Iterators

std::iter::new(any x) -> iterator | null: wraps a string, list, or map into an iterator.
std::iter::next(iterator) -> any | null: advances the iterator.
std::iter::range(int start, int stop, int step) -> iterator: numeric range.

Use with for:

use pie/std;

def void main() {
    let any it = std::iter::range(0, 3, 1);
    for i in it { std::print(i); }
}