Rust Operators and Overloading Overloading the addition operator (+)
Example
Overloading the addition operator (+) requires implement the std::ops::Add trait.
From the documentation, the full definition of the trait is:
pub trait Add<RHS = Self> {
type Output;
fn add(self, rhs: RHS) -> Self::Output;
}
How does it work?
- the trait is implemented for the Left Hand Side type
- the trait is implemented for one Right Hand Side argument, unless specified it defaults to having the same type as the Left Hand Side one
- the type of the result of the addition is specified in the associated type
Output
Thus, having 3 different types is possible.
Note: the trait consumes is left-hand side and right-hand side arguments, you may prefer to implement it for references to your type rather than the bare types.
Implementing + for a custom type:
use std::ops::Add;
#[derive(Clone)]
struct List<T> {
data: Vec<T>,
}
// Implementation which consumes both LHS and RHS
impl<T> Add for List<T> {
type Output = List<T>;
fn add(self, rhs: List<T>) -> List<T> {
self.data.extend(rhs.data.drain(..));
self
}
}
// Implementation which only consumes RHS (and thus where LHS != RHS)
impl<'a, T: Clone> Add<List<T>> for &'a List<T> {
type Output = List<T>;
fn add(self, rhs: List<T>) -> List<T> {
self.clone() + rhs
}
}
