Rust Basics

Rust Data Types: Integers, Floats, bool and char

Pick the right type for each value and convert between numbers with as.

Beginner
2 min read
1 runnable example

What you'll learn

u8, i32, i64 and f64
bool and char
Converting with as

Run code →

Value → type

30u8, a small whole number

-4.5f64, a decimal number

truebool

'A'char

Every value has a type known at compile time

Rust is statically typed: every value has a type that the compiler knows. Integers come in sizes such as u8 and i64, f64 holds decimal numbers, bool is true or false, and char is one Unicode character.

Rust never converts numbers silently, so age as f64 is needed before adding a float. Underscores in 1_000_000 only make the number easier to read. u8::MAX is the largest value a u8 can hold.

Key points

Integer types say their size: u8 holds 0 to 255.
Rust never converts numbers silently: write age as f64.
char is one Unicode character, written in single quotes.

Runnable Rust example

Rust

Run code →

main.rs

fn main() {
    let age: u8 = 30;
    let temperature: f64 = -4.5;
    let is_ready: bool = true;
    let grade: char = 'A';
    let big = 1_000_000i64;

    let total = age as f64 + temperature;
    println!("{age} {temperature} {is_ready} {grade} {big}");
    println!("total = {total}");
    println!("u8 max = {}", u8::MAX);
}

Get a Run button for this example Result of running the code

30 -4.5 true A 1000000
total = 25.5
u8 max = 255

Practice

Open the example in the online compiler, change a value or add a line, and predict the output before you run it. Then break the code on purpose and read the compiler's message.

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