// Copyright (c) 2016, 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
/// 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, as if by:
///
///  var value = initialValue;
///  for (E element in this) {
///      value = combine(value, element);
///  }
///  return value;
///  Example of calculating the sum of an iterable:
///  iterable.fold(0, (prev, element) => prev + element);
/// @description Checks that fold is called for each element of this Iterable
/// @author sgrekhov@unipro.ru

library fold_A01_t02;
import "../../../Utils/expect.dart";

num combine(num previousValue, element) => ++previousValue;

check(Iterable a) {
  num actual = a.fold(0, combine);
  Expect.equals(a.length, actual);
}

test(Iterable create([Iterable content])) {
  check(create([]));
  check(create([1]));
  check(create([0, 0, 0]));
  check(create([1, 2, 3, 4, 5, 6, 7, 8]));
}