| // Copyright (c) 2017, 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. |
| |
| /// @assertion dynamic fold(initialValue, combine(previousValue, E element)) |
| /// Reduces a collection to a single value by iteratively combining each |
| /// [element] of the collection with an existing value. |
| /// Uses [initialValue] as the initial value, then iterates through the elements |
| /// and updates the [value] with each element using the [combine] function. |
| /// @description Checks that the result of folding is correct. |
| /// @author iarkh@unipro.ru |
| |
| import "dart:collection"; |
| import "dart:math"; |
| import "../../../Utils/expect.dart"; |
| |
| class MyIterable extends Object with IterableMixin { |
| List _content; |
| MyIterable(List list): _content = list; |
| |
| Iterator get iterator { |
| return _content.iterator; |
| } |
| } |
| |
| check(List list, num init, num combine(value, element), num expected) { |
| IterableMixin iterable = new MyIterable(list); |
| num actual = iterable.fold(init, combine); |
| Expect.equals(expected, actual); |
| } |
| |
| main() { |
| check([1, 2, -3], 0, (value, element) => value + element, 0); |
| check([1, 2, -3], 1, (value, element) => value * element, -6); |
| check([0, 2, -3], 1, (value, element) => value * element, 0); |
| check(const[1, 2, -5, -6], -1000, |
| (value, element) => max(value, element), 2); |
| } |