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 <__ranges/dangling.h>
22 #include <__utility/move.h>
23 
24 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
25 #  pragma GCC system_header
26 #endif
27 
28 #if _LIBCPP_STD_VER > 17 && !defined(_LIBCPP_HAS_NO_INCOMPLETE_RANGES)
29 
30 _LIBCPP_BEGIN_NAMESPACE_STD
31 
32 namespace ranges {
33 
34 template <class _Iter, class _Func>
35 using for_each_n_result = in_fun_result<_Iter, _Func>;
36 
37 namespace __for_each_n {
38 struct __fn {
39 
40   template <input_iterator _Iter,
41             class _Proj = identity,
42             indirectly_unary_invocable<projected<_Iter, _Proj>> _Func>
43   _LIBCPP_HIDE_FROM_ABI constexpr
44   for_each_n_result<_Iter, _Func> operator()(_Iter __first,
45                                              iter_difference_t<_Iter> __count,
46                                              _Func __func,
47                                              _Proj __proj = {}) const {
48     while (__count-- > 0) {
49       std::invoke(__func, std::invoke(__proj, *__first));
50       ++__first;
51     }
52     return {std::move(__first), std::move(__func)};
53   }
54 
55 };
56 } // namespace __for_each_n
57 
58 inline namespace __cpo {
59   inline constexpr auto for_each_n = __for_each_n::__fn{};
60 } // namespace __cpo
61 } // namespace ranges
62 
63 _LIBCPP_END_NAMESPACE_STD
64 
65 #endif // _LIBCPP_STD_VER > 17 && !defined(_LIBCPP_HAS_NO_INCOMPLETE_RANGES)
66 
67 #endif // _LIBCPP___ALGORITHM_RANGES_FOR_EACH_N_H
68