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 // std::views::lazy_split
13 
14 #include <ranges>
15 
16 #include <array>
17 #include <cassert>
18 #include <concepts>
19 #include <string_view>
20 #include <utility>
21 
22 #include "test_iterators.h"
23 #include "types.h"
24 
25 template <class View, class T>
26 concept CanBePiped = requires (View&& view, T&& t) {
27   { std::forward<View>(view) | std::forward<T>(t) };
28 };
29 
30 struct SomeView : std::ranges::view_base {
31   const std::string_view* v_;
32   constexpr SomeView(const std::string_view& v) : v_(&v) {}
33   constexpr auto begin() const { return v_->begin(); }
34   constexpr auto end() const { return v_->end(); }
35 };
36 
37 struct NotAView { };
38 
39 static_assert(!std::is_invocable_v<decltype(std::views::lazy_split)>);
40 static_assert(!std::is_invocable_v<decltype(std::views::lazy_split), SomeView, NotAView>);
41 static_assert(!std::is_invocable_v<decltype(std::views::lazy_split), NotAView, SomeView>);
42 static_assert( std::is_invocable_v<decltype(std::views::lazy_split), SomeView, SomeView>);
43 
44 static_assert( CanBePiped<SomeView&,    decltype(std::views::lazy_split)>);
45 static_assert( CanBePiped<char(&)[10],  decltype(std::views::lazy_split)>);
46 static_assert(!CanBePiped<char(&&)[10], decltype(std::views::lazy_split)>);
47 static_assert(!CanBePiped<NotAView,     decltype(std::views::lazy_split)>);
48 
49 static_assert(std::same_as<decltype(std::views::lazy_split), decltype(std::ranges::views::lazy_split)>);
50 
51 constexpr bool test() {
52   std::string_view input = "abc";
53   std::string_view sep = "a";
54 
55   // Test that `std::views::lazy_split` is a range adaptor.
56 
57   // Test `views::lazy_split(input, sep)`.
58   {
59     SomeView view(input);
60 
61     using Result = std::ranges::lazy_split_view<SomeView, std::string_view>;
62     std::same_as<Result> decltype(auto) result = std::views::lazy_split(view, sep);
63     assert(result.base().begin() == input.begin());
64     assert(result.base().end() == input.end());
65   }
66 
67   // Test `views::lazy_split(sep)(input)`.
68   {
69     SomeView view(input);
70 
71     using Result = std::ranges::lazy_split_view<SomeView, std::string_view>;
72     std::same_as<Result> decltype(auto) result = std::views::lazy_split(sep)(view);
73     assert(result.base().begin() == input.begin());
74     assert(result.base().end() == input.end());
75   }
76 
77   // Test `view | views::lazy_split`.
78   {
79     SomeView view(input);
80 
81     using Result = std::ranges::lazy_split_view<SomeView, std::string_view>;
82     std::same_as<Result> decltype(auto) result = view | std::views::lazy_split(sep);
83     assert(result.base().begin() == input.begin());
84     assert(result.base().end() == input.end());
85   }
86 
87   // Test `adaptor | views::lazy_split`.
88   {
89     SomeView view(input);
90     auto f = [](char c) { return c; };
91     auto partial = std::views::transform(f) | std::views::lazy_split(sep);
92 
93     using Result = std::ranges::lazy_split_view<std::ranges::transform_view<SomeView, decltype(f)>, std::string_view>;
94     std::same_as<Result> decltype(auto) result = partial(view);
95     assert(result.base().base().begin() == input.begin());
96     assert(result.base().base().end() == input.end());
97   }
98 
99   // Test `views::lazy_split | adaptor`.
100   {
101     SomeView view(input);
102     auto f = [](auto v) { return v; };
103     auto partial = std::views::lazy_split(sep) | std::views::transform(f);
104 
105     using Result = std::ranges::transform_view<std::ranges::lazy_split_view<SomeView, std::string_view>, decltype(f)>;
106     std::same_as<Result> decltype(auto) result = partial(view);
107     assert(result.base().base().begin() == input.begin());
108     assert(result.base().base().end() == input.end());
109   }
110 
111   // Test that one can call `std::views::lazy_split` with arbitrary stuff, as long as we
112   // don't try to actually complete the call by passing it a range.
113   //
114   // That makes no sense and we can't do anything with the result, but it's valid.
115   {
116     struct X { };
117     [[maybe_unused]] auto partial = std::views::lazy_split(X{});
118   }
119 
120   return true;
121 }
122 
123 int main(int, char**) {
124   test();
125   static_assert(test());
126 
127   return 0;
128 }
129