gistfile1.rs

struct Person {
    first: String,
    last: String
}

fn main() {
    let person = Person { first: "Alex".to_string(), last: "Matchneer".to_string() };
    yehuda(&person);
}

// this is a compile-time error
fn yehuda(person: &Person) {
    person.first = "Yehuda".to_string() // lol

    set_yehuda(person) // this is also an error, because I don't have a mutable Person to send
}

// this is valid, because you borrowed mutably
fn set_yehuda(person: &mut Person) {
    person.first = "Yehuda".to_string()
}