[wizzwizz4]

> Have you tried writing low level IO? The logic is too complex to capture on types, if you try to use them you'll have a huge problem.

Rust's got a very Haskell-like type system, but it's a systems programming language. People are literally writing kernels in it. I think this is a pure-functional-is-a-bad-way-to-do-real-time-I/O thing, not a typing thing.

[steveklabnik]

While this is true in some senses, Rust's type system is very different than Haskell's when it comes to handling IO.

That said, I don't think it's impossible to type IO. https://lexi-lambda.github.io/blog/2020/01/19/no-dynamic-typ... isn't the same problem, but it's related.

[marcosdumay]

Hum... Pure functional is a bad way to do real time I/O, but my point was about types.

If you try to verify the kind of state machines that low level I/O normally use with Haskell-like types, you will gain a huge amount of complexity and probably end with more bugs than without.

[wizzwizz4]

Low-level I/O doesn't seem to have that much complexity, unless you're trying to handle all of the engineers' levels of abstraction at once.

Let's say you're writing a /dev/console driver for an RS-232 connection. Trying to represent "ring indicator", "parity failure", "invalid UTF-8 sequence", "keyboard interrupt", "hup" and "buffer full" at the same level in the type system will fail abysmally, but that's not a sensible way of doing it.

I could definitely implement this while leveraging the power of Rust's type system – Haskell would be a stretch, but only because it's side-effect free and I/O is pretty much all side-effects.