1//===----------------------------------------------------------------------===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8
9// UNSUPPORTED: c++03, c++11, c++14
10
11// <algorithm>
12
13// template <class PopulationIterator, class SampleIterator, class Distance,
14// class UniformRandomNumberGenerator>
15// SampleIterator sample(PopulationIterator first, PopulationIterator last,
16// SampleIterator out, Distance n,
17// UniformRandomNumberGenerator &&g);
18
19#include <algorithm>
20#include <random>
21#include <cassert>
22
23#include "test_macros.h"
24#include "test_iterators.h"
25
26// Stable if and only if PopulationIterator meets the requirements of a
27// ForwardIterator type.
28template <class PopulationIterator, class SampleIterator>
29void test_stability(bool expect_stable) {
30 const unsigned kPopulationSize = 100;
31 int ia[kPopulationSize];
32 for (unsigned i = 0; i < kPopulationSize; ++i)
33 ia[i] = i;
34 PopulationIterator first(ia);
35 PopulationIterator last(ia + kPopulationSize);
36
37 const unsigned kSampleSize = 20;
38 int oa[kPopulationSize];
39 SampleIterator out(oa);
40
41 std::minstd_rand g;
42
43 const int kIterations = 1000;
44 bool unstable = false;
45 for (int i = 0; i < kIterations; ++i) {
46 std::sample(first, last, out, kSampleSize, g);
47 unstable |= !std::is_sorted(first: oa, last: oa + kSampleSize);
48 }
49 assert(expect_stable == !unstable);
50}
51
52int main(int, char**) {
53 test_stability<forward_iterator<int *>, cpp17_output_iterator<int *> >(true);
54 test_stability<cpp17_input_iterator<int *>, random_access_iterator<int *> >(false);
55
56 return 0;
57}
58

source code of libcxx/test/std/algorithms/alg.modifying.operations/alg.random.sample/sample.stable.pass.cpp