Add, Mul, …

Operator overloading is implemented via traits in std::ops:

1. #[derive(Debug, Copy, Clone)]
2. struct Point { x: i32, y: i32 }

4. impl std::ops::Add for Point {
5. type Output = Self;

7. fn add(self, other: Self) -> Self {
8. Self {x: self.x + other.x, y: self.y + other.y}
9. }
10. }

12. fn main() {
13. let p1 = Point { x: 10, y: 20 };
14. let p2 = Point { x: 100, y: 200 };
15. println!("{:?} + {:?} = {:?}", p1, p2, p1 + p2);
16. }

Discussion points:

• You could implement Add for &Point. In which situations is that useful?
• Answer: Add:add consumes self. If type T for which you are overloading the operator is not Copy, you should consider overloading the operator for &T as well. This avoids unnecessary cloning on the call site.
• Why is Output an associated type? Could it be made a type parameter?
• Short answer: Type parameters are controlled by the caller, but associated types (like Output) are controlled by the implementor of a trait.