Trait Add

1.0.0 · Source

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

§`Add`able 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 });

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;

Source §

Trait AddCopy item path

§Examples

§Addable points

§Implementing Add with generics

Required Associated Types§

type Output

Required Methods§

fn add(self, rhs: Rhs) -> Self::Output

§Example

Implementors§

impl Add for f16

type Output = f16

impl Add for f32

type Output = f32

impl Add for f64

type Output = f64

impl Add for f128

type Output = f128

impl Add for i8

type Output = i8

impl Add for i16

type Output = i16

impl Add for i32

type Output = i32

impl Add for i64

type Output = i64

impl Add for i128

type Output = i128

impl Add for isize

type Output = isize

impl Add for u8

type Output = u8

impl Add for u16

type Output = u16

impl Add for u32

type Output = u32

impl Add for u64

type Output = u64

impl Add for u128

type Output = u128

impl Add for usize

type Output = usize

impl Add for ConstDecimals<0usize>

type Output = ConstDecimals<0>

impl Add for ConstDecimals<1usize>

type Output = ConstDecimals<2>

impl Add for ConstDecimals<2usize>

type Output = ConstDecimals<4>

impl Add for ConstDecimals<3usize>

type Output = ConstDecimals<6>

impl Add for ConstDecimals<4usize>

type Output = ConstDecimals<8>

impl Add for ConstDecimals<5usize>

type Output = ConstDecimals<10>

impl Add for ConstDecimals<6usize>

type Output = ConstDecimals<12>

impl Add for ConstDecimals<7usize>

type Output = ConstDecimals<14>

impl Add for ConstDecimals<8usize>

type Output = ConstDecimals<16>

impl Add for ConstDecimals<9usize>

type Output = ConstDecimals<18>

impl Add for ConstDecimals<10usize>

type Output = ConstDecimals<20>

impl Add for ConstDecimals<11usize>

type Output = ConstDecimals<22>

impl Add for ConstDecimals<12usize>

type Output = ConstDecimals<24>

impl Add for ConstDecimals<13usize>

type Output = ConstDecimals<26>

impl Add for ConstDecimals<14usize>

type Output = ConstDecimals<28>

impl Add for ConstDecimals<15usize>

type Output = ConstDecimals<30>

impl Add for ConstDecimals<16usize>

type Output = ConstDecimals<32>

impl Add for ConstDecimals<17usize>

type Output = ConstDecimals<34>

impl Add for ConstDecimals<18usize>

type Output = ConstDecimals<36>

Trait Add

§`Add`able points

§Implementing `Add` with generics