元组是不同类型的值的集合。 元组使用括号构造 (), 每个元组本身是类型签名值 (T1, T2, ...), 这里 T1, T2 是其成员的类型。 函数可以使用元组返回多个值，元组可以包含任意数量的值。
// Tuples can be used as function arguments and as return values
fn reverse(pair: (i32, bool)) -> (bool, i32) {
// `let` can be used to bind the members of a tuple to variables
let (integer, boolean) = pair;
(boolean, integer)
}
fn main() {
// A tuple with a bunch of different types
let long_tuple = (1u8, 2u16, 3u32, 4u64,
-1i8, -2i16, -3i32, -4i64,
0.1f32, 0.2f64,
'a', true);
// Values can be extracted from the tuple using tuple indexing
println!("long tuple first value: {}", long_tuple.0);
println!("long tuple second value: {}", long_tuple.1);
// Tuples can be tuple members
let tuple_of_tuples = ((1u8, 2u16, 2u32), (4u64, -1i8), -2i16);
// Tuples are printable
println!("tuple of tuples: {:?}", tuple_of_tuples);
let pair = (1, true);
println!("pair is {:?}", pair);
println!("the reversed pair is {:?}", reverse(pair));
// To create one element tuples, the comma is required to tell them apart
// from a literal surrounded by parentheses
println!("one element tuple: {:?}", (5u32,));
println!("just an integer: {:?}", (5u32));
}
