// https://basarat.gitbooks.io/typescript/docs/iterators.html
export interface IteratorResult<T> {
  done: boolean
  value: T
}

export interface Iterator<T, S> {
  next(value?: any): IteratorResult<T>
  return?(value?: any): IteratorResult<T>
  throw?(e?: any): IteratorResult<T>
  [Symbol.toStringTag]: S
}

// export type IteratorProto = typeof Iterator.prototype

export type MapIterator = Iterator<any, 'Map Iterator'>
export type SetIterator = Iterator<any, 'Set Iterator'>
export type StringIterator = Iterator<any, 'String Iterator'>
export type ArrayIterator = Iterator<any, 'Array Iterator'>
export type Generator = Iterator<any, 'GeneratorFunction'>

export type BuiltInIterators =
  | MapIterator
  | SetIterator
  | StringIterator
  | ArrayIterator
  | AsyncIterator<any>
  | Iterator<any, any>

export function isIterator(x: any): x is BuiltInIterators


export function fromArrayToIterator(x: Array): Iterator<x>