| Contents |

5 Types

5.2 Literals

Numeric literals can be type annotated by adding the type as a suffix. As an example, to specify that the literal 42 should have the type i32, write 42i32.

The type of unsuffixed numeric literals will depend on how they are used. If no constraint exists, the compiler will use i32 for integers, and f64 for floating-point numbers.

fn main() {
    // Suffixed literals, their types are known at initialization
    let x = 1u8;
    let y = 2u32;
    let z = 3f32;

    // Unsuffixed literals, their types depend on how they are used
    let i = 1;
    let f = 1.0;

    // `size_of_val` returns the size of a variable in bytes
    println!("size of `x` in bytes: {}", std::mem::size_of_val(&x));
    println!("size of `y` in bytes: {}", std::mem::size_of_val(&y));
    println!("size of `z` in bytes: {}", std::mem::size_of_val(&z));
    println!("size of `i` in bytes: {}", std::mem::size_of_val(&i));
    println!("size of `f` in bytes: {}", std::mem::size_of_val(&f));
}

There are some concepts used in the previous code that haven’t been explained yet, here’s a brief explanation for the impatient readers:

| Contents |