, you won't be. #Lisp

Post Scarcity state of play, April 2026
I write up the state of play of the Post Scarcity Software Environment in a developer's log on a fairly regular basis; but it only gets published (here) when I publish a new release, which is to say, rarely... I thought I would publish soft-of-monthly updates on my blog. The discipline of doing so may help me stay focused on the project, too. So here's the first such.

@simon_brooke@mastodon.scot
2026-04-20 15:44:18

It being an astonishingly beautiful afternoon here, instead of sitting indoors hacking #Lisp, I am out in the wood with my pussy cat hauling out timber for the sawmill.
It's a hard life.
#TheJoyOfCrofting (unironically, for once)

Hitching up a log for hauling. The log, which is already cut and lying in a tangle of other timber, is attached to the steel winch cable with a webbing strop. Horrible, my silver grey cat, lies in the sun waiting to assist.
View from the tractor. The cable stretches away into the wood to a turning block, and from there to the log, which is just being pulled into the picture from the right. The floor of the wood is green and grassy; the whole scene is bathed in sunlight.
The log has been dragged right into the middle of the picture, where it has a clear line to the tractor, and the turning block has been removed.
The Little Tractor That Can parked at the edge of the wood, with the log drawn up close behind it.
@simon_brooke@mastodon.scot
2026-03-20 13:10:45

I've written another essay about my mad #PostScarcitySoftware #Lisp system.
"We don't need to know, or have known, these people to build on their work. We don't have to, and cannot in detail, fully understand their work. There is simply too much of it, its complexity wou…

Don't know, don't care
Modern computing systems are extremely complex. It is impossible for someone to be expert on every component of the system. To produce excellent work, it is necessary to specialise, to avoid being distracted by the necessary intricacies of the things on which your work depends, or of the (not yet conceived) intricacies of the work of other people which will ultimately depend on yours. It is necessary to trust

@simon_brooke@mastodon.scot
2026-04-17 10:23:35

OK, if I have an environment pointer *in the stack frame*, then not only does it greatly simplify the #Lisp calling convention, it also means that the evaluation time environment is captured in any stack trace and can be inspected in any break.
Downside: it's one more inc_ref/dec_ref for every function call, which is a performance hit.
H'mmm...

@simon_brooke@mastodon.scot
2026-04-18 10:37:57

Well,. the good news this morning is that i found a stupid bug in `cdr` which, once you've seen it, you can't unsee, so the seventh #PostScarcitySoftware #Lisp prototype is now completing initialisation and entering the REPL.
The bad news is that there's an unterminating recu…

Hot damn! When you see an obvious, stupid bug you created, you can't unsee it! · 02a4bc3e28
post-scarcity - Prototype work towards building a post-scarcity software system

@simon_brooke@mastodon.scot
2026-03-14 00:52:27

I have written another essay for my blog. This one is about where I'm up to with my mad #Lisp system, and is *really* obscure!
journeyman.cc/blog/posts-outpu

Vector space, Pages, Mark-but-don't-sweep, and the world's slowest ever rapid prototype
...it was intended, largely, to be a giant thought experiment. But now enough of it *does* work that I can see fundamental design mistakes, and I'm thinking about whether it's time to treat it as a rapid prototype...