pub trait Add<Rhs = Self> {
type Output;
// Required method
fn add(self, rhs: Rhs) -> Self::Output;
}Expand description
The addition operator +.
Note that Rhs is Self by default, but this is not mandatory. For
example, std::time::SystemTime implements Add<Duration>, which permits
operations of the form SystemTime = SystemTime + Duration.
Examples
Addable points
use std::ops::Add;
#[derive(Debug, Copy, Clone, PartialEq)]
struct Point {
x: i32,
y: i32,
}
impl Add for Point {
type Output = Self;
fn add(self, other: Self) -> Self {
Self {
x: self.x + other.x,
y: self.y + other.y,
}
}
}
assert_eq!(Point { x: 1, y: 0 } + Point { x: 2, y: 3 },
Point { x: 3, y: 3 });Implementing Add with generics
Here is an example of the same Point struct implementing the Add trait
using generics.
use std::ops::Add;
#[derive(Debug, Copy, Clone, PartialEq)]
struct Point<T> {
x: T,
y: T,
}
// Notice that the implementation uses the associated type `Output`.
impl<T: Add<Output = T>> Add for Point<T> {
type Output = Self;
fn add(self, other: Self) -> Self::Output {
Self {
x: self.x + other.x,
y: self.y + other.y,
}
}
}
assert_eq!(Point { x: 1, y: 0 } + Point { x: 2, y: 3 },
Point { x: 3, y: 3 });Required Associated Types§
Required Methods§
Implementors§
source§impl Add<&str> for String
impl Add<&str> for String
Implements the + operator for concatenating two strings.
This consumes the String on the left-hand side and re-uses its buffer (growing it if
necessary). This is done to avoid allocating a new String and copying the entire contents on
every operation, which would lead to O(n^2) running time when building an n-byte string by
repeated concatenation.
The string on the right-hand side is only borrowed; its contents are copied into the returned
String.
Examples
Concatenating two Strings takes the first by value and borrows the second:
let a = String::from("hello");
let b = String::from(" world");
let c = a + &b;
// `a` is moved and can no longer be used here.If you want to keep using the first String, you can clone it and append to the clone instead:
let a = String::from("hello");
let b = String::from(" world");
let c = a.clone() + &b;
// `a` is still valid here.Concatenating &str slices can be done by converting the first to a String:
let a = "hello";
let b = " world";
let c = a.to_string() + b;