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-no-concepts
11 // UNSUPPORTED: libcpp-has-no-incomplete-ranges
12 
13 // Some basic examples of how transform_view might be used in the wild. This is a general
14 // collection of sample algorithms and functions that try to mock general usage of
15 // this view.
16 
17 #include <ranges>
18 
19 #include <cctype>
20 #include <functional>
21 #include <list>
22 #include <numeric>
23 #include <string>
24 #include <vector>
25 
26 #include <cassert>
27 #include "test_macros.h"
28 #include "test_iterators.h"
29 #include "types.h"
30 
31 template<class T, class F>
32 concept ValidTransformView = requires { typename std::ranges::transform_view<T, F>; };
33 
34 struct BadFunction { };
35 static_assert( ValidTransformView<MoveOnlyView, PlusOne>);
36 static_assert(!ValidTransformView<Range, PlusOne>);
37 static_assert(!ValidTransformView<MoveOnlyView, BadFunction>);
38 
39 template<std::ranges::range R>
40 auto toUpper(R range) {
41   return std::ranges::transform_view(range, [](char c) { return std::toupper(c); });
42 }
43 
44 unsigned badRandom() { return 42; }
45 
46 template<std::ranges::range R, class Fn = std::plus<std::iter_value_t<R>>>
47 auto withRandom(R&& range, Fn func = Fn()) {
48   return std::ranges::transform_view(range, std::bind_front(func, badRandom()));
49 }
50 
51 template<class E1, class E2, size_t N, class Join = std::plus<E1>>
52 auto joinArrays(E1 (&a)[N], E2 (&b)[N], Join join = Join()) {
53   return std::ranges::transform_view(a, [&a, &b, join](auto& x) {
54     auto idx = (&x) - a;
55     return join(x, b[idx]);
56   });
57 }
58 
59 int main(int, char**) {
60   {
61     std::vector vec = {1, 2, 3, 4};
62     auto sortOfRandom = withRandom(vec);
63     std::vector check = {43, 44, 45, 46};
64     assert(std::equal(sortOfRandom.begin(), sortOfRandom.end(), check.begin(), check.end()));
65   }
66 
67   {
68     int a[4] = {1, 2, 3, 4};
69     int b[4] = {4, 3, 2, 1};
70     auto out = joinArrays(a, b);
71     int check[4] = {5, 5, 5, 5};
72     assert(std::equal(out.begin(), out.end(), check));
73   }
74 
75   {
76     std::string_view str = "Hello, World.";
77     auto upp = toUpper(str);
78     std::string_view check = "HELLO, WORLD.";
79     assert(std::equal(upp.begin(), upp.end(), check.begin(), check.end()));
80   }
81 
82   return 0;
83 }
84