Generic Data Types

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

  1. #[derive(Debug)]
  2. struct Point<T> {
  3.     x: T,
  4.     y: T,
  5. }
  7. impl<T> Point<T> {
  8.     fn coords(&self) -> (&T, &T) {
  9.         (&self.x, &self.y)
  10.     }
  12.     fn set_x(&mut self, x: T) {
  13.         self.x = x;
  14.     }
  15. }
  17. fn main() {
  18.     let integer = Point { x: 5, y: 10 };
  19.     let float = Point { x: 1.0, y: 4.0 };
  20.     println!("{integer:?} and {float:?}");
  21.     println!("coords: {:?}", integer.coords());
  22. }

This slide should take about 10 minutes.

  • 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.