// -*- C++ -*-
//===----------------------------------------------------------------------===//
//
// 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___NUMERIC_ADJACENT_DIFFERENCE_H
#define _LIBCPP___NUMERIC_ADJACENT_DIFFERENCE_H

#include <__config>
#include <__iterator/iterator_traits.h>
#include <__utility/move.h>

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

_LIBCPP_BEGIN_NAMESPACE_STD

template <class _InputIterator, class _OutputIterator>
_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX20
_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);
#if _LIBCPP_STD_VER >= 20
            *__result = __val - _VSTD::move(__acc);
#else
            *__result = __val - __acc;
#endif
            __acc = _VSTD::move(__val);
        }
    }
    return __result;
}

template <class _InputIterator, class _OutputIterator, class _BinaryOperation>
_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX20
_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);
#if _LIBCPP_STD_VER >= 20
            *__result = __binary_op(__val, _VSTD::move(__acc));
#else
            *__result = __binary_op(__val, __acc);
#endif
            __acc = _VSTD::move(__val);
        }
    }
    return __result;
}

_LIBCPP_END_NAMESPACE_STD

#endif // _LIBCPP___NUMERIC_ADJACENT_DIFFERENCE_H