[libcxx-commits] [libcxx] [libc++] implement adjacent_view (PR #165089)
via libcxx-commits
libcxx-commits at lists.llvm.org
Sat Nov 22 07:55:16 PST 2025
================
@@ -0,0 +1,408 @@
+// -*- 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___RANGES_ADJACENT_VIEW_H
+#define _LIBCPP___RANGES_ADJACENT_VIEW_H
+
+#include <__config>
+
+#include <__algorithm/min.h>
+#include <__compare/three_way_comparable.h>
+#include <__concepts/constructible.h>
+#include <__concepts/convertible_to.h>
+#include <__concepts/equality_comparable.h>
+#include <__cstddef/size_t.h>
+#include <__functional/invoke.h>
+#include <__functional/operations.h>
+#include <__iterator/concepts.h>
+#include <__iterator/incrementable_traits.h>
+#include <__iterator/iter_move.h>
+#include <__iterator/iter_swap.h>
+#include <__iterator/iterator_traits.h>
+#include <__iterator/next.h>
+#include <__iterator/prev.h>
+#include <__ranges/access.h>
+#include <__ranges/all.h>
+#include <__ranges/concepts.h>
+#include <__ranges/empty_view.h>
+#include <__ranges/enable_borrowed_range.h>
+#include <__ranges/range_adaptor.h>
+#include <__ranges/size.h>
+#include <__ranges/view_interface.h>
+#include <__ranges/zip_utils.h>
+#include <__type_traits/common_type.h>
+#include <__type_traits/is_nothrow_constructible.h>
+#include <__type_traits/make_unsigned.h>
+#include <__type_traits/maybe_const.h>
+#include <__utility/declval.h>
+#include <__utility/forward.h>
+#include <__utility/integer_sequence.h>
+#include <__utility/move.h>
+#include <array>
+#include <tuple>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+# pragma GCC system_header
+#endif
+
+_LIBCPP_PUSH_MACROS
+#include <__undef_macros>
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+#if _LIBCPP_STD_VER >= 23
+
+namespace ranges {
+
+template <forward_range _View, size_t _Np>
+ requires view<_View> && (_Np > 0)
+class adjacent_view : public view_interface<adjacent_view<_View, _Np>> {
+private:
+ _LIBCPP_NO_UNIQUE_ADDRESS _View __base_ = _View();
+
+ template <bool>
+ class __iterator;
+
+ template <bool>
+ class __sentinel;
+
+ struct __as_sentinel {};
+
+public:
+ _LIBCPP_HIDE_FROM_ABI adjacent_view()
+ requires default_initializable<_View>
+ = default;
+
+ _LIBCPP_HIDE_FROM_ABI constexpr explicit adjacent_view(_View __base) : __base_(std::move(__base)) {}
+
+ _LIBCPP_HIDE_FROM_ABI constexpr _View base() const&
+ requires copy_constructible<_View>
+ {
+ return __base_;
+ }
+ _LIBCPP_HIDE_FROM_ABI constexpr _View base() && { return std::move(__base_); }
+
+ _LIBCPP_HIDE_FROM_ABI constexpr auto begin()
+ requires(!__simple_view<_View>)
+ {
+ return __iterator<false>(ranges::begin(__base_), ranges::end(__base_));
+ }
+
+ _LIBCPP_HIDE_FROM_ABI constexpr auto begin() const
+ requires range<const _View> // todo: this seems under-constrained. lwg issue?
+ {
+ return __iterator<true>(ranges::begin(__base_), ranges::end(__base_));
+ }
+
+ _LIBCPP_HIDE_FROM_ABI constexpr auto end()
+ requires(!__simple_view<_View>)
+ {
+ if constexpr (common_range<_View>) {
+ return __iterator<false>(__as_sentinel{}, ranges::begin(__base_), ranges::end(__base_));
+ } else {
+ return __sentinel<false>(ranges::end(__base_));
+ }
+ }
+
+ _LIBCPP_HIDE_FROM_ABI constexpr auto end() const
+ requires range<const _View>
+ {
+ if constexpr (common_range<const _View>) {
+ return __iterator<true>(__as_sentinel{}, ranges::begin(__base_), ranges::end(__base_));
+ } else {
+ return __sentinel<true>(ranges::end(__base_));
+ }
+ }
+
+ _LIBCPP_HIDE_FROM_ABI constexpr auto size()
+ requires sized_range<_View>
+ {
+ using _ST = decltype(ranges::size(__base_));
+ using _CT = common_type_t<_ST, size_t>;
+ auto __sz = static_cast<_CT>(ranges::size(__base_));
+ __sz -= std::min<_CT>(__sz, _Np - 1);
+ return static_cast<_ST>(__sz);
+ }
+
+ _LIBCPP_HIDE_FROM_ABI constexpr auto size() const
+ requires sized_range<const _View>
+ {
+ using _ST = decltype(ranges::size(__base_));
+ using _CT = common_type_t<_ST, size_t>;
+ auto __sz = static_cast<_CT>(ranges::size(__base_));
+ __sz -= std::min<_CT>(__sz, _Np - 1);
+ return static_cast<_ST>(__sz);
+ }
+};
+
+template <forward_range _View, size_t _Np>
+ requires view<_View> && (_Np > 0)
+template <bool _Const>
+class adjacent_view<_View, _Np>::__iterator {
+ friend adjacent_view;
+ using _Base _LIBCPP_NODEBUG = __maybe_const<_Const, _View>;
+ array<iterator_t<_Base>, _Np> __current_ = array<iterator_t<_Base>, _Np>();
+
+ _LIBCPP_HIDE_FROM_ABI constexpr __iterator(iterator_t<_Base> __first, sentinel_t<_Base> __last) {
+ __current_[0] = __first;
+ for (int __i = 1; __i < static_cast<int>(_Np); ++__i) {
+ __current_[__i] = ranges::next(__current_[__i - 1], 1, __last);
+ }
+ }
+
+ _LIBCPP_HIDE_FROM_ABI constexpr __iterator(__as_sentinel, iterator_t<_Base> __first, iterator_t<_Base> __last) {
+ if constexpr (!bidirectional_range<_Base>) {
+ __current_.fill(__last);
+ } else {
+ __current_[_Np - 1] = __last;
+ for (int __i = static_cast<int>(_Np) - 2; __i >= 0; --__i) {
+ __current_[__i] = ranges::prev(__current_[__i + 1], 1, __first);
+ }
+ }
+ }
+
+ template <class _Iter, size_t... _Is>
+ _LIBCPP_HIDE_FROM_ABI explicit constexpr __iterator(_Iter&& __i, index_sequence<_Is...>)
+ : __current_{std::move(__i.__current_[_Is])...} {}
+
+ static consteval auto __get_iterator_concept() {
+ if constexpr (random_access_range<_Base>)
+ return random_access_iterator_tag{};
+ else if constexpr (bidirectional_range<_Base>)
+ return bidirectional_iterator_tag{};
+ else
+ return forward_iterator_tag{};
+ }
+
+ template <class _Tp, size_t... _Is>
+ static auto __repeat_tuple_helper(index_sequence<_Is...>) -> tuple<decltype((_Is, std::declval<_Tp (*)()>()()))...>;
+
+public:
+ using iterator_category = input_iterator_tag;
+ using iterator_concept = decltype(__get_iterator_concept());
+ using value_type = decltype(__repeat_tuple_helper<range_value_t<_Base>>(make_index_sequence<_Np>{}));
+ using difference_type = range_difference_t<_Base>;
+
+ _LIBCPP_HIDE_FROM_ABI __iterator() = default;
+ _LIBCPP_HIDE_FROM_ABI constexpr __iterator(__iterator<!_Const> __i)
+ requires _Const && convertible_to<iterator_t<_View>, iterator_t<_Base>>
+ : __iterator(std::move(__i), make_index_sequence<_Np>{}) {}
+
+ _LIBCPP_HIDE_FROM_ABI constexpr auto operator*() const {
+ return ranges::__tuple_transform([](auto& __i) -> decltype(auto) { return *__i; }, __current_);
+ }
+
+ _LIBCPP_HIDE_FROM_ABI constexpr __iterator& operator++() {
+ for (auto& __i : __current_) {
+ ++__i;
+ }
+ return *this;
+ }
+
+ _LIBCPP_HIDE_FROM_ABI constexpr __iterator operator++(int) {
+ auto __tmp = *this;
+ ++*this;
+ return __tmp;
+ }
+
+ _LIBCPP_HIDE_FROM_ABI constexpr __iterator& operator--()
+ requires bidirectional_range<_Base>
+ {
+ for (auto& __i : __current_) {
+ --__i;
+ }
+ return *this;
+ }
+
+ _LIBCPP_HIDE_FROM_ABI constexpr __iterator operator--(int)
+ requires bidirectional_range<_Base>
+ {
+ auto __tmp = *this;
+ --*this;
+ return __tmp;
+ }
+
+ _LIBCPP_HIDE_FROM_ABI constexpr __iterator& operator+=(difference_type __x)
+ requires random_access_range<_Base>
+ {
+ for (auto& __i : __current_) {
+ __i += __x;
+ }
+ return *this;
+ }
+
+ _LIBCPP_HIDE_FROM_ABI constexpr __iterator& operator-=(difference_type __x)
+ requires random_access_range<_Base>
+ {
+ for (auto& __i : __current_) {
+ __i -= __x;
+ }
+ return *this;
+ }
+
+ _LIBCPP_HIDE_FROM_ABI constexpr auto operator[](difference_type __n) const
+ requires random_access_range<_Base>
+ {
+ return ranges::__tuple_transform([&](auto& __i) -> decltype(auto) { return __i[__n]; }, __current_);
+ }
+
+ _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator==(const __iterator& __x, const __iterator& __y) {
+ return __x.__current_.back() == __y.__current_.back();
+ }
+
+ _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator<(const __iterator& __x, const __iterator& __y)
+ requires random_access_range<_Base>
+ {
+ return __x.__current_.back() < __y.__current_.back();
+ }
+
+ _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator>(const __iterator& __x, const __iterator& __y)
+ requires random_access_range<_Base>
+ {
+ return __y < __x;
+ }
+
+ _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator<=(const __iterator& __x, const __iterator& __y)
+ requires random_access_range<_Base>
+ {
+ return !(__y < __x);
+ }
+
+ _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator>=(const __iterator& __x, const __iterator& __y)
+ requires random_access_range<_Base>
+ {
+ return !(__x < __y);
+ }
+
+ _LIBCPP_HIDE_FROM_ABI friend constexpr auto operator<=>(const __iterator& __x, const __iterator& __y)
+ requires random_access_range<_Base> && three_way_comparable<iterator_t<_Base>>
+ {
+ return __x.__current_.back() <=> __y.__current_.back();
+ }
+
+ _LIBCPP_HIDE_FROM_ABI friend constexpr __iterator operator+(const __iterator& __i, difference_type __n)
+ requires random_access_range<_Base>
+ {
+ auto __r = __i;
+ __r += __n;
+ return __r;
+ }
+
+ _LIBCPP_HIDE_FROM_ABI friend constexpr __iterator operator+(difference_type __n, const __iterator& __i)
+ requires random_access_range<_Base>
+ {
+ return __i + __n;
+ }
+
+ _LIBCPP_HIDE_FROM_ABI friend constexpr __iterator operator-(const __iterator& __i, difference_type __n)
+ requires random_access_range<_Base>
+ {
+ auto __r = __i;
+ __r -= __n;
+ return __r;
+ }
+
+ _LIBCPP_HIDE_FROM_ABI friend constexpr difference_type operator-(const __iterator& __x, const __iterator& __y)
+ requires sized_sentinel_for<iterator_t<_Base>, iterator_t<_Base>>
+ {
+ return __x.__current_.back() - __y.__current_.back();
+ }
+
+ _LIBCPP_HIDE_FROM_ABI friend constexpr auto iter_move(const __iterator& __i) noexcept(
+ noexcept(ranges::iter_move(std::declval<const iterator_t<_Base>&>())) &&
+ is_nothrow_move_constructible_v<range_rvalue_reference_t<_Base>>) {
+ return ranges::__tuple_transform(ranges::iter_move, __i.__current_);
+ }
+
+ _LIBCPP_HIDE_FROM_ABI friend constexpr void iter_swap(const __iterator& __l, const __iterator& __r) noexcept(
+ noexcept(ranges::iter_swap(std::declval<iterator_t<_Base>>(), std::declval<iterator_t<_Base>>())))
+ requires indirectly_swappable<iterator_t<_Base>>
+ {
+ for (size_t __i = 0; __i < _Np; ++__i) {
+ ranges::iter_swap(__l.__current_[__i], __r.__current_[__i]);
+ }
+ }
+};
+
+template <forward_range _View, size_t _Np>
+ requires view<_View> && (_Np > 0)
+template <bool _Const>
+class adjacent_view<_View, _Np>::__sentinel {
+ friend adjacent_view;
+ using _Base _LIBCPP_NODEBUG = __maybe_const<_Const, _View>;
+ sentinel_t<_Base> __end_ = sentinel_t<_Base>();
+
+ _LIBCPP_HIDE_FROM_ABI constexpr explicit __sentinel(sentinel_t<_Base> __end) { __end_ = std::move(__end); }
+
+public:
+ _LIBCPP_HIDE_FROM_ABI __sentinel() = default;
+
+ _LIBCPP_HIDE_FROM_ABI constexpr __sentinel(__sentinel<!_Const> __i)
+ requires _Const && convertible_to<sentinel_t<_View>, sentinel_t<_Base>>
+ : __end_(std::move(__i.__end_)) {}
+
+ template <bool _OtherConst>
+ requires sentinel_for<sentinel_t<_Base>, iterator_t<__maybe_const<_OtherConst, _View>>>
+ _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator==(const __iterator<_OtherConst>& __x, const __sentinel& __y) {
+ return __x.__current_.back() == __y.__end_;
+ }
+
+ template <bool _OtherConst>
+ requires sized_sentinel_for<sentinel_t<_Base>, iterator_t<__maybe_const<_OtherConst, _View>>>
+ _LIBCPP_HIDE_FROM_ABI friend constexpr range_difference_t<__maybe_const<_OtherConst, _View>>
+ operator-(const __iterator<_OtherConst>& __x, const __sentinel& __y) {
+ return __x.__current_.back() - __y.__end_;
+ }
+
+ template <bool _OtherConst>
+ requires sized_sentinel_for<sentinel_t<_Base>, iterator_t<__maybe_const<_OtherConst, _View>>>
+ _LIBCPP_HIDE_FROM_ABI friend constexpr range_difference_t<__maybe_const<_OtherConst, _View>>
+ operator-(const __sentinel& __y, const __iterator<_OtherConst>& __x) {
+ return __y.__end_ - __x.__current_.back();
+ }
+};
+
+template <class _View, size_t _Np>
+constexpr bool enable_borrowed_range<adjacent_view<_View, _Np>> = enable_borrowed_range<_View>;
+
+namespace views {
+namespace __adjacent {
+
+template <size_t _Np>
+struct __fn : __range_adaptor_closure<__fn<_Np>> {
+ template <class _Range>
+ requires(_Np == 0 && forward_range<_Range &&>)
+ _LIBCPP_HIDE_FROM_ABI static constexpr auto operator()(_Range&&) noexcept {
+ return empty_view<tuple<>>{};
+ }
+
+ template <class _Ranges>
+ _LIBCPP_HIDE_FROM_ABI static constexpr auto operator()(_Ranges&& __range) noexcept(
+ noexcept(adjacent_view<views::all_t<_Ranges&&>, _Np>(std::forward<_Ranges>(__range))))
+ -> decltype(adjacent_view<views::all_t<_Ranges&&>, _Np>(std::forward<_Ranges>(__range))) {
+ return adjacent_view<views::all_t<_Ranges&&>, _Np>(std::forward<_Ranges>(__range));
+ }
+};
+
+} // namespace __adjacent
+inline namespace __cpo {
+template <size_t _Np>
+inline constexpr auto adjacent = __adjacent::__fn<_Np>{};
+inline constexpr auto pairwise = adjacent<2>;
----------------
huixie90 wrote:
yes we have
https://github.com/llvm/llvm-project/pull/165089
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