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, c++17
10
11// constexpr const Pred& pred() const;
12
13#include <cassert>
14#include <ranges>
15#include <type_traits>
16#include <utility>
17
18struct View : std::ranges::view_interface<View> {
19 int* begin() const;
20 int* end() const;
21};
22
23struct Pred {
24 int i;
25 bool operator()(int) const;
26};
27
28constexpr bool test() {
29 // &
30 {
31 std::ranges::take_while_view<View, Pred> twv{{}, Pred{5}};
32 decltype(auto) x = twv.pred();
33 static_assert(std::same_as<decltype(x), Pred const&>);
34 assert(x.i == 5);
35 }
36
37 // const &
38 {
39 const std::ranges::take_while_view<View, Pred> twv{{}, Pred{5}};
40 decltype(auto) x = twv.pred();
41 static_assert(std::same_as<decltype(x), Pred const&>);
42 assert(x.i == 5);
43 }
44
45 // &&
46 {
47 std::ranges::take_while_view<View, Pred> twv{{}, Pred{5}};
48 decltype(auto) x = std::move(twv).pred();
49 static_assert(std::same_as<decltype(x), Pred const&>);
50 assert(x.i == 5);
51 }
52
53 // const &&
54 {
55 const std::ranges::take_while_view<View, Pred> twv{{}, Pred{5}};
56 decltype(auto) x = std::move(twv).pred();
57 static_assert(std::same_as<decltype(x), Pred const&>);
58 assert(x.i == 5);
59 }
60
61 return true;
62}
63
64int main(int, char**) {
65 test();
66 static_assert(test());
67 return 0;
68}
69

source code of libcxx/test/std/ranges/range.adaptors/range.take.while/pred.pass.cpp