Simple snippet showing how to skip the last item in an iterator.

skip_last.rs

fn main() {
    let x = [0, 1, 2];

    let y: Vec<_> = x
        .iter()
        .scan(None, |prev, i| Some(prev.replace(i)))
        .flatten()
        .collect();

    println!("x = {:?}", x); // x = [0, 1, 2]
    println!("y = {:?}", y); // y = [0, 1]
}

This works by transforming

[0, 1, 2]

using scan() into

[None, Some(0), Some(1)]

and then calling flatten() to get

[0, 1]