Viewing profile — rtfeldman

> Does roc run tests in the same process as the compiler? We do for tests of pure functions, yes. > Your tests run in an entirely separate process from the compiler (and from cargo…

Also a good point! TIL that Rust and C++ use interpreters for const, although of course that wouldn't work for running tests. Then again, in the specific case of Rust I believe rus…

> I think that for the hot binary patching / code reloading features, yes, that is going to need unsafe. But for regular old "producing an executable" compilation? Emitting machine…

Roc defaults functions to being pure, and functions that can run side effects are inferred to have a different type by the compiler based on usage. By convention, their names shoul…

You can disable all AI features in Zed with a single setting: https://zed.dev/blog/disable-ai-features

> The best at that that I've found is Conductor, but I can't use it at work because we only have Copilot and they're locked to a Claude/Codex backend. FYI, you can use Copilot dire…

I maintain a ~250K LoC Zig compiler code base [0]. We've been through several breaking Zig releases (although the code base was much smaller for most of that time; Writergate is th…

Very cool! The permission model is almost identical to Roc's - https://www.roc-lang.org/platforms - although Roc isn't designed for "Syntax only an AI could love" (among many other…

That's a much better test!

If a stranger asks me, "Should I walk or drive to this car wash?" then I assume they're asking in good faith and both options are reasonable for their situation. So it's a safe ass…

> Whether functions are introduced with an explicit keyword; how return types are marked; whether semicolons can be omitted at end of line; how types are named (and the overall sys…

Wow, this is one of the most surprising comments I've ever read on HN! Personally, I bucket C++ and Rust and Swift under "basically the same syntax." When I think about major synta…

Claude Opus 4.5 is completely fluent in Zig. I use it constantly, and it never occurred to me that someone might think there was a problem to be solved there.

Just based on timing, I am almost 100% sure whatever code is responsible was handwritten before anyone working on Windows was using LLMs...but anyway, thank you for the bug report …

Definitely more than a faster keyboard (e.g. I also ask the model to track down the source of a bug, or questions about the state of the code base after others have changed it, bou…

> Do you think it can replace you basically one-shotting features/bugs in Zed? Nobody is one-shotting anything nontrivial in Zed's code base, with Opus 4.5 or any other model. What…

Zed's entire code base is already open source, so Anthropic has a much more straightforward way to see our code: https://github.com/zed-industries/zed

Anecdotally, we use Opus 4.5 constantly on Zed's code base, which is almost a million lines of Rust code and has over 150K active users, and we use it for basically every task you …

If you're feeling adventurous and would like to try Roc's new compiler, I put together a quick tutorial for it! https://gist.github.com/rtfeldman/f46bcbfe5132d62c4095dfa687...

My understanding is that the reasoning behind all this is: - In 1985 there were a ton of different hardware floating-point implementations with incompatible instructions, making it…

> I’ve tried all the popular alternatives (Copilot, Claude Code, Codex, Gemini CLI, Cline) Can't help but notice you haven't tried Zed!

As of August 2025, Zed had 150K monthly active users. That was before it supported Windows; the number is much higher now (although not publicly reported). I'd be very surprised to…

You don't have to use Codex in its terminal UI - e.g. you can use it in the Zed IDE out-the-box: https://zed.dev/blog/codex-is-live-in-zed

When I wrote Elm in Action for Manning, I talked with them explicitly about the language being pre-1.0 and what would happen if there were breaking changes. The short answer was th…

> I get it, pausing some work to ship AI integration plumbing is a good strategy to keep momentum up with competition. By every metric - lines of code shipped, hours per week spent…