xref: /llvm-project/libcxx/include/__flat_map/flat_map.h (revision def50f701f6a2c1e0550bb341fd8b64bed299e72)
1 // -*- C++ -*-
2 //===----------------------------------------------------------------------===//
3 //
4 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
5 // See https://llvm.org/LICENSE.txt for license information.
6 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
7 //
8 //===----------------------------------------------------------------------===//
9 
10 #ifndef _LIBCPP___FLAT_MAP_FLAT_MAP_H
11 #define _LIBCPP___FLAT_MAP_FLAT_MAP_H
12 
13 #include <__algorithm/lexicographical_compare_three_way.h>
14 #include <__algorithm/min.h>
15 #include <__algorithm/ranges_adjacent_find.h>
16 #include <__algorithm/ranges_equal.h>
17 #include <__algorithm/ranges_inplace_merge.h>
18 #include <__algorithm/ranges_lower_bound.h>
19 #include <__algorithm/ranges_partition_point.h>
20 #include <__algorithm/ranges_sort.h>
21 #include <__algorithm/ranges_unique.h>
22 #include <__algorithm/ranges_upper_bound.h>
23 #include <__algorithm/remove_if.h>
24 #include <__assert>
25 #include <__compare/synth_three_way.h>
26 #include <__concepts/swappable.h>
27 #include <__config>
28 #include <__cstddef/byte.h>
29 #include <__cstddef/ptrdiff_t.h>
30 #include <__flat_map/key_value_iterator.h>
31 #include <__flat_map/sorted_unique.h>
32 #include <__flat_map/utils.h>
33 #include <__functional/invoke.h>
34 #include <__functional/is_transparent.h>
35 #include <__functional/operations.h>
36 #include <__fwd/vector.h>
37 #include <__iterator/concepts.h>
38 #include <__iterator/distance.h>
39 #include <__iterator/iterator_traits.h>
40 #include <__iterator/next.h>
41 #include <__iterator/ranges_iterator_traits.h>
42 #include <__iterator/reverse_iterator.h>
43 #include <__memory/allocator_traits.h>
44 #include <__memory/uses_allocator.h>
45 #include <__memory/uses_allocator_construction.h>
46 #include <__ranges/access.h>
47 #include <__ranges/concepts.h>
48 #include <__ranges/container_compatible_range.h>
49 #include <__ranges/drop_view.h>
50 #include <__ranges/from_range.h>
51 #include <__ranges/ref_view.h>
52 #include <__ranges/size.h>
53 #include <__ranges/subrange.h>
54 #include <__ranges/zip_view.h>
55 #include <__type_traits/conjunction.h>
56 #include <__type_traits/container_traits.h>
57 #include <__type_traits/invoke.h>
58 #include <__type_traits/is_allocator.h>
59 #include <__type_traits/is_nothrow_constructible.h>
60 #include <__type_traits/is_same.h>
61 #include <__utility/exception_guard.h>
62 #include <__utility/move.h>
63 #include <__utility/pair.h>
64 #include <__utility/scope_guard.h>
65 #include <__vector/vector.h>
66 #include <initializer_list>
67 #include <stdexcept>
68 
69 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
70 #  pragma GCC system_header
71 #endif
72 
73 _LIBCPP_PUSH_MACROS
74 #include <__undef_macros>
75 
76 #if _LIBCPP_STD_VER >= 23
77 
78 _LIBCPP_BEGIN_NAMESPACE_STD
79 
80 template <class _Key,
81           class _Tp,
82           class _Compare         = less<_Key>,
83           class _KeyContainer    = vector<_Key>,
84           class _MappedContainer = vector<_Tp>>
85 class flat_map {
86   template <class, class, class, class, class>
87   friend class flat_map;
88 
89   static_assert(is_same_v<_Key, typename _KeyContainer::value_type>);
90   static_assert(is_same_v<_Tp, typename _MappedContainer::value_type>);
91   static_assert(!is_same_v<_KeyContainer, std::vector<bool>>, "vector<bool> is not a sequence container");
92   static_assert(!is_same_v<_MappedContainer, std::vector<bool>>, "vector<bool> is not a sequence container");
93 
94   template <bool _Const>
95   using __iterator _LIBCPP_NODEBUG = __key_value_iterator<flat_map, _KeyContainer, _MappedContainer, _Const>;
96 
97 public:
98   // types
99   using key_type               = _Key;
100   using mapped_type            = _Tp;
101   using value_type             = pair<key_type, mapped_type>;
102   using key_compare            = __type_identity_t<_Compare>;
103   using reference              = pair<const key_type&, mapped_type&>;
104   using const_reference        = pair<const key_type&, const mapped_type&>;
105   using size_type              = size_t;
106   using difference_type        = ptrdiff_t;
107   using iterator               = __iterator<false>; // see [container.requirements]
108   using const_iterator         = __iterator<true>;  // see [container.requirements]
109   using reverse_iterator       = std::reverse_iterator<iterator>;
110   using const_reverse_iterator = std::reverse_iterator<const_iterator>;
111   using key_container_type     = _KeyContainer;
112   using mapped_container_type  = _MappedContainer;
113 
114   class value_compare {
115   private:
116     key_compare __comp_;
117     _LIBCPP_HIDE_FROM_ABI value_compare(key_compare __c) : __comp_(__c) {}
118     friend flat_map;
119 
120   public:
121     _LIBCPP_HIDE_FROM_ABI bool operator()(const_reference __x, const_reference __y) const {
122       return __comp_(__x.first, __y.first);
123     }
124   };
125 
126   struct containers {
127     key_container_type keys;
128     mapped_container_type values;
129   };
130 
131 private:
132   template <class _Allocator>
133   _LIBCPP_HIDE_FROM_ABI static constexpr bool __allocator_ctor_constraint =
134       _And<uses_allocator<key_container_type, _Allocator>, uses_allocator<mapped_container_type, _Allocator>>::value;
135 
136   _LIBCPP_HIDE_FROM_ABI static constexpr bool __is_compare_transparent = __is_transparent_v<_Compare>;
137 
138 public:
139   // [flat.map.cons], construct/copy/destroy
140   _LIBCPP_HIDE_FROM_ABI flat_map() noexcept(
141       is_nothrow_default_constructible_v<_KeyContainer> && is_nothrow_default_constructible_v<_MappedContainer> &&
142       is_nothrow_default_constructible_v<_Compare>)
143       : __containers_(), __compare_() {}
144 
145   _LIBCPP_HIDE_FROM_ABI flat_map(const flat_map&) = default;
146 
147   _LIBCPP_HIDE_FROM_ABI flat_map(flat_map&& __other) noexcept(
148       is_nothrow_move_constructible_v<_KeyContainer> && is_nothrow_move_constructible_v<_MappedContainer> &&
149       is_nothrow_move_constructible_v<_Compare>)
150 #  if _LIBCPP_HAS_EXCEPTIONS
151       try
152 #  endif // _LIBCPP_HAS_EXCEPTIONS
153       : __containers_(std::move(__other.__containers_)), __compare_(std::move(__other.__compare_)) {
154     __other.clear();
155 #  if _LIBCPP_HAS_EXCEPTIONS
156   } catch (...) {
157     __other.clear();
158     // gcc does not like the `throw` keyword in a conditionally noexcept function
159     if constexpr (!(is_nothrow_move_constructible_v<_KeyContainer> &&
160                     is_nothrow_move_constructible_v<_MappedContainer> && is_nothrow_move_constructible_v<_Compare>)) {
161       throw;
162     }
163 #  endif // _LIBCPP_HAS_EXCEPTIONS
164   }
165 
166   template <class _Allocator>
167     requires __allocator_ctor_constraint<_Allocator>
168   _LIBCPP_HIDE_FROM_ABI flat_map(const flat_map& __other, const _Allocator& __alloc)
169       : flat_map(__ctor_uses_allocator_tag{},
170                  __alloc,
171                  __other.__containers_.keys,
172                  __other.__containers_.values,
173                  __other.__compare_) {}
174 
175   template <class _Allocator>
176     requires __allocator_ctor_constraint<_Allocator>
177   _LIBCPP_HIDE_FROM_ABI flat_map(flat_map&& __other, const _Allocator& __alloc)
178 #  if _LIBCPP_HAS_EXCEPTIONS
179       try
180 #  endif // _LIBCPP_HAS_EXCEPTIONS
181       : flat_map(__ctor_uses_allocator_tag{},
182                  __alloc,
183                  std::move(__other.__containers_.keys),
184                  std::move(__other.__containers_.values),
185                  std::move(__other.__compare_)) {
186     __other.clear();
187 #  if _LIBCPP_HAS_EXCEPTIONS
188   } catch (...) {
189     __other.clear();
190     throw;
191 #  endif // _LIBCPP_HAS_EXCEPTIONS
192   }
193 
194   _LIBCPP_HIDE_FROM_ABI flat_map(
195       key_container_type __key_cont, mapped_container_type __mapped_cont, const key_compare& __comp = key_compare())
196       : __containers_{.keys = std::move(__key_cont), .values = std::move(__mapped_cont)}, __compare_(__comp) {
197     _LIBCPP_ASSERT_VALID_INPUT_RANGE(__containers_.keys.size() == __containers_.values.size(),
198                                      "flat_map keys and mapped containers have different size");
199     __sort_and_unique();
200   }
201 
202   template <class _Allocator>
203     requires __allocator_ctor_constraint<_Allocator>
204   _LIBCPP_HIDE_FROM_ABI
205   flat_map(const key_container_type& __key_cont, const mapped_container_type& __mapped_cont, const _Allocator& __alloc)
206       : flat_map(__ctor_uses_allocator_tag{}, __alloc, __key_cont, __mapped_cont) {
207     _LIBCPP_ASSERT_VALID_INPUT_RANGE(__containers_.keys.size() == __containers_.values.size(),
208                                      "flat_map keys and mapped containers have different size");
209     __sort_and_unique();
210   }
211 
212   template <class _Allocator>
213     requires __allocator_ctor_constraint<_Allocator>
214   _LIBCPP_HIDE_FROM_ABI
215   flat_map(const key_container_type& __key_cont,
216            const mapped_container_type& __mapped_cont,
217            const key_compare& __comp,
218            const _Allocator& __alloc)
219       : flat_map(__ctor_uses_allocator_tag{}, __alloc, __key_cont, __mapped_cont, __comp) {
220     _LIBCPP_ASSERT_VALID_INPUT_RANGE(__containers_.keys.size() == __containers_.values.size(),
221                                      "flat_map keys and mapped containers have different size");
222     __sort_and_unique();
223   }
224 
225   _LIBCPP_HIDE_FROM_ABI
226   flat_map(sorted_unique_t,
227            key_container_type __key_cont,
228            mapped_container_type __mapped_cont,
229            const key_compare& __comp = key_compare())
230       : __containers_{.keys = std::move(__key_cont), .values = std::move(__mapped_cont)}, __compare_(__comp) {
231     _LIBCPP_ASSERT_VALID_INPUT_RANGE(__containers_.keys.size() == __containers_.values.size(),
232                                      "flat_map keys and mapped containers have different size");
233     _LIBCPP_ASSERT_SEMANTIC_REQUIREMENT(
234         __is_sorted_and_unique(__containers_.keys), "Either the key container is not sorted or it contains duplicates");
235   }
236 
237   template <class _Allocator>
238     requires __allocator_ctor_constraint<_Allocator>
239   _LIBCPP_HIDE_FROM_ABI
240   flat_map(sorted_unique_t,
241            const key_container_type& __key_cont,
242            const mapped_container_type& __mapped_cont,
243            const _Allocator& __alloc)
244       : flat_map(__ctor_uses_allocator_tag{}, __alloc, __key_cont, __mapped_cont) {
245     _LIBCPP_ASSERT_VALID_INPUT_RANGE(__containers_.keys.size() == __containers_.values.size(),
246                                      "flat_map keys and mapped containers have different size");
247     _LIBCPP_ASSERT_SEMANTIC_REQUIREMENT(
248         __is_sorted_and_unique(__containers_.keys), "Either the key container is not sorted or it contains duplicates");
249   }
250 
251   template <class _Allocator>
252     requires __allocator_ctor_constraint<_Allocator>
253   _LIBCPP_HIDE_FROM_ABI
254   flat_map(sorted_unique_t,
255            const key_container_type& __key_cont,
256            const mapped_container_type& __mapped_cont,
257            const key_compare& __comp,
258            const _Allocator& __alloc)
259       : flat_map(__ctor_uses_allocator_tag{}, __alloc, __key_cont, __mapped_cont, __comp) {
260     _LIBCPP_ASSERT_VALID_INPUT_RANGE(__containers_.keys.size() == __containers_.values.size(),
261                                      "flat_map keys and mapped containers have different size");
262     _LIBCPP_ASSERT_SEMANTIC_REQUIREMENT(
263         __is_sorted_and_unique(__containers_.keys), "Either the key container is not sorted or it contains duplicates");
264   }
265 
266   _LIBCPP_HIDE_FROM_ABI explicit flat_map(const key_compare& __comp) : __containers_(), __compare_(__comp) {}
267 
268   template <class _Allocator>
269     requires __allocator_ctor_constraint<_Allocator>
270   _LIBCPP_HIDE_FROM_ABI flat_map(const key_compare& __comp, const _Allocator& __alloc)
271       : flat_map(__ctor_uses_allocator_empty_tag{}, __alloc, __comp) {}
272 
273   template <class _Allocator>
274     requires __allocator_ctor_constraint<_Allocator>
275   _LIBCPP_HIDE_FROM_ABI explicit flat_map(const _Allocator& __alloc)
276       : flat_map(__ctor_uses_allocator_empty_tag{}, __alloc) {}
277 
278   template <class _InputIterator>
279     requires __has_input_iterator_category<_InputIterator>::value
280   _LIBCPP_HIDE_FROM_ABI
281   flat_map(_InputIterator __first, _InputIterator __last, const key_compare& __comp = key_compare())
282       : __containers_(), __compare_(__comp) {
283     insert(__first, __last);
284   }
285 
286   template <class _InputIterator, class _Allocator>
287     requires(__has_input_iterator_category<_InputIterator>::value && __allocator_ctor_constraint<_Allocator>)
288   _LIBCPP_HIDE_FROM_ABI
289   flat_map(_InputIterator __first, _InputIterator __last, const key_compare& __comp, const _Allocator& __alloc)
290       : flat_map(__ctor_uses_allocator_empty_tag{}, __alloc, __comp) {
291     insert(__first, __last);
292   }
293 
294   template <class _InputIterator, class _Allocator>
295     requires(__has_input_iterator_category<_InputIterator>::value && __allocator_ctor_constraint<_Allocator>)
296   _LIBCPP_HIDE_FROM_ABI flat_map(_InputIterator __first, _InputIterator __last, const _Allocator& __alloc)
297       : flat_map(__ctor_uses_allocator_empty_tag{}, __alloc) {
298     insert(__first, __last);
299   }
300 
301   template <_ContainerCompatibleRange<value_type> _Range>
302   _LIBCPP_HIDE_FROM_ABI flat_map(from_range_t __fr, _Range&& __rg)
303       : flat_map(__fr, std::forward<_Range>(__rg), key_compare()) {}
304 
305   template <_ContainerCompatibleRange<value_type> _Range, class _Allocator>
306     requires __allocator_ctor_constraint<_Allocator>
307   _LIBCPP_HIDE_FROM_ABI flat_map(from_range_t, _Range&& __rg, const _Allocator& __alloc)
308       : flat_map(__ctor_uses_allocator_empty_tag{}, __alloc) {
309     insert_range(std::forward<_Range>(__rg));
310   }
311 
312   template <_ContainerCompatibleRange<value_type> _Range>
313   _LIBCPP_HIDE_FROM_ABI flat_map(from_range_t, _Range&& __rg, const key_compare& __comp) : flat_map(__comp) {
314     insert_range(std::forward<_Range>(__rg));
315   }
316 
317   template <_ContainerCompatibleRange<value_type> _Range, class _Allocator>
318     requires __allocator_ctor_constraint<_Allocator>
319   _LIBCPP_HIDE_FROM_ABI flat_map(from_range_t, _Range&& __rg, const key_compare& __comp, const _Allocator& __alloc)
320       : flat_map(__ctor_uses_allocator_empty_tag{}, __alloc, __comp) {
321     insert_range(std::forward<_Range>(__rg));
322   }
323 
324   template <class _InputIterator>
325     requires __has_input_iterator_category<_InputIterator>::value
326   _LIBCPP_HIDE_FROM_ABI
327   flat_map(sorted_unique_t, _InputIterator __first, _InputIterator __last, const key_compare& __comp = key_compare())
328       : __containers_(), __compare_(__comp) {
329     insert(sorted_unique, __first, __last);
330   }
331   template <class _InputIterator, class _Allocator>
332     requires(__has_input_iterator_category<_InputIterator>::value && __allocator_ctor_constraint<_Allocator>)
333   _LIBCPP_HIDE_FROM_ABI
334   flat_map(sorted_unique_t,
335            _InputIterator __first,
336            _InputIterator __last,
337            const key_compare& __comp,
338            const _Allocator& __alloc)
339       : flat_map(__ctor_uses_allocator_empty_tag{}, __alloc, __comp) {
340     insert(sorted_unique, __first, __last);
341   }
342 
343   template <class _InputIterator, class _Allocator>
344     requires(__has_input_iterator_category<_InputIterator>::value && __allocator_ctor_constraint<_Allocator>)
345   _LIBCPP_HIDE_FROM_ABI
346   flat_map(sorted_unique_t, _InputIterator __first, _InputIterator __last, const _Allocator& __alloc)
347       : flat_map(__ctor_uses_allocator_empty_tag{}, __alloc) {
348     insert(sorted_unique, __first, __last);
349   }
350 
351   _LIBCPP_HIDE_FROM_ABI flat_map(initializer_list<value_type> __il, const key_compare& __comp = key_compare())
352       : flat_map(__il.begin(), __il.end(), __comp) {}
353 
354   template <class _Allocator>
355     requires __allocator_ctor_constraint<_Allocator>
356   _LIBCPP_HIDE_FROM_ABI
357   flat_map(initializer_list<value_type> __il, const key_compare& __comp, const _Allocator& __alloc)
358       : flat_map(__il.begin(), __il.end(), __comp, __alloc) {}
359 
360   template <class _Allocator>
361     requires __allocator_ctor_constraint<_Allocator>
362   _LIBCPP_HIDE_FROM_ABI flat_map(initializer_list<value_type> __il, const _Allocator& __alloc)
363       : flat_map(__il.begin(), __il.end(), __alloc) {}
364 
365   _LIBCPP_HIDE_FROM_ABI
366   flat_map(sorted_unique_t, initializer_list<value_type> __il, const key_compare& __comp = key_compare())
367       : flat_map(sorted_unique, __il.begin(), __il.end(), __comp) {}
368 
369   template <class _Allocator>
370     requires __allocator_ctor_constraint<_Allocator>
371   _LIBCPP_HIDE_FROM_ABI
372   flat_map(sorted_unique_t, initializer_list<value_type> __il, const key_compare& __comp, const _Allocator& __alloc)
373       : flat_map(sorted_unique, __il.begin(), __il.end(), __comp, __alloc) {}
374 
375   template <class _Allocator>
376     requires __allocator_ctor_constraint<_Allocator>
377   _LIBCPP_HIDE_FROM_ABI flat_map(sorted_unique_t, initializer_list<value_type> __il, const _Allocator& __alloc)
378       : flat_map(sorted_unique, __il.begin(), __il.end(), __alloc) {}
379 
380   _LIBCPP_HIDE_FROM_ABI flat_map& operator=(initializer_list<value_type> __il) {
381     clear();
382     insert(__il);
383     return *this;
384   }
385 
386   _LIBCPP_HIDE_FROM_ABI flat_map& operator=(const flat_map&) = default;
387 
388   _LIBCPP_HIDE_FROM_ABI flat_map& operator=(flat_map&& __other) noexcept(
389       is_nothrow_move_assignable_v<_KeyContainer> && is_nothrow_move_assignable_v<_MappedContainer> &&
390       is_nothrow_move_assignable_v<_Compare>) {
391     // No matter what happens, we always want to clear the other container before returning
392     // since we moved from it
393     auto __clear_other_guard = std::__make_scope_guard([&]() noexcept { __other.clear() /* noexcept */; });
394     {
395       // If an exception is thrown, we have no choice but to clear *this to preserve invariants
396       auto __on_exception = std::__make_exception_guard([&]() noexcept { clear() /* noexcept */; });
397       __containers_       = std::move(__other.__containers_);
398       __compare_          = std::move(__other.__compare_);
399       __on_exception.__complete();
400     }
401     return *this;
402   }
403 
404   // iterators
405   _LIBCPP_HIDE_FROM_ABI iterator begin() noexcept {
406     return iterator(__containers_.keys.begin(), __containers_.values.begin());
407   }
408 
409   _LIBCPP_HIDE_FROM_ABI const_iterator begin() const noexcept {
410     return const_iterator(__containers_.keys.begin(), __containers_.values.begin());
411   }
412 
413   _LIBCPP_HIDE_FROM_ABI iterator end() noexcept {
414     return iterator(__containers_.keys.end(), __containers_.values.end());
415   }
416 
417   _LIBCPP_HIDE_FROM_ABI const_iterator end() const noexcept {
418     return const_iterator(__containers_.keys.end(), __containers_.values.end());
419   }
420 
421   _LIBCPP_HIDE_FROM_ABI reverse_iterator rbegin() noexcept { return reverse_iterator(end()); }
422   _LIBCPP_HIDE_FROM_ABI const_reverse_iterator rbegin() const noexcept { return const_reverse_iterator(end()); }
423   _LIBCPP_HIDE_FROM_ABI reverse_iterator rend() noexcept { return reverse_iterator(begin()); }
424   _LIBCPP_HIDE_FROM_ABI const_reverse_iterator rend() const noexcept { return const_reverse_iterator(begin()); }
425 
426   _LIBCPP_HIDE_FROM_ABI const_iterator cbegin() const noexcept { return begin(); }
427   _LIBCPP_HIDE_FROM_ABI const_iterator cend() const noexcept { return end(); }
428   _LIBCPP_HIDE_FROM_ABI const_reverse_iterator crbegin() const noexcept { return const_reverse_iterator(end()); }
429   _LIBCPP_HIDE_FROM_ABI const_reverse_iterator crend() const noexcept { return const_reverse_iterator(begin()); }
430 
431   // [flat.map.capacity], capacity
432   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI bool empty() const noexcept { return __containers_.keys.empty(); }
433 
434   _LIBCPP_HIDE_FROM_ABI size_type size() const noexcept { return __containers_.keys.size(); }
435 
436   _LIBCPP_HIDE_FROM_ABI size_type max_size() const noexcept {
437     return std::min<size_type>(__containers_.keys.max_size(), __containers_.values.max_size());
438   }
439 
440   // [flat.map.access], element access
441   _LIBCPP_HIDE_FROM_ABI mapped_type& operator[](const key_type& __x)
442     requires is_constructible_v<mapped_type>
443   {
444     return try_emplace(__x).first->second;
445   }
446 
447   _LIBCPP_HIDE_FROM_ABI mapped_type& operator[](key_type&& __x)
448     requires is_constructible_v<mapped_type>
449   {
450     return try_emplace(std::move(__x)).first->second;
451   }
452 
453   template <class _Kp>
454     requires(__is_compare_transparent && is_constructible_v<key_type, _Kp> && is_constructible_v<mapped_type> &&
455              !is_convertible_v<_Kp &&, const_iterator> && !is_convertible_v<_Kp &&, iterator>)
456   _LIBCPP_HIDE_FROM_ABI mapped_type& operator[](_Kp&& __x) {
457     return try_emplace(std::forward<_Kp>(__x)).first->second;
458   }
459 
460   _LIBCPP_HIDE_FROM_ABI mapped_type& at(const key_type& __x) {
461     auto __it = find(__x);
462     if (__it == end()) {
463       std::__throw_out_of_range("flat_map::at(const key_type&): Key does not exist");
464     }
465     return __it->second;
466   }
467 
468   _LIBCPP_HIDE_FROM_ABI const mapped_type& at(const key_type& __x) const {
469     auto __it = find(__x);
470     if (__it == end()) {
471       std::__throw_out_of_range("flat_map::at(const key_type&) const: Key does not exist");
472     }
473     return __it->second;
474   }
475 
476   template <class _Kp>
477     requires __is_compare_transparent
478   _LIBCPP_HIDE_FROM_ABI mapped_type& at(const _Kp& __x) {
479     auto __it = find(__x);
480     if (__it == end()) {
481       std::__throw_out_of_range("flat_map::at(const K&): Key does not exist");
482     }
483     return __it->second;
484   }
485 
486   template <class _Kp>
487     requires __is_compare_transparent
488   _LIBCPP_HIDE_FROM_ABI const mapped_type& at(const _Kp& __x) const {
489     auto __it = find(__x);
490     if (__it == end()) {
491       std::__throw_out_of_range("flat_map::at(const K&) const: Key does not exist");
492     }
493     return __it->second;
494   }
495 
496   // [flat.map.modifiers], modifiers
497   template <class... _Args>
498     requires is_constructible_v<pair<key_type, mapped_type>, _Args...>
499   _LIBCPP_HIDE_FROM_ABI pair<iterator, bool> emplace(_Args&&... __args) {
500     std::pair<key_type, mapped_type> __pair(std::forward<_Args>(__args)...);
501     return __try_emplace(std::move(__pair.first), std::move(__pair.second));
502   }
503 
504   template <class... _Args>
505     requires is_constructible_v<pair<key_type, mapped_type>, _Args...>
506   _LIBCPP_HIDE_FROM_ABI iterator emplace_hint(const_iterator __hint, _Args&&... __args) {
507     std::pair<key_type, mapped_type> __pair(std::forward<_Args>(__args)...);
508     return __try_emplace_hint(__hint, std::move(__pair.first), std::move(__pair.second)).first;
509   }
510 
511   _LIBCPP_HIDE_FROM_ABI pair<iterator, bool> insert(const value_type& __x) { return emplace(__x); }
512 
513   _LIBCPP_HIDE_FROM_ABI pair<iterator, bool> insert(value_type&& __x) { return emplace(std::move(__x)); }
514 
515   _LIBCPP_HIDE_FROM_ABI iterator insert(const_iterator __hint, const value_type& __x) {
516     return emplace_hint(__hint, __x);
517   }
518 
519   _LIBCPP_HIDE_FROM_ABI iterator insert(const_iterator __hint, value_type&& __x) {
520     return emplace_hint(__hint, std::move(__x));
521   }
522 
523   template <class _PairLike>
524     requires is_constructible_v<pair<key_type, mapped_type>, _PairLike>
525   _LIBCPP_HIDE_FROM_ABI pair<iterator, bool> insert(_PairLike&& __x) {
526     return emplace(std::forward<_PairLike>(__x));
527   }
528 
529   template <class _PairLike>
530     requires is_constructible_v<pair<key_type, mapped_type>, _PairLike>
531   _LIBCPP_HIDE_FROM_ABI iterator insert(const_iterator __hint, _PairLike&& __x) {
532     return emplace_hint(__hint, std::forward<_PairLike>(__x));
533   }
534 
535   template <class _InputIterator>
536     requires __has_input_iterator_category<_InputIterator>::value
537   _LIBCPP_HIDE_FROM_ABI void insert(_InputIterator __first, _InputIterator __last) {
538     if constexpr (sized_sentinel_for<_InputIterator, _InputIterator>) {
539       __reserve(__last - __first);
540     }
541     __append_sort_merge_unique</*WasSorted = */ false>(std::move(__first), std::move(__last));
542   }
543 
544   template <class _InputIterator>
545     requires __has_input_iterator_category<_InputIterator>::value
546   _LIBCPP_HIDE_FROM_ABI void insert(sorted_unique_t, _InputIterator __first, _InputIterator __last) {
547     if constexpr (sized_sentinel_for<_InputIterator, _InputIterator>) {
548       __reserve(__last - __first);
549     }
550 
551     __append_sort_merge_unique</*WasSorted = */ true>(std::move(__first), std::move(__last));
552   }
553 
554   template <_ContainerCompatibleRange<value_type> _Range>
555   _LIBCPP_HIDE_FROM_ABI void insert_range(_Range&& __range) {
556     if constexpr (ranges::sized_range<_Range>) {
557       __reserve(ranges::size(__range));
558     }
559 
560     __append_sort_merge_unique</*WasSorted = */ false>(ranges::begin(__range), ranges::end(__range));
561   }
562 
563   _LIBCPP_HIDE_FROM_ABI void insert(initializer_list<value_type> __il) { insert(__il.begin(), __il.end()); }
564 
565   _LIBCPP_HIDE_FROM_ABI void insert(sorted_unique_t, initializer_list<value_type> __il) {
566     insert(sorted_unique, __il.begin(), __il.end());
567   }
568 
569   _LIBCPP_HIDE_FROM_ABI containers extract() && {
570     auto __guard = std::__make_scope_guard([&]() noexcept { clear() /* noexcept */; });
571     auto __ret   = std::move(__containers_);
572     return __ret;
573   }
574 
575   _LIBCPP_HIDE_FROM_ABI void replace(key_container_type&& __key_cont, mapped_container_type&& __mapped_cont) {
576     _LIBCPP_ASSERT_VALID_INPUT_RANGE(
577         __key_cont.size() == __mapped_cont.size(), "flat_map keys and mapped containers have different size");
578 
579     _LIBCPP_ASSERT_SEMANTIC_REQUIREMENT(
580         __is_sorted_and_unique(__key_cont), "Either the key container is not sorted or it contains duplicates");
581     auto __guard         = std::__make_exception_guard([&]() noexcept { clear() /* noexcept */; });
582     __containers_.keys   = std::move(__key_cont);
583     __containers_.values = std::move(__mapped_cont);
584     __guard.__complete();
585   }
586 
587   template <class... _Args>
588     requires is_constructible_v<mapped_type, _Args...>
589   _LIBCPP_HIDE_FROM_ABI pair<iterator, bool> try_emplace(const key_type& __key, _Args&&... __args) {
590     return __try_emplace(__key, std::forward<_Args>(__args)...);
591   }
592 
593   template <class... _Args>
594     requires is_constructible_v<mapped_type, _Args...>
595   _LIBCPP_HIDE_FROM_ABI pair<iterator, bool> try_emplace(key_type&& __key, _Args&&... __args) {
596     return __try_emplace(std::move(__key), std::forward<_Args>(__args)...);
597   }
598 
599   template <class _Kp, class... _Args>
600     requires(__is_compare_transparent && is_constructible_v<key_type, _Kp> &&
601              is_constructible_v<mapped_type, _Args...> && !is_convertible_v<_Kp &&, const_iterator> &&
602              !is_convertible_v<_Kp &&, iterator>)
603   _LIBCPP_HIDE_FROM_ABI pair<iterator, bool> try_emplace(_Kp&& __key, _Args&&... __args) {
604     return __try_emplace(std::forward<_Kp>(__key), std::forward<_Args>(__args)...);
605   }
606 
607   template <class... _Args>
608     requires is_constructible_v<mapped_type, _Args...>
609   _LIBCPP_HIDE_FROM_ABI iterator try_emplace(const_iterator __hint, const key_type& __key, _Args&&... __args) {
610     return __try_emplace_hint(__hint, __key, std::forward<_Args>(__args)...).first;
611   }
612 
613   template <class... _Args>
614     requires is_constructible_v<mapped_type, _Args...>
615   _LIBCPP_HIDE_FROM_ABI iterator try_emplace(const_iterator __hint, key_type&& __key, _Args&&... __args) {
616     return __try_emplace_hint(__hint, std::move(__key), std::forward<_Args>(__args)...).first;
617   }
618 
619   template <class _Kp, class... _Args>
620     requires __is_compare_transparent && is_constructible_v<key_type, _Kp> && is_constructible_v<mapped_type, _Args...>
621   _LIBCPP_HIDE_FROM_ABI iterator try_emplace(const_iterator __hint, _Kp&& __key, _Args&&... __args) {
622     return __try_emplace_hint(__hint, std::forward<_Kp>(__key), std::forward<_Args>(__args)...).first;
623   }
624 
625   template <class _Mapped>
626     requires is_assignable_v<mapped_type&, _Mapped> && is_constructible_v<mapped_type, _Mapped>
627   _LIBCPP_HIDE_FROM_ABI pair<iterator, bool> insert_or_assign(const key_type& __key, _Mapped&& __obj) {
628     return __insert_or_assign(__key, std::forward<_Mapped>(__obj));
629   }
630 
631   template <class _Mapped>
632     requires is_assignable_v<mapped_type&, _Mapped> && is_constructible_v<mapped_type, _Mapped>
633   _LIBCPP_HIDE_FROM_ABI pair<iterator, bool> insert_or_assign(key_type&& __key, _Mapped&& __obj) {
634     return __insert_or_assign(std::move(__key), std::forward<_Mapped>(__obj));
635   }
636 
637   template <class _Kp, class _Mapped>
638     requires __is_compare_transparent && is_constructible_v<key_type, _Kp> && is_assignable_v<mapped_type&, _Mapped> &&
639              is_constructible_v<mapped_type, _Mapped>
640   _LIBCPP_HIDE_FROM_ABI pair<iterator, bool> insert_or_assign(_Kp&& __key, _Mapped&& __obj) {
641     return __insert_or_assign(std::forward<_Kp>(__key), std::forward<_Mapped>(__obj));
642   }
643 
644   template <class _Mapped>
645     requires is_assignable_v<mapped_type&, _Mapped> && is_constructible_v<mapped_type, _Mapped>
646   _LIBCPP_HIDE_FROM_ABI iterator insert_or_assign(const_iterator __hint, const key_type& __key, _Mapped&& __obj) {
647     return __insert_or_assign(__hint, __key, std::forward<_Mapped>(__obj));
648   }
649 
650   template <class _Mapped>
651     requires is_assignable_v<mapped_type&, _Mapped> && is_constructible_v<mapped_type, _Mapped>
652   _LIBCPP_HIDE_FROM_ABI iterator insert_or_assign(const_iterator __hint, key_type&& __key, _Mapped&& __obj) {
653     return __insert_or_assign(__hint, std::move(__key), std::forward<_Mapped>(__obj));
654   }
655 
656   template <class _Kp, class _Mapped>
657     requires __is_compare_transparent && is_constructible_v<key_type, _Kp> && is_assignable_v<mapped_type&, _Mapped> &&
658              is_constructible_v<mapped_type, _Mapped>
659   _LIBCPP_HIDE_FROM_ABI iterator insert_or_assign(const_iterator __hint, _Kp&& __key, _Mapped&& __obj) {
660     return __insert_or_assign(__hint, std::forward<_Kp>(__key), std::forward<_Mapped>(__obj));
661   }
662 
663   _LIBCPP_HIDE_FROM_ABI iterator erase(iterator __position) {
664     return __erase(__position.__key_iter_, __position.__mapped_iter_);
665   }
666 
667   _LIBCPP_HIDE_FROM_ABI iterator erase(const_iterator __position) {
668     return __erase(__position.__key_iter_, __position.__mapped_iter_);
669   }
670 
671   _LIBCPP_HIDE_FROM_ABI size_type erase(const key_type& __x) {
672     auto __iter = find(__x);
673     if (__iter != end()) {
674       erase(__iter);
675       return 1;
676     }
677     return 0;
678   }
679 
680   template <class _Kp>
681     requires(__is_compare_transparent && !is_convertible_v<_Kp &&, iterator> &&
682              !is_convertible_v<_Kp &&, const_iterator>)
683   _LIBCPP_HIDE_FROM_ABI size_type erase(_Kp&& __x) {
684     auto [__first, __last] = equal_range(__x);
685     auto __res             = __last - __first;
686     erase(__first, __last);
687     return __res;
688   }
689 
690   _LIBCPP_HIDE_FROM_ABI iterator erase(const_iterator __first, const_iterator __last) {
691     auto __on_failure = std::__make_exception_guard([&]() noexcept { clear() /* noexcept */; });
692     auto __key_it     = __containers_.keys.erase(__first.__key_iter_, __last.__key_iter_);
693     auto __mapped_it  = __containers_.values.erase(__first.__mapped_iter_, __last.__mapped_iter_);
694     __on_failure.__complete();
695     return iterator(std::move(__key_it), std::move(__mapped_it));
696   }
697 
698   _LIBCPP_HIDE_FROM_ABI void swap(flat_map& __y) noexcept {
699     // warning: The spec has unconditional noexcept, which means that
700     // if any of the following functions throw an exception,
701     // std::terminate will be called.
702     // This is discussed in P2767, which hasn't been voted on yet.
703     ranges::swap(__compare_, __y.__compare_);
704     ranges::swap(__containers_.keys, __y.__containers_.keys);
705     ranges::swap(__containers_.values, __y.__containers_.values);
706   }
707 
708   _LIBCPP_HIDE_FROM_ABI void clear() noexcept {
709     __containers_.keys.clear();
710     __containers_.values.clear();
711   }
712 
713   // observers
714   _LIBCPP_HIDE_FROM_ABI key_compare key_comp() const { return __compare_; }
715   _LIBCPP_HIDE_FROM_ABI value_compare value_comp() const { return value_compare(__compare_); }
716 
717   _LIBCPP_HIDE_FROM_ABI const key_container_type& keys() const noexcept { return __containers_.keys; }
718   _LIBCPP_HIDE_FROM_ABI const mapped_container_type& values() const noexcept { return __containers_.values; }
719 
720   // map operations
721   _LIBCPP_HIDE_FROM_ABI iterator find(const key_type& __x) { return __find_impl(*this, __x); }
722 
723   _LIBCPP_HIDE_FROM_ABI const_iterator find(const key_type& __x) const { return __find_impl(*this, __x); }
724 
725   template <class _Kp>
726     requires __is_compare_transparent
727   _LIBCPP_HIDE_FROM_ABI iterator find(const _Kp& __x) {
728     return __find_impl(*this, __x);
729   }
730 
731   template <class _Kp>
732     requires __is_compare_transparent
733   _LIBCPP_HIDE_FROM_ABI const_iterator find(const _Kp& __x) const {
734     return __find_impl(*this, __x);
735   }
736 
737   _LIBCPP_HIDE_FROM_ABI size_type count(const key_type& __x) const { return contains(__x) ? 1 : 0; }
738 
739   template <class _Kp>
740     requires __is_compare_transparent
741   _LIBCPP_HIDE_FROM_ABI size_type count(const _Kp& __x) const {
742     return contains(__x) ? 1 : 0;
743   }
744 
745   _LIBCPP_HIDE_FROM_ABI bool contains(const key_type& __x) const { return find(__x) != end(); }
746 
747   template <class _Kp>
748     requires __is_compare_transparent
749   _LIBCPP_HIDE_FROM_ABI bool contains(const _Kp& __x) const {
750     return find(__x) != end();
751   }
752 
753   _LIBCPP_HIDE_FROM_ABI iterator lower_bound(const key_type& __x) { return __lower_bound<iterator>(*this, __x); }
754 
755   _LIBCPP_HIDE_FROM_ABI const_iterator lower_bound(const key_type& __x) const {
756     return __lower_bound<const_iterator>(*this, __x);
757   }
758 
759   template <class _Kp>
760     requires __is_compare_transparent
761   _LIBCPP_HIDE_FROM_ABI iterator lower_bound(const _Kp& __x) {
762     return __lower_bound<iterator>(*this, __x);
763   }
764 
765   template <class _Kp>
766     requires __is_compare_transparent
767   _LIBCPP_HIDE_FROM_ABI const_iterator lower_bound(const _Kp& __x) const {
768     return __lower_bound<const_iterator>(*this, __x);
769   }
770 
771   _LIBCPP_HIDE_FROM_ABI iterator upper_bound(const key_type& __x) { return __upper_bound<iterator>(*this, __x); }
772 
773   _LIBCPP_HIDE_FROM_ABI const_iterator upper_bound(const key_type& __x) const {
774     return __upper_bound<const_iterator>(*this, __x);
775   }
776 
777   template <class _Kp>
778     requires __is_compare_transparent
779   _LIBCPP_HIDE_FROM_ABI iterator upper_bound(const _Kp& __x) {
780     return __upper_bound<iterator>(*this, __x);
781   }
782 
783   template <class _Kp>
784     requires __is_compare_transparent
785   _LIBCPP_HIDE_FROM_ABI const_iterator upper_bound(const _Kp& __x) const {
786     return __upper_bound<const_iterator>(*this, __x);
787   }
788 
789   _LIBCPP_HIDE_FROM_ABI pair<iterator, iterator> equal_range(const key_type& __x) {
790     return __equal_range_impl(*this, __x);
791   }
792 
793   _LIBCPP_HIDE_FROM_ABI pair<const_iterator, const_iterator> equal_range(const key_type& __x) const {
794     return __equal_range_impl(*this, __x);
795   }
796 
797   template <class _Kp>
798     requires __is_compare_transparent
799   _LIBCPP_HIDE_FROM_ABI pair<iterator, iterator> equal_range(const _Kp& __x) {
800     return __equal_range_impl(*this, __x);
801   }
802   template <class _Kp>
803     requires __is_compare_transparent
804   _LIBCPP_HIDE_FROM_ABI pair<const_iterator, const_iterator> equal_range(const _Kp& __x) const {
805     return __equal_range_impl(*this, __x);
806   }
807 
808   friend _LIBCPP_HIDE_FROM_ABI bool operator==(const flat_map& __x, const flat_map& __y) {
809     return ranges::equal(__x, __y);
810   }
811 
812   friend _LIBCPP_HIDE_FROM_ABI auto operator<=>(const flat_map& __x, const flat_map& __y) {
813     return std::lexicographical_compare_three_way(
814         __x.begin(), __x.end(), __y.begin(), __y.end(), std::__synth_three_way);
815   }
816 
817   friend _LIBCPP_HIDE_FROM_ABI void swap(flat_map& __x, flat_map& __y) noexcept { __x.swap(__y); }
818 
819 private:
820   struct __ctor_uses_allocator_tag {
821     explicit _LIBCPP_HIDE_FROM_ABI __ctor_uses_allocator_tag() = default;
822   };
823   struct __ctor_uses_allocator_empty_tag {
824     explicit _LIBCPP_HIDE_FROM_ABI __ctor_uses_allocator_empty_tag() = default;
825   };
826 
827   template <class _Allocator, class _KeyCont, class _MappedCont, class... _CompArg>
828     requires __allocator_ctor_constraint<_Allocator>
829   _LIBCPP_HIDE_FROM_ABI
830   flat_map(__ctor_uses_allocator_tag,
831            const _Allocator& __alloc,
832            _KeyCont&& __key_cont,
833            _MappedCont&& __mapped_cont,
834            _CompArg&&... __comp)
835       : __containers_{.keys = std::make_obj_using_allocator<key_container_type>(
836                           __alloc, std::forward<_KeyCont>(__key_cont)),
837                       .values = std::make_obj_using_allocator<mapped_container_type>(
838                           __alloc, std::forward<_MappedCont>(__mapped_cont))},
839         __compare_(std::forward<_CompArg>(__comp)...) {}
840 
841   template <class _Allocator, class... _CompArg>
842     requires __allocator_ctor_constraint<_Allocator>
843   _LIBCPP_HIDE_FROM_ABI flat_map(__ctor_uses_allocator_empty_tag, const _Allocator& __alloc, _CompArg&&... __comp)
844       : __containers_{.keys   = std::make_obj_using_allocator<key_container_type>(__alloc),
845                       .values = std::make_obj_using_allocator<mapped_container_type>(__alloc)},
846         __compare_(std::forward<_CompArg>(__comp)...) {}
847 
848   _LIBCPP_HIDE_FROM_ABI bool __is_sorted_and_unique(auto&& __key_container) const {
849     auto __greater_or_equal_to = [this](const auto& __x, const auto& __y) { return !__compare_(__x, __y); };
850     return ranges::adjacent_find(__key_container, __greater_or_equal_to) == ranges::end(__key_container);
851   }
852 
853   // This function is only used in constructors. So there is not exception handling in this function.
854   // If the function exits via an exception, there will be no flat_map object constructed, thus, there
855   // is no invariant state to preserve
856   _LIBCPP_HIDE_FROM_ABI void __sort_and_unique() {
857     auto __zv = ranges::views::zip(__containers_.keys, __containers_.values);
858     ranges::sort(__zv, __compare_, [](const auto& __p) -> decltype(auto) { return std::get<0>(__p); });
859     auto __dup_start = ranges::unique(__zv, __key_equiv(__compare_)).begin();
860     auto __dist      = ranges::distance(__zv.begin(), __dup_start);
861     __containers_.keys.erase(__containers_.keys.begin() + __dist, __containers_.keys.end());
862     __containers_.values.erase(__containers_.values.begin() + __dist, __containers_.values.end());
863   }
864 
865   template <bool _WasSorted, class _InputIterator, class _Sentinel>
866   _LIBCPP_HIDE_FROM_ABI void __append_sort_merge_unique(_InputIterator __first, _Sentinel __last) {
867     auto __on_failure        = std::__make_exception_guard([&]() noexcept { clear() /* noexcept */; });
868     size_t __num_of_appended = __flat_map_utils::__append(*this, std::move(__first), std::move(__last));
869     if (__num_of_appended != 0) {
870       auto __zv                  = ranges::views::zip(__containers_.keys, __containers_.values);
871       auto __append_start_offset = __containers_.keys.size() - __num_of_appended;
872       auto __end                 = __zv.end();
873       auto __compare_key         = [this](const auto& __p1, const auto& __p2) {
874         return __compare_(std::get<0>(__p1), std::get<0>(__p2));
875       };
876       if constexpr (!_WasSorted) {
877         ranges::sort(__zv.begin() + __append_start_offset, __end, __compare_key);
878       } else {
879         _LIBCPP_ASSERT_SEMANTIC_REQUIREMENT(
880             __is_sorted_and_unique(__containers_.keys | ranges::views::drop(__append_start_offset)),
881             "Either the key container is not sorted or it contains duplicates");
882       }
883       ranges::inplace_merge(__zv.begin(), __zv.begin() + __append_start_offset, __end, __compare_key);
884 
885       auto __dup_start = ranges::unique(__zv, __key_equiv(__compare_)).begin();
886       auto __dist      = ranges::distance(__zv.begin(), __dup_start);
887       __containers_.keys.erase(__containers_.keys.begin() + __dist, __containers_.keys.end());
888       __containers_.values.erase(__containers_.values.begin() + __dist, __containers_.values.end());
889     }
890     __on_failure.__complete();
891   }
892 
893   template <class _Self, class _Kp>
894   _LIBCPP_HIDE_FROM_ABI static auto __find_impl(_Self&& __self, const _Kp& __key) {
895     auto __it   = __self.lower_bound(__key);
896     auto __last = __self.end();
897     if (__it == __last || __self.__compare_(__key, __it->first)) {
898       return __last;
899     }
900     return __it;
901   }
902 
903   template <class _Self, class _Kp>
904   _LIBCPP_HIDE_FROM_ABI static auto __key_equal_range(_Self&& __self, const _Kp& __key) {
905     auto __it   = ranges::lower_bound(__self.__containers_.keys, __key, __self.__compare_);
906     auto __last = __self.__containers_.keys.end();
907     if (__it == __last || __self.__compare_(__key, *__it)) {
908       return std::make_pair(__it, __it);
909     }
910     return std::make_pair(__it, std::next(__it));
911   }
912 
913   template <class _Self, class _Kp>
914   _LIBCPP_HIDE_FROM_ABI static auto __equal_range_impl(_Self&& __self, const _Kp& __key) {
915     auto [__key_first, __key_last] = __key_equal_range(__self, __key);
916 
917     const auto __make_mapped_iter = [&](const auto& __key_iter) {
918       return __self.__containers_.values.begin() +
919              static_cast<ranges::range_difference_t<mapped_container_type>>(
920                  ranges::distance(__self.__containers_.keys.begin(), __key_iter));
921     };
922 
923     using __iterator_type = ranges::iterator_t<decltype(__self)>;
924     return std::make_pair(__iterator_type(__key_first, __make_mapped_iter(__key_first)),
925                           __iterator_type(__key_last, __make_mapped_iter(__key_last)));
926   }
927 
928   template <class _Res, class _Self, class _Kp>
929   _LIBCPP_HIDE_FROM_ABI static _Res __lower_bound(_Self&& __self, _Kp& __x) {
930     return __binary_search<_Res>(__self, ranges::lower_bound, __x);
931   }
932 
933   template <class _Res, class _Self, class _Kp>
934   _LIBCPP_HIDE_FROM_ABI static _Res __upper_bound(_Self&& __self, _Kp& __x) {
935     return __binary_search<_Res>(__self, ranges::upper_bound, __x);
936   }
937 
938   template <class _Res, class _Self, class _Fn, class _Kp>
939   _LIBCPP_HIDE_FROM_ABI static _Res __binary_search(_Self&& __self, _Fn __search_fn, _Kp& __x) {
940     auto __key_iter = __search_fn(__self.__containers_.keys, __x, __self.__compare_);
941     auto __mapped_iter =
942         __self.__containers_.values.begin() +
943         static_cast<ranges::range_difference_t<mapped_container_type>>(
944             ranges::distance(__self.__containers_.keys.begin(), __key_iter));
945 
946     return _Res(std::move(__key_iter), std::move(__mapped_iter));
947   }
948 
949   template <class _KeyArg, class... _MArgs>
950   _LIBCPP_HIDE_FROM_ABI pair<iterator, bool> __try_emplace(_KeyArg&& __key, _MArgs&&... __mapped_args) {
951     auto __key_it    = ranges::lower_bound(__containers_.keys, __key, __compare_);
952     auto __mapped_it = __containers_.values.begin() + ranges::distance(__containers_.keys.begin(), __key_it);
953 
954     if (__key_it == __containers_.keys.end() || __compare_(__key, *__key_it)) {
955       return pair<iterator, bool>(
956           __flat_map_utils::__emplace_exact_pos(
957               *this,
958               std::move(__key_it),
959               std::move(__mapped_it),
960               std::forward<_KeyArg>(__key),
961               std::forward<_MArgs>(__mapped_args)...),
962           true);
963     } else {
964       return pair<iterator, bool>(iterator(std::move(__key_it), std::move(__mapped_it)), false);
965     }
966   }
967 
968   template <class _Kp>
969   _LIBCPP_HIDE_FROM_ABI bool __is_hint_correct(const_iterator __hint, _Kp&& __key) {
970     if (__hint != cbegin() && !__compare_((__hint - 1)->first, __key)) {
971       return false;
972     }
973     if (__hint != cend() && __compare_(__hint->first, __key)) {
974       return false;
975     }
976     return true;
977   }
978 
979   template <class _Kp, class... _Args>
980   _LIBCPP_HIDE_FROM_ABI pair<iterator, bool> __try_emplace_hint(const_iterator __hint, _Kp&& __key, _Args&&... __args) {
981     if (__is_hint_correct(__hint, __key)) {
982       if (__hint == cend() || __compare_(__key, __hint->first)) {
983         return {__flat_map_utils::__emplace_exact_pos(
984                     *this,
985                     __hint.__key_iter_,
986                     __hint.__mapped_iter_,
987                     std::forward<_Kp>(__key),
988                     std::forward<_Args>(__args)...),
989                 true};
990       } else {
991         // key equals
992         auto __dist = __hint - cbegin();
993         return {iterator(__containers_.keys.begin() + __dist, __containers_.values.begin() + __dist), false};
994       }
995     } else {
996       return __try_emplace(std::forward<_Kp>(__key), std::forward<_Args>(__args)...);
997     }
998   }
999 
1000   template <class _Kp, class _Mapped>
1001   _LIBCPP_HIDE_FROM_ABI pair<iterator, bool> __insert_or_assign(_Kp&& __key, _Mapped&& __mapped) {
1002     auto __r = try_emplace(std::forward<_Kp>(__key), std::forward<_Mapped>(__mapped));
1003     if (!__r.second) {
1004       __r.first->second = std::forward<_Mapped>(__mapped);
1005     }
1006     return __r;
1007   }
1008 
1009   template <class _Kp, class _Mapped>
1010   _LIBCPP_HIDE_FROM_ABI iterator __insert_or_assign(const_iterator __hint, _Kp&& __key, _Mapped&& __mapped) {
1011     auto __r = __try_emplace_hint(__hint, std::forward<_Kp>(__key), std::forward<_Mapped>(__mapped));
1012     if (!__r.second) {
1013       __r.first->second = std::forward<_Mapped>(__mapped);
1014     }
1015     return __r.first;
1016   }
1017 
1018   _LIBCPP_HIDE_FROM_ABI void __reserve(size_t __size) {
1019     if constexpr (requires { __containers_.keys.reserve(__size); }) {
1020       __containers_.keys.reserve(__size);
1021     }
1022 
1023     if constexpr (requires { __containers_.values.reserve(__size); }) {
1024       __containers_.values.reserve(__size);
1025     }
1026   }
1027 
1028   template <class _KIter, class _MIter>
1029   _LIBCPP_HIDE_FROM_ABI iterator __erase(_KIter __key_iter_to_remove, _MIter __mapped_iter_to_remove) {
1030     auto __on_failure  = std::__make_exception_guard([&]() noexcept { clear() /* noexcept */; });
1031     auto __key_iter    = __containers_.keys.erase(__key_iter_to_remove);
1032     auto __mapped_iter = __containers_.values.erase(__mapped_iter_to_remove);
1033     __on_failure.__complete();
1034     return iterator(std::move(__key_iter), std::move(__mapped_iter));
1035   }
1036 
1037   template <class _Key2, class _Tp2, class _Compare2, class _KeyContainer2, class _MappedContainer2, class _Predicate>
1038   friend typename flat_map<_Key2, _Tp2, _Compare2, _KeyContainer2, _MappedContainer2>::size_type
1039   erase_if(flat_map<_Key2, _Tp2, _Compare2, _KeyContainer2, _MappedContainer2>&, _Predicate);
1040 
1041   friend __flat_map_utils;
1042 
1043   containers __containers_;
1044   _LIBCPP_NO_UNIQUE_ADDRESS key_compare __compare_;
1045 
1046   struct __key_equiv {
1047     _LIBCPP_HIDE_FROM_ABI __key_equiv(key_compare __c) : __comp_(__c) {}
1048     _LIBCPP_HIDE_FROM_ABI bool operator()(const_reference __x, const_reference __y) const {
1049       return !__comp_(std::get<0>(__x), std::get<0>(__y)) && !__comp_(std::get<0>(__y), std::get<0>(__x));
1050     }
1051     key_compare __comp_;
1052   };
1053 };
1054 
1055 template <class _KeyContainer, class _MappedContainer, class _Compare = less<typename _KeyContainer::value_type>>
1056   requires(!__is_allocator<_Compare>::value && !__is_allocator<_KeyContainer>::value &&
1057            !__is_allocator<_MappedContainer>::value &&
1058            is_invocable_v<const _Compare&,
1059                           const typename _KeyContainer::value_type&,
1060                           const typename _KeyContainer::value_type&>)
1061 flat_map(_KeyContainer, _MappedContainer, _Compare = _Compare())
1062     -> flat_map<typename _KeyContainer::value_type,
1063                 typename _MappedContainer::value_type,
1064                 _Compare,
1065                 _KeyContainer,
1066                 _MappedContainer>;
1067 
1068 template <class _KeyContainer, class _MappedContainer, class _Allocator>
1069   requires(uses_allocator_v<_KeyContainer, _Allocator> && uses_allocator_v<_MappedContainer, _Allocator> &&
1070            !__is_allocator<_KeyContainer>::value && !__is_allocator<_MappedContainer>::value)
1071 flat_map(_KeyContainer, _MappedContainer, _Allocator)
1072     -> flat_map<typename _KeyContainer::value_type,
1073                 typename _MappedContainer::value_type,
1074                 less<typename _KeyContainer::value_type>,
1075                 _KeyContainer,
1076                 _MappedContainer>;
1077 
1078 template <class _KeyContainer, class _MappedContainer, class _Compare, class _Allocator>
1079   requires(!__is_allocator<_Compare>::value && !__is_allocator<_KeyContainer>::value &&
1080            !__is_allocator<_MappedContainer>::value && uses_allocator_v<_KeyContainer, _Allocator> &&
1081            uses_allocator_v<_MappedContainer, _Allocator> &&
1082            is_invocable_v<const _Compare&,
1083                           const typename _KeyContainer::value_type&,
1084                           const typename _KeyContainer::value_type&>)
1085 flat_map(_KeyContainer, _MappedContainer, _Compare, _Allocator)
1086     -> flat_map<typename _KeyContainer::value_type,
1087                 typename _MappedContainer::value_type,
1088                 _Compare,
1089                 _KeyContainer,
1090                 _MappedContainer>;
1091 
1092 template <class _KeyContainer, class _MappedContainer, class _Compare = less<typename _KeyContainer::value_type>>
1093   requires(!__is_allocator<_Compare>::value && !__is_allocator<_KeyContainer>::value &&
1094            !__is_allocator<_MappedContainer>::value &&
1095            is_invocable_v<const _Compare&,
1096                           const typename _KeyContainer::value_type&,
1097                           const typename _KeyContainer::value_type&>)
1098 flat_map(sorted_unique_t, _KeyContainer, _MappedContainer, _Compare = _Compare())
1099     -> flat_map<typename _KeyContainer::value_type,
1100                 typename _MappedContainer::value_type,
1101                 _Compare,
1102                 _KeyContainer,
1103                 _MappedContainer>;
1104 
1105 template <class _KeyContainer, class _MappedContainer, class _Allocator>
1106   requires(uses_allocator_v<_KeyContainer, _Allocator> && uses_allocator_v<_MappedContainer, _Allocator> &&
1107            !__is_allocator<_KeyContainer>::value && !__is_allocator<_MappedContainer>::value)
1108 flat_map(sorted_unique_t, _KeyContainer, _MappedContainer, _Allocator)
1109     -> flat_map<typename _KeyContainer::value_type,
1110                 typename _MappedContainer::value_type,
1111                 less<typename _KeyContainer::value_type>,
1112                 _KeyContainer,
1113                 _MappedContainer>;
1114 
1115 template <class _KeyContainer, class _MappedContainer, class _Compare, class _Allocator>
1116   requires(!__is_allocator<_Compare>::value && !__is_allocator<_KeyContainer>::value &&
1117            !__is_allocator<_MappedContainer>::value && uses_allocator_v<_KeyContainer, _Allocator> &&
1118            uses_allocator_v<_MappedContainer, _Allocator> &&
1119            is_invocable_v<const _Compare&,
1120                           const typename _KeyContainer::value_type&,
1121                           const typename _KeyContainer::value_type&>)
1122 flat_map(sorted_unique_t, _KeyContainer, _MappedContainer, _Compare, _Allocator)
1123     -> flat_map<typename _KeyContainer::value_type,
1124                 typename _MappedContainer::value_type,
1125                 _Compare,
1126                 _KeyContainer,
1127                 _MappedContainer>;
1128 
1129 template <class _InputIterator, class _Compare = less<__iter_key_type<_InputIterator>>>
1130   requires(__has_input_iterator_category<_InputIterator>::value && !__is_allocator<_Compare>::value)
1131 flat_map(_InputIterator, _InputIterator, _Compare = _Compare())
1132     -> flat_map<__iter_key_type<_InputIterator>, __iter_mapped_type<_InputIterator>, _Compare>;
1133 
1134 template <class _InputIterator, class _Compare = less<__iter_key_type<_InputIterator>>>
1135   requires(__has_input_iterator_category<_InputIterator>::value && !__is_allocator<_Compare>::value)
1136 flat_map(sorted_unique_t, _InputIterator, _InputIterator, _Compare = _Compare())
1137     -> flat_map<__iter_key_type<_InputIterator>, __iter_mapped_type<_InputIterator>, _Compare>;
1138 
1139 template <ranges::input_range _Range,
1140           class _Compare   = less<__range_key_type<_Range>>,
1141           class _Allocator = allocator<byte>,
1142           class            = __enable_if_t<!__is_allocator<_Compare>::value && __is_allocator<_Allocator>::value>>
1143 flat_map(from_range_t, _Range&&, _Compare = _Compare(), _Allocator = _Allocator()) -> flat_map<
1144     __range_key_type<_Range>,
1145     __range_mapped_type<_Range>,
1146     _Compare,
1147     vector<__range_key_type<_Range>, __allocator_traits_rebind_t<_Allocator, __range_key_type<_Range>>>,
1148     vector<__range_mapped_type<_Range>, __allocator_traits_rebind_t<_Allocator, __range_mapped_type<_Range>>>>;
1149 
1150 template <ranges::input_range _Range, class _Allocator, class = __enable_if_t<__is_allocator<_Allocator>::value>>
1151 flat_map(from_range_t, _Range&&, _Allocator) -> flat_map<
1152     __range_key_type<_Range>,
1153     __range_mapped_type<_Range>,
1154     less<__range_key_type<_Range>>,
1155     vector<__range_key_type<_Range>, __allocator_traits_rebind_t<_Allocator, __range_key_type<_Range>>>,
1156     vector<__range_mapped_type<_Range>, __allocator_traits_rebind_t<_Allocator, __range_mapped_type<_Range>>>>;
1157 
1158 template <class _Key, class _Tp, class _Compare = less<_Key>>
1159   requires(!__is_allocator<_Compare>::value)
1160 flat_map(initializer_list<pair<_Key, _Tp>>, _Compare = _Compare()) -> flat_map<_Key, _Tp, _Compare>;
1161 
1162 template <class _Key, class _Tp, class _Compare = less<_Key>>
1163   requires(!__is_allocator<_Compare>::value)
1164 flat_map(sorted_unique_t, initializer_list<pair<_Key, _Tp>>, _Compare = _Compare()) -> flat_map<_Key, _Tp, _Compare>;
1165 
1166 template <class _Key, class _Tp, class _Compare, class _KeyContainer, class _MappedContainer, class _Allocator>
1167 struct uses_allocator<flat_map<_Key, _Tp, _Compare, _KeyContainer, _MappedContainer>, _Allocator>
1168     : bool_constant<uses_allocator_v<_KeyContainer, _Allocator> && uses_allocator_v<_MappedContainer, _Allocator>> {};
1169 
1170 template <class _Key, class _Tp, class _Compare, class _KeyContainer, class _MappedContainer, class _Predicate>
1171 _LIBCPP_HIDE_FROM_ABI typename flat_map<_Key, _Tp, _Compare, _KeyContainer, _MappedContainer>::size_type
1172 erase_if(flat_map<_Key, _Tp, _Compare, _KeyContainer, _MappedContainer>& __flat_map, _Predicate __pred) {
1173   auto __zv     = ranges::views::zip(__flat_map.__containers_.keys, __flat_map.__containers_.values);
1174   auto __first  = __zv.begin();
1175   auto __last   = __zv.end();
1176   auto __guard  = std::__make_exception_guard([&] { __flat_map.clear(); });
1177   auto __it     = std::remove_if(__first, __last, [&](auto&& __zipped) -> bool {
1178     using _Ref = typename flat_map<_Key, _Tp, _Compare, _KeyContainer, _MappedContainer>::const_reference;
1179     return __pred(_Ref(std::get<0>(__zipped), std::get<1>(__zipped)));
1180   });
1181   auto __res    = __last - __it;
1182   auto __offset = __it - __first;
1183 
1184   const auto __erase_container = [&](auto& __cont) { __cont.erase(__cont.begin() + __offset, __cont.end()); };
1185 
1186   __erase_container(__flat_map.__containers_.keys);
1187   __erase_container(__flat_map.__containers_.values);
1188 
1189   __guard.__complete();
1190   return __res;
1191 }
1192 
1193 _LIBCPP_END_NAMESPACE_STD
1194 
1195 #endif // _LIBCPP_STD_VER >= 23
1196 
1197 _LIBCPP_POP_MACROS
1198 
1199 #endif // _LIBCPP___FLAT_MAP_FLAT_MAP_H
1200