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> This is a far superior workflow when you factor in outcomes.

I’m a strong-typing enthousiast, too, but still, I’m not fully convinced that’s true.

It seems you can’t iterate fast at all in Rust because the code wouldn’t compile, but can iterate fast in C++, except for the fact that the resulting code may be/often is unstable.

If you need to try out a lot of things before finding the right solution, the ability to iterate fast may be worth those crashes.

Maybe, using C++ for fast iterations, and only using various tools to hunt down issues the borrow checker would catch on the iteration you want to keep beats using Rust.

Or do Rust programmers iterate fast using unsafe where needed and then fix things once they’ve settled on a design?

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> It seems you can’t iterate fast at all in Rust because the code wouldn’t compile

Yup, this is correct - and the reason is because Rust forces you to care about efficiency concerns (lifetimes) everywhere. There's no option to "turn the borrow checker off" - which means that when you're in prototyping mode, you pay this huge productivity penalty for no benefit.

A language that was designed to be good at iteration would allow you to temporarily turn the borrow checker off, punch holes in your type system (e.g. with Python's "Any"), and manage memory for you - and then let you turn those features on again when you're starting to optimize and debug. (plus, an interactive shell and fast compilation times - that's non-negotiable) Rust was never designed to be good at prototyping.

I heard a saying a few years ago that I like - "it's designed to make hardware [rigid, inflexible programs], not software". (it's from Steve Yegge - I could track it down if I cared)

>There's no option to "turn the borrow checker off" - which means that when you're in prototyping mode, you pay this huge productivity penalty for no benefit

That’s not really true. The standard workaround for this is just to .clone() or Rc<RefCell<>> to unblock yourself, then come back later and fix it.

It is true that this needs to be done with some care otherwise you can end up infecting your whole codebase with the “workaround”. That comes with experience.

> It is true that this needs to be done with some care otherwise you can end up infecting your whole codebase with the “workaround”

It's a "workaround" precisely because the language does not support it. My statement is correct - you cannot turn the borrow-checker off, and you pay a significant productivity penalty for no benefit. "Rc" can't detect cycles. ".clone()" doesn't work for complex data structures.

You can’t turn off undefined behavior in C++ either. Lifetimes exist whether the language acknowledges them or not.

Except if you go to a GC language, but then you’re prototyping other types of stuff than you’d probably pick Rust for.

You can use unsafe if you really want to "turn the borrow-checker off", no?

No, because that doesn't give you automatic memory management, which is the point. When I'm prototyping, there's zero reason for me to care about lifetimes - I just want to allocate an object and let the runtime handle it. When you mark everything in your codebase unsafe (a laborious and unnecessary process that then has to be laboriously undone), you still have to ask the Rust runtime for dynamic memory manually, and then track the lifetimes in your head.

If you're saying you want GC/Arc then that's more than just "turning off the borrow checker".

Pedantry. Later on in my comment I literally say "manage memory for you" - it should be pretty clear that my intent was to talk about a hypothetical language that allowed you to change between use of a borrow checker and managed memory, even if I didn't use the correct wording ("turn off the borrow checker") in that particular very small section of it.

Bit much to complain about pedantry with how prickly your tone has been in this whole thread. If you only want this functionality for rapid iteration/prototyping, which was what you originally said, then leaking memory in those circumstances is not such a problem.

You're right, I have been overly aggressive. I apologize.

> If you only want this functionality for rapid iteration/prototyping, which was what you originally said, then leaking memory in those circumstances is not such a problem.

There's use-cases for wanting your language to be productive outside of prototyping, such as scripting (which I explicitly mentioned earlier in this thread[1] - omission here was not intentional), and quickly setting up tools (such as long-running web services) that don't need to be fast, but should not leak memory.

"Use Rust, but turn the borrow checker off" is inadequate.

[1] https://news.ycombinator.com/item?id=37441120

Yeah, I do think the space where manual memory management is actually desirable is pretty narrow - and so I'm kind of baffled that Rust caught on where the likes of OCaml didn't. But seemingly there's demand for it. (Either that, or programming is a dumb pop culture that elevates performance microbenchmarks beyond all reason)

> There's no option to "turn the borrow checker off" - which means that when you're in prototyping mode, you pay this huge productivity penalty for no benefit.

Frankly I think this is a good thing! And I disagree with your "no benefit" assertion.

I don't like prototyping. Or rather, I don't like to characterize any phase of development as prototyping. In my experience it's very rare that the prototype actually gets thrown away and rewritten "the right way". And if and when it does happen, it happens years after the prototype has been running in production and there's a big scramble to rewrite it because the team has hit some sort of hard limit on fixing bugs or adding features that they can't overcome within the constraints of the prototype.

So I never prototype. I do things as "correctly" as possible from the get-go. And you know what? It doesn't really slow me down all that much. I personally don't want to be in the kind of markets where I can't add 10-20% onto a project schedule without failing. And I suspect markets where those sorts of time constraints matter are much rarer than most people tell themselves.

(And also consider that most projects are late anyway. I'd rather be late because I was spending more time to write better, safer code, than because I was frantically debugging issues in my prototype-quality code.)

The dev cycle is slower, yes, but once it compiles, there is no debug cycle.

Wildly false. Rust's design does virtually nothing to prevent logic errors.

I have found someone that never introduces logic errors, and found out a way to use dependent types in Rust. /s

95% of my "logic errors" are related to surprise nulls (causing a data leak of sensitive data) or surprise mutability. The idea that there is no debug cycle is ridiculous but I am confident that there will be less of them in Rust.

I bet it won't survive a pentest attack, and there are more things missing on program expectations than only nullability.

On the type system theory, Rust still has quite something to catch up to theorem provers, which even those aren't without issues.

So then tests are optional?

Most bugs are elementary logic bugs expressible in every programming language.

> So then tests are optional?

Yes and no. You're gonna write far fewer tests in a language like Rust than in a language like Python. In Python you'll have to write tests to eliminate the possibility of bugs that the Rust compiler can eliminate for you. I would much rather just write logic tests.

> Most bugs are elementary logic bugs expressible in every programming language.

I don't think that's true. I would expect that most bugs are around memory safety, type confusion, or concurrency issues (data races and other race conditions).

Python is not a language I would consider to be meaningfully comparable to Rust. They have very different use cases.

In modern C++, memory safety and type confusion aren’t common sources of bugs in my experience. The standard idiomatic design patterns virtually guarantee this. The kinds of concurrency issues that tend to cause bugs can happen in any language, including Rust. Modern C++, for all its deficiencies, has an excellent type safety story, sometimes better than Rust. It doesn’t require the language to provide it though, which is both a blessing and a curse.

I think mostly you just need less iteration with Rust because the language seems to guide you towards nice, clean solutions once you learn not to fight the borrow checker.

Rust programmers don't iterate using unsafe because every single line of unsafe gives you more to think and worry about, not less. But they might iterate using more copying/cloning/state-sharing-with-ref-counting-and-RefCell than necessary, and clean up the ownership graph later if needed.

> I think mostly you just need less iteration with Rust because the language seems to guide you towards nice, clean solutions once you learn not to fight the borrow checker.

That's not iteration. That's debugging. "Iteration" includes design work. Rust's requirement to consider memory management and lifetimes actively interferes with design work with effectively zero contributions towards functional correctness (unlike types, which actually help you write less buggy code - but Rust's type system is not unique and is massively inferior to the likes of Haskell and Idris), let alone creating things.

> Rust's requirement to consider memory management and lifetimes actively interferes with design work with effectively zero contributions towards functional correctness

I don't really agree with that. If you've decided on a design in Rust where you're constantly fighting with lifetimes (for example), that's a sign that you may have designed your data ownership wrong. And while it's not going to be the case all the time, it's possible that a similar design in another language would also be "wrong", but in ways that you don't find out until much later (when it's much harder to change).

> Rust's type system is not unique and is massively inferior to the likes of Haskell and Idris

Sure, but few people use Haskell or Idris in the real world for actual production code. Most companies would laugh me out of an interview if I told them I wanted to introduce Haskell or Idris into their production code base. That doesn't invalidate the fact that they have better type systems than Rust, but a language I can't/won't use for most things in most places isn't particularly useful to me.

No, I was not talking about debugging or correctness. The point was that Rust does not merely guide you towards correct code, it tends to guide you towards good code.

The point of iteration is not typically to find the best implementation for a given algorithm, it's to find the best algorithm for solving a given problem.

I can see the argument that Rust encourages by its design a clean implementation to any given algorithm. But no language's design can guide you to finding a good algorithm for solving a given problem - you often need to quickly try out many different algorithms and see which works best for your constraints.

I don't think iteration is usually about testing different algorithms – it's much more about finding out what the problem is in the first place (that is, attaining a good enough understanding of the problem to solve it), and secondarily about finding out a solution to the problem that satisfies any relevant boundary conditions.

In Rust you have the option to Box and/or Rc everything. That gets you out of all the borrowing problems at the cost of rubtime performance (it basically puts you in the C++ world). This is a perfectly reasonable way to program but people forget about it due to the more "purist" approach that's available. But it's a good way to go for iteration and simplicity, and (in my opinion) still miles better than C++, due to the traits, pattern matching, error handling, and tooling.

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