libcxx/include/__algorithm/partition_point.h

//===----------------------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//

#ifndef _LIBCPP___ALGORITHM_PARTITION_POINT_H
#define _LIBCPP___ALGORITHM_PARTITION_POINT_H

#include <__algorithm/half_positive.h>
#include <__config>
#include <__iterator/advance.h>
#include <__iterator/distance.h>
#include <__iterator/iterator_traits.h>

#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
#  pragma GCC system_header
#endif

_LIBCPP_BEGIN_NAMESPACE_STD

template <class _ForwardIterator, class _Predicate>
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _ForwardIterator
partition_point(_ForwardIterator __first, _ForwardIterator __last, _Predicate __pred) {
  typedef typename iterator_traits<_ForwardIterator>::difference_type difference_type;
  difference_type __len = std::distance(__first, __last);
  while (__len != 0) {
    difference_type __l2 = std::__half_positive(__len);
    _ForwardIterator __m = __first;
    std::advance(__m, __l2);
    if (__pred(*__m)) {
      __first = ++__m;
      __len -= __l2 + 1;
    } else
      __len = __l2;
  }
  return __first;
}

_LIBCPP_END_NAMESPACE_STD

#endif // _LIBCPP___ALGORITHM_PARTITION_POINT_H