Yeah sorry - that’s just unnecessarily obtuse. Programming languages just don’t need to be that convoluted. Hello world should look something like this:

print("Hello, World!")

And when you need more complexity, it can still be far simpler than Unison (or Haskel). For example this (in Swift):

func processNumbers(_ numbers: [Int]) -> [Int] {
    return numbers.filter { $0 % 2 == 0 }.map { $0 * $0 }
}

let numbers = [1, 2, 3, 4, 5, 6]
let processedNumbers = processNumbers(numbers)
print(processedNumbers)

Yes, in functional programming you want to use pure functions. Exceptions are impure, therefore it has to be declared.

Other functional languages don’t even have exceptions

Functional languages typically have type inference, so the type signatures are entirely optional. I haven’t looked that deeply at unison, but I’d be entirely unsurprised if it had global type inference and if all or most type signatures were optimal.

It’s less that you have to declare something can do IO or throw an exception, and more that you’re calling something from the standard library that does IO or throws an exception.

Most stuff does neither. There’s a type level distinction between normal, regular pure code, and impure effectful code, so it’s easy to tell from the type signature whether a function is pure or not.

That’s one of the things I appreciate in a language/framework. Drives me nuts getting an exception from a dependency of a dependency of a dependency.

Even better if its baked into the type system and I can’t run my code without handling it.