blob: 9671eaf3f717f21c5f358c7b5cb5ad44428d44e8 [file] [log] [blame]
// Copyright (c) 2013, the Dart project authors. Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.
import 'dart:collection';
/// Iterable that iterates over lists of values from other iterables.
/// When [iterator] is read, an [Iterator] is created for each [Iterable] in
/// the [Iterable] passed to the constructor.
/// As long as all these iterators have a next value, those next values are
/// combined into a single list, which becomes the next value of this
/// [Iterable]'s [Iterator]. As soon as any of the iterators run out,
/// the zipped iterator also stops.
class IterableZip<T> extends IterableBase<List<T>> {
final Iterable<Iterable<T>> _iterables;
IterableZip(Iterable<Iterable<T>> iterables) : _iterables = iterables;
/// Returns an iterator that combines values of the iterables' iterators
/// as long as they all have values.
Iterator<List<T>> get iterator {
var iterators = => x.iterator).toList(growable: false);
return _IteratorZip<T>(iterators);
class _IteratorZip<T> implements Iterator<List<T>> {
final List<Iterator<T>> _iterators;
List<T>? _current;
_IteratorZip(List<Iterator<T>> iterators) : _iterators = iterators;
bool moveNext() {
if (_iterators.isEmpty) return false;
for (var i = 0; i < _iterators.length; i++) {
if (!_iterators[i].moveNext()) {
_current = null;
return false;
_current = List.generate(_iterators.length, (i) => _iterators[i].current,
growable: false);
return true;
List<T> get current => _current ?? (throw StateError('No element'));