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 #ifndef _LIBCPP___ALGORITHM_RANGES_FOR_EACH_N_H
10 #define _LIBCPP___ALGORITHM_RANGES_FOR_EACH_N_H
11 
12 #include <__algorithm/in_fun_result.h>
13 #include <__config>
14 #include <__functional/identity.h>
15 #include <__functional/invoke.h>
16 #include <__iterator/concepts.h>
17 #include <__iterator/incrementable_traits.h>
18 #include <__iterator/iterator_traits.h>
19 #include <__iterator/projected.h>
20 #include <__ranges/concepts.h>
21 #include <__utility/move.h>
22 
23 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
24 #  pragma GCC system_header
25 #endif
26 
27 #if _LIBCPP_STD_VER >= 20
28 
29 _LIBCPP_BEGIN_NAMESPACE_STD
30 
31 namespace ranges {
32 
33 template <class _Iter, class _Func>
34 using for_each_n_result = in_fun_result<_Iter, _Func>;
35 
36 namespace __for_each_n {
37 struct __fn {
38   template <input_iterator _Iter, class _Proj = identity, indirectly_unary_invocable<projected<_Iter, _Proj>> _Func>
39   _LIBCPP_HIDE_FROM_ABI constexpr for_each_n_result<_Iter, _Func>
40   operator()(_Iter __first, iter_difference_t<_Iter> __count, _Func __func, _Proj __proj = {}) const {
41     while (__count-- > 0) {
42       std::invoke(__func, std::invoke(__proj, *__first));
43       ++__first;
44     }
45     return {std::move(__first), std::move(__func)};
46   }
47 };
48 } // namespace __for_each_n
49 
50 inline namespace __cpo {
51 inline constexpr auto for_each_n = __for_each_n::__fn{};
52 } // namespace __cpo
53 } // namespace ranges
54 
55 _LIBCPP_END_NAMESPACE_STD
56 
57 #endif // _LIBCPP_STD_VER >= 20
58 
59 #endif // _LIBCPP___ALGORITHM_RANGES_FOR_EACH_N_H
60