Repeating array in Swift

Question

In Python I can create a repeating list like this:

>>> [1,2,3]*3
[1, 2, 3, 1, 2, 3, 1, 2, 3]

Is there a concise way to do this in

Answer 1

You can use modulo operations for index calculations of your base collection and functional programming for this:

let base = [1, 2, 3]
let n = 3 //number of repetitions
let r = (0..<(n*base.count)).map{base[$0%base.count]}

You can create a custom overload for the * operator, which accepts an array on the left and an integer on the right side.

func * (left: [T], right: Int) -> [T] {
    return (0..<(right*left.count)).map{left[$0%left.count]}
}

You can then use your function just like in python:

[1, 2, 3] * 3
// will evaluate to [1, 2, 3, 1, 2, 3, 1, 2, 3]