fn main() {
let pair = (2, -2);
// 试一试 ^ 将不同的值赋给 `pair`

println!("Tell me about {:?}", pair);
match pair {
(x, y) if x == y => println!("These are twins"),
// ^ `if` 条件部分是一个卫语句
(x, y) if x + y == 0 => println!("Antimatter, kaboom!"),
(x, _) if x % 2 == 1 => println!("The first one is odd"),
_ => println!("No correlation..."),
}
}