Types

Rust's empty value, means "nothing"

When a function returns nothing meaningful

fn greet() { println!("hi"); }
// returns () by default

true or false, nothing else

Status flags: is_paid, is_verified

let is_paid: bool = true;
let is_verified: bool = false;

One character, single quotes

'A', '🔥', single symbols, not strings

let letter: char = 'A';
let emoji: char = '🔥';

Prints a line to the terminal

Debugging or showing output

let name = "Alice";
println!("Hello, {}!", name);

Debug print formatting

Printing arrays and tuples that {} cannot print

let arr = [1, 2, 3];
println!("{:?}", arr);

An array of exactly 32 unsigned bytes

Wallet addresses on Solana

let addr: [u8; 32] = [0; 32];
println!("{:?}", addr);

An unsigned integer whose size matches the computer's architecture, 8 bytes on 64-bit

Used for memory sizes, slice lengths, and array indexes, the type Rust uses internally for positions

let len: usize = 32;
let i: usize = 0;

Converting a value from one type to another using the as keyword, always explicit, never automatic

let x: i32 = 1000; let y = x as u8;

let x: i32 = 1000;
let y = x as u8;

The numeric code that represents a character

'a' as u8 gives 97; 97u8 as char gives 'a'

let n: u8 = 'a' as u8;
let c: char = 97u8 as char;