A tuple type is a heterogeneous product of other types, called the elements of the tuple. It has no nominal name and is instead structurally typed.
Tuple types and values are denoted by listing the types or values of their elements, respectively, in a parenthesized, comma-separated list.
Because tuple elements don't have a name, they can only be accessed by
pattern-matching or by using N directly as a field to access the Nth
element.
An example of a tuple type and its use:
type Pair<'a> = (i32, &'a str);
let p: Pair<'static> = (10, "ten");
let (a, b) = p;
assert_eq!(a, 10);
assert_eq!(b, "ten");
assert_eq!(p.0, 10);
assert_eq!(p.1, "ten");For historical reasons and convenience, the tuple type with no elements (())
is often called ‘unit’ or ‘the unit type’.