Ancestors

Written by Kira, in convalescence 🌙 on 2025-01-30 at 00:08

What a fun week and a half:

https://codeberg.org/kira/forth32/

This is an implementation of FORTH, following the jonesforth tutorial[1]. The original is written in x86 assembly, mine is in C.

It works! I'm so thrilled. I've bounced off of trying to implement this perhaps, say, 3 or 4 times? Each time I'd get stuck, and a couple of months later I'd have another go at it, and I'd grok the thing I had been stuck on the previous time.

And this time I made it to the end (of the main implementation).

The base system is 3900 bytes: that includes the stacks, string buffer, and all of the built-in words.

What a joy! It's so cool to finally understand how FORTH works from the ground up. It's complicated but elegant & simple.

[1] https://github.com/nornagon/jonesforth/blob/master/jonesforth.S

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Written by Kira, in convalescence 🌙 on 2025-01-30 at 00:11

What gets me is that, if someone unfamiliar with FORTH tries to read this or run it, they're going to have a terribly confusing time.

I haven't figured out yet how to present this in a way that's accessible. 🤔

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Written by Kira, in convalescence 🌙 on 2025-01-30 at 01:41

I wish I could explain how cool this is, how powerful it is!

FORTH can rewrite its own interpreter/compiler at runtime or compile-time (as you prefer). You can write words that run their own logic at compile-time (like Lisp macros). You can replace any built-in core function with your own. You can define IF...THEN yourself and any loop construct from with in FORTH itself. FORTH has full access to the same memory it runs in (including the dictionary of all words), so it can modify itself in any way.

You can even create new types of syntax for single- and multi-line comments from within FORTH!

🤯 🤯 🤯

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Toot

Written by Kira, in convalescence 🌙 on 2025-01-31 at 02:07

Adding multi-line comments to FORTH, in FORTH:

: (

KEY CHAR ) = 0BRANCH [ -20 , ]

;

• : defines a new word, named by the next word, "("

• KEY reads the next character of source code

• CHAR is a word I wrote that reads the next character and puts it onto the stack ("(" here)

• = checks if the char read from the source code stream matches the close paren character ")"

• 0BRANCH jumps by N bytes if what's on top of the stack is false (zero), by the offset compiled right after it (-16 here), causing it to loop back to KEY

There's more to be understood here re: [ and ] and , but that's the high level!

Now I can write comments like,

( hello world! this input is ignored! )

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Descendants

Written by Kira, in convalescence 🌙 on 2025-01-31 at 02:55

Now I've written DO...WHILE loops in FORTH itself! giggles This is too fun.

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