[]Keyword loop

Loop indefinitely.

loop is used to define the simplest kind of loop supported in Rust. It runs the code inside it until the code uses break or the program exits.

loop {
    println!("hello world forever!");
}

let mut i = 1;
loop {
    println!("i is {}", i);
    if i > 100 {
        break;
    }
    i *= 2;
}
assert_eq!(i, 128);
Run

Unlike the other kinds of loops in Rust (while, while let, and for), loops can be used as expressions that return values via break.

let mut i = 1;
let something = loop {
    i *= 2;
    if i > 100 {
        break i;
    }
};
assert_eq!(something, 128);
Run

Every break in a loop has to have the same type. When it's not explicitly giving something, break; returns ().

For more information on loop and loops in general, see the Reference.