lib/src/iterables/zip.dart

// Copyright 2013 Google Inc. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

/// Returns an [Iterable] of [List]s where the nth element in the returned
/// iterable contains the nth element from every Iterable in [iterables]. The
/// returned Iterable is as long as the shortest Iterable in the argument. If
/// [iterables] is empty, it returns an empty list.
Iterable<List<T>> zip<T>(Iterable<Iterable<T>> iterables) sync* {
  if (iterables.isEmpty) return;
  final iterators = iterables.map((e) => e.iterator).toList(growable: false);
  while (iterators.every((e) => e.moveNext())) {
    yield iterators.map((e) => e.current).toList(growable: false);
  }
}