Rust中的枚举及模式匹配

这个enum的用法，比c要强，和GO类似。

enum Coin {
    Penny,
    Nickel,
    Dime,
    Quarter,
}

fn value_in_cents(coin: Coin) -> u32 {
    match coin {
    Coin::Penny => {
        println!("Lucky penny!");
        1
    },
    Coin::Nickel => 5,
    Coin::Dime => 10,
    Coin::Quarter => 25,
    }
}

fn main() {
    let penny = value_in_cents(Coin::Penny);
    println!("The coin is {}.", penny);

    let nickel = value_in_cents(Coin::Nickel);
    println!("The coin is {}.", nickel);

    let dime = value_in_cents(Coin::Dime);
    println!("The coin is {}.", dime);

    let quarter = value_in_cents(Coin::Quarter);
    println!("The coin is {}.", quarter);
}