What is the idiomatic way to pop the last N elements in a mutable Vec?

Question

I am contributing Rust code to RosettaCode to both learn Rust and contribute to the Rust community at the same time. What is the best idiomatic way to pop the last n

Answer 1

An alternate approach would be to use Vec::drain instead. This gives you an iterator so you can actually use the elements that are removed.

fn main() {
    let mut nums: Vec = Vec::new();
    nums.push(1);
    nums.push(2);
    nums.push(3);
    nums.push(4);
    nums.push(5);

    let n = 2;
    let new_len = nums.len() - n;

    for removed_element in nums.drain(new_len..) {
        println!("removed: {}", removed_element);
    }

    for retained_element in nums {
        println!("retained: {}", retained_element);
    }
}

The drain method accepts a RangeArgument in the form of ... Both start and end may be omitted to default to the beginning/end of the vector. So above, we're really just saying start at new_len and drain to the end.