Indexing means choosing an item by its position. In a Rust array, put the position in square brackets after the array name. Positions start at 0: `[0]` gets the first item, and `[1]` gets the second. section 3.1.1
Get one array item
With `let my_numbers = [0, 10, -20];`, `my_numbers[1]` gets `10`, the second item. Starting at 0 can feel unusual at first; just count the first item as position 0. section 3.1.1
You can also use positions to take a slice—a piece of an array. In `&array_of_ten[2..5]`, the `&` makes a reference to the piece, while `2..5` selects positions 2, 3, and 4. The end position is not included. Use `..=` when you want to include it. section 3.1.1
fn main() {
let array_of_ten = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9];
let two_to_five = &array_of_ten[2..5]; #1
let start_at_one = &array_of_ten[1..]; #2
let end_at_five = &array_of_ten[..5]; #3
let everything = &array_of_ten[..]; #4
println!("Two to five: {two_to_five:?},
Start at one: {start_at_one:?},
End at five: {end_at_five:?},
Everything: {everything:?}");
}
Compare the four slices: a range with both endpoints, a range without a final endpoint, one without a starting endpoint, and the whole array. section 3.1.1
Rust uses `usize` for index numbers. An index cannot be negative, and `usize` provides a size suited to the computer running the program. section 1.3
