1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
|
//===----------------------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
// <algorithm>
// UNSUPPORTED: c++03, c++11, c++14, c++17
// UNSUPPORTED: libcpp-has-no-incomplete-ranges
// Older Clangs don't properly deduce decltype(auto) with a concept constraint
// XFAIL: apple-clang-13.0
// template<class T, class Proj = identity,
// indirect_strict_weak_order<projected<const T*, Proj>> Comp = ranges::less>
// constexpr const T&
// ranges::clamp(const T& v, const T& lo, const T& hi, Comp comp = {}, Proj proj = {});
#include <algorithm>
#include <cassert>
#include <functional>
#include <utility>
template <class T, class Comp = std::ranges::less, class Proj = std::identity>
concept HasClamp =
requires(T&& val, T&& low, T&& high, Comp&& comp, Proj&& proj) {
std::ranges::clamp(std::forward<T>(val), std::forward<T>(low), std::forward<T>(high),
std::forward<Comp>(comp), std::forward<Proj>(proj));
};
struct NoComp {};
struct CreateNoComp {
auto operator()(int) const { return NoComp(); }
};
static_assert(HasClamp<int, std::ranges::less, std::identity>);
static_assert(!HasClamp<NoComp>);
static_assert(!HasClamp<int, NoComp>);
static_assert(!HasClamp<int, std::ranges::less, CreateNoComp>);
constexpr bool test() {
{ // low < val < high
int val = 2;
int low = 1;
int high = 3;
std::same_as<const int&> decltype(auto) ret = std::ranges::clamp(val, low, high);
assert(ret == 2);
assert(&ret == &val);
}
{ // low > val < high
assert(std::ranges::clamp(10, 20, 30) == 20);
}
{ // low < val > high
assert(std::ranges::clamp(15, 5, 10) == 10);
}
{ // low == val == high
int val = 10;
assert(&std::ranges::clamp(val, 10, 10) == &val);
}
{ // Check that a custom comparator works.
assert(std::ranges::clamp(10, 30, 20, std::ranges::greater{}) == 20);
}
{ // Check that a custom projection works.
struct S {
int i;
constexpr const int& lvalue_proj() const { return i; }
constexpr int prvalue_proj() const { return i; }
};
struct Comp {
constexpr bool operator()(const int& lhs, const int& rhs) const { return lhs < rhs; }
constexpr bool operator()(int&& lhs, int&& rhs) const { return lhs > rhs; }
};
auto val = S{10};
auto low = S{20};
auto high = S{30};
// Check that the value category of the projection return type is preserved.
assert(&std::ranges::clamp(val, low, high, Comp{}, &S::lvalue_proj) == &low);
assert(&std::ranges::clamp(val, high, low, Comp{}, &S::prvalue_proj) == &low);
}
{ // Check that the implementation doesn't cause double moves (which could result from calling the projection on
// `value` once and then forwarding the result into the comparator).
struct CheckDoubleMove {
int i;
bool moved = false;
constexpr explicit CheckDoubleMove(int set_i) : i(set_i) {}
constexpr CheckDoubleMove(const CheckDoubleMove&) = default;
constexpr CheckDoubleMove(CheckDoubleMove&& rhs) noexcept : i(rhs.i) {
assert(!rhs.moved);
rhs.moved = true;
}
};
auto val = CheckDoubleMove{20};
auto low = CheckDoubleMove{10};
auto high = CheckDoubleMove{30};
auto moving_comp = [](CheckDoubleMove lhs, CheckDoubleMove rhs) { return lhs.i < rhs.i; };
auto prvalue_proj = [](const CheckDoubleMove& x) -> CheckDoubleMove { return x; };
assert(&std::ranges::clamp(val, low, high, moving_comp, prvalue_proj) == &val);
}
return true;
}
int main(int, char**) {
test();
static_assert(test());
return 0;
}
|
