Tuples (元组) 类型 用于混合数据类型，最多可以有 12 种混合类型。

定义元组并取值:

let a_tuple: (&str, u8, char) = ("ok", 0, 'd');
let first_item = a_tuple.0;
println!("first_item is {}", first_item); // "ok"

修改元组的值：

let mut b_tuples = ("ok", 0);
b_tuples.0 = "ko";
b_tuples.1 += 1;
println!("b_tuples.0 is {}, b_tuples.1 is {}", b_tuples.0, b_tuples.1);

元组的解构赋值:

let c_tuple = ("zh", "CN", 1);
let (language, country, code) = c_tuple;
println!(
    "language is: {}, country is: {}, code is: {}",
    language, country, code
); // language is: en, country is: US, code is: 1