c-style-for.swift

func sequence<T>(_ initial: T, _ cond: (T) -> Bool, _ update: (inout T) -> ()) -> UnfoldSequence<T, T> {
  return sequence(state: initial, next: { (state: inout T) -> T? in
    guard cond(state) else { return nil }
    update(&state)
    return state
  })
}

for x in sequence(4, { $0 < 10 }, { $0 = $0 + 1 }) {
  print(x)
}