rust_book_code 0.2.1

pub fn match_coin() {
    enum Coin {
        Penny,
        Nickel,
        Dime,
        Quarter,
    }

    fn value_in_cents(coin: Coin) -> u8 {
        match coin {
            Coin::Penny => {
                println!("Lucky penny!");
                1
            } // 大括号分支后的逗号是可选的
            Coin::Nickel => 5, // 中间分支后的逗号是必选的
            Coin::Dime => 10,
            Coin::Quarter => 25, // 最后分支后的逗号是可选的
        }
    }
}

pub fn bind_values() {
    #[derive(Debug)]
    enum UsState {
        Alabama,
        Alaska,
        // --snip--
    }

    enum Coin {
        Penny,
        Nickel,
        Dime,
        Quarter(UsState),
    }

    fn value_in_cents(coin: Coin) -> u8 {
        match coin {
            Coin::Penny => {
                println!("Lucky penny!");
                1
            }
            Coin::Nickel => 5,
            Coin::Dime => 10,
            Coin::Quarter(state) => {
                println!("State quarter from {:?}!", state);
                25
            }
        }
    }

    value_in_cents(Coin::Quarter(UsState::Alaska));
}

pub fn match_option() {
    fn plus_one(x: Option<i32>) -> Option<i32> {
        // Matches must be Exhaustive
        match x {
            None => None,
            Some(i) => Some(i + 1),
        }
    }

    let five = Some(5);
    let six = plus_one(five);
    let none = plus_one(None);
    println!("six: {:?}, none: {:?}", six, none)
}

pub fn match_catch_all() {
    let dice_roll = 9;
    match dice_roll {
        3 => add_fancy_hat(),
        7 => remove_fancy_hat(),
        other => move_player(other),
    }

    match dice_roll {
        3 => add_fancy_hat(),
        7 => remove_fancy_hat(),
        _ => reroll(),
    }

    match dice_roll {
        3 => add_fancy_hat(),
        7 => remove_fancy_hat(),
        _ => (),
    }

    fn add_fancy_hat() {}
    fn remove_fancy_hat() {}
    fn move_player(num_spaces: u8) {}
    fn reroll() {}
}