Andrew Healey

software engineer @vercel • I write about performance, compilers, puzzles, &more on my website • @recursecenter alum

[Andrew Healey @healeycodes]

plus how the game AI scores your pizza designs!

[Andrew Healey @healeycodes]

I spent a few days decompiling my favorite childhood game, Fast Food Tycoon 2, and figuring out:

‣ world rendering
‣ sprite animations/character movement
‣ light mechanics

so much to dig through and discover the dev team were on fire here: https://t.co/sHvmjbdOGs

[Andrew Healey @healeycodes]

pizzeria pipeline!

[Andrew Healey @healeycodes]

the stronger the searcher, the more dangerous metadata about the existence of an answer becomes

in security: "just a rumour of a bug is enough to find an exploit these days"

in chess: Carlsen would be MUCH stronger with just one bit per game: "this position is critical"

[Andrew Healey @healeycodes]

I wrote about the performance of LLM tokenizers

like most things you want to go fast, it's better to use compact contiguous state instead of complex data structures!

https://t.co/yxMmVGXFXY

[Andrew Healey @healeycodes]

however, I haven't given up and have high hopes for "We Could Have Had Coding Agents in 2̴0̴1̴9̴ 2021"

[Andrew Healey @healeycodes]

I wanted to write a blog post titled (provocatively) "We Could Have Had Coding Agents in 2019"

I used the GPT‑2 XL weights (no post-training) and backported several later agent-design breakthroughs (action/observation loops, filesystem tools, etc.)

[Andrew Healey @healeycodes]

but GPT-2 can't reliably emit JSON, or call tools in a meaningful way.

the only hint of agency came from leaning into text completion: Programmer → ACTION, Computer → observation, etc.

to get it to fix tests, the examples were so close to the answer that it was kinda useless

[Andrew Healey @healeycodes]

I added 𝚍𝚎𝚏𝚎𝚛 to the typescript compiler

but along the way, I realised that what I want is different syntax for 𝚞𝚜𝚒𝚗𝚐

I just want to be able to write:

𝚞𝚜𝚒𝚗𝚐 𝚊𝚠𝚊𝚒𝚝 𝚜𝚎𝚖𝚊.𝚊𝚌𝚚𝚞𝚒𝚛𝚎()

but you can't

↧

https://t.co/Xkfk9Aq3Cw

[Andrew Healey @healeycodes]

@aaaronson do you count CHACHALACA?

[Andrew Healey @healeycodes]

two sum in lisp is actually really cute

[Andrew Healey @healeycodes]

https://t.co/tcvSJH0D74

read all about it ⇩

[Andrew Healey @healeycodes]

new post!

I wrote a tiny compiler that lowers simple kernel loops into explicit data-parallel code (lanes! masks!)

ofc I made up a language to make the input/output code easier to read

[Andrew Healey @healeycodes]

https://t.co/gJiiXbyxMZ

hope you've been enjoying the C posts

[Andrew Healey @healeycodes]

quickjs is GOATed

delightful API surface

I was able to hack together a tiny runtime and event loop v quickly with it

[Andrew Healey @healeycodes]

read my notes and code snippets and thoughts
https://t.co/wBy0yo2VUI

[Andrew Healey @healeycodes]

I built a tiny shell with C so I could learn more about syscalls and pipes

great fun

I found C to be quite suited for the task (fork, execvp) ... until I had to manage some string lifetime stuff 🥲

[Andrew Healey @healeycodes]

glad y'all like this one 🫡

[Andrew Healey @healeycodes]

https://t.co/QCS2yn8Qoc

[Andrew Healey @healeycodes]

I suggested to my friend that writing a semaphore is fairly trivial but when I sat down to write one I was pretty humbled

the edge cases around context cancellation are no joke

more notes and my solution below down there ⇣