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 // Some basic examples of how transform_view might be used in the wild. This is a general
12 // collection of sample algorithms and functions that try to mock general usage of
13 // this view.
14
15 #include <ranges>
16
17 #include <cctype>
18 #include <functional>
19 #include <list>
20 #include <numeric>
21 #include <string>
22 #include <vector>
23
24 #include <cassert>
25 #include "MoveOnly.h"
26 #include "test_macros.h"
27 #include "test_iterators.h"
28 #include "types.h"
29
30 template<class T, class F>
31 concept ValidTransformView = requires { typename std::ranges::transform_view<T, F>; };
32
33 struct BadFunction { };
34 static_assert( ValidTransformView<MoveOnlyView, PlusOne>);
35 static_assert(!ValidTransformView<Range, PlusOne>);
36 static_assert(!ValidTransformView<MoveOnlyView, BadFunction>);
37
38 template<std::ranges::range R>
toUpper(R range)39 auto toUpper(R range) {
40 return std::ranges::transform_view(range, [](char c) { return std::toupper(c); });
41 }
42
43 template<class E1, class E2, std::size_t N, class Join = std::plus<E1>>
joinArrays(E1 (& a)[N],E2 (& b)[N],Join join=Join ())44 auto joinArrays(E1 (&a)[N], E2 (&b)[N], Join join = Join()) {
45 return std::ranges::transform_view(a, [&a, &b, join](auto& x) {
46 auto idx = (&x) - a;
47 return join(x, b[idx]);
48 });
49 }
50
51 #if _LIBCPP_STD_VER >= 23
52 struct MoveOnlyFunction : public MoveOnly {
53 template <class T>
operator ()MoveOnlyFunction54 constexpr T operator()(T x) const {
55 return x + 42;
56 }
57 };
58 #endif
59
60 struct NonConstView : std::ranges::view_base {
NonConstViewNonConstView61 explicit NonConstView(int *b, int *e) : b_(b), e_(e) {}
beginNonConstView62 const int *begin() { return b_; } // deliberately non-const
endNonConstView63 const int *end() { return e_; } // deliberately non-const
64 const int *b_;
65 const int *e_;
66 };
67
main(int,char **)68 int main(int, char**) {
69 {
70 std::vector<int> vec = {1, 2, 3, 4};
71 auto transformed = std::ranges::transform_view(vec, [](int x) { return x + 42; });
72 int expected[] = {43, 44, 45, 46};
73 assert(std::equal(transformed.begin(), transformed.end(), expected, expected + 4));
74 const auto& ct = transformed;
75 assert(std::equal(ct.begin(), ct.end(), expected, expected + 4));
76 }
77
78 {
79 // Test a view type that is not const-iterable.
80 int a[] = {1, 2, 3, 4};
81 auto transformed = NonConstView(a, a + 4) | std::views::transform([](int x) { return x + 42; });
82 int expected[4] = {43, 44, 45, 46};
83 assert(std::equal(transformed.begin(), transformed.end(), expected, expected + 4));
84 }
85
86 {
87 int a[4] = {1, 2, 3, 4};
88 int b[4] = {4, 3, 2, 1};
89 auto out = joinArrays(a, b);
90 int check[4] = {5, 5, 5, 5};
91 assert(std::equal(out.begin(), out.end(), check, check + 4));
92 }
93
94 {
95 std::string_view str = "Hello, World.";
96 auto upp = toUpper(str);
97 std::string_view check = "HELLO, WORLD.";
98 assert(std::equal(upp.begin(), upp.end(), check.begin(), check.end()));
99 }
100 #if _LIBCPP_STD_VER >= 23
101 // [P2494R2] Relaxing range adaptors to allow for move only types.
102 // Test transform_view is valid when the function object is a move only type.
103 {
104 int a[] = {1, 2, 3, 4};
105 auto transformed = NonConstView(a, a + 4) | std::views::transform(MoveOnlyFunction());
106 int expected[] = {43, 44, 45, 46};
107 assert(std::equal(transformed.begin(), transformed.end(), expected, expected + 4));
108 }
109 #endif
110
111 // GH issue #70506
112 // movable_box::operator= overwrites underlying view
113 {
114 auto f = [l = 0.0L, b = false](int i) {
115 (void)l;
116 (void)b;
117 return i;
118 };
119
120 auto v1 = std::vector{1, 2, 3, 4} | std::views::transform(f);
121 auto v2 = std::vector{1, 2, 3, 4} | std::views::transform(f);
122
123 v1 = std::move(v2);
124 int expected[] = {1, 2, 3, 4};
125 assert(std::equal(v1.begin(), v1.end(), expected, expected + 4));
126 }
127
128 return 0;
129 }
130