Primitive Type tuple [−]
A finite heterogeneous sequence, (T, U, ..).
Let's cover each of those in turn:
Tuples are finite. In other words, a tuple has a length. Here's a tuple
of length 3:
("hello", 5, 'c');
'Length' is also sometimes called 'arity' here; each tuple of a different length is a different, distinct type.
Tuples are heterogeneous. This means that each element of the tuple can have a different type. In that tuple above, it has the type:
fn main() { (&'static str, i32, char) }(&'static str, i32, char)
Tuples are a sequence. This means that they can be accessed by position; this is called 'tuple indexing', and it looks like this:
fn main() { let tuple = ("hello", 5, 'c'); assert_eq!(tuple.0, "hello"); assert_eq!(tuple.1, 5); assert_eq!(tuple.2, 'c'); }let tuple = ("hello", 5, 'c'); assert_eq!(tuple.0, "hello"); assert_eq!(tuple.1, 5); assert_eq!(tuple.2, 'c');
For more about tuples, see the book.
Trait implementations
If every type inside a tuple implements one of the following traits, then a tuple itself also implements it.
Due to a temporary restriction in Rust's type system, these traits are only implemented on tuples of arity 32 or less. In the future, this may change.
Examples
Basic usage:
fn main() { let tuple = ("hello", 5, 'c'); assert_eq!(tuple.0, "hello"); }let tuple = ("hello", 5, 'c'); assert_eq!(tuple.0, "hello");
Tuples are often used as a return type when you want to return more than one value:
fn main() { fn calculate_point() -> (i32, i32) { // Don't do a calculation, that's not the point of the example (4, 5) } let point = calculate_point(); assert_eq!(point.0, 4); assert_eq!(point.1, 5); // Combining this with patterns can be nicer. let (x, y) = calculate_point(); assert_eq!(x, 4); assert_eq!(y, 5); }fn calculate_point() -> (i32, i32) { // Don't do a calculation, that's not the point of the example (4, 5) } let point = calculate_point(); assert_eq!(point.0, 4); assert_eq!(point.1, 5); // Combining this with patterns can be nicer. let (x, y) = calculate_point(); assert_eq!(x, 4); assert_eq!(y, 5);