Tuples

A tuple groups two or more values by position. Its type lists theirs: (i32, str).

CalxOutput

Tested

fn min_max(xs: [i32; 4]) -> (i32, i32) {
    var lo = xs[0]
    var hi = xs[0]
    for x in xs {
        lo = lo.min(x)
        hi = hi.max(x)
    }
    return (lo, hi)
}

fn main() {
    let (lo, hi) = min_max([4, -2, 9, 3])
    println("{lo} {hi}")

    let t = (1, 2.5, true)
    println("{t.0} {t.1} {t.2}")

    var p = (0, 0)
    p.1 = 5
    println("{p.0} {p.1}")
}

• (a, b, ...) builds one, running its parts left to right. A tuple has at least two parts: (x) is just x in parentheses, and () is the unit value.
• t.0, t.1 and so on read a part. On a var they can be assigned.
• Tuples are values, copied when assigned, like structs.
• Tuples compare with == part by part, and print as (1, a, true) (comparing and printing). match sees inside them.

Destructuring

A tuple pattern takes a tuple apart. It works in let, var, for, match and if let (patterns), and _ skips a part:

CalxOutput

Tested

fn main() {
    let ((a, _), c) = ((1, 2), 3)
    var (x, y) = (1, 2)                  // `var` makes each name a variable
    x += a
    y *= c
    println("{x} {y}")

    for (i, ch) in [(1, 'a'), (2, 'b')] {
        print("{i}{ch};")
    }
    println()
}

A tuple in C is a struct with one field per part, so it costs what the separate values would.