export function counterIter(start = 0, end = Infinity) {
  let i = start
  let ended = false

  const iter: IterableIterator<number> = {
    [Symbol.iterator]: () => iter,
    next() {
      if (ended) {
        return { value: undefined, done: true }
      }

      if (i > end) {
        return { value: undefined, done: true }
      }

      return { value: i++, done: false }
    },
  }
  return {
    iter,
    end: () => {
      ended = true
    },
  }
}