[libcxx-commits] [libcxx] [libc++] Implement `std::flat_multiset` (PR #128363)
Louis Dionne via libcxx-commits
libcxx-commits at lists.llvm.org
Fri Mar 28 12:05:14 PDT 2025
================
@@ -0,0 +1,790 @@
+// -*- 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___FLAT_MAP_FLAT_MULTISET_H
+#define _LIBCPP___FLAT_MAP_FLAT_MULTISET_H
+
+#include "utils.h"
+#include <__algorithm/lexicographical_compare_three_way.h>
+#include <__algorithm/min.h>
+#include <__algorithm/ranges_equal.h>
+#include <__algorithm/ranges_equal_range.h>
+#include <__algorithm/ranges_inplace_merge.h>
+#include <__algorithm/ranges_is_sorted.h>
+#include <__algorithm/ranges_lower_bound.h>
+#include <__algorithm/ranges_partition_point.h>
+#include <__algorithm/ranges_sort.h>
+#include <__algorithm/ranges_unique.h>
+#include <__algorithm/ranges_upper_bound.h>
+#include <__algorithm/remove_if.h>
+#include <__assert>
+#include <__compare/synth_three_way.h>
+#include <__concepts/convertible_to.h>
+#include <__concepts/swappable.h>
+#include <__config>
+#include <__cstddef/byte.h>
+#include <__cstddef/ptrdiff_t.h>
+#include <__flat_map/key_value_iterator.h>
+#include <__flat_map/sorted_equivalent.h>
+#include <__flat_set/ra_iterator.h>
+#include <__flat_set/utils.h>
+#include <__functional/invoke.h>
+#include <__functional/is_transparent.h>
+#include <__functional/operations.h>
+#include <__fwd/vector.h>
+#include <__iterator/concepts.h>
+#include <__iterator/distance.h>
+#include <__iterator/iterator_traits.h>
+#include <__iterator/ranges_iterator_traits.h>
+#include <__iterator/reverse_iterator.h>
+#include <__memory/allocator_traits.h>
+#include <__memory/uses_allocator.h>
+#include <__memory/uses_allocator_construction.h>
+#include <__ranges/access.h>
+#include <__ranges/concepts.h>
+#include <__ranges/container_compatible_range.h>
+#include <__ranges/drop_view.h>
+#include <__ranges/from_range.h>
+#include <__ranges/ref_view.h>
+#include <__ranges/size.h>
+#include <__ranges/subrange.h>
+#include <__ranges/zip_view.h>
+#include <__type_traits/conjunction.h>
+#include <__type_traits/container_traits.h>
+#include <__type_traits/invoke.h>
+#include <__type_traits/is_allocator.h>
+#include <__type_traits/is_nothrow_constructible.h>
+#include <__type_traits/is_same.h>
+#include <__type_traits/maybe_const.h>
+#include <__utility/as_const.h>
+#include <__utility/exception_guard.h>
+#include <__utility/move.h>
+#include <__utility/pair.h>
+#include <__utility/scope_guard.h>
+#include <__vector/vector.h>
+#include <initializer_list>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+# pragma GCC system_header
+#endif
+
+_LIBCPP_PUSH_MACROS
+#include <__undef_macros>
+
+#if _LIBCPP_STD_VER >= 23
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+template <class _Key, class _Compare = less<_Key>, class _KeyContainer = vector<_Key>>
+class flat_multiset {
+ template <class, class, class>
+ friend class flat_multiset;
+
+ friend __flat_set_utils;
+
+ static_assert(is_same_v<_Key, typename _KeyContainer::value_type>);
+ static_assert(!is_same_v<_KeyContainer, std::vector<bool>>, "vector<bool> is not a sequence container");
+
+public:
+ // types
+ using key_type = _Key;
+ using value_type = _Key;
+ using key_compare = __type_identity_t<_Compare>;
+ using value_compare = _Compare;
+ using reference = value_type&;
+ using const_reference = const value_type&;
+ using size_type = typename _KeyContainer::size_type;
+ using difference_type = typename _KeyContainer::difference_type;
+ using iterator = __ra_iterator<flat_multiset, typename _KeyContainer::const_iterator>;
+ using const_iterator = iterator;
+ using reverse_iterator = std::reverse_iterator<iterator>;
+ using const_reverse_iterator = std::reverse_iterator<const_iterator>;
+ using container_type = _KeyContainer;
+
+public:
+ // [flat.multiset.cons], constructors
+ _LIBCPP_HIDE_FROM_ABI flat_multiset() noexcept(is_nothrow_default_constructible_v<_KeyContainer> &&
+ is_nothrow_default_constructible_v<_Compare>)
+ : __keys_(), __compare_() {}
+
+ _LIBCPP_HIDE_FROM_ABI flat_multiset(const flat_multiset&) = default;
+
+ // The copy/move constructors are not specified in the spec, which means they should be defaulted.
+ // However, the move constructor can potentially leave a moved-from object in an inconsistent
+ // state if an exception is thrown.
+ _LIBCPP_HIDE_FROM_ABI flat_multiset(flat_multiset&& __other) noexcept(
+ is_nothrow_move_constructible_v<_KeyContainer> && is_nothrow_move_constructible_v<_Compare>)
+# if _LIBCPP_HAS_EXCEPTIONS
+ try
+# endif // _LIBCPP_HAS_EXCEPTIONS
+ : __keys_(std::move(__other.__keys_)), __compare_(std::move(__other.__compare_)) {
+ __other.clear();
+# if _LIBCPP_HAS_EXCEPTIONS
+ } catch (...) {
+ __other.clear();
+ // gcc does not like the `throw` keyword in a conditionally noexcept function
+ if constexpr (!(is_nothrow_move_constructible_v<_KeyContainer> && is_nothrow_move_constructible_v<_Compare>)) {
+ throw;
+ }
+# endif // _LIBCPP_HAS_EXCEPTIONS
+ }
+
+ _LIBCPP_HIDE_FROM_ABI explicit flat_multiset(const key_compare& __comp) : __keys_(), __compare_(__comp) {}
+
+ _LIBCPP_HIDE_FROM_ABI explicit flat_multiset(container_type __keys, const key_compare& __comp = key_compare())
+ : __keys_(std::move(__keys)), __compare_(__comp) {
+ ranges::sort(__keys_, __compare_);
+ }
+
+ _LIBCPP_HIDE_FROM_ABI
+ flat_multiset(sorted_equivalent_t, container_type __keys, const key_compare& __comp = key_compare())
+ : __keys_(std::move(__keys)), __compare_(__comp) {
+ _LIBCPP_ASSERT_SEMANTIC_REQUIREMENT(ranges::is_sorted(__keys_, __compare_), "Key container is not sorted");
+ }
+
+ template <class _InputIterator>
+ requires __has_input_iterator_category<_InputIterator>::value
+ _LIBCPP_HIDE_FROM_ABI
+ flat_multiset(_InputIterator __first, _InputIterator __last, const key_compare& __comp = key_compare())
+ : __keys_(), __compare_(__comp) {
+ insert(__first, __last);
+ }
+
+ template <class _InputIterator>
+ requires __has_input_iterator_category<_InputIterator>::value
+ _LIBCPP_HIDE_FROM_ABI flat_multiset(
+ sorted_equivalent_t, _InputIterator __first, _InputIterator __last, const key_compare& __comp = key_compare())
+ : __keys_(__first, __last), __compare_(__comp) {
+ _LIBCPP_ASSERT_SEMANTIC_REQUIREMENT(ranges::is_sorted(__keys_, __compare_), "Key container is not sorted");
+ }
+
+ template <_ContainerCompatibleRange<value_type> _Range>
+ _LIBCPP_HIDE_FROM_ABI flat_multiset(from_range_t __fr, _Range&& __rg)
+ : flat_multiset(__fr, std::forward<_Range>(__rg), key_compare()) {}
+
+ template <_ContainerCompatibleRange<value_type> _Range>
+ _LIBCPP_HIDE_FROM_ABI flat_multiset(from_range_t, _Range&& __rg, const key_compare& __comp) : flat_multiset(__comp) {
+ insert_range(std::forward<_Range>(__rg));
+ }
+
+ _LIBCPP_HIDE_FROM_ABI flat_multiset(initializer_list<value_type> __il, const key_compare& __comp = key_compare())
+ : flat_multiset(__il.begin(), __il.end(), __comp) {}
+
+ _LIBCPP_HIDE_FROM_ABI
+ flat_multiset(sorted_equivalent_t, initializer_list<value_type> __il, const key_compare& __comp = key_compare())
+ : flat_multiset(sorted_equivalent, __il.begin(), __il.end(), __comp) {}
+
+ template <class _Allocator>
+ requires uses_allocator<container_type, _Allocator>::value
+ _LIBCPP_HIDE_FROM_ABI explicit flat_multiset(const _Allocator& __alloc)
+ : __keys_(std::make_obj_using_allocator<container_type>(__alloc)), __compare_() {}
+
+ template <class _Allocator>
+ requires uses_allocator<container_type, _Allocator>::value
+ _LIBCPP_HIDE_FROM_ABI flat_multiset(const key_compare& __comp, const _Allocator& __alloc)
+ : __keys_(std::make_obj_using_allocator<container_type>(__alloc)), __compare_(__comp) {}
+
+ template <class _Allocator>
+ requires uses_allocator<container_type, _Allocator>::value
+ _LIBCPP_HIDE_FROM_ABI flat_multiset(const container_type& __keys, const _Allocator& __alloc)
+ : __keys_(std::make_obj_using_allocator<container_type>(__alloc, __keys)), __compare_() {
+ ranges::sort(__keys_, __compare_);
+ }
+
+ template <class _Allocator>
+ requires uses_allocator<container_type, _Allocator>::value
+ _LIBCPP_HIDE_FROM_ABI
+ flat_multiset(const container_type& __keys, const key_compare& __comp, const _Allocator& __alloc)
+ : __keys_(std::make_obj_using_allocator<container_type>(__alloc, __keys)), __compare_(__comp) {
+ ranges::sort(__keys_, __compare_);
+ }
+
+ template <class _Allocator>
+ requires uses_allocator<container_type, _Allocator>::value
+ _LIBCPP_HIDE_FROM_ABI flat_multiset(sorted_equivalent_t, const container_type& __keys, const _Allocator& __alloc)
+ : __keys_(std::make_obj_using_allocator<container_type>(__alloc, __keys)), __compare_() {
+ _LIBCPP_ASSERT_SEMANTIC_REQUIREMENT(ranges::is_sorted(__keys_, __compare_), "Key container is not sorted");
+ }
+
+ template <class _Allocator>
+ requires uses_allocator<container_type, _Allocator>::value
+ _LIBCPP_HIDE_FROM_ABI
+ flat_multiset(sorted_equivalent_t, const container_type& __keys, const key_compare& __comp, const _Allocator& __alloc)
+ : __keys_(std::make_obj_using_allocator<container_type>(__alloc, __keys)), __compare_(__comp) {
+ _LIBCPP_ASSERT_SEMANTIC_REQUIREMENT(ranges::is_sorted(__keys_, __compare_), "Key container is not sorted");
+ }
+
+ template <class _Allocator>
+ requires uses_allocator<container_type, _Allocator>::value
+ _LIBCPP_HIDE_FROM_ABI flat_multiset(const flat_multiset& __other, const _Allocator& __alloc)
+ : __keys_(std::make_obj_using_allocator<container_type>(__alloc, __other.__keys_)),
+ __compare_(__other.__compare_) {}
+
+ template <class _Allocator>
+ requires uses_allocator<container_type, _Allocator>::value
+ _LIBCPP_HIDE_FROM_ABI flat_multiset(flat_multiset&& __other, const _Allocator& __alloc)
+# if _LIBCPP_HAS_EXCEPTIONS
+ try
+# endif // _LIBCPP_HAS_EXCEPTIONS
+ : __keys_(std::make_obj_using_allocator<container_type>(__alloc, std::move(__other.__keys_))),
+ __compare_(std::move(__other.__compare_)) {
+ __other.clear();
+# if _LIBCPP_HAS_EXCEPTIONS
+ } catch (...) {
+ __other.clear();
+ throw;
+# endif // _LIBCPP_HAS_EXCEPTIONS
+ }
+
+ template <class _InputIterator, class _Allocator>
+ requires(__has_input_iterator_category<_InputIterator>::value && uses_allocator<container_type, _Allocator>::value)
+ _LIBCPP_HIDE_FROM_ABI flat_multiset(_InputIterator __first, _InputIterator __last, const _Allocator& __alloc)
+ : __keys_(std::make_obj_using_allocator<container_type>(__alloc)), __compare_() {
+ insert(__first, __last);
+ }
+
+ template <class _InputIterator, class _Allocator>
+ requires(__has_input_iterator_category<_InputIterator>::value && uses_allocator<container_type, _Allocator>::value)
+ _LIBCPP_HIDE_FROM_ABI
+ flat_multiset(_InputIterator __first, _InputIterator __last, const key_compare& __comp, const _Allocator& __alloc)
+ : __keys_(std::make_obj_using_allocator<container_type>(__alloc)), __compare_(__comp) {
+ insert(__first, __last);
+ }
+
+ template <class _InputIterator, class _Allocator>
+ requires(__has_input_iterator_category<_InputIterator>::value && uses_allocator<container_type, _Allocator>::value)
+ _LIBCPP_HIDE_FROM_ABI
+ flat_multiset(sorted_equivalent_t, _InputIterator __first, _InputIterator __last, const _Allocator& __alloc)
+ : __keys_(std::make_obj_using_allocator<container_type>(__alloc, __first, __last)), __compare_() {
+ _LIBCPP_ASSERT_SEMANTIC_REQUIREMENT(ranges::is_sorted(__keys_, __compare_), "Key container is not sorted");
+ }
+
+ template <class _InputIterator, class _Allocator>
+ requires(__has_input_iterator_category<_InputIterator>::value && uses_allocator<container_type, _Allocator>::value)
+ _LIBCPP_HIDE_FROM_ABI
+ flat_multiset(sorted_equivalent_t,
+ _InputIterator __first,
+ _InputIterator __last,
+ const key_compare& __comp,
+ const _Allocator& __alloc)
+ : __keys_(std::make_obj_using_allocator<container_type>(__alloc, __first, __last)), __compare_(__comp) {
+ _LIBCPP_ASSERT_SEMANTIC_REQUIREMENT(ranges::is_sorted(__keys_, __compare_), "Key container is not sorted");
+ }
+
+ template <_ContainerCompatibleRange<value_type> _Range, class _Allocator>
+ requires uses_allocator<container_type, _Allocator>::value
+ _LIBCPP_HIDE_FROM_ABI flat_multiset(from_range_t, _Range&& __rg, const _Allocator& __alloc)
+ : __keys_(std::make_obj_using_allocator<container_type>(__alloc)), __compare_() {
+ insert_range(std::forward<_Range>(__rg));
+ }
+
+ template <_ContainerCompatibleRange<value_type> _Range, class _Allocator>
+ requires uses_allocator<container_type, _Allocator>::value
+ _LIBCPP_HIDE_FROM_ABI flat_multiset(from_range_t, _Range&& __rg, const key_compare& __comp, const _Allocator& __alloc)
+ : __keys_(std::make_obj_using_allocator<container_type>(__alloc)), __compare_(__comp) {
+ insert_range(std::forward<_Range>(__rg));
+ }
+
+ template <class _Allocator>
+ requires uses_allocator<container_type, _Allocator>::value
+ _LIBCPP_HIDE_FROM_ABI flat_multiset(initializer_list<value_type> __il, const _Allocator& __alloc)
+ : flat_multiset(__il.begin(), __il.end(), __alloc) {}
+
+ template <class _Allocator>
+ requires uses_allocator<container_type, _Allocator>::value
+ _LIBCPP_HIDE_FROM_ABI
+ flat_multiset(initializer_list<value_type> __il, const key_compare& __comp, const _Allocator& __alloc)
+ : flat_multiset(__il.begin(), __il.end(), __comp, __alloc) {}
+
+ template <class _Allocator>
+ requires uses_allocator<container_type, _Allocator>::value
+ _LIBCPP_HIDE_FROM_ABI flat_multiset(sorted_equivalent_t, initializer_list<value_type> __il, const _Allocator& __alloc)
+ : flat_multiset(sorted_equivalent, __il.begin(), __il.end(), __alloc) {}
+
+ template <class _Allocator>
+ requires uses_allocator<container_type, _Allocator>::value
+ _LIBCPP_HIDE_FROM_ABI flat_multiset(
+ sorted_equivalent_t, initializer_list<value_type> __il, const key_compare& __comp, const _Allocator& __alloc)
+ : flat_multiset(sorted_equivalent, __il.begin(), __il.end(), __comp, __alloc) {}
+
+ _LIBCPP_HIDE_FROM_ABI flat_multiset& operator=(initializer_list<value_type> __il) {
+ clear();
+ insert(__il);
+ return *this;
+ }
+
+ // copy/move assignment are not specified in the spec (defaulted)
+ // but move assignment can potentially leave moved from object in an inconsistent
+ // state if an exception is thrown
+ _LIBCPP_HIDE_FROM_ABI flat_multiset& operator=(const flat_multiset&) = default;
+
+ _LIBCPP_HIDE_FROM_ABI flat_multiset& operator=(flat_multiset&& __other) noexcept(
+ is_nothrow_move_assignable_v<_KeyContainer> && is_nothrow_move_assignable_v<_Compare>) {
+ auto __clear_other_guard = std::__make_scope_guard([&]() noexcept { __other.clear() /* noexcept */; });
+ auto __clear_self_guard = std::__make_exception_guard([&]() noexcept { clear() /* noexcept */; });
+ __keys_ = std::move(__other.__keys_);
+ __compare_ = std::move(__other.__compare_);
+ __clear_self_guard.__complete();
+ return *this;
+ }
+
+ // iterators
+ _LIBCPP_HIDE_FROM_ABI iterator begin() noexcept { return iterator(std::as_const(__keys_).begin()); }
+ _LIBCPP_HIDE_FROM_ABI const_iterator begin() const noexcept { return const_iterator(__keys_.begin()); }
+ _LIBCPP_HIDE_FROM_ABI iterator end() noexcept { return iterator(std::as_const(__keys_).end()); }
+ _LIBCPP_HIDE_FROM_ABI const_iterator end() const noexcept { return const_iterator(__keys_.end()); }
+
+ _LIBCPP_HIDE_FROM_ABI reverse_iterator rbegin() noexcept { return reverse_iterator(end()); }
+ _LIBCPP_HIDE_FROM_ABI const_reverse_iterator rbegin() const noexcept { return const_reverse_iterator(end()); }
+ _LIBCPP_HIDE_FROM_ABI reverse_iterator rend() noexcept { return reverse_iterator(begin()); }
+ _LIBCPP_HIDE_FROM_ABI const_reverse_iterator rend() const noexcept { return const_reverse_iterator(begin()); }
+
+ _LIBCPP_HIDE_FROM_ABI const_iterator cbegin() const noexcept { return begin(); }
+ _LIBCPP_HIDE_FROM_ABI const_iterator cend() const noexcept { return end(); }
+ _LIBCPP_HIDE_FROM_ABI const_reverse_iterator crbegin() const noexcept { return const_reverse_iterator(end()); }
+ _LIBCPP_HIDE_FROM_ABI const_reverse_iterator crend() const noexcept { return const_reverse_iterator(begin()); }
+
+ // capacity
+ [[nodiscard]] _LIBCPP_HIDE_FROM_ABI bool empty() const noexcept { return __keys_.empty(); }
+ _LIBCPP_HIDE_FROM_ABI size_type size() const noexcept { return __keys_.size(); }
+ _LIBCPP_HIDE_FROM_ABI size_type max_size() const noexcept { return __keys_.max_size(); }
+
+ // [flat.multiset.modifiers], modifiers
+ template <class... _Args>
+ requires is_constructible_v<value_type, _Args...>
+ _LIBCPP_HIDE_FROM_ABI iterator emplace(_Args&&... __args) {
+ if constexpr (sizeof...(__args) == 1 && (is_same_v<remove_cvref_t<_Args>, _Key> && ...)) {
+ return __emplace(std::forward<_Args>(__args)...);
+ } else {
+ return __emplace(_Key(std::forward<_Args>(__args)...));
+ }
+ }
+
+ template <class... _Args>
+ requires is_constructible_v<value_type, _Args...>
+ _LIBCPP_HIDE_FROM_ABI iterator emplace_hint(const_iterator __hint, _Args&&... __args) {
+ if constexpr (sizeof...(__args) == 1 && (is_same_v<remove_cvref_t<_Args>, _Key> && ...)) {
+ return __emplace_hint(std::move(__hint), std::forward<_Args>(__args)...);
+ } else {
+ return __emplace_hint(std::move(__hint), _Key(std::forward<_Args>(__args)...));
+ }
+ }
+
+ _LIBCPP_HIDE_FROM_ABI iterator insert(const value_type& __x) { return emplace(__x); }
+
+ _LIBCPP_HIDE_FROM_ABI iterator insert(value_type&& __x) { return emplace(std::move(__x)); }
+
+ _LIBCPP_HIDE_FROM_ABI iterator insert(const_iterator __hint, const value_type& __x) {
+ return emplace_hint(__hint, __x);
+ }
+
+ _LIBCPP_HIDE_FROM_ABI iterator insert(const_iterator __hint, value_type&& __x) {
+ return emplace_hint(__hint, std::move(__x));
+ }
+
+ template <class _InputIterator>
+ requires __has_input_iterator_category<_InputIterator>::value
+ _LIBCPP_HIDE_FROM_ABI void insert(_InputIterator __first, _InputIterator __last) {
+ if constexpr (sized_sentinel_for<_InputIterator, _InputIterator>) {
+ __reserve(__last - __first);
+ }
+ __append_sort_merge</*WasSorted = */ false>(std::move(__first), std::move(__last));
+ }
+
+ template <class _InputIterator>
+ requires __has_input_iterator_category<_InputIterator>::value
+ _LIBCPP_HIDE_FROM_ABI void insert(sorted_equivalent_t, _InputIterator __first, _InputIterator __last) {
+ if constexpr (sized_sentinel_for<_InputIterator, _InputIterator>) {
+ __reserve(__last - __first);
+ }
+
+ __append_sort_merge</*WasSorted = */ true>(std::move(__first), std::move(__last));
+ }
+
+ template <_ContainerCompatibleRange<value_type> _Range>
+ _LIBCPP_HIDE_FROM_ABI void insert_range(_Range&& __range) {
+ if constexpr (ranges::sized_range<_Range>) {
+ __reserve(ranges::size(__range));
+ }
+
+ __append_sort_merge</*WasSorted = */ false>(std::forward<_Range>(__range));
+ }
+
+ _LIBCPP_HIDE_FROM_ABI void insert(initializer_list<value_type> __il) { insert(__il.begin(), __il.end()); }
+
+ _LIBCPP_HIDE_FROM_ABI void insert(sorted_equivalent_t, initializer_list<value_type> __il) {
+ insert(sorted_equivalent, __il.begin(), __il.end());
+ }
+
+ _LIBCPP_HIDE_FROM_ABI container_type extract() && {
+ auto __guard = std::__make_scope_guard([&]() noexcept { clear() /* noexcept */; });
+ auto __ret = std::move(__keys_);
+ return __ret;
+ }
+
+ _LIBCPP_HIDE_FROM_ABI void replace(container_type&& __keys) {
+ _LIBCPP_ASSERT_SEMANTIC_REQUIREMENT(ranges::is_sorted(__keys, __compare_), "Key container is not sorted");
+ auto __guard = std::__make_exception_guard([&]() noexcept { clear() /* noexcept */; });
+ __keys_ = std::move(__keys);
+ __guard.__complete();
+ }
+
+ _LIBCPP_HIDE_FROM_ABI iterator erase(iterator __position) {
+ auto __on_failure = std::__make_exception_guard([&]() noexcept { clear() /* noexcept */; });
+ auto __key_iter = __keys_.erase(__position.__base());
+ __on_failure.__complete();
+ return iterator(__key_iter);
+ }
+
+ // iterator and const_iterator are the same type
+ // iterator erase(const_iterator __position);
+
+ _LIBCPP_HIDE_FROM_ABI size_type erase(const key_type& __x) {
+ auto [__first, __last] = equal_range(__x);
+ auto __res = __last - __first;
+ erase(__first, __last);
+ return __res;
+ }
+
+ template <class _Kp>
+ requires(__is_transparent_v<_Compare> && !is_convertible_v<_Kp &&, iterator> &&
+ !is_convertible_v<_Kp &&, const_iterator>)
+ _LIBCPP_HIDE_FROM_ABI size_type erase(_Kp&& __x) {
+ auto [__first, __last] = equal_range(__x);
+ auto __res = __last - __first;
+ erase(__first, __last);
+ return __res;
+ }
+
+ _LIBCPP_HIDE_FROM_ABI iterator erase(const_iterator __first, const_iterator __last) {
+ auto __on_failure = std::__make_exception_guard([&]() noexcept { clear() /* noexcept */; });
+ auto __key_it = __keys_.erase(__first.__base(), __last.__base());
+ __on_failure.__complete();
+ return iterator(std::move(__key_it));
+ }
+
+ _LIBCPP_HIDE_FROM_ABI void swap(flat_multiset& __y) noexcept {
+ // warning: The spec has unconditional noexcept, which means that
+ // if any of the following functions throw an exception,
+ // std::terminate will be called
+ // This is discussed in P2767, which hasn't been voted on yet.
+ ranges::swap(__compare_, __y.__compare_);
+ ranges::swap(__keys_, __y.__keys_);
+ }
+
+ _LIBCPP_HIDE_FROM_ABI void clear() noexcept { __keys_.clear(); }
+
+ // observers
+ _LIBCPP_HIDE_FROM_ABI key_compare key_comp() const { return __compare_; }
+ _LIBCPP_HIDE_FROM_ABI value_compare value_comp() const { return __compare_; }
+
+ // map operations
+ _LIBCPP_HIDE_FROM_ABI iterator find(const key_type& __x) { return __find_impl(*this, __x); }
+
+ _LIBCPP_HIDE_FROM_ABI const_iterator find(const key_type& __x) const { return __find_impl(*this, __x); }
+
+ template <class _Kp>
+ requires __is_transparent_v<_Compare>
+ _LIBCPP_HIDE_FROM_ABI iterator find(const _Kp& __x) {
+ return __find_impl(*this, __x);
+ }
+
+ template <class _Kp>
+ requires __is_transparent_v<_Compare>
+ _LIBCPP_HIDE_FROM_ABI const_iterator find(const _Kp& __x) const {
+ return __find_impl(*this, __x);
+ }
+
+ _LIBCPP_HIDE_FROM_ABI size_type count(const key_type& __x) const {
+ auto [__first, __last] = equal_range(__x);
+ return __last - __first;
+ }
+
+ template <class _Kp>
+ requires __is_transparent_v<_Compare>
+ _LIBCPP_HIDE_FROM_ABI size_type count(const _Kp& __x) const {
+ auto [__first, __last] = equal_range(__x);
+ return __last - __first;
+ }
+
+ _LIBCPP_HIDE_FROM_ABI bool contains(const key_type& __x) const { return find(__x) != end(); }
+
+ template <class _Kp>
+ requires __is_transparent_v<_Compare>
+ _LIBCPP_HIDE_FROM_ABI bool contains(const _Kp& __x) const {
+ return find(__x) != end();
+ }
+
+ _LIBCPP_HIDE_FROM_ABI iterator lower_bound(const key_type& __x) {
+ return iterator(ranges::lower_bound(std::as_const(__keys_), __x, __compare_));
+ }
+
+ _LIBCPP_HIDE_FROM_ABI const_iterator lower_bound(const key_type& __x) const {
+ return const_iterator(ranges::lower_bound(__keys_, __x, __compare_));
+ }
+
+ template <class _Kp>
+ requires __is_transparent_v<_Compare>
+ _LIBCPP_HIDE_FROM_ABI iterator lower_bound(const _Kp& __x) {
+ return iterator(ranges::lower_bound(std::as_const(__keys_), __x, __compare_));
+ }
+
+ template <class _Kp>
+ requires __is_transparent_v<_Compare>
+ _LIBCPP_HIDE_FROM_ABI const_iterator lower_bound(const _Kp& __x) const {
+ return const_iterator(ranges::lower_bound(__keys_, __x, __compare_));
+ }
+
+ _LIBCPP_HIDE_FROM_ABI iterator upper_bound(const key_type& __x) {
+ return iterator(ranges::upper_bound(std::as_const(__keys_), __x, __compare_));
+ }
+
+ _LIBCPP_HIDE_FROM_ABI const_iterator upper_bound(const key_type& __x) const {
+ return const_iterator(ranges::upper_bound(__keys_, __x, __compare_));
+ }
+
+ template <class _Kp>
+ requires __is_transparent_v<_Compare>
+ _LIBCPP_HIDE_FROM_ABI iterator upper_bound(const _Kp& __x) {
+ return iterator(ranges::upper_bound(std::as_const(__keys_), __x, __compare_));
+ }
+
+ template <class _Kp>
+ requires __is_transparent_v<_Compare>
+ _LIBCPP_HIDE_FROM_ABI const_iterator upper_bound(const _Kp& __x) const {
+ return const_iterator(ranges::upper_bound(__keys_, __x, __compare_));
+ }
+
+ _LIBCPP_HIDE_FROM_ABI pair<iterator, iterator> equal_range(const key_type& __x) {
+ return __equal_range_impl(*this, __x);
+ }
+
+ _LIBCPP_HIDE_FROM_ABI pair<const_iterator, const_iterator> equal_range(const key_type& __x) const {
+ return __equal_range_impl(*this, __x);
+ }
+
+ template <class _Kp>
+ requires __is_transparent_v<_Compare>
+ _LIBCPP_HIDE_FROM_ABI pair<iterator, iterator> equal_range(const _Kp& __x) {
+ return __equal_range_impl(*this, __x);
+ }
+ template <class _Kp>
+ requires __is_transparent_v<_Compare>
+ _LIBCPP_HIDE_FROM_ABI pair<const_iterator, const_iterator> equal_range(const _Kp& __x) const {
+ return __equal_range_impl(*this, __x);
+ }
+
+ friend _LIBCPP_HIDE_FROM_ABI bool operator==(const flat_multiset& __x, const flat_multiset& __y) {
+ return ranges::equal(__x, __y);
+ }
+
+ friend _LIBCPP_HIDE_FROM_ABI auto operator<=>(const flat_multiset& __x, const flat_multiset& __y) {
+ return std::lexicographical_compare_three_way(
+ __x.begin(), __x.end(), __y.begin(), __y.end(), std::__synth_three_way);
+ }
+
+ friend _LIBCPP_HIDE_FROM_ABI void swap(flat_multiset& __x, flat_multiset& __y) noexcept { __x.swap(__y); }
+
+private:
+ template <bool _WasSorted, class... _Args>
+ _LIBCPP_HIDE_FROM_ABI void __append_sort_merge(_Args&&... __args) {
+ auto __on_failure = std::__make_exception_guard([&]() noexcept { clear() /* noexcept */; });
+ size_type __old_size = size();
+ __flat_set_utils::__append(*this, std::forward<_Args>(__args)...);
+ if (size() != __old_size) {
----------------
ldionne wrote:
It might not be worth handling this special case explicitly. We certainly don't expect an empty range to be inserted very often. I'd remove the `if`.
https://github.com/llvm/llvm-project/pull/128363
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