trait 接口

where 写法

pub fn notify<T: Summary + Display, U: <Clone + Debug>(a: T, b:U) -> String {  
format !( "Breaking news! {l", a.summarize())  
}  
pub fn notify2<T, U>(a:T,b: u) -> String  
    where  
        T: Summary + Display,  
        U: Clone + Debug {  
    format ! ( "Breaking news! {}", a. summarize())  
}