libcxx/include/__algorithm/ranges_generate_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_GENERATE_N_H
  10 #define _LIBCPP___ALGORITHM_RANGES_GENERATE_N_H
  11
  12 #include <__concepts/constructible.h>
  13 #include <__concepts/invocable.h>
  14 #include <__config>
  15 #include <__functional/identity.h>
  16 #include <__functional/invoke.h>
  17 #include <__iterator/concepts.h>
  18 #include <__iterator/incrementable_traits.h>
  19 #include <__iterator/iterator_traits.h>
  20 #include <__ranges/access.h>
  21 #include <__ranges/concepts.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 >= 20
  29
  30 _LIBCPP_BEGIN_NAMESPACE_STD
  31
  32 namespace ranges {
  33 namespace __generate_n {
  34
  35 struct __fn {
  36   template <input_or_output_iterator _OutIter, copy_constructible _Func>
  37     requires invocable<_Func&> && indirectly_writable<_OutIter, invoke_result_t<_Func&>>
  38   _LIBCPP_HIDE_FROM_ABI constexpr _OutIter
  39   operator()(_OutIter __first, iter_difference_t<_OutIter> __n, _Func __gen) const {
  40     for (; __n > 0; --__n) {
  41       *__first = __gen();
  42       ++__first;
  43     }
  44
  45     return __first;
  46   }
  47 };
  48
  49 } // namespace __generate_n
  50
  51 inline namespace __cpo {
  52 inline constexpr auto generate_n = __generate_n::__fn{};
  53 } // namespace __cpo
  54 } // namespace ranges
  55
  56 _LIBCPP_END_NAMESPACE_STD
  57
  58 #endif // _LIBCPP_STD_VER >= 20
  59
  60 #endif // _LIBCPP___ALGORITHM_RANGES_GENERATE_N_H