How to use functions with default arguments in Swift

import Cocoa

struct Robot {
    let a: Int
    let b: Int
    let c: Int

    init(a: Int = 1, c: Int = 3) {
        self.a = a
        self.b = 0
        self.c = c
        print("Init with a=\(a) and c=\(c)")
    }

    init(a: Int = 1, b: Int = 2, c: Int = 3) {
        self.a = a
        self.b = b
        self.c = c

        print("Init with a\(a), b=\(b) and c=\(c)")
    }
}

let r1 = Robot(c: 10)
let r2 = Robot(a: 5, c: 10)
let r3 = Robot(a: 5, b: 7, c: 10)
let r4 = Robot(a: 5)
let r5 = Robot(b: 5)

Init with a=1 and c=10
Init with a=5 and c=10
Init with a5, b=7 and c=10
Init with a=5 and c=3
Init with a1, b=5 and c=3