Generics: Works With Anything

Imagine one labeled box. You can put a phone in it, a notebook, or a set of keys — the box doesn’t care! It just holds whatever you give it. In Rust, that kind of box is called a generic. 🧰

A generic lets you write one piece of code that works with many kinds of things, instead of writing it over and over for each kind.

The Big Idea A generic uses a placeholder name — usually T — that stands for "some type, any type." Rust fills in the real type later, when you actually use your code.

A placeholder called T

When you write <T>, you’re telling Rust: “I don’t know the exact type yet — call it T for now.” T is just a nickname. It could turn into a number, a word, or anything else when the code runs.

Think of it like this… T is like a name tag that says "fill me in later." One box, but it can hold anything. One piece of code, but it works with any type!

A point that fits any number

Let’s make a Point that has an x and a y. Using <T>, the same Point can hold whole numbers or numbers with dots (decimals). Press ▶ Run!

struct Point<T> {
    x: T,
    y: T,
}

fn main() {
    let whole = Point { x: 3, y: 7 };
    let dotty = Point { x: 1.5, y: 9.2 };

    println!("Whole point: ({}, {})", whole.x, whole.y);
    println!("Dotty point: ({}, {})", dotty.x, dotty.y);
}
</textarea>
<textarea class="rk-out">
Whole point: (3, 7)
Dotty point: (1.5, 9.2)

</div> We wrote `Point` **once**, but used it two different ways. The first time `T` became a whole number, and the second time `T` became a decimal. Same box, different contents! 🎁

Ferris says: Generics save you from copy-pasting the same code again and again. Write it once, use it everywhere. Less typing, fewer mistakes! 🦀

Try this! Add a third point with the values x: 0 and y: 0, then print it too. Press ▶ Run to see all three!

## Quick quiz

What does the T in Point<T> mean?

Yes! T is a stand-in for "any type." Rust fills in the real type when you use it. 🎉

You learned… Generics let one function or struct work with many types using a placeholder like <T> — like a labeled box that fits anything. Next up: Traits: Shared Superpowers, where different types learn to share the same ability! ⭐