window method

Iterable<List<E>> window(int size, { int step = 1, bool includePartial = false, })

Sliding window of given size over this Iterable.

The following expression yields [1, 2, 3], [2, 3, 4], and [3, 4, 5]:

[1, 2, 3, 4, 5].window(3);

Implementation

Iterable<List<E>> window(
  int size, {
  int step = 1,
  bool includePartial = false,
}) sync* {
  checkNonZeroPositive(size, 'size');
  checkNonZeroPositive(step, 'step');
  final buffer = ListQueue<E>();
  final iterator = this.iterator;
  while (true) {
    while (buffer.length < size && iterator.moveNext()) {
      buffer.addLast(iterator.current);
    }
    if (buffer.length < size) {
      if (includePartial && buffer.isNotEmpty) {
        yield buffer.toList(growable: false);
      }
      break;
    }
    yield buffer.toList(growable: false);
    if (step < size) {
      for (var i = 0; i < step; i++) {
        buffer.removeFirst();
      }
    } else {
      buffer.clear();
      for (var i = 0; i < step - size; i++) {
        if (!iterator.moveNext()) {
          return;
        }
      }
    }
  }
}