Assignment operators in Rust

Introduction

Assignment operators help you store or update values in variables easily.

When you want to save a value in a variable.

When you want to add or subtract a number from a variable's current value.

When you want to multiply or divide a variable by a number and save the result.

When you want to combine updating and assigning a value in one step.

Syntax

Rust

let mut variable = value;
variable = new_value; // simple assignment
variable += value; // add and assign
variable -= value; // subtract and assign
variable *= value; // multiply and assign
variable /= value; // divide and assign
variable %= value; // remainder and assign

Variables must be declared with mut to allow changing their value.

Assignment operators combine an operation and assignment in one step.

Examples

Assign a new value 10 to variable x.

Rust

let mut x = 5;
x = 10;

Add 3 to x and save the result back to x.

Rust

let mut x = 5;
x += 3; // x is now 8

Multiply x by 2 and save the result.

Rust

let mut x = 10;
x *= 2; // x is now 20

Assign the remainder of x divided by 3 back to x.

Rust

let mut x = 10;
x %= 3; // x is now 1

Sample Program

This program shows how to use different assignment operators to update the variable score step by step.

Rust

fn main() {
    let mut score = 10;
    println!("Initial score: {}", score);
    score += 5;
    println!("After adding 5: {}", score);
    score *= 2;
    println!("After doubling: {}", score);
    score -= 4;
    println!("After subtracting 4: {}", score);
    score /= 3;
    println!("After dividing by 3: {}", score);
    score %= 3;
    println!("After remainder by 3: {}", score);
}

Important Notes

Remember to declare variables with mut if you want to change their values.

Assignment operators make code shorter and easier to read when updating variables.

Using assignment operators is like doing math and saving the answer back to the same box.

Summary

Assignment operators store or update values in variables.

Use +=, -=, *=, /=, and %= to combine math and assignment.

Variables must be mutable (mut) to use assignment operators.