zip3 for swift

Zip.swift

struct Zip3Generator<A: IteratorProtocol, B: IteratorProtocol, C: IteratorProtocol>: IteratorProtocol {

  private var first: A
  private var second: B
  private var third: C

  private var index = 0

  init(_ first: A, _ second: B, _ third: C) {
    self.first = first
    self.second = second
    self.third = third
  }

  mutating func next() -> (A.Element, B.Element, C.Element)? { // swiftlint:disable:this large_tuple
    if let a = first.next(), let b = second.next(), let c = third.next() {
      return (a, b, c)
    }
    return nil
  }
}

func zip<A: Sequence, B: Sequence, C: Sequence>(_ a: A,_  b: B,_  c: C) -> IteratorSequence<Zip3Generator<A.Iterator, B.Iterator, C.Iterator>> {
  return IteratorSequence(Zip3Generator(a.makeIterator(), b.makeIterator(), c.makeIterator()))
}