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// -*- 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___ITERATOR_DISTANCE_H
#define _LIBCPP___ITERATOR_DISTANCE_H
#include <__config>
#include <__iterator/concepts.h>
#include <__iterator/incrementable_traits.h>
#include <__iterator/iterator_traits.h>
#include <__ranges/access.h>
#include <__ranges/concepts.h>
#include <__ranges/size.h>
#include <__type_traits/decay.h>
#include <__type_traits/remove_cvref.h>
#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
# pragma GCC system_header
#endif
_LIBCPP_BEGIN_NAMESPACE_STD
template <class _InputIter>
inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 typename iterator_traits<_InputIter>::difference_type
__distance(_InputIter __first, _InputIter __last, input_iterator_tag) {
typename iterator_traits<_InputIter>::difference_type __r(0);
for (; __first != __last; ++__first)
++__r;
return __r;
}
template <class _RandIter>
inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 typename iterator_traits<_RandIter>::difference_type
__distance(_RandIter __first, _RandIter __last, random_access_iterator_tag) {
return __last - __first;
}
template <class _InputIter>
inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 typename iterator_traits<_InputIter>::difference_type
distance(_InputIter __first, _InputIter __last) {
return std::__distance(__first, __last, typename iterator_traits<_InputIter>::iterator_category());
}
#if _LIBCPP_STD_VER >= 20
// [range.iter.op.distance]
namespace ranges {
namespace __distance {
struct __fn {
template <class _Ip, sentinel_for<_Ip> _Sp>
requires(!sized_sentinel_for<_Sp, _Ip>)
_LIBCPP_HIDE_FROM_ABI constexpr iter_difference_t<_Ip> operator()(_Ip __first, _Sp __last) const {
iter_difference_t<_Ip> __n = 0;
while (__first != __last) {
++__first;
++__n;
}
return __n;
}
template <class _Ip, sized_sentinel_for<decay_t<_Ip>> _Sp>
_LIBCPP_HIDE_FROM_ABI constexpr iter_difference_t<_Ip> operator()(_Ip&& __first, _Sp __last) const {
if constexpr (sized_sentinel_for<_Sp, __remove_cvref_t<_Ip>>) {
return __last - __first;
} else {
return __last - decay_t<_Ip>(__first);
}
}
template <range _Rp>
_LIBCPP_HIDE_FROM_ABI constexpr range_difference_t<_Rp> operator()(_Rp&& __r) const {
if constexpr (sized_range<_Rp>) {
return static_cast<range_difference_t<_Rp>>(ranges::size(__r));
} else {
return operator()(ranges::begin(__r), ranges::end(__r));
}
}
};
} // namespace __distance
inline namespace __cpo {
inline constexpr auto distance = __distance::__fn{};
} // namespace __cpo
} // namespace ranges
#endif // _LIBCPP_STD_VER >= 20
_LIBCPP_END_NAMESPACE_STD
#endif // _LIBCPP___ITERATOR_DISTANCE_H
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