Destructuring Arrays

You can destructure arrays, tuples, and slices by matching on their elements:

#[rustfmt::skip]
fn main() {
    let triple = [0, -2, 3];
    println!("Tell me about {triple:?}");
    match triple {
        [0, y, z] => println!("First is 0, y = {y}, and z = {z}"),
        [1, ..]   => println!("First is 1 and the rest were ignored"),
        _         => println!("All elements were ignored"),
    }
}

  • Destructuring of slices of unknown length also works with patterns of fixed length.

    fn main() {
    inspect(&[0, -2, 3]);
    inspect(&[0, -2, 3, 4]);
}

#[rustfmt::skip]
fn inspect(slice: &[i32]) {
    println!("Tell me about {slice:?}");
    match slice {
        &[0, y, z] => println!("First is 0, y = {y}, and z = {z}"),
        &[1, ..]   => println!("First is 1 and the rest were ignored"),
        _          => println!("All elements were ignored"),
    }
}

  • Create a new pattern using _ to represent an element.

  • Add more values to the array.

  • Point out that how .. will expand to account for different number of elements.

  • Show matching against the tail with patterns [.., b] and [a@..,b]