libcxx/include/__algorithm/ranges_for_each_n.h

   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 _LIBCPP_PUSH_MACROS
  28 #include <__undef_macros>
  29
  30 #if _LIBCPP_STD_VER >= 20
  31
  32 _LIBCPP_BEGIN_NAMESPACE_STD
  33
  34 namespace ranges {
  35
  36 template <class _Iter, class _Func>
  37 using for_each_n_result = in_fun_result<_Iter, _Func>;
  38
  39 namespace __for_each_n {
  40 struct __fn {
  41   template <input_iterator _Iter, class _Proj = identity, indirectly_unary_invocable<projected<_Iter, _Proj>> _Func>
  42   _LIBCPP_HIDE_FROM_ABI constexpr for_each_n_result<_Iter, _Func>
  43   operator()(_Iter __first, iter_difference_t<_Iter> __count, _Func __func, _Proj __proj = {}) const {
  44     while (__count-- > 0) {
  45       std::invoke(__func, std::invoke(__proj, *__first));
  46       ++__first;
  47     }
  48     return {std::move(__first), std::move(__func)};
  49   }
  50 };
  51 } // namespace __for_each_n
  52
  53 inline namespace __cpo {
  54 inline constexpr auto for_each_n = __for_each_n::__fn{};
  55 } // namespace __cpo
  56 } // namespace ranges
  57
  58 _LIBCPP_END_NAMESPACE_STD
  59
  60 #endif // _LIBCPP_STD_VER >= 20
  61
  62 _LIBCPP_POP_MACROS
  63
  64 #endif // _LIBCPP___ALGORITHM_RANGES_FOR_EACH_N_H