closure.rs

fn apply<F>(mut f: F)
where
    F: FnMut(),
{
    f();
    f();
}

fn main() {
    let mut farewell = "goodbye".to_owned();

    let mut diary = move || {
        farewell.push_str("!!!");
        println!("{}.", farewell);
    };
    apply(diary.clone());
    apply(&mut diary);
    apply(diary);
}