4 ms·

And? This is absolutely the correct and standardized way to do mechanical rewrites: you do a rewrite that maps directly to the original source so you can rely o

And? This is absolutely the correct and standardized way to do mechanical rewrites: you do a rewrite that maps directly to the original source so you can rely on the original correctness guarantees and bug-for-bug compatibility and log issues, and then you go into the next phase where you begin to use idiomatic constructs. This is the same in COBOL-to-Java ports that have been done in banking and insurance for the past 20 years.

Barrin92 5mo ago
>This is the same in COBOL-to-Java ports it isn't, because those guys didn't think a naive 1-1 machine translation would give them the benefits of Java, which somehow the people involved in this rust rewriting seem to think they've already gained despite the virtually identical code. If the whole point genuinely would have been to do a purely mechanical translation they could and should have written a transpiler, which would have had significantly higher correctness guarantees than this given that it'd be deterministic, but of course that would have defeated the PR purpose of this whole thing, which just looks like a marketing for Anthropic frankly
- Daishiman 5mo ago
  > If the whole point genuinely would have been to do a purely mechanical translation they could and should have written a transpiler, which would have had significantly higher correctness guarantees than this given that it'd be deterministic, but of course that would have defeated the PR purpose of this whole thing, which just looks like a marketing for Anthropic frankly If it were just a marketing stunt you wouldn't have a fraction of a percent of the test suite passing with the remaining bugs being realistically very fixable, and everything written in languages with type systems that give far more guarantees than what COBOL is possible. You're being extremely negative about this whole endeavour without looking at the evidence that this effort is going far more smoothly than expected, and maps with many people's experience with using LLMs for tasks like these.
  - Barrin92 5mo ago
    >You're being extremely negative about this whole endeavour without looking at the evidence that this effort is going far more smoothly than expected no I'm being negative because as I just said, if you want to do a purely syntactic translation you don't even need an LLM, that's called transpilation and we've been doing it programmatically for decades. This is the kind of thing that looks great to people who can't program, think this is some new superpower unlocked by the mystery magic of LLMs and that is exactly the kind of impression Claude wants to sell.
    - famouswaffles 5mo ago
      Transpilation won't get you passing 99.8% of a comprehensive test suite of a 700K+ codebase in a week (and maybe none at all) and that's assuming transpilation is practical for the pair in question. So if you remotely want these kinds of results, then you most certainly do need an LLM.
      - drzaiusx11 5mo ago
        There are literally formally verified language transpilers out there today. They can get you 100% coverage without "cheating" like LLMs tend to do by modifying test suites to pass, etc. I'm currently using an LLM in my day job to accelerate such a 1:1translation, and it's certainly "working"/making progress but God I wish I had a formally verified machine translator instead of this probalistic bullshitting LLM. Don't get me wrong, it's extremely helpful and impressive in what it can do. But I trust it somewhat less than if I had done it myself, and for good reason. The lies I tell myself tend not to take down production. The lies my LLM tells me do however.
        famouswaffles 5mo ago
        I mean No-one is forcing you to not use a transpiler right? If it was quicker to use one or build a specific, limited one for your existing codebase and run it then you would certainly have done that already.
- vintermann 5mo ago
  You gain some benefits. You could in theory gain benefits in compilation speed, portability or even memory use and execution speed, from an automatic language translation. But everyone, including the bun people, understand that you certainly don't get code clarity benefits, and safety benefits is extremely dubious.
tempest_ 5mo ago
If the rewrite was zig to C and half the code was in __asm blocks is that different or the same?
- Daishiman 5mo ago
  You know that it's different so why are you asking a meaningless rhetorical question.
bmitc 5mo ago
COBOL to Java is a completely different thing and pretty much unrelated. Rust can easily call C libraries and vice versa and so can Zig. A more appropriate and designed rewrite would identify the core pieces of the Zig code that were the primary sources of all the big issues. Then, you rewrite that component in Rust and verify that you get the expected improvements. That keeps the codebase stable, it keeps you honest on actually reducing bugs and issues, and other benefits. Then you either just keep it that way or slowly rinse and repeat. Without doing the analysis of what the core issues were in the first place, the author of Bun can make no claims towards the rewrite. He claims to have fixed flaky tests and improved memory safety. Where is the analysis that shows this? Where is the proof and data? Does he even know where the issues in the Zig codebase were at? I saw a commit where a test had a one second sleep put in place. Compare this to say the Racket rewrite where a significant portion of the C core was replaced by Chez Scheme and Racket itself. There were several blog posts doing both pre- and post-analysis, and Racket has far less users than Bun. This rewrite is totally unprofessional and has been poorly and even antagonistically communicated. The author was on this site just days ago telling everyone to relax and that he'd probably throw out this code, and that was even after it had been brought up that this wasn't pre-communicated to users. If I was a dependent in Bun, I would migrate off immediately. So I push back in the idea that this is the way to do a rewrite like this.
- Daishiman 5mo ago
  > This rewrite is totally unprofessional and has been poorly and even antagonistically communicated. The author was on this site just days ago telling everyone to relax and that he'd probably throw out this code, and that was even after it had been brought up that this wasn't pre-communicated to users. That was until he empirically checked that, contrary to his hypothesis, Claude is _really_ good at mechanical rewrites that preserve functionality and add a type system that prevents the general class of errors that are inherent in Zig's language features, which he has mentioned previously. I push back against the idea that you need extremely thorough analysis for certain things that end up becoming obvious after working a long time with a codebase. It's clear that Zig doesn't cover certain guarantees that make code robust but Rust does, and this has been documented over and over again because we have examples (with better and worse execution) of the classes of bugs Rust helps and uncover and how a port can go better or worse. A language with a thorough test suite written in another language with complete coverage is about as good a use case as you can get to support a language rewrite. Ultimately this is about the developer's preference of one language over the other and avoiding simple bugs. What more do you need?

Barrin92 5mo ago

>This is the same in COBOL-to-Java ports it isn't, because those guys didn't think a naive 1-1 machine translation would give them the benefits of Java, which somehow the people involved in this rust rewriting seem to think they've already gained despite the virtually identical code. If the whole point genuinely would have been to do a purely mechanical translation they could and should have written a transpiler, which would have had significantly higher correctness guarantees than this given that it'd be deterministic, but of course that would have defeated the PR purpose of this whole thing, which just looks like a marketing for Anthropic frankly

Daishiman 5mo ago
> If the whole point genuinely would have been to do a purely mechanical translation they could and should have written a transpiler, which would have had significantly higher correctness guarantees than this given that it'd be deterministic, but of course that would have defeated the PR purpose of this whole thing, which just looks like a marketing for Anthropic frankly If it were just a marketing stunt you wouldn't have a fraction of a percent of the test suite passing with the remaining bugs being realistically very fixable, and everything written in languages with type systems that give far more guarantees than what COBOL is possible. You're being extremely negative about this whole endeavour without looking at the evidence that this effort is going far more smoothly than expected, and maps with many people's experience with using LLMs for tasks like these.
- Barrin92 5mo ago
  >You're being extremely negative about this whole endeavour without looking at the evidence that this effort is going far more smoothly than expected no I'm being negative because as I just said, if you want to do a purely syntactic translation you don't even need an LLM, that's called transpilation and we've been doing it programmatically for decades. This is the kind of thing that looks great to people who can't program, think this is some new superpower unlocked by the mystery magic of LLMs and that is exactly the kind of impression Claude wants to sell.
  - famouswaffles 5mo ago
    Transpilation won't get you passing 99.8% of a comprehensive test suite of a 700K+ codebase in a week (and maybe none at all) and that's assuming transpilation is practical for the pair in question. So if you remotely want these kinds of results, then you most certainly do need an LLM.
    - drzaiusx11 5mo ago
      There are literally formally verified language transpilers out there today. They can get you 100% coverage without "cheating" like LLMs tend to do by modifying test suites to pass, etc. I'm currently using an LLM in my day job to accelerate such a 1:1translation, and it's certainly "working"/making progress but God I wish I had a formally verified machine translator instead of this probalistic bullshitting LLM. Don't get me wrong, it's extremely helpful and impressive in what it can do. But I trust it somewhat less than if I had done it myself, and for good reason. The lies I tell myself tend not to take down production. The lies my LLM tells me do however.
      - famouswaffles 5mo ago
        I mean No-one is forcing you to not use a transpiler right? If it was quicker to use one or build a specific, limited one for your existing codebase and run it then you would certainly have done that already.
vintermann 5mo ago
You gain some benefits. You could in theory gain benefits in compilation speed, portability or even memory use and execution speed, from an automatic language translation. But everyone, including the bun people, understand that you certainly don't get code clarity benefits, and safety benefits is extremely dubious.

tempest_ 5mo ago

If the rewrite was zig to C and half the code was in __asm blocks is that different or the same?

Daishiman 5mo ago
You know that it's different so why are you asking a meaningless rhetorical question.

bmitc 5mo ago

COBOL to Java is a completely different thing and pretty much unrelated. Rust can easily call C libraries and vice versa and so can Zig. A more appropriate and designed rewrite would identify the core pieces of the Zig code that were the primary sources of all the big issues. Then, you rewrite that component in Rust and verify that you get the expected improvements. That keeps the codebase stable, it keeps you honest on actually reducing bugs and issues, and other benefits. Then you either just keep it that way or slowly rinse and repeat. Without doing the analysis of what the core issues were in the first place, the author of Bun can make no claims towards the rewrite. He claims to have fixed flaky tests and improved memory safety. Where is the analysis that shows this? Where is the proof and data? Does he even know where the issues in the Zig codebase were at? I saw a commit where a test had a one second sleep put in place. Compare this to say the Racket rewrite where a significant portion of the C core was replaced by Chez Scheme and Racket itself. There were several blog posts doing both pre- and post-analysis, and Racket has far less users than Bun. This rewrite is totally unprofessional and has been poorly and even antagonistically communicated. The author was on this site just days ago telling everyone to relax and that he'd probably throw out this code, and that was even after it had been brought up that this wasn't pre-communicated to users. If I was a dependent in Bun, I would migrate off immediately. So I push back in the idea that this is the way to do a rewrite like this.

Daishiman 5mo ago
> This rewrite is totally unprofessional and has been poorly and even antagonistically communicated. The author was on this site just days ago telling everyone to relax and that he'd probably throw out this code, and that was even after it had been brought up that this wasn't pre-communicated to users. That was until he empirically checked that, contrary to his hypothesis, Claude is _really_ good at mechanical rewrites that preserve functionality and add a type system that prevents the general class of errors that are inherent in Zig's language features, which he has mentioned previously. I push back against the idea that you need extremely thorough analysis for certain things that end up becoming obvious after working a long time with a codebase. It's clear that Zig doesn't cover certain guarantees that make code robust but Rust does, and this has been documented over and over again because we have examples (with better and worse execution) of the classes of bugs Rust helps and uncover and how a port can go better or worse. A language with a thorough test suite written in another language with complete coverage is about as good a use case as you can get to support a language rewrite. Ultimately this is about the developer's preference of one language over the other and avoiding simple bugs. What more do you need?