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: gcc-10
12 // UNSUPPORTED: libcpp-has-no-incomplete-ranges
13 
14 // Some basic examples of how transform_view might be used in the wild. This is a general
15 // collection of sample algorithms and functions that try to mock general usage of
16 // this view.
17 
18 #include <ranges>
19 
20 #include <cctype>
21 #include <functional>
22 #include <list>
23 #include <numeric>
24 #include <string>
25 #include <vector>
26 
27 #include <cassert>
28 #include "test_macros.h"
29 #include "test_iterators.h"
30 #include "types.h"
31 
32 template<class T, class F>
33 concept ValidTransformView = requires { typename std::ranges::transform_view<T, F>; };
34 
35 struct BadFunction { };
36 static_assert( ValidTransformView<ContiguousView, Increment>);
37 static_assert(!ValidTransformView<Range, Increment>);
38 static_assert(!ValidTransformView<ContiguousView, BadFunction>);
39 
40 template<std::ranges::range R>
41 auto toUpper(R range) {
42   return std::ranges::transform_view(range, [](char c) { return std::toupper(c); });
43 }
44 
45 unsigned badRandom() { return 42; }
46 
47 template<std::ranges::range R, class Fn = std::plus<std::iter_value_t<R>>>
48 auto withRandom(R&& range, Fn func = Fn()) {
49   return std::ranges::transform_view(range, std::bind_front(func, badRandom()));
50 }
51 
52 template<class E1, class E2, size_t N, class Join = std::plus<E1>>
53 auto joinArrays(E1 (&a)[N], E2 (&b)[N], Join join = Join()) {
54   return std::ranges::transform_view(a, [&a, &b, join](auto& x) {
55     auto idx = (&x) - a;
56     return join(x, b[idx]);
57   });
58 }
59 
60 int main(int, char**) {
61   {
62     std::vector vec = {1, 2, 3, 4};
63     auto sortOfRandom = withRandom(vec);
64     std::vector check = {43, 44, 45, 46};
65     assert(std::equal(sortOfRandom.begin(), sortOfRandom.end(), check.begin(), check.end()));
66   }
67 
68   {
69     int a[4] = {1, 2, 3, 4};
70     int b[4] = {4, 3, 2, 1};
71     auto out = joinArrays(a, b);
72     int check[4] = {5, 5, 5, 5};
73     assert(std::equal(out.begin(), out.end(), check));
74   }
75 
76   {
77     std::string_view str = "Hello, World.";
78     auto upp = toUpper(str);
79     std::string_view check = "HELLO, WORLD.";
80     assert(std::equal(upp.begin(), upp.end(), check.begin(), check.end()));
81   }
82 
83   return 0;
84 }
85