enum Message {
    Quit,
    Move { x: i32, y: i32 },
    Write(String),
    ChangeColor(i32, i32, i32),
}

impl Message {
    fn call(&self) {
        // method body would be defined here
    }
}

fn main() {
    let m = Message::Write(String::from("hello"));
    m.call();
}

// 复杂枚举定义
#[derive(Debug)]
enum Message {
    Move { x: i32, y: i32 },
    Echo(String),
    ChangeColor(i32, i32, i32),
    Quit,
}

impl Message {
    fn call(&self) {
        println!("{:?}", &self);
    }
}

fn main() {
    let messages = [
        Message::Move { x: 10, y: 30 },
        Message::Echo(String::from("hello world")),
        Message::ChangeColor(200, 255, 255),
        Message::Quit,
    ];

    for message in &messages {
        message.call();
    }
}

#[derive(Debug)] // so we can inspect the state in a minute
enum UsState {
    Alabama,
    Alaska,
    // --snip--
}

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

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

fn main() {
    let value = value_in_cents(Coin::Quarter(UsState::Alabama));
}

fn plus_one(x: Option<i32>) -> Option<i32> {
    match x {
        None => None,
        Some(i) => Some(i + 1),
    }
}

fn main() {
    let five = Some(5);
    let six = plus_one(five);
    let none = plus_one(None);
}

fn plus_one(x: Option<i32>) -> Option<i32> {
    // !!! ERROR: Match must be exhaustive
    match x {
        Some(i) => Some(i + 1),
    }
}

fn main() {
    // put you code here to launch it
}

// 修改后
fn plus_one(x: Option<i32>) -> Option<i32> {
    // !!! ERROR: Match must be exhaustive
    match x {
        Some(i) => Some(i + 1),
        None => None,
    }
}

fn main() {
    // put you code here to launch it
    plus_one(Some(1));
}

use std::fs::File;
use std::io::{BufRead, BufReader, Result};

fn main() -> Result<()> {
    let reader = BufReader::new(File::open("oor.txt")?);
    for line in reader.lines() {
        println!("{}", line?);
    }
    Ok(())
}