split into chunks

[vincevargadev]

extension SplitInto<T> on Iterable<T> {
  Iterable<Iterable<T>> splitInto(int n) sync* {
    final it = _sizes(length, n).iterator;
    for (int i = 0, a = 0, size = 0; i < n; i++, a += size) {
      size = (it..moveNext()).current;
      yield skip(a).take(size);
    }
  }
}

Iterable<int> _sizes(int length, int n) sync* {
  final largeCount = (length % n);
  final size = length ~/ n;
  for (var i = 0; i < n; i++) {
    yield i < largeCount ? size + 1 : size;
  }
}