rust.quest

Fearless concurrency. Memory safety. Zero-cost abstractions. Begin your quest into systems programming.

Ownership

Each value in Rust has a single owner. When the owner goes out of scope, the value is dropped. This is Rust's fundamental contract.

let s1 = String::from("hello");
let s2 = s1; // s1 is moved
// println!("{}", s1); // ERROR: value used after move
println!("{}", s2); // OK

Borrowing

References allow you to refer to a value without taking ownership. Immutable references (&T) share freely; mutable references (&mut T) are exclusive.

fn calculate_length(s: &String) -> usize {
    s.len()
} // s goes out of scope, but doesn't drop the value

let s1 = String::from("hello");
let len = calculate_length(&s1);
println!("len of '{}' is {}", s1, len);

Lifetimes

Lifetimes ensure references are valid for as long as they're used. The borrow checker verifies this at compile time.

fn longest<'a>(x: &'a str, y: &'a str) -> &'a str {
    if x.len() > y.len() { x } else { y }
}

Compilation Successful

    _~^~^~_
\) /  o o  \ (/
  '_   -   _'
  / '-----' \