Tuples

A tuple groups a fixed number of values — possibly of different types — into a single value, without declaring a named struct. Tuples are written as a parenthesized, comma-separated list in both type position and value position.

let pair: (int, float64) = (1, 2.5);
let triple = ("Rux", 3, true);   // (Slice<char8>, int, bool)

When the type can be inferred from the values, the annotation may be omitted, as in triple above.

Type Identity

The number and types of elements are fixed at compile time and are part of the tuple's type. Order is significant, so (int, float64) and (float64, int) are different, incompatible types:

let a: (int, float64) = (1, 2.5);
let b: (float64, int) = a;   // error: types do not match

A tuple type carries no field names — only positions — which is what distinguishes it from a struct.

Value Semantics

Like a struct, a tuple is a value type. Assigning it, or passing it to a function, copies every element; the copy and the original are independent.

var p = (1, 2);
var q = p;        // full copy
q = (9, 9);       // reassigns q only — p is still (1, 2)

Nesting

A tuple element may be any type, including another tuple. This lets you build small structured values without a dedicated type:

let nested: (int, (float64, float64)) = (1, (2.0, 3.0));

Memory Layout

A tuple is laid out like an unnamed struct: its elements are stored in order, each at the next offset that satisfies its natural alignment, with padding inserted where needed. The tuple's alignment is that of its strictest element, and its size is rounded up to a multiple of that alignment.

let t: (uint8, uint32) = (1, 2);
// element 0 at offset 0, element 1 at offset 4 (3 padding bytes between)
// alignment 4, size 8

The only layout difference from a struct is that the elements are reached by position rather than by name.

Further Topics

See Also

• Structures — named aggregates with typed fields
• Slices — sequences of a single element type