libcxx/include/__algorithm/ranges_merge.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_MERGE_H
  10 #define _LIBCPP___ALGORITHM_RANGES_MERGE_H
  11
  12 #include <__algorithm/in_in_out_result.h>
  13 #include <__algorithm/ranges_copy.h>
  14 #include <__config>
  15 #include <__functional/identity.h>
  16 #include <__functional/invoke.h>
  17 #include <__functional/ranges_operations.h>
  18 #include <__iterator/concepts.h>
  19 #include <__iterator/mergeable.h>
  20 #include <__ranges/access.h>
  21 #include <__ranges/concepts.h>
  22 #include <__ranges/dangling.h>
  23 #include <__type_traits/remove_cvref.h>
  24 #include <__utility/move.h>
  25
  26 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  27 #  pragma GCC system_header
  28 #endif
  29
  30 #if _LIBCPP_STD_VER >= 20
  31
  32 _LIBCPP_BEGIN_NAMESPACE_STD
  33
  34 namespace ranges {
  35
  36 template <class _InIter1, class _InIter2, class _OutIter>
  37 using merge_result = in_in_out_result<_InIter1, _InIter2, _OutIter>;
  38
  39 namespace __merge {
  40
  41 template < class _InIter1,
  42            class _Sent1,
  43            class _InIter2,
  44            class _Sent2,
  45            class _OutIter,
  46            class _Comp,
  47            class _Proj1,
  48            class _Proj2>
  49 _LIBCPP_HIDE_FROM_ABI constexpr merge_result<__remove_cvref_t<_InIter1>,
  50                                              __remove_cvref_t<_InIter2>,
  51                                              __remove_cvref_t<_OutIter>>
  52 __merge_impl(_InIter1&& __first1,
  53              _Sent1&& __last1,
  54              _InIter2&& __first2,
  55              _Sent2&& __last2,
  56              _OutIter&& __result,
  57              _Comp&& __comp,
  58              _Proj1&& __proj1,
  59              _Proj2&& __proj2) {
  60   for (; __first1 != __last1 && __first2 != __last2; ++__result) {
  61     if (std::invoke(__comp, std::invoke(__proj2, *__first2), std::invoke(__proj1, *__first1))) {
  62       *__result = *__first2;
  63       ++__first2;
  64     } else {
  65       *__result = *__first1;
  66       ++__first1;
  67     }
  68   }
  69   auto __ret1 = ranges::copy(std::move(__first1), std::move(__last1), std::move(__result));
  70   auto __ret2 = ranges::copy(std::move(__first2), std::move(__last2), std::move(__ret1.out));
  71   return {std::move(__ret1.in), std::move(__ret2.in), std::move(__ret2.out)};
  72 }
  73
  74 struct __fn {
  75   template <input_iterator _InIter1,
  76             sentinel_for<_InIter1> _Sent1,
  77             input_iterator _InIter2,
  78             sentinel_for<_InIter2> _Sent2,
  79             weakly_incrementable _OutIter,
  80             class _Comp  = less,
  81             class _Proj1 = identity,
  82             class _Proj2 = identity>
  83     requires mergeable<_InIter1, _InIter2, _OutIter, _Comp, _Proj1, _Proj2>
  84   _LIBCPP_HIDE_FROM_ABI constexpr merge_result<_InIter1, _InIter2, _OutIter> operator()(
  85       _InIter1 __first1,
  86       _Sent1 __last1,
  87       _InIter2 __first2,
  88       _Sent2 __last2,
  89       _OutIter __result,
  90       _Comp __comp   = {},
  91       _Proj1 __proj1 = {},
  92       _Proj2 __proj2 = {}) const {
  93     return __merge::__merge_impl(__first1, __last1, __first2, __last2, __result, __comp, __proj1, __proj2);
  94   }
  95
  96   template <input_range _Range1,
  97             input_range _Range2,
  98             weakly_incrementable _OutIter,
  99             class _Comp  = less,
 100             class _Proj1 = identity,
 101             class _Proj2 = identity>
 102     requires mergeable<iterator_t<_Range1>, iterator_t<_Range2>, _OutIter, _Comp, _Proj1, _Proj2>
 103   _LIBCPP_HIDE_FROM_ABI constexpr merge_result<borrowed_iterator_t<_Range1>, borrowed_iterator_t<_Range2>, _OutIter>
 104   operator()(_Range1&& __range1,
 105              _Range2&& __range2,
 106              _OutIter __result,
 107              _Comp __comp   = {},
 108              _Proj1 __proj1 = {},
 109              _Proj2 __proj2 = {}) const {
 110     return __merge::__merge_impl(
 111         ranges::begin(__range1),
 112         ranges::end(__range1),
 113         ranges::begin(__range2),
 114         ranges::end(__range2),
 115         __result,
 116         __comp,
 117         __proj1,
 118         __proj2);
 119   }
 120 };
 121
 122 } // namespace __merge
 123
 124 inline namespace __cpo {
 125 inline constexpr auto merge = __merge::__fn{};
 126 } // namespace __cpo
 127 } // namespace ranges
 128
 129 _LIBCPP_END_NAMESPACE_STD
 130
 131 #endif // _LIBCPP_STD_VER >= 20
 132
 133 #endif // _LIBCPP___ALGORITHM_RANGES_MERGE_H