v1/__algorithm/partition_point.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_POINT_H
0010 #define _LIBCPP___ALGORITHM_PARTITION_POINT_H
0011
0012 #include <__algorithm/half_positive.h>
0013 #include <__config>
0014 #include <__iterator/advance.h>
0015 #include <__iterator/distance.h>
0016 #include <__iterator/iterator_traits.h>
0017
0018 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
0019 #  pragma GCC system_header
0020 #endif
0021
0022 _LIBCPP_BEGIN_NAMESPACE_STD
0023
0024 template <class _ForwardIterator, class _Predicate>
0025 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _ForwardIterator
0026 partition_point(_ForwardIterator __first, _ForwardIterator __last, _Predicate __pred) {
0027   typedef typename iterator_traits<_ForwardIterator>::difference_type difference_type;
0028   difference_type __len = std::distance(__first, __last);
0029   while (__len != 0) {
0030     difference_type __l2 = std::__half_positive(__len);
0031     _ForwardIterator __m = __first;
0032     std::advance(__m, __l2);
0033     if (__pred(*__m)) {
0034       __first = ++__m;
0035       __len -= __l2 + 1;
0036     } else
0037       __len = __l2;
0038   }
0039   return __first;
0040 }
0041
0042 _LIBCPP_END_NAMESPACE_STD
0043
0044 #endif // _LIBCPP___ALGORITHM_PARTITION_POINT_H