rust/src/doc/trpl/arrays.md

% Arrays

Like many programming languages, Rust has list types to represent a sequence of things. The most basic is the array, a fixed-size list of elements of the same type. By default, arrays are immutable.

let a = [1, 2, 3]; // a: [i32; 3]
let mut m = [1, 2, 3]; // mut m: [i32; 3]

There's a shorthand for initializing each element of an array to the same value. In this example, each element of a will be initialized to 0:

let a = [0; 20]; // a: [i32; 20]

Arrays have type [T; N]. We'll talk about this T notation later, when we cover generics.

You can get the number of elements in an array a with a.len(), and use a.iter() to iterate over them with a for loop. This code will print each number in order:

let a = [1, 2, 3];

println!("a has {} elements", a.len());
for e in a.iter() {
    println!("{}", e);
}

You can access a particular element of an array with subscript notation:

let names = ["Graydon", "Brian", "Niko"]; // names: [&str; 3]

println!("The second name is: {}", names[1]);

Subscripts start at zero, like in most programming languages, so the first name is names[0] and the second name is names[1]. The above example prints The second name is: Brian. If you try to use a subscript that is not in the array, you will get an error: array access is bounds-checked at run-time. Such errant access is the source of many bugs in other systems programming languages.