[libcxx-commits] [libcxx] [clang] [lld] [llvm] [clang-tools-extra] [flang] [compiler-rt] [libc++][ranges] P2116R9: Implements `views::enumerate` (PR #73617)
Christopher Di Bella via libcxx-commits
libcxx-commits at lists.llvm.org
Tue Jan 2 14:17:02 PST 2024
================
@@ -0,0 +1,333 @@
+// -*- 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_ENUMERATE_VIEW_H
+#define _LIBCPP___RANGES_ENUMERATE_VIEW_H
+
+#include <__concepts/convertible_to.h>
+#include <__config>
+#include <__iterator/concepts.h>
+#include <__iterator/distance.h>
+#include <__iterator/iter_move.h>
+#include <__iterator/iterator_traits.h>
+#include <__ranges/access.h>
+#include <__ranges/all.h>
+#include <__ranges/concepts.h>
+#include <__ranges/enable_borrowed_range.h>
+#include <__ranges/range_adaptor.h>
+#include <__ranges/size.h>
+#include <__ranges/view_interface.h>
+#include <__type_traits/maybe_const.h>
+#include <__utility/forward.h>
+#include <__utility/move.h>
+#include <tuple>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+# pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+#if _LIBCPP_STD_VER >= 23
+
+namespace ranges {
+
+// [concept.object]
+
+template <class _Rp>
+concept __range_with_movable_references =
+ ranges::input_range<_Rp> && std::move_constructible<ranges::range_reference_t<_Rp>> &&
+ std::move_constructible<ranges::range_rvalue_reference_t<_Rp>>;
+
+// [range.enumerate.view]
+
+template <view _View>
+ requires __range_with_movable_references<_View>
+class enumerate_view : public view_interface<enumerate_view<_View>> {
+ _View __base_ = _View();
+
+ // [range.enumerate.iterator]
+ template <bool _Const>
+ class __iterator;
+
+ // [range.enumerate.sentinel]
+ template <bool _Const>
+ class __sentinel;
+
+ template <bool _AnyConst>
+ _LIBCPP_HIDE_FROM_ABI static constexpr decltype(auto) __get_current(const __iterator<_AnyConst>& __iter) {
+ return (__iter.__current_);
+ }
+
+public:
+ _LIBCPP_HIDE_FROM_ABI constexpr enumerate_view()
+ requires(default_initializable<_View>)
+ = default;
+ _LIBCPP_HIDE_FROM_ABI constexpr explicit enumerate_view(_View __base) : __base_(std::move(__base)){};
+
+ _LIBCPP_HIDE_FROM_ABI constexpr auto begin()
+ requires(!__simple_view<_View>)
+ {
+ return __iterator<false>(ranges::begin(__base_), 0);
+ }
+ _LIBCPP_HIDE_FROM_ABI constexpr auto begin() const
+ requires __range_with_movable_references<const _View>
+ {
+ return __iterator<true>(ranges::begin(__base_), 0);
+ }
+
+ _LIBCPP_HIDE_FROM_ABI constexpr auto end()
+ requires(!__simple_view<_View>)
+ {
+ if constexpr (common_range<_View> && sized_range<_View>)
+ return __iterator<false>(ranges::end(__base_), ranges::distance(__base_));
+ else
+ return __sentinel<false>(ranges::end(__base_));
+ }
+ _LIBCPP_HIDE_FROM_ABI constexpr auto end() const
+ requires __range_with_movable_references<const _View>
+ {
+ if constexpr (common_range<const _View> && sized_range<const _View>)
+ return __iterator<true>(ranges::end(__base_), ranges::distance(__base_));
+ else
+ return __sentinel<true>(ranges::end(__base_));
+ }
+
+ _LIBCPP_HIDE_FROM_ABI constexpr auto size()
+ requires sized_range<_View>
+ {
+ return ranges::size(__base_);
+ }
+ _LIBCPP_HIDE_FROM_ABI constexpr auto size() const
+ requires sized_range<const _View>
+ {
+ return ranges::size(__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_); }
+};
+
+template <class _Range>
+enumerate_view(_Range&&) -> enumerate_view<views::all_t<_Range>>;
+
+// [range.enumerate.iterator]
+
+template <view _View>
+ requires __range_with_movable_references<_View>
+template <bool _Const>
+class enumerate_view<_View>::__iterator {
+ using _Base = __maybe_const<_Const, _View>;
+
+ 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 if constexpr (forward_range<_Base>) {
+ return forward_iterator_tag{};
+ } else {
+ return input_iterator_tag{};
+ }
+ }
+
+ friend class enumerate_view<_View>;
+
+public:
+ using iterator_category = input_iterator_tag;
+ using iterator_concept = decltype(__get_iterator_concept());
+ using difference_type = range_difference_t<_Base>;
+ using value_type = tuple<difference_type, range_value_t<_Base>>;
+
+private:
+ using __reference_type = tuple<difference_type, range_reference_t<_Base>>;
+ iterator_t<_Base> __current_ = iterator_t<_Base>();
+ difference_type __pos_ = 0;
+
+ _LIBCPP_HIDE_FROM_ABI constexpr explicit __iterator(iterator_t<_Base> __current, difference_type __pos)
+ : __current_(std::move(__current)), __pos_(__pos) {}
+
+public:
+ _LIBCPP_HIDE_FROM_ABI __iterator()
+ requires(default_initializable<iterator_t<_Base>>)
+ = default;
+ _LIBCPP_HIDE_FROM_ABI constexpr __iterator(__iterator<!_Const> __i)
+ requires _Const && convertible_to<iterator_t<_View>, iterator_t<_Base>>
+ : __current_(std::move(__i.__current_)), __pos_(__i.__pos_) {}
+
+ _LIBCPP_HIDE_FROM_ABI constexpr const iterator_t<_Base>& base() const& noexcept { return __current_; }
+ _LIBCPP_HIDE_FROM_ABI constexpr iterator_t<_Base> base() && { return std::move(__current_); }
+
+ _LIBCPP_HIDE_FROM_ABI constexpr difference_type index() const noexcept { return __pos_; }
+
+ _LIBCPP_HIDE_FROM_ABI constexpr auto operator*() const { return __reference_type(__pos_, *__current_); }
+
+ _LIBCPP_HIDE_FROM_ABI constexpr __iterator& operator++() {
+ ++__current_;
+ ++__pos_;
+ return *this;
+ }
+ _LIBCPP_HIDE_FROM_ABI constexpr void operator++(int) { return ++*this; }
+ _LIBCPP_HIDE_FROM_ABI constexpr __iterator operator++(int)
+ requires forward_range<_Base>
+ {
+ auto __temp = *this;
+ ++*this;
+ return __temp;
+ }
+
+ _LIBCPP_HIDE_FROM_ABI constexpr __iterator& operator--()
+ requires bidirectional_range<_Base>
+ {
+ --__current_;
+ --__pos_;
+ return *this;
+ }
+ _LIBCPP_HIDE_FROM_ABI constexpr __iterator operator--(int)
+ requires bidirectional_range<_Base>
+ {
+ auto __temp = *this;
+ --*this;
+ return *__temp;
+ }
+
+ _LIBCPP_HIDE_FROM_ABI constexpr __iterator& operator+=(difference_type __n)
+ requires random_access_range<_Base>
+ {
+ __current_ += __n;
+ __pos_ += __n;
+ return *this;
+ }
+ _LIBCPP_HIDE_FROM_ABI constexpr __iterator& operator-=(difference_type __n)
+ requires random_access_range<_Base>
+ {
+ __current_ -= __n;
+ __pos_ -= __n;
+ return *this;
+ }
+
+ _LIBCPP_HIDE_FROM_ABI constexpr auto operator[](difference_type __n) const
+ requires random_access_range<_Base>
+ {
+ return __reference_type(__pos_ + __n, __current_[__n]);
+ }
+
+ _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator==(const __iterator& __x, const __iterator& __y) noexcept {
+ return __x.__pos_ == __y.__pos_;
+ }
+ _LIBCPP_HIDE_FROM_ABI friend constexpr strong_ordering
+ operator<=>(const __iterator& __x, const __iterator& __y) noexcept {
+ return __x.__pos_ <=> __y.__pos_;
+ }
+
+ _LIBCPP_HIDE_FROM_ABI friend constexpr __iterator operator+(const __iterator& __i, difference_type __n)
+ requires random_access_range<_Base>
+ {
+ auto __temp = __i;
+ __temp += __n;
+ return __temp;
+ }
+ _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 __temp = __i;
+ __temp -= __n;
+ return __temp;
+ }
+ _LIBCPP_HIDE_FROM_ABI friend constexpr difference_type
+ operator-(const __iterator& __x, const __iterator& __y) noexcept {
+ return __x.__pos_ - __y.__pos_;
+ }
+
+ _LIBCPP_HIDE_FROM_ABI friend constexpr auto iter_move(const __iterator& __i) noexcept(
+ noexcept(ranges::iter_move(__i.__current_)) && is_nothrow_move_constructible_v<range_rvalue_reference_t<_Base>>) {
+ return tuple<difference_type, range_rvalue_reference_t<_Base>>(__i.__pos_, ranges::iter_move(__i.__current_));
+ }
+};
+
+// [range.enumerate.sentinel]
+
+template <view _View>
+ requires __range_with_movable_references<_View>
+template <bool _Const>
+class enumerate_view<_View>::__sentinel {
+ using _Base = __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)) {}
+
+ friend class enumerate_view<_View>;
+
+public:
+ _LIBCPP_HIDE_FROM_ABI __sentinel() = default;
+ _LIBCPP_HIDE_FROM_ABI constexpr __sentinel(__sentinel<!_Const> __other)
+ requires _Const && convertible_to<sentinel_t<_View>, sentinel_t<_Base>>
+ : __end_(std::move(__other.__end_)) {}
+
+ _LIBCPP_HIDE_FROM_ABI constexpr sentinel_t<_Base> base() const { return __end_; }
----------------
cjdb wrote:
This should be marked with `_LIBCPP_NODISCARD`.
https://github.com/llvm/llvm-project/pull/73617
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