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 auto begin() requires (!simple-view<V>)
12// { return ranges::begin(base_); }
13//
14// constexpr auto begin() const
15// requires range<const V> &&
16// indirect_unary_predicate<const Pred, iterator_t<const V>>
17// { return ranges::begin(base_); }
18
19#include <cassert>
20#include <ranges>
21#include <type_traits>
22#include <utility>
23
24#include "types.h"
25
26// Test Constraints
27template <class T>
28concept HasConstBegin = requires(const T& ct) { ct.begin(); };
29
30template <class T>
31concept HasBegin = requires(T& t) { t.begin(); };
32
33template <class T>
34concept HasConstAndNonConstBegin =
35 HasConstBegin<T> &&
36 requires(T& t, const T& ct) { requires !std::same_as<decltype(t.begin()), decltype(ct.begin())>; };
37
38template <class T>
39concept HasOnlyNonConstBegin = HasBegin<T> && !HasConstBegin<T>;
40
41template <class T>
42concept HasOnlyConstBegin = HasConstBegin<T> && !HasConstAndNonConstBegin<T>;
43
44struct Pred {
45 constexpr bool operator()(int i) const { return i > 5; }
46};
47
48static_assert(HasOnlyConstBegin<std::ranges::take_while_view<SimpleView, Pred>>);
49
50static_assert(HasOnlyNonConstBegin<std::ranges::take_while_view<ConstNotRange, Pred>>);
51
52static_assert(HasConstAndNonConstBegin<std::ranges::take_while_view<NonSimple, Pred>>);
53
54struct NotPredForConst {
55 constexpr bool operator()(int& i) const { return i > 5; }
56};
57static_assert(HasOnlyNonConstBegin<std::ranges::take_while_view<NonSimple, NotPredForConst>>);
58
59constexpr bool test() {
60 // simple-view
61 {
62 int buffer[] = {1, 2, 3, 4, 5, 6, 5, 4, 3, 2, 1};
63 SimpleView v{buffer};
64 std::ranges::take_while_view twv(v, Pred{});
65 std::same_as<int*> decltype(auto) it1 = twv.begin();
66 assert(it1 == buffer);
67 std::same_as<int*> decltype(auto) it2 = std::as_const(twv).begin();
68 assert(it2 == buffer);
69 }
70
71 // const not range
72 {
73 int buffer[] = {1, 2, 3, 4, 5, 6, 5, 4, 3, 2, 1};
74 ConstNotRange v{buffer};
75 std::ranges::take_while_view twv(v, Pred{});
76 std::same_as<int*> decltype(auto) it1 = twv.begin();
77 assert(it1 == buffer);
78 }
79
80 // NonSimple
81 {
82 int buffer[] = {1, 2, 3, 4, 5, 6, 5, 4, 3, 2, 1};
83 NonSimple v{buffer};
84 std::ranges::take_while_view twv(v, Pred{});
85 std::same_as<int*> decltype(auto) it1 = twv.begin();
86 assert(it1 == buffer);
87 std::same_as<const int*> decltype(auto) it2 = std::as_const(twv).begin();
88 assert(it2 == buffer);
89 }
90
91 // NotPredForConst
92 // LWG 3450: The const overloads of `take_while_view::begin/end` are underconstrained
93 {
94 int buffer[] = {1, 2, 3, 4, 5, 6, 5, 4, 3, 2, 1};
95 NonSimple v{buffer};
96 std::ranges::take_while_view twv(v, NotPredForConst{});
97 std::same_as<int*> decltype(auto) it1 = twv.begin();
98 assert(it1 == buffer);
99 }
100
101 return true;
102}
103
104int main(int, char**) {
105 test();
106 static_assert(test());
107 return 0;
108}
109

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