// 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 Iterable expand(Iterable f(E element))
/// Expands each element of this Iterable into zero or more elements.
/// The resulting Iterable runs through the elements returned by f for each
/// element of this, in iteration order.
/// The returned Iterable is lazy, and calls f for each element of this every
/// time it's iterated.
/// @description Checks that the returned Iterable is lazy. Function f is
/// called each time when the object is iterated
/// @author sgrekhov@unipro.ru

library expand_A02_t02;
import "../../../Utils/expect.dart";

void check(Iterable a) {
  int count = 0;
  Iterable expanded = a.expand((element) {
    count++;
    return [element];
  });
  Expect.equals(0, count);
  expanded.length;
  Expect.equals(a.length, count);
  expanded.length;
  Expect.equals(2 * a.length, count);
}

test(Iterable create([Iterable content])) {
  check(create());
  check(create([1]));
  check(create([1, 2]));
  check(create([1, 2, 2]));
  check(create([1, 2, 2, 3]));
}