Easy Rust

Tuples

Tuples in Rust use (). We have seen many empty tuples already, because nothing in a function actually means an empty tuple:

fn do_something() {}

is actually short for:

fn do_something() -> () {}

That function gets nothing (an empty tuple), and returns nothing (an empty tuple). So we have been using tuples a lot already. When you don't return anything in a function, you actually return an empty tuple.

fn just_prints() {
    println!("I am printing"); // Adding ; means we return an empty tuple
}

fn main() {}

But tuples can hold many things, and can hold different types too. Items inside a tuple are also indexed with numbers 0, 1, 2, and so on. But to access them, you use a . instead of a []. Let's put a whole bunch of types into a single tuple.

fn main() {
    let random_tuple = ("Here is a name", 8, vec!['a'], 'b', [8, 9, 10], 7.7);
    println!(
        "Inside the tuple is: First item: {:?}
Second item: {:?}
Third item: {:?}
Fourth item: {:?}
Fifth item: {:?}
Sixth item: {:?}",
        random_tuple.0,
        random_tuple.1,
        random_tuple.2,
        random_tuple.3,
        random_tuple.4,
        random_tuple.5,
    )
}

This prints:

Inside the tuple is: First item: "Here is a name"
Second item: 8
Third item: ['a']
Fourth item: 'b'
Fifth item: [8, 9, 10]
Sixth item: 7.7

That tuple is of type (&str, i32, Vec<char>, char, [i32; 3], f64).

You can use a tuple to create multiple variables. Take a look at this code:

fn main() {
    let str_vec = vec!["one", "two", "three"];
}

str_vec has three items in it. What if we want to pull them out? That's where we can use a tuple.

fn main() {
    let str_vec = vec!["one", "two", "three"];

    let (a, b, c) = (str_vec[0], str_vec[1], str_vec[2]); // call them a, b, and c
    println!("{:?}", b);
}

That prints "two", which is what b is. This is called destructuring. That is because first the variables are inside a structure, but then we made a, b, and c that are not inside a structure.

If you need to destructure but don't want all the variables, you can use _.

fn main() {
    let str_vec = vec!["one", "two", "three"];

    let (_, _, variable) = (str_vec[0], str_vec[1], str_vec[2]);
}

Now it only creates a variable called variable but doesn't make a variable for the others.

There are many more collection types, and many more ways to use arrays, vecs, and tuples. We will learn more about them too, but first we will learn control flow.