function zip<V, W> (arr1: Array<V>, arr2: Array<W>): Array<[V, W]> {
  if (arr1.length === arr2.length) {
    return arr1.map((v, i) => [v, arr2[i]])
  } else {
    throw new Error("Array lengths must match for zip")
  }
}

function isString (s: any): s is string {
  return typeof s === 'string' || s instanceof String
}

export {
  isString,
  zip
}