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quiver/lib/src/iterables/cycle.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.
-
-part of quiver.iterables;
-
-/**
- * Returns an [Iterable] that infinitely cycles through the elements of
- * [iterable]. If [iterable] is empty, the returned Iterable will also be empty.
- */
-Iterable cycle(Iterable iterable) => new _Cycle(iterable);
-
-class _Cycle<T> extends InfiniteIterable<T> {
-  final Iterable<T> _iterable;
-
-  _Cycle(this._iterable);
-
-  Iterator<T> get iterator => new _CycleIterator(_iterable);
-
-  bool get isEmpty => _iterable.isEmpty;
-
-  bool get isNotEmpty => _iterable.isNotEmpty;
-
-  // TODO(justin): add methods that can be answered by the wrapped iterable
-}
-
-class _CycleIterator<T> implements Iterator<T> {
-  final Iterable<T> _iterable;
-  Iterator<T> _iterator;
-
-  _CycleIterator(_iterable)
-      : _iterable = _iterable,
-        _iterator = _iterable.iterator;
-
-  T get current => _iterator.current;
-
-  bool moveNext() {
-    if (!_iterator.moveNext()) {
-      _iterator = _iterable.iterator;
-      return _iterator.moveNext();
-    }
-    return true;
-  }
-}