Math and Formatting — Rust

Programs run from top to bottom, one line at a time. Let's learn how to do math and build text in Rust!

Doing Math

Rust can do math with these operators:

rust

fn main() {

println!("{}", 3 + 2); // Addition: 5

println!("{}", 10 - 4); // Subtraction: 6

println!("{}", 3 * 5); // Multiplication: 15

println!("{}", 10.0 / 3.0); // Division: 3.3333...

println!("{}", 10 % 3); // Remainder: 1

}

Output

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Integer vs Float Division

In Rust, dividing two integers gives an integer (the decimal part is dropped). Use floats to get a decimal result:

rust

fn main() {

println!("{}", 10 / 3); // Integer division: 3

println!("{}", 10.0 / 3.0); // Float division: 3.3333333333333335

}

Output

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If you want a decimal answer, make sure your numbers have .0 at the end!

Math with Variables

You can store numbers in variables and compute results:

rust

fn main() {

let width = 5;

let height = 3;

let area = width * height;

println!("{}", area);

}

Output

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Output:

Building Strings with format!()

The format!() macro lets you build strings by plugging in values:

rust

fn main() {

let name = "Alex";

let age = 10;

let message = format!("Hello, {}! You are {} years old.", name, age);

println!("{}", message);

}

Output

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Output:

Hello, Alex! You are 10 years old.

Use {} as a placeholder and pass the values after the format string.

Printing Directly with println!()

You can also put values right into println!() without using format!() first:

rust

fn main() {

let color = "blue";

let count = 7;

println!("I have {} {} balloons!", count, color);

}

Output

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Output:

I have 7 blue balloons!

Order of Operations

Rust follows math rules — multiplication and division happen before addition and subtraction:

rust

fn main() {

println!("{}", 2 + 3 * 4); // 14, not 20

println!("{}", (2 + 3) * 4); // 20, parentheses first

}

Output

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Use parentheses () when you want to change the order!