string-chunks.swift

extension String {
  func chunks(_ size: Int) -> [String] {
    stride(from: 0, to: self.count, by: size).map {
      let i0 = self.index(self.startIndex, offsetBy: $0)
      let i1 = self.index(self.startIndex, offsetBy: min($0 + size, self.count))
      return "\(self[i0..<i1])"
    }
  }
}