// -*- C++ -*-
//===----------------------------------------------------------------------===//
//
// Part of libcu++, the C++ Standard Library for your entire system,
// 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
// SPDX-FileCopyrightText: Copyright (c) 2024 NVIDIA CORPORATION & AFFILIATES.
//
//===----------------------------------------------------------------------===//

#ifndef _LIBCUDACXX___NUMERIC_ADJACENT_DIFFERENCE_H
#define _LIBCUDACXX___NUMERIC_ADJACENT_DIFFERENCE_H

#include <cuda/std/detail/__config>

#if defined(_CCCL_IMPLICIT_SYSTEM_HEADER_GCC)
#  pragma GCC system_header
#elif defined(_CCCL_IMPLICIT_SYSTEM_HEADER_CLANG)
#  pragma clang system_header
#elif defined(_CCCL_IMPLICIT_SYSTEM_HEADER_MSVC)
#  pragma system_header
#endif // no system header

#include <cuda/std/__iterator/iterator_traits.h>
#include <cuda/std/__utility/move.h>

_LIBCUDACXX_BEGIN_NAMESPACE_STD

template <class _InputIterator, class _OutputIterator>
_LIBCUDACXX_HIDE_FROM_ABI constexpr _OutputIterator
adjacent_difference(_InputIterator __first, _InputIterator __last, _OutputIterator __result)
{
  if (__first != __last)
  {
    typename iterator_traits<_InputIterator>::value_type __acc(*__first);
    *__result = __acc;
    for (++__first, (void) ++__result; __first != __last; ++__first, (void) ++__result)
    {
      typename iterator_traits<_InputIterator>::value_type __val(*__first);
      *__result = __val - _CUDA_VSTD::move(__acc);
      __acc     = _CUDA_VSTD::move(__val);
    }
  }
  return __result;
}

template <class _InputIterator, class _OutputIterator, class _BinaryOperation>
_LIBCUDACXX_HIDE_FROM_ABI constexpr _OutputIterator adjacent_difference(
  _InputIterator __first, _InputIterator __last, _OutputIterator __result, _BinaryOperation __binary_op)
{
  if (__first != __last)
  {
    typename iterator_traits<_InputIterator>::value_type __acc(*__first);
    *__result = __acc;
    for (++__first, (void) ++__result; __first != __last; ++__first, (void) ++__result)
    {
      typename iterator_traits<_InputIterator>::value_type __val(*__first);
      *__result = __binary_op(__val, _CUDA_VSTD::move(__acc));
      __acc     = _CUDA_VSTD::move(__val);
    }
  }
  return __result;
}

_LIBCUDACXX_END_NAMESPACE_STD

#endif // _LIBCUDACXX___NUMERIC_ADJACENT_DIFFERENCE_H
