[libcxx-commits] [libcxx] [libc++] implement `adjacent_transform` (PR #168208)
Louis Dionne via libcxx-commits
libcxx-commits at lists.llvm.org
Fri Dec 12 11:04:44 PST 2025
================
@@ -0,0 +1,411 @@
+// -*- 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_TRANSFORM_VIEW_H
+#define _LIBCPP___RANGES_ADJACENT_TRANSFORM_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 <__memory/addressof.h>
+#include <__ranges/access.h>
+#include <__ranges/adjacent_view.h>
+#include <__ranges/all.h>
+#include <__ranges/concepts.h>
+#include <__ranges/empty_view.h>
+#include <__ranges/movable_box.h>
+#include <__ranges/range_adaptor.h>
+#include <__ranges/size.h>
+#include <__ranges/view_interface.h>
+#include <__ranges/zip_transform_view.h>
+#include <__ranges/zip_utils.h>
+#include <__type_traits/common_type.h>
+#include <__type_traits/is_nothrow_constructible.h>
+#include <__type_traits/is_referenceable.h>
+#include <__type_traits/make_unsigned.h>
+#include <__type_traits/maybe_const.h>
+#include <__utility/declval.h>
+#include <__utility/forward.h>
+#include <__utility/in_place.h>
+#include <__utility/integer_sequence.h>
+#include <__utility/move.h>
+#include <concepts>
+#include <ranges>
+#include <tuple>
+#include <type_traits>
+
+#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 <class _Fn, size_t _Np>
+struct __apply_n {
+ template <class... _Ts>
+ static auto __apply(tuple<_Ts...>&&) -> invoke_result_t<_Fn, _Ts...>;
+
+ template <class _Tp, size_t... _Is>
+ static auto __make_tuple_impl(index_sequence<_Is...>) -> tuple<decltype((_Is, std::declval<_Tp (*)()>()()))...>;
+
+ template <class _Tp>
+ static constexpr auto operator()(_Tp&&) -> decltype(__apply(__make_tuple_impl<_Tp&&>(make_index_sequence<_Np>{})));
+};
+
+template <forward_range _View, move_constructible _Fn, size_t _Np>
+ requires view<_View> && (_Np > 0) && is_object_v<_Fn> &&
+ regular_invocable<__apply_n<_Fn&, _Np>, range_reference_t<_View>> &&
+ __referenceable<invoke_result_t<__apply_n<_Fn&, _Np>, range_reference_t<_View>>>
+class adjacent_transform_view : public view_interface<adjacent_transform_view<_View, _Fn, _Np>> {
+private:
+ _LIBCPP_NO_UNIQUE_ADDRESS adjacent_view<_View, _Np> __inner_;
+ _LIBCPP_NO_UNIQUE_ADDRESS __movable_box<_Fn> __fun_;
+
+ using _InnerView _LIBCPP_NODEBUG = adjacent_view<_View, _Np>;
+
+ template <bool _Const>
+ using __inner_iterator _LIBCPP_NODEBUG = iterator_t<__maybe_const<_Const, _InnerView>>;
+
+ template <bool _Const>
+ using __inner_sentinel _LIBCPP_NODEBUG = sentinel_t<__maybe_const<_Const, _InnerView>>;
+
+ template <bool>
+ class __iterator;
+
+ template <bool>
+ class __sentinel;
+
+public:
+ _LIBCPP_HIDE_FROM_ABI adjacent_transform_view() = default;
+
+ _LIBCPP_HIDE_FROM_ABI constexpr explicit adjacent_transform_view(_View __base, _Fn __fun)
+ : __inner_(std::move(__base)), __fun_(std::in_place, std::move(__fun)) {}
+
+ _LIBCPP_HIDE_FROM_ABI constexpr _View base() const&
+ requires copy_constructible<_View>
+ {
+ return __inner_.base();
+ }
+ _LIBCPP_HIDE_FROM_ABI constexpr _View base() && { return std::move(__inner_).base(); }
+
+ _LIBCPP_HIDE_FROM_ABI constexpr auto begin() { return __iterator<false>(*this, __inner_.begin()); }
+
+ _LIBCPP_HIDE_FROM_ABI constexpr auto begin() const
+ requires range<const _InnerView> && regular_invocable<__apply_n<const _Fn&, _Np>, range_reference_t<const _View>>
+ {
+ return __iterator<true>(*this, __inner_.begin());
+ }
+
+ _LIBCPP_HIDE_FROM_ABI constexpr auto end() {
+ if constexpr (common_range<_InnerView>) {
+ return __iterator<false>(*this, __inner_.end());
+ } else {
+ return __sentinel<false>(__inner_.end());
+ }
+ }
+
+ _LIBCPP_HIDE_FROM_ABI constexpr auto end() const
+ requires range<const _InnerView> && regular_invocable<__apply_n<const _Fn&, _Np>, range_reference_t<const _View>>
+ {
+ if constexpr (common_range<const _InnerView>) {
+ return __iterator<true>(*this, __inner_.end());
+ } else {
+ return __sentinel<true>(__inner_.end());
+ }
+ }
+
+ _LIBCPP_HIDE_FROM_ABI constexpr auto size()
+ requires sized_range<_InnerView>
+ {
+ return __inner_.size();
+ }
+
+ _LIBCPP_HIDE_FROM_ABI constexpr auto size() const
+ requires sized_range<const _InnerView>
+ {
+ return __inner_.size();
+ }
+};
+
+template <forward_range _View, move_constructible _Fn, size_t _Np>
+ requires view<_View> && (_Np > 0) && is_object_v<_Fn> &&
+ regular_invocable<__apply_n<_Fn&, _Np>, range_reference_t<_View>> &&
+ __referenceable<invoke_result_t<__apply_n<_Fn&, _Np>, range_reference_t<_View>>>
+template <bool _Const>
+class adjacent_transform_view<_View, _Fn, _Np>::__iterator {
+ friend adjacent_transform_view;
+
+ using _Parent _LIBCPP_NODEBUG = __maybe_const<_Const, adjacent_transform_view>;
+ using _Base _LIBCPP_NODEBUG = __maybe_const<_Const, _View>;
+
+ _Parent* __parent_ = nullptr;
+ __inner_iterator<_Const> __inner_;
+
+ _LIBCPP_HIDE_FROM_ABI constexpr __iterator(_Parent& __parent, __inner_iterator<_Const> __inner)
+ : __parent_(std::addressof(__parent)), __inner_(std::move(__inner)) {}
+
+ static consteval auto __get_iterator_category() {
+ using _Cat = iterator_traits<iterator_t<_Base>>::iterator_category;
+ if constexpr (!is_reference_v<
+ invoke_result_t<__apply_n<__maybe_const<_Const, _Fn>&, _Np>, range_reference_t<_Base>>>)
+ return input_iterator_tag{};
+ else if constexpr (derived_from<_Cat, random_access_iterator_tag>)
+ return random_access_iterator_tag{};
+ else if constexpr (derived_from<_Cat, bidirectional_iterator_tag>)
+ return bidirectional_iterator_tag{};
+ else if constexpr (derived_from<_Cat, forward_iterator_tag>)
+ return forward_iterator_tag{};
+ else
+ return input_iterator_tag{};
+ }
+
+ template <size_t... _Is>
+ static consteval bool __noexcept_dereference(index_sequence<_Is...>) {
+ return noexcept(std::invoke(
+ std::declval<__maybe_const<_Const, _Fn>&>(),
+ *std::get<_Is>(
+ __adjacent_view_iter_access::__get_current(std::declval<const __inner_iterator<_Const>&>()))...));
----------------
ldionne wrote:
```suggestion
return noexcept(std::invoke(
std::declval<__maybe_const<_Const, _Fn>&>(),
((void)_Is, *std::declval<iterator_t<_Base> const&>())...));
```
https://github.com/llvm/llvm-project/pull/168208
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