[iimblack]

Dup is very interesting to me. Does that mean that in Nim all functions will be impure by default, and that it's considered idiomatic to modify the input? I guess it's nice that they're trying to make behavior consistent. It just seems like the opposite of the recent directions I've seen other languages take.

[jrhurst]

I haven't played with nim for a few months, but only parameters with var will get mutated. I suspect you want to use someone else's cursed function and don't want to poison your blessed code

[iimblack]

I see. I know nothing about Nim but I do see in their example they used var when declaring the function. This way seems like it's hidden to the consumer of the function but hopefully editor tooling helps with this.

[juki]

You have to declare the variable as `var` as well, eg.

    var arr1 = [4, 2, 3, 6]
    sort arr1

    # Doesn't work
    let arr2 = [4, 2, 3, 6]
    sort arr2

You'll get a warning about the latter from the compiler (and nimsuggest for editors).

[treeform]

Mutating in place is often times faster and is more straightforward.

I do feel Nim embraces mutation more than other recent languages.

[eindiran]

Yeah, the 'discard' keyword is a pretty cool way to note that you're using a procedure only for its side effects.

[iimblack]

I'm not arguing either way, just noting that it's counter to what I've seen recently in other languages.