How do I sort an array?

Question

Why cannot I not sort an array as expected?

fn main() {
    let mut a = [1,3,2];
    let s = a.sort();
    println!("{:?}", s);
}

Answer 1

a is sorted, but the method sorts the array in place. Read the signature of sort: sort takes &mut self and returns unit (i.e. nothing), so when you print s, you print ().

Working code:

fn main() {
    let mut a = [1, 3, 2];
    a.sort();
    
    assert_eq!(a, [1, 2, 3]);
    println!("{:?}", a);
}

Writing a function that returns a sorted array

You can write a function that does what you want:

fn sort<A, T>(mut array: A) -> A
where
    A: AsMut<[T]>,
    T: Ord,
{
    let slice = array.as_mut();
    slice.sort();

    array
}

fn main() {
    let a = [1, 3, 2];

    assert_eq!(sort(a), [1, 2, 3]);
}