libcxx/include/__algorithm/partition.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_PARTITION_H
  10 #define _LIBCPP___ALGORITHM_PARTITION_H
  11
  12 #include <__algorithm/iterator_operations.h>
  13 #include <__config>
  14 #include <__iterator/iterator_traits.h>
  15 #include <__utility/move.h>
  16 #include <__utility/pair.h>
  17
  18 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  19 #  pragma GCC system_header
  20 #endif
  21
  22 _LIBCPP_BEGIN_NAMESPACE_STD
  23
  24 template <class _Predicate, class _AlgPolicy, class _ForwardIterator, class _Sentinel>
  25 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 pair<_ForwardIterator, _ForwardIterator>
  26 __partition_impl(_ForwardIterator __first, _Sentinel __last, _Predicate __pred, forward_iterator_tag)
  27 {
  28     while (true)
  29     {
  30         if (__first == __last)
  31             return std::make_pair(std::move(__first), std::move(__first));
  32         if (!__pred(*__first))
  33             break;
  34         ++__first;
  35     }
  36
  37     _ForwardIterator __p = __first;
  38     while (++__p != __last)
  39     {
  40         if (__pred(*__p))
  41         {
  42             _IterOps<_AlgPolicy>::iter_swap(__first, __p);
  43             ++__first;
  44         }
  45     }
  46     return std::make_pair(std::move(__first), std::move(__p));
  47 }
  48
  49 template <class _Predicate, class _AlgPolicy, class _BidirectionalIterator, class _Sentinel>
  50 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 pair<_BidirectionalIterator, _BidirectionalIterator>
  51 __partition_impl(_BidirectionalIterator __first, _Sentinel __sentinel, _Predicate __pred,
  52             bidirectional_iterator_tag)
  53 {
  54     _BidirectionalIterator __original_last = _IterOps<_AlgPolicy>::next(__first, __sentinel);
  55     _BidirectionalIterator __last = __original_last;
  56
  57     while (true)
  58     {
  59         while (true)
  60         {
  61             if (__first == __last)
  62                 return std::make_pair(std::move(__first), std::move(__original_last));
  63             if (!__pred(*__first))
  64                 break;
  65             ++__first;
  66         }
  67         do
  68         {
  69             if (__first == --__last)
  70                 return std::make_pair(std::move(__first), std::move(__original_last));
  71         } while (!__pred(*__last));
  72         _IterOps<_AlgPolicy>::iter_swap(__first, __last);
  73         ++__first;
  74     }
  75 }
  76
  77 template <class _AlgPolicy, class _ForwardIterator, class _Sentinel, class _Predicate, class _IterCategory>
  78 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20
  79 pair<_ForwardIterator, _ForwardIterator> __partition(
  80     _ForwardIterator __first, _Sentinel __last, _Predicate&& __pred, _IterCategory __iter_category) {
  81   return std::__partition_impl<__remove_cvref_t<_Predicate>&, _AlgPolicy>(
  82       std::move(__first), std::move(__last), __pred, __iter_category);
  83 }
  84
  85 template <class _ForwardIterator, class _Predicate>
  86 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX20
  87 _ForwardIterator
  88 partition(_ForwardIterator __first, _ForwardIterator __last, _Predicate __pred)
  89 {
  90   using _IterCategory = typename iterator_traits<_ForwardIterator>::iterator_category;
  91   auto __result = std::__partition<_ClassicAlgPolicy>(std::move(__first), std::move(__last), __pred, _IterCategory());
  92   return __result.first;
  93 }
  94
  95 _LIBCPP_END_NAMESPACE_STD
  96
  97 #endif // _LIBCPP___ALGORITHM_PARTITION_H