What is the proper way to split one source array into a couple of copies?

Question

Something like this:

let source = [0u8; 40];
let a = source[0..11];
let b = source[11..40];

Answer 1

Use slice::split_at:

fn main() {
    let source = [0u8; 40];
    let (a, b) = source.split_at(11);
    println!("{}, {}", a.len(), b.len())
}

There's also split_at_mut, discussed in How to operate on 2 mutable slices of a Rust array.

In this case, you can also take multiple subslices because it's immutable. These may be overlapping:

fn main() {
    let source = [0u8; 40];
    let a = &source[0..11];
    let b = &source[11..40];
    println!("{}, {}", a.len(), b.len())
}

into couple of copies?

The point of slices is that copies aren't made. A slice is just a pointer to the start of the data and a length. The data itself is shared.

I want to make 'a' and 'b' arrays instead of slices

Then you should check out How to get a slice as an array in Rust?