O Que Rust Tem de Legal

Borrow Checker


a = 2

"Variável a tem o valor 2"

"Posição de memória apontada por a tem o valor 2"


0x3f5cbf89 = 2

A language that doesn't affect the way you think about programming, is not worth knowing.

-- Alan Perlis, "ALGOL"


fn main() {
    let a = String::from("hello");
    let _b = a;
    println!("{}", a)
}


error[E0382]: borrow of moved value: `a`
 --> src/main.rs:5:20
  |
4 |     let _b = a;
  |              - value moved here
5 |     println!("{}", a)
  |                    ^ value borrowed here after move
  |
  = note: move occurs because `a` has type `std::string::String`, which does not implement the `Copy` trait


fn main() {
    let a = 2;
    let b = a;
    println!("{}", a);
    println!("{}", b);
}

2
2

Swift 5 Exclusivity Enforcement

Imutabilidade por Default


fn main() {
    let a = 2;
    a = 3;
    println!("{}", a);
}


3 |     let a = 2;
  |         -
  |         |
  |         first assignment to `a`
  |         help: make this binding mutable: `mut a`
4 |     a = 3;
  |     ^^^^^ cannot assign twice to immutable variable


fn main() {
    let mut a = 2;
    a = 3;
    println!("{}", a);
}

Enums


enum IpAddr {
   V4,
   V6
}


enum IpAddr {
    V4(String),
    V6(String),
}


let home = IpAddr::V4(String::from("127.0.0.1");

match home {
    V4(address) => println!("IPv4 addr: {}", address),
    V6(address) => println!("Ipv6 addr: {}", address),
}


enum Option<T> {
    Some(T),
    None
}

Error Control


try:
    something()
except Exception:
    pass


try {
   something();
} catch (Exception ex) {
   System.out.println(ex);
}


FILE* f = fopen("someting.txt", "wb");
fprintf(f, "Done!");
fclose(f);

Onde o erro foi tratado nisso?


enum Result<T, E> {
    Ok(T),
    Err(E),
}


File::create("something.txt") match {
    Ok(fp) => fp.write_all(b"Hello world"),
    Err(err) => println!("Failure! {}", err),
}


File::create("something.txt") match {
    Ok(fp) => fp.write_all(b"Hello world") match {
        Ok(_) => (),
        Err(err) => println!("Can't write! {}", err),
    }
    Err(err) => println!("Failure! {}", err),
}


let mut file = File::create("something.txt).unwrap();
file.write(b"Hello world").unwrap();


let mut file = File::create("something.txt)?;
file.write(b"Hello world")?;
OK(())