函数生成器

main() {
  Iterator<dynamic> it = iter(5).iterator;
  while (it.moveNext()) {
    print(it.current);
  }
}
//
Iterable iter(n) sync* {
  print("Begin");
  int k = 0;
  while (k < n) {
    yield k++;
  }
  print("End");
}

main() {
  iter(5).listen((k)=>print(k));
}
//
Stream iter(n) async* {
  print("Begin");
  int k = 0;
  while (k < n) {
    yield k++;
  }
  print("End");
}