v1/__algorithm/partition.h

0001 //===----------------------------------------------------------------------===//
0002 //
0003 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
0004 // See https://llvm.org/LICENSE.txt for license information.
0005 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
0006 //
0007 //===----------------------------------------------------------------------===//
0008
0009 #ifndef _LIBCPP___ALGORITHM_PARTITION_H
0010 #define _LIBCPP___ALGORITHM_PARTITION_H
0011
0012 #include <__algorithm/iterator_operations.h>
0013 #include <__config>
0014 #include <__iterator/iterator_traits.h>
0015 #include <__type_traits/remove_cvref.h>
0016 #include <__utility/move.h>
0017 #include <__utility/pair.h>
0018
0019 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
0020 #  pragma GCC system_header
0021 #endif
0022
0023 _LIBCPP_PUSH_MACROS
0024 #include <__undef_macros>
0025
0026 _LIBCPP_BEGIN_NAMESPACE_STD
0027
0028 template <class _Predicate, class _AlgPolicy, class _ForwardIterator, class _Sentinel>
0029 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 pair<_ForwardIterator, _ForwardIterator>
0030 __partition_impl(_ForwardIterator __first, _Sentinel __last, _Predicate __pred, forward_iterator_tag) {
0031   while (true) {
0032     if (__first == __last)
0033       return std::make_pair(__first, __first);
0034     if (!__pred(*__first))
0035       break;
0036     ++__first;
0037   }
0038
0039   _ForwardIterator __p = __first;
0040   while (++__p != __last) {
0041     if (__pred(*__p)) {
0042       _IterOps<_AlgPolicy>::iter_swap(__first, __p);
0043       ++__first;
0044     }
0045   }
0046   return std::make_pair(std::move(__first), std::move(__p));
0047 }
0048
0049 template <class _Predicate, class _AlgPolicy, class _BidirectionalIterator, class _Sentinel>
0050 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 pair<_BidirectionalIterator, _BidirectionalIterator>
0051 __partition_impl(_BidirectionalIterator __first, _Sentinel __sentinel, _Predicate __pred, bidirectional_iterator_tag) {
0052   _BidirectionalIterator __original_last = _IterOps<_AlgPolicy>::next(__first, __sentinel);
0053   _BidirectionalIterator __last          = __original_last;
0054
0055   while (true) {
0056     while (true) {
0057       if (__first == __last)
0058         return std::make_pair(std::move(__first), std::move(__original_last));
0059       if (!__pred(*__first))
0060         break;
0061       ++__first;
0062     }
0063     do {
0064       if (__first == --__last)
0065         return std::make_pair(std::move(__first), std::move(__original_last));
0066     } while (!__pred(*__last));
0067     _IterOps<_AlgPolicy>::iter_swap(__first, __last);
0068     ++__first;
0069   }
0070 }
0071
0072 template <class _AlgPolicy, class _ForwardIterator, class _Sentinel, class _Predicate, class _IterCategory>
0073 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 pair<_ForwardIterator, _ForwardIterator>
0074 __partition(_ForwardIterator __first, _Sentinel __last, _Predicate&& __pred, _IterCategory __iter_category) {
0075   return std::__partition_impl<__remove_cvref_t<_Predicate>&, _AlgPolicy>(
0076       std::move(__first), std::move(__last), __pred, __iter_category);
0077 }
0078
0079 template <class _ForwardIterator, class _Predicate>
0080 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _ForwardIterator
0081 partition(_ForwardIterator __first, _ForwardIterator __last, _Predicate __pred) {
0082   using _IterCategory = typename iterator_traits<_ForwardIterator>::iterator_category;
0083   auto __result = std::__partition<_ClassicAlgPolicy>(std::move(__first), std::move(__last), __pred, _IterCategory());
0084   return __result.first;
0085 }
0086
0087 _LIBCPP_END_NAMESPACE_STD
0088
0089 _LIBCPP_POP_MACROS
0090
0091 #endif // _LIBCPP___ALGORITHM_PARTITION_H