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 // UNSUPPORTED: libcpp-has-no-incomplete-ranges
11
12 // Some basic examples of how transform_view might be used in the wild. This is a general
13 // collection of sample algorithms and functions that try to mock general usage of
14 // this view.
15
16 #include <ranges>
17
18 #include <cctype>
19 #include <functional>
20 #include <list>
21 #include <numeric>
22 #include <string>
23 #include <vector>
24
25 #include <cassert>
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, 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 struct NonConstView : std::ranges::view_base {
NonConstViewNonConstView52 explicit NonConstView(int *b, int *e) : b_(b), e_(e) {}
beginNonConstView53 const int *begin() { return b_; } // deliberately non-const
endNonConstView54 const int *end() { return e_; } // deliberately non-const
55 const int *b_;
56 const int *e_;
57 };
58
main(int,char **)59 int main(int, char**) {
60 {
61 std::vector<int> vec = {1, 2, 3, 4};
62 auto transformed = std::ranges::transform_view(vec, [](int x) { return x + 42; });
63 int expected[] = {43, 44, 45, 46};
64 assert(std::equal(transformed.begin(), transformed.end(), expected, expected + 4));
65 const auto& ct = transformed;
66 assert(std::equal(ct.begin(), ct.end(), expected, expected + 4));
67 }
68
69 {
70 // Test a view type that is not const-iterable.
71 int a[] = {1, 2, 3, 4};
72 auto transformed = NonConstView(a, a + 4) | std::views::transform([](int x) { return x + 42; });
73 int expected[4] = {43, 44, 45, 46};
74 assert(std::equal(transformed.begin(), transformed.end(), expected, expected + 4));
75 }
76
77 {
78 int a[4] = {1, 2, 3, 4};
79 int b[4] = {4, 3, 2, 1};
80 auto out = joinArrays(a, b);
81 int check[4] = {5, 5, 5, 5};
82 assert(std::equal(out.begin(), out.end(), check, check + 4));
83 }
84
85 {
86 std::string_view str = "Hello, World.";
87 auto upp = toUpper(str);
88 std::string_view check = "HELLO, WORLD.";
89 assert(std::equal(upp.begin(), upp.end(), check.begin(), check.end()));
90 }
91
92 return 0;
93 }
94