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
30template<class T, class F>
31concept ValidTransformView = requires { typename std::ranges::transform_view<T, F>; };
32
33struct BadFunction { };
34static_assert( ValidTransformView<MoveOnlyView, PlusOne>);
35static_assert(!ValidTransformView<Range, PlusOne>);
36static_assert(!ValidTransformView<MoveOnlyView, BadFunction>);
37
38template<std::ranges::range R>
39auto toUpper(R range) {
40 return std::ranges::transform_view(range, [](char c) { return std::toupper(c); });
41}
42
43template<class E1, class E2, std::size_t N, class Join = std::plus<E1>>
44auto 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
52struct MoveOnlyFunction : public MoveOnly {
53 template <class T>
54 constexpr T operator()(T x) const {
55 return x + 42;
56 }
57};
58#endif
59
60struct NonConstView : std::ranges::view_base {
61 explicit NonConstView(int *b, int *e) : b_(b), e_(e) {}
62 const int *begin() { return b_; } // deliberately non-const
63 const int *end() { return e_; } // deliberately non-const
64 const int *b_;
65 const int *e_;
66};
67
68int 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

source code of libcxx/test/std/ranges/range.adaptors/range.transform/general.pass.cpp