`loop` expressions

Finally, there is a loop keyword which creates an endless loop.

Here you must either break or return to stop the loop:

fn main() {
    let mut x = 10;
    loop {
        x = if x % 2 == 0 {
            x / 2
        } else {
            3 * x + 1
        };
        if x == 1 {
            break;
        }
    }
    println!("x: {x}");
}

Break the loop with a value (e.g. break 8) and print it out.
Note that loop is the only looping construct which returns a non-trivial value. This is because it’s guaranteed to be entered at least once (unlike while and for loops).