fn range(from: int, to: int) -> (fn() -> (int, bool)) {
    i := from - 1

    fn() -> (int, bool) {
        i = i + 1
        if i >= to {
            (-1, false)
        } else {
            (i, true)
        }
    }
}

for i in range(0, 10) {
    println(i)
}

fn chars(s: str) -> (fn() -> (str, bool)) {
    i := 0

    fn() -> (str, bool) {
        if i >= s.length() {
            ("", false)
        } else {
            c := s[i]
            i = i + 1

            (c, true)
        }
    }
}

for c in chars("hello") {
    print(c)
    print(" ")
}

println("")

fn items(l: [any]) -> (fn() -> (any, bool)) {
    i := 0

    fn() -> (any, bool) {
        if i >= l.length() {
            (nil, false)
        } else {
            i = i + 1
            (l[i - 1], true)
        }
    }
}