Fizzbuzz.swift

struct Fizzbuzz: Sequence, IteratorProtocol {
  
  enum FizzbuzzValue: CustomDebugStringConvertible {
    case fizz
    case buzz
    case fizzbuzz
    case other(Int)

    var debugDescription: String {
      switch self {
      case .fizz: return "Fizz"
      case .buzz: return "Buzz"
      case .fizzbuzz: return "FizzBuzz"
      case let .other(value): return "\(value)"
      }
    }
  }

  typealias Element = FizzbuzzValue

  let fizzDivisor: Int
  let buzzDivisor: Int

  var current = 1

  init(fizzDivisor: Int = 3, buzzDivisor: Int = 5) {
    self.fizzDivisor = fizzDivisor
    self.buzzDivisor = buzzDivisor
  }

  mutating func next() -> FizzbuzzValue? {
    defer { current += 1 }

    let isFizz = current % fizzDivisor == 0
    let isBuzz = current % buzzDivisor == 0

    if isFizz && isBuzz { return .fizzbuzz }

    if isFizz { return .fizz }

    if isBuzz { return .buzz }

    return .other(current)
  }

}

print(Fizzbuzz()
  .prefix(100)
  .map { "\($0)"}
  .joined(separator: "\n"))