That's how I learned programming at the university. A function returns something, a procedure doesn't. Koka has something a bit like that with typed effects https://koka-lang.github.io/koka/doc/index.html.

This is one of the big things I love about Haskell. Its way of making effects explicit and easy to spot in the function signature always struck me as insanely useful for exactly those reasons (though, obviously, it goes a step further where every function always has to return something, even if it is an effect or an effected state). In retrospect, I wish Rust had adopted something like this since it took a lot of inspiration from Haskell anyways, but I am very glad that there are people like you out there that are trying to remind people of this insanely useful concept of making effects more explicit!

Wish you all the best with Bagel!

> In retrospect, I wish Rust had adopted something like this since it took a lot of inspiration from Haskell anyways

Aside from the traits (typeclasses), most of the inspiration actually comes from OCaml/ML rather than Haskell. The philosohpy is also way closer to the pragmatism of OCaml. I think Rust wouldn't be as popular as it is right now if IO needed a monad, like in Haskell. This would have been too much for a single language. I also don't think that monadic IO is the way. Maybe effects system will bring a more usable way of typing effects (Koka, OCaml soon), but I doubt that they'll come to Rust.

I agree, and I intend for Bagel to be a pragmatic language (striking a balance between idealism and pragmatism very similar to what Rust strikes), which is why I'm not going the monad route. I believe that the combination of the functional subset + reactivity to any state that does exist will get you 90% of the benefits without the learning curve