Anonymous Records

● Intermediate4 minBefore this: Records, TuplesSpec 2.14

(times: 3, wait_ms: 200) is a record written on the spot, with no type declared for it.

fn minmax(xs: [Int]) -> (lo: Int, hi: Int) {
    (lo: xs.min() ?? 0, hi: xs.max() ?? 0)
}

fn main() {
    const r = minmax([3, 1, 4])
    print("lo {r.lo}, hi {r.hi}")
    const retry = (times: 3, wait_ms: 200)
    print(retry.times)
}

kavach run anon.kav

lo 1, hi 43

A function can give back several named values: r.lo reads better than the position in a tuple. Two anonymous records with the same fields fit each other, in any order. Name the shape with an alias when you use it often:

type Retry = (times: Int, wait_ms: Int)

fn describe(r: Retry) -> String {
    "{r.times} tries, {r.wait_ms} ms apart"
}

fn main() {
    print(describe((times: 3, wait_ms: 200)))
    print(describe((wait_ms: 50, times: 5)))
}

kavach run alias.kav

3 tries, 200 ms apart5 tries, 50 ms apart

Start with an anonymous record while a design settles; turn it into a type when it needs methods.