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 literal, 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:
fun(&foo)is used to pass an argument to a function by reference, rather than by value (fun(foo)). For more details see borrowing.std::mem::size_of_valis a function, but called with its full path. Code can be split in logical units called modules. In this case, thesize_of_valfunction is defined in thememmodule, and thememmodule is defined in thestdcrate. For more details, see modules and crates.