Tuples

A tuple groups a fixed number of values, possibly of different types, into a single value. Use them when you need to return more than one thing from a function and the combination doesn't deserve its own struct.

Creating

let pair = (42, "answer");
let triple: (Int, Int, Int) = (1, 2, 3);

Type is (Int, String) for the first; tuple types are written the same way they're constructed.

Access

By position, with .0, .1, etc.:

let pair = (42, "answer");
println("\(pair.0)");   // 42
println(pair.1);        // answer

Or by destructuring:

let pair = (42, "answer");
let (number, name) = pair;
println("\(name): \(number)");

Tuple fields are positional only — there are no named tuple fields in Kestrel. The moment the meaning of each slot deserves a name, reach for a struct instead.

Returning multiple values

The most common use:

func minMax(of xs: [Int]) -> (Int, Int) {
    var lo = xs(0);
    var hi = xs(0);
    for n in xs {
        if n < lo { lo = n; }
        if n > hi { hi = n; }
    }
    (lo, hi)
}

let (low, high) = minMax(of: [3, 1, 4, 1, 5, 9, 2, 6]);

When the result has more than two or three elements, or the meaning isn't clear from position alone, prefer a struct — readers shouldn't have to remember whether result.0 is the count or the average.

In pattern matching

Tuples destructure in match and if let:

let x = 0;
let y = 4;
let place = match (x, y) {
    (0, 0) => "origin",
    (_, 0) => "on x-axis",
    (0, _) => "on y-axis",
    _ => "elsewhere"
};

This is what makes for (key, value) in dict work — the tuple destructures into named bindings.