comprehensive-rust/src/generics/generic-data.md

---
minutes: 15
---

# Generic Data Types

You can use generics to abstract over the concrete field type:

```rust,editable
#[derive(Debug)]
struct Point<T> {
    x: T,
    y: T,
}

impl<T> Point<T> {
    fn coords(&self) -> (&T, &T) {
        (&self.x, &self.y)
    }

    // fn set_x(&mut self, x: T)
}

fn main() {
    let integer = Point { x: 5, y: 10 };
    let float = Point { x: 1.0, y: 4.0 };
    println!("{integer:?} and {float:?}");
    println!("coords: {:?}", integer.coords());
}
```

<details>

- _Q:_ Why `T` is specified twice in `impl<T> Point<T> {}`? Isn't that
  redundant?
  - This is because it is a generic implementation section for generic type.
    They are independently generic.
  - It means these methods are defined for any `T`.
  - It is possible to write `impl Point<u32> { .. }`.
    - `Point` is still generic and you can use `Point<f64>`, but methods in this
      block will only be available for `Point<u32>`.

- Try declaring a new variable `let p = Point { x: 5, y: 10.0 };`. Update the
  code to allow points that have elements of different types, by using two type
  variables, e.g., `T` and `U`.

</details>