// 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.

// @dart = 2.9

/// @assertion T fold<T>(T initialValue, T combine(T 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 returned value is correct.
/// @author msyabro


import "dart:typed_data";
import "../../../Utils/expect.dart";

checkInt(List<int> list, int expected) {
  var l = new Int32List.fromList(list);
  var res = l.fold(0, (prev, cur) => prev + cur);
  Expect.equals(expected, res);
}

checkString(List<int> list, String expected) {
  var l = new Int32List.fromList(list);
  var res = l.fold("", (prev, cur) => "${prev}${cur}");
  Expect.equals(expected, res);
}

checkConst(List<int> list, int expected) {
  var l = new Int32List.fromList(list);
  var res = l.fold(0, (prev, cur) => 1);
  Expect.equals(expected, res);
}


main() {
  checkInt([], 0);
  checkInt([1, 2, 3, 4, 5, 6, 7, 8, 9, 10], 55);
  checkInt([10, -1, -2, -3, -4], 0);

  checkString([], "");
  checkString([1], "1");
  checkString([1, 2, 3, 4, 5], "12345");

  checkConst([], 0);
  checkConst([1, 2, 3], 1);
}