191 lines
7.3 KiB
C++
191 lines
7.3 KiB
C++
// -*- C++ -*-
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//===----------------------------------------------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#ifndef _LIBCPP___RANGES_REVERSE_VIEW_H
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#define _LIBCPP___RANGES_REVERSE_VIEW_H
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#include <__concepts/constructible.h>
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#include <__config>
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#include <__iterator/concepts.h>
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#include <__iterator/next.h>
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#include <__iterator/reverse_iterator.h>
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#include <__ranges/access.h>
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#include <__ranges/all.h>
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#include <__ranges/concepts.h>
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#include <__ranges/enable_borrowed_range.h>
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#include <__ranges/non_propagating_cache.h>
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#include <__ranges/range_adaptor.h>
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#include <__ranges/size.h>
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#include <__ranges/subrange.h>
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#include <__ranges/view_interface.h>
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#include <__utility/forward.h>
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#include <__utility/move.h>
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#include <type_traits>
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#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
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# pragma GCC system_header
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#endif
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_LIBCPP_BEGIN_NAMESPACE_STD
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#if _LIBCPP_STD_VER > 17 && !defined(_LIBCPP_HAS_NO_INCOMPLETE_RANGES)
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namespace ranges {
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template<view _View>
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requires bidirectional_range<_View>
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class reverse_view : public view_interface<reverse_view<_View>> {
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// We cache begin() whenever ranges::next is not guaranteed O(1) to provide an
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// amortized O(1) begin() method.
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static constexpr bool _UseCache = !random_access_range<_View> && !common_range<_View>;
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using _Cache = _If<_UseCache, __non_propagating_cache<reverse_iterator<iterator_t<_View>>>, __empty_cache>;
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_LIBCPP_NO_UNIQUE_ADDRESS _Cache __cached_begin_ = _Cache();
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_LIBCPP_NO_UNIQUE_ADDRESS _View __base_ = _View();
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public:
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_LIBCPP_HIDE_FROM_ABI
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reverse_view() requires default_initializable<_View> = default;
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_LIBCPP_HIDE_FROM_ABI
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constexpr explicit reverse_view(_View __view) : __base_(std::move(__view)) {}
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_LIBCPP_HIDE_FROM_ABI
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constexpr _View base() const& requires copy_constructible<_View> { return __base_; }
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_LIBCPP_HIDE_FROM_ABI
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constexpr _View base() && { return std::move(__base_); }
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_LIBCPP_HIDE_FROM_ABI
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constexpr reverse_iterator<iterator_t<_View>> begin() {
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if constexpr (_UseCache)
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if (__cached_begin_.__has_value())
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return *__cached_begin_;
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auto __tmp = std::make_reverse_iterator(ranges::next(ranges::begin(__base_), ranges::end(__base_)));
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if constexpr (_UseCache)
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__cached_begin_.__emplace(__tmp);
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return __tmp;
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}
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_LIBCPP_HIDE_FROM_ABI
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constexpr reverse_iterator<iterator_t<_View>> begin() requires common_range<_View> {
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return std::make_reverse_iterator(ranges::end(__base_));
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}
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_LIBCPP_HIDE_FROM_ABI
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constexpr auto begin() const requires common_range<const _View> {
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return std::make_reverse_iterator(ranges::end(__base_));
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}
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_LIBCPP_HIDE_FROM_ABI
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constexpr reverse_iterator<iterator_t<_View>> end() {
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return std::make_reverse_iterator(ranges::begin(__base_));
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}
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_LIBCPP_HIDE_FROM_ABI
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constexpr auto end() const requires common_range<const _View> {
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return std::make_reverse_iterator(ranges::begin(__base_));
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}
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_LIBCPP_HIDE_FROM_ABI
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constexpr auto size() requires sized_range<_View> {
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return ranges::size(__base_);
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}
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_LIBCPP_HIDE_FROM_ABI
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constexpr auto size() const requires sized_range<const _View> {
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return ranges::size(__base_);
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}
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};
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template<class _Range>
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reverse_view(_Range&&) -> reverse_view<views::all_t<_Range>>;
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template<class _Tp>
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inline constexpr bool enable_borrowed_range<reverse_view<_Tp>> = enable_borrowed_range<_Tp>;
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namespace views {
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namespace __reverse {
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template<class _Tp>
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inline constexpr bool __is_reverse_view = false;
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template<class _Tp>
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inline constexpr bool __is_reverse_view<reverse_view<_Tp>> = true;
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template<class _Tp>
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inline constexpr bool __is_sized_reverse_subrange = false;
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template<class _Iter>
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inline constexpr bool __is_sized_reverse_subrange<subrange<reverse_iterator<_Iter>, reverse_iterator<_Iter>, subrange_kind::sized>> = true;
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template<class _Tp>
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inline constexpr bool __is_unsized_reverse_subrange = false;
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template<class _Iter, subrange_kind _Kind>
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inline constexpr bool __is_unsized_reverse_subrange<subrange<reverse_iterator<_Iter>, reverse_iterator<_Iter>, _Kind>> = _Kind == subrange_kind::unsized;
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template<class _Tp>
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struct __unwrapped_reverse_subrange {
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using type = void; // avoid SFINAE-ing out the overload below -- let the concept requirements do it for better diagnostics
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};
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template<class _Iter, subrange_kind _Kind>
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struct __unwrapped_reverse_subrange<subrange<reverse_iterator<_Iter>, reverse_iterator<_Iter>, _Kind>> {
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using type = subrange<_Iter, _Iter, _Kind>;
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};
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struct __fn : __range_adaptor_closure<__fn> {
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template<class _Range>
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requires __is_reverse_view<remove_cvref_t<_Range>>
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[[nodiscard]] _LIBCPP_HIDE_FROM_ABI
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constexpr auto operator()(_Range&& __range) const
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noexcept(noexcept(std::forward<_Range>(__range).base()))
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-> decltype( std::forward<_Range>(__range).base())
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{ return std::forward<_Range>(__range).base(); }
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template<class _Range,
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class _UnwrappedSubrange = typename __unwrapped_reverse_subrange<remove_cvref_t<_Range>>::type>
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requires __is_sized_reverse_subrange<remove_cvref_t<_Range>>
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[[nodiscard]] _LIBCPP_HIDE_FROM_ABI
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constexpr auto operator()(_Range&& __range) const
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noexcept(noexcept(_UnwrappedSubrange(__range.end().base(), __range.begin().base(), __range.size())))
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-> decltype( _UnwrappedSubrange(__range.end().base(), __range.begin().base(), __range.size()))
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{ return _UnwrappedSubrange(__range.end().base(), __range.begin().base(), __range.size()); }
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template<class _Range,
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class _UnwrappedSubrange = typename __unwrapped_reverse_subrange<remove_cvref_t<_Range>>::type>
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requires __is_unsized_reverse_subrange<remove_cvref_t<_Range>>
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[[nodiscard]] _LIBCPP_HIDE_FROM_ABI
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constexpr auto operator()(_Range&& __range) const
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noexcept(noexcept(_UnwrappedSubrange(__range.end().base(), __range.begin().base())))
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-> decltype( _UnwrappedSubrange(__range.end().base(), __range.begin().base()))
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{ return _UnwrappedSubrange(__range.end().base(), __range.begin().base()); }
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template<class _Range>
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requires (!__is_reverse_view<remove_cvref_t<_Range>> &&
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!__is_sized_reverse_subrange<remove_cvref_t<_Range>> &&
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!__is_unsized_reverse_subrange<remove_cvref_t<_Range>>)
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[[nodiscard]] _LIBCPP_HIDE_FROM_ABI
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constexpr auto operator()(_Range&& __range) const
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noexcept(noexcept(reverse_view{std::forward<_Range>(__range)}))
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-> decltype( reverse_view{std::forward<_Range>(__range)})
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{ return reverse_view{std::forward<_Range>(__range)}; }
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};
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} // namespace __reverse
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inline namespace __cpo {
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inline constexpr auto reverse = __reverse::__fn{};
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} // namespace __cpo
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} // namespace views
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} // namespace ranges
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#endif // _LIBCPP_STD_VER > 17 && !defined(_LIBCPP_HAS_NO_INCOMPLETE_RANGES)
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_LIBCPP_END_NAMESPACE_STD
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#endif // _LIBCPP___RANGES_REVERSE_VIEW_H
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