1// unordered_map implementation -*- C++ -*- 
2 
3// Copyright (C) 2010-2019 Free Software Foundation, Inc. 
4// 
5// This file is part of the GNU ISO C++ Library. This library is free 
6// software; you can redistribute it and/or modify it under the 
7// terms of the GNU General Public License as published by the 
8// Free Software Foundation; either version 3, or (at your option) 
9// any later version. 
10 
11// This library is distributed in the hope that it will be useful, 
12// but WITHOUT ANY WARRANTY; without even the implied warranty of 
13// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 
14// GNU General Public License for more details. 
15 
16// Under Section 7 of GPL version 3, you are granted additional 
17// permissions described in the GCC Runtime Library Exception, version 
18// 3.1, as published by the Free Software Foundation. 
19 
20// You should have received a copy of the GNU General Public License and 
21// a copy of the GCC Runtime Library Exception along with this program; 
22// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see 
23// <http://www.gnu.org/licenses/>. 
24 
25/** @file bits/unordered_map.h 
26 * This is an internal header file, included by other library headers. 
27 * Do not attempt to use it directly. @headername{unordered_map} 
28 */ 
29 
30#ifndef _UNORDERED_MAP_H 
31#define _UNORDERED_MAP_H 
32 
33namespace std _GLIBCXX_VISIBILITY(default) 
34{ 
35_GLIBCXX_BEGIN_NAMESPACE_VERSION 
36_GLIBCXX_BEGIN_NAMESPACE_CONTAINER 
37 
38 /// Base types for unordered_map. 
39 template<bool _Cache> 
40 using __umap_traits = __detail::_Hashtable_traits<_Cache, false, true>; 
41 
42 template<typename _Key, 
43 typename _Tp, 
44 typename _Hash = hash<_Key>, 
45 typename _Pred = std::equal_to<_Key>, 
46 typename _Alloc = std::allocator<std::pair<const _Key, _Tp> >, 
47 typename _Tr = __umap_traits<__cache_default<_Key, _Hash>::value>> 
48 using __umap_hashtable = _Hashtable<_Key, std::pair<const _Key, _Tp>, 
49 _Alloc, __detail::_Select1st, 
50 _Pred, _Hash, 
51 __detail::_Mod_range_hashing, 
52 __detail::_Default_ranged_hash, 
53 __detail::_Prime_rehash_policy, _Tr>; 
54 
55 /// Base types for unordered_multimap. 
56 template<bool _Cache> 
57 using __ummap_traits = __detail::_Hashtable_traits<_Cache, false, false>; 
58 
59 template<typename _Key, 
60 typename _Tp, 
61 typename _Hash = hash<_Key>, 
62 typename _Pred = std::equal_to<_Key>, 
63 typename _Alloc = std::allocator<std::pair<const _Key, _Tp> >, 
64 typename _Tr = __ummap_traits<__cache_default<_Key, _Hash>::value>> 
65 using __ummap_hashtable = _Hashtable<_Key, std::pair<const _Key, _Tp>, 
66 _Alloc, __detail::_Select1st, 
67 _Pred, _Hash, 
68 __detail::_Mod_range_hashing, 
69 __detail::_Default_ranged_hash, 
70 __detail::_Prime_rehash_policy, _Tr>; 
71 
72 template<class _Key, class _Tp, class _Hash, class _Pred, class _Alloc> 
73 class unordered_multimap; 
74 
75 /** 
76 * @brief A standard container composed of unique keys (containing 
77 * at most one of each key value) that associates values of another type 
78 * with the keys. 
79 * 
80 * @ingroup unordered_associative_containers 
81 * 
82 * @tparam _Key Type of key objects. 
83 * @tparam _Tp Type of mapped objects. 
84 * @tparam _Hash Hashing function object type, defaults to hash<_Value>. 
85 * @tparam _Pred Predicate function object type, defaults 
86 * to equal_to<_Value>. 
87 * @tparam _Alloc Allocator type, defaults to  
88 * std::allocator<std::pair<const _Key, _Tp>>. 
89 * 
90 * Meets the requirements of a <a href="tables.html#65">container</a>, and 
91 * <a href="tables.html#xx">unordered associative container</a> 
92 * 
93 * The resulting value type of the container is std::pair<const _Key, _Tp>. 
94 * 
95 * Base is _Hashtable, dispatched at compile time via template 
96 * alias __umap_hashtable. 
97 */ 
98 template<typename _Key, typename _Tp, 
99 typename _Hash = hash<_Key>, 
100 typename _Pred = equal_to<_Key>, 
101 typename _Alloc = allocator<std::pair<const _Key, _Tp>>> 
102 class unordered_map 
103 { 
104 typedef __umap_hashtable<_Key, _Tp, _Hash, _Pred, _Alloc> _Hashtable; 
105 _Hashtable _M_h; 
106 
107 public: 
108 // typedefs: 
109 //@{ 
110 /// Public typedefs. 
111 typedef typename _Hashtable::key_type key_type; 
112 typedef typename _Hashtable::value_type value_type; 
113 typedef typename _Hashtable::mapped_type mapped_type; 
114 typedef typename _Hashtable::hasher hasher; 
115 typedef typename _Hashtable::key_equal key_equal; 
116 typedef typename _Hashtable::allocator_type allocator_type; 
117 //@} 
118 
119 //@{ 
120 /// Iterator-related typedefs. 
121 typedef typename _Hashtable::pointer pointer; 
122 typedef typename _Hashtable::const_pointer const_pointer; 
123 typedef typename _Hashtable::reference reference; 
124 typedef typename _Hashtable::const_reference const_reference; 
125 typedef typename _Hashtable::iterator iterator; 
126 typedef typename _Hashtable::const_iterator const_iterator; 
127 typedef typename _Hashtable::local_iterator local_iterator; 
128 typedef typename _Hashtable::const_local_iterator const_local_iterator; 
129 typedef typename _Hashtable::size_type size_type; 
130 typedef typename _Hashtable::difference_type difference_type; 
131 //@} 
132 
133#if __cplusplus > 201402L 
134 using node_type = typename _Hashtable::node_type; 
135 using insert_return_type = typename _Hashtable::insert_return_type; 
136#endif 
137 
138 //construct/destroy/copy 
139 
140 /// Default constructor. 
141 unordered_map() = default; 
142 
143 /** 
144 * @brief Default constructor creates no elements. 
145 * @param __n Minimal initial number of buckets. 
146 * @param __hf A hash functor. 
147 * @param __eql A key equality functor. 
148 * @param __a An allocator object. 
149 */ 
150 explicit 
151 unordered_map(size_type __n, 
152 const hasher& __hf = hasher(), 
153 const key_equal& __eql = key_equal(), 
154 const allocator_type& __a = allocator_type()) 
155 : _M_h(__n, __hf, __eql, __a) 
156 { } 
157 
158 /** 
159 * @brief Builds an %unordered_map from a range. 
160 * @param __first An input iterator. 
161 * @param __last An input iterator. 
162 * @param __n Minimal initial number of buckets. 
163 * @param __hf A hash functor. 
164 * @param __eql A key equality functor. 
165 * @param __a An allocator object. 
166 * 
167 * Create an %unordered_map consisting of copies of the elements from 
168 * [__first,__last). This is linear in N (where N is 
169 * distance(__first,__last)). 
170 */ 
171 template<typename _InputIterator> 
172 unordered_map(_InputIterator __first, _InputIterator __last, 
173 size_type __n = 0, 
174 const hasher& __hf = hasher(), 
175 const key_equal& __eql = key_equal(), 
176 const allocator_type& __a = allocator_type()) 
177 : _M_h(__first, __last, __n, __hf, __eql, __a) 
178 { } 
179 
180 /// Copy constructor. 
181 unordered_map(const unordered_map&) = default; 
182 
183 /// Move constructor. 
184 unordered_map(unordered_map&&) = default; 
185 
186 /** 
187 * @brief Creates an %unordered_map with no elements. 
188 * @param __a An allocator object. 
189 */ 
190 explicit 
191 unordered_map(const allocator_type& __a) 
192 : _M_h(__a) 
193 { } 
194 
195 /* 
196 * @brief Copy constructor with allocator argument. 
197 * @param __uset Input %unordered_map to copy. 
198 * @param __a An allocator object. 
199 */ 
200 unordered_map(const unordered_map& __umap, 
201 const allocator_type& __a) 
202 : _M_h(__umap._M_h, __a) 
203 { } 
204 
205 /* 
206 * @brief Move constructor with allocator argument. 
207 * @param __uset Input %unordered_map to move. 
208 * @param __a An allocator object. 
209 */ 
210 unordered_map(unordered_map&& __umap, 
211 const allocator_type& __a) 
212 : _M_h(std::move(__umap._M_h), __a) 
213 { } 
214 
215 /** 
216 * @brief Builds an %unordered_map from an initializer_list. 
217 * @param __l An initializer_list. 
218 * @param __n Minimal initial number of buckets. 
219 * @param __hf A hash functor. 
220 * @param __eql A key equality functor. 
221 * @param __a An allocator object. 
222 * 
223 * Create an %unordered_map consisting of copies of the elements in the 
224 * list. This is linear in N (where N is @a __l.size()). 
225 */ 
226 unordered_map(initializer_list<value_type> __l, 
227 size_type __n = 0, 
228 const hasher& __hf = hasher(), 
229 const key_equal& __eql = key_equal(), 
230 const allocator_type& __a = allocator_type()) 
231 : _M_h(__l, __n, __hf, __eql, __a) 
232 { } 
233 
234 unordered_map(size_type __n, const allocator_type& __a) 
235 : unordered_map(__n, hasher(), key_equal(), __a) 
236 { } 
237 
238 unordered_map(size_type __n, const hasher& __hf, 
239 const allocator_type& __a) 
240 : unordered_map(__n, __hf, key_equal(), __a) 
241 { } 
242 
243 template<typename _InputIterator> 
244 unordered_map(_InputIterator __first, _InputIterator __last, 
245 size_type __n, 
246 const allocator_type& __a) 
247 : unordered_map(__first, __last, __n, hasher(), key_equal(), __a) 
248 { } 
249 
250 template<typename _InputIterator> 
251 unordered_map(_InputIterator __first, _InputIterator __last, 
252 size_type __n, const hasher& __hf, 
253 const allocator_type& __a) 
254 : unordered_map(__first, __last, __n, __hf, key_equal(), __a) 
255 { } 
256 
257 unordered_map(initializer_list<value_type> __l, 
258 size_type __n, 
259 const allocator_type& __a) 
260 : unordered_map(__l, __n, hasher(), key_equal(), __a) 
261 { } 
262 
263 unordered_map(initializer_list<value_type> __l, 
264 size_type __n, const hasher& __hf, 
265 const allocator_type& __a) 
266 : unordered_map(__l, __n, __hf, key_equal(), __a) 
267 { } 
268 
269 /// Copy assignment operator. 
270 unordered_map& 
271 operator=(const unordered_map&) = default; 
272 
273 /// Move assignment operator. 
274 unordered_map& 
275 operator=(unordered_map&&) = default; 
276 
277 /** 
278 * @brief %Unordered_map list assignment operator. 
279 * @param __l An initializer_list. 
280 * 
281 * This function fills an %unordered_map with copies of the elements in 
282 * the initializer list @a __l. 
283 * 
284 * Note that the assignment completely changes the %unordered_map and 
285 * that the resulting %unordered_map's size is the same as the number 
286 * of elements assigned. 
287 */ 
288 unordered_map& 
289 operator=(initializer_list<value_type> __l) 
290 { 
291 _M_h = __l; 
292 return *this; 
293 } 
294 
295 /// Returns the allocator object used by the %unordered_map. 
296 allocator_type 
297 get_allocator() const noexcept 
298 { return _M_h.get_allocator(); } 
299 
300 // size and capacity: 
301 
302 /// Returns true if the %unordered_map is empty. 
303 _GLIBCXX_NODISCARD bool 
304 empty() const noexcept 
305 { return _M_h.empty(); } 
306 
307 /// Returns the size of the %unordered_map. 
308 size_type 
309 size() const noexcept 
310 { return _M_h.size(); } 
311 
312 /// Returns the maximum size of the %unordered_map. 
313 size_type 
314 max_size() const noexcept 
315 { return _M_h.max_size(); } 
316 
317 // iterators. 
318 
319 /** 
320 * Returns a read/write iterator that points to the first element in the 
321 * %unordered_map. 
322 */ 
323 iterator 
324 begin() noexcept 
325 { return _M_h.begin(); } 
326 
327 //@{ 
328 /** 
329 * Returns a read-only (constant) iterator that points to the first 
330 * element in the %unordered_map. 
331 */ 
332 const_iterator 
333 begin() const noexcept 
334 { return _M_h.begin(); } 
335 
336 const_iterator 
337 cbegin() const noexcept 
338 { return _M_h.begin(); } 
339 //@} 
340 
341 /** 
342 * Returns a read/write iterator that points one past the last element in 
343 * the %unordered_map. 
344 */ 
345 iterator 
346 end() noexcept 
347 { return _M_h.end(); } 
348 
349 //@{ 
350 /** 
351 * Returns a read-only (constant) iterator that points one past the last 
352 * element in the %unordered_map. 
353 */ 
354 const_iterator 
355 end() const noexcept 
356 { return _M_h.end(); } 
357 
358 const_iterator 
359 cend() const noexcept 
360 { return _M_h.end(); } 
361 //@} 
362 
363 // modifiers. 
364 
365 /** 
366 * @brief Attempts to build and insert a std::pair into the 
367 * %unordered_map. 
368 * 
369 * @param __args Arguments used to generate a new pair instance (see 
370 * std::piecewise_contruct for passing arguments to each 
371 * part of the pair constructor). 
372 * 
373 * @return A pair, of which the first element is an iterator that points 
374 * to the possibly inserted pair, and the second is a bool that 
375 * is true if the pair was actually inserted. 
376 * 
377 * This function attempts to build and insert a (key, value) %pair into 
378 * the %unordered_map. 
379 * An %unordered_map relies on unique keys and thus a %pair is only 
380 * inserted if its first element (the key) is not already present in the 
381 * %unordered_map. 
382 * 
383 * Insertion requires amortized constant time. 
384 */ 
385 template<typename... _Args> 
386 std::pair<iterator, bool> 
387 emplace(_Args&&... __args) 
388 { return _M_h.emplace(std::forward<_Args>(__args)...); } 
389 
390 /** 
391 * @brief Attempts to build and insert a std::pair into the 
392 * %unordered_map. 
393 * 
394 * @param __pos An iterator that serves as a hint as to where the pair 
395 * should be inserted. 
396 * @param __args Arguments used to generate a new pair instance (see 
397 * std::piecewise_contruct for passing arguments to each 
398 * part of the pair constructor). 
399 * @return An iterator that points to the element with key of the 
400 * std::pair built from @a __args (may or may not be that 
401 * std::pair). 
402 * 
403 * This function is not concerned about whether the insertion took place, 
404 * and thus does not return a boolean like the single-argument emplace() 
405 * does. 
406 * Note that the first parameter is only a hint and can potentially 
407 * improve the performance of the insertion process. A bad hint would 
408 * cause no gains in efficiency. 
409 * 
410 * See 
411 * https://gcc.gnu.org/onlinedocs/libstdc++/manual/associative.html#containers.associative.insert_hints 
412 * for more on @a hinting. 
413 * 
414 * Insertion requires amortized constant time. 
415 */ 
416 template<typename... _Args> 
417 iterator 
418 emplace_hint(const_iterator __pos, _Args&&... __args) 
419 { return _M_h.emplace_hint(__pos, std::forward<_Args>(__args)...); } 
420 
421#if __cplusplus > 201402L 
422 /// Extract a node. 
423 node_type 
424 extract(const_iterator __pos) 
425 { 
426 __glibcxx_assert(__pos != end()); 
427 return _M_h.extract(__pos); 
428 } 
429 
430 /// Extract a node. 
431 node_type 
432 extract(const key_type& __key) 
433 { return _M_h.extract(__key); } 
434 
435 /// Re-insert an extracted node. 
436 insert_return_type 
437 insert(node_type&& __nh) 
438 { return _M_h._M_reinsert_node(std::move(__nh)); } 
439 
440 /// Re-insert an extracted node. 
441 iterator 
442 insert(const_iterator, node_type&& __nh) 
443 { return _M_h._M_reinsert_node(std::move(__nh)).position; } 
444 
445#define __cpp_lib_unordered_map_try_emplace 201411 
446 /** 
447 * @brief Attempts to build and insert a std::pair into the 
448 * %unordered_map. 
449 * 
450 * @param __k Key to use for finding a possibly existing pair in 
451 * the unordered_map. 
452 * @param __args Arguments used to generate the .second for a  
453 * new pair instance. 
454 * 
455 * @return A pair, of which the first element is an iterator that points 
456 * to the possibly inserted pair, and the second is a bool that 
457 * is true if the pair was actually inserted. 
458 * 
459 * This function attempts to build and insert a (key, value) %pair into 
460 * the %unordered_map. 
461 * An %unordered_map relies on unique keys and thus a %pair is only 
462 * inserted if its first element (the key) is not already present in the 
463 * %unordered_map. 
464 * If a %pair is not inserted, this function has no effect. 
465 * 
466 * Insertion requires amortized constant time. 
467 */ 
468 template <typename... _Args> 
469 pair<iterator, bool> 
470 try_emplace(const key_type& __k, _Args&&... __args) 
471 { 
472 iterator __i = find(__k); 
473 if (__i == end()) 
474 { 
475 __i = emplace(std::piecewise_construct, 
476 std::forward_as_tuple(__k), 
477 std::forward_as_tuple( 
478 std::forward<_Args>(__args)...)) 
479 .first; 
480 return {__i, true}; 
481 } 
482 return {__i, false}; 
483 } 
484 
485 // move-capable overload 
486 template <typename... _Args> 
487 pair<iterator, bool> 
488 try_emplace(key_type&& __k, _Args&&... __args) 
489 { 
490 iterator __i = find(__k); 
491 if (__i == end()) 
492 { 
493 __i = emplace(std::piecewise_construct, 
494 std::forward_as_tuple(std::move(__k)), 
495 std::forward_as_tuple( 
496 std::forward<_Args>(__args)...)) 
497 .first; 
498 return {__i, true}; 
499 } 
500 return {__i, false}; 
501 } 
502 
503 /** 
504 * @brief Attempts to build and insert a std::pair into the 
505 * %unordered_map. 
506 * 
507 * @param __hint An iterator that serves as a hint as to where the pair 
508 * should be inserted. 
509 * @param __k Key to use for finding a possibly existing pair in 
510 * the unordered_map. 
511 * @param __args Arguments used to generate the .second for a  
512 * new pair instance. 
513 * @return An iterator that points to the element with key of the 
514 * std::pair built from @a __args (may or may not be that 
515 * std::pair). 
516 * 
517 * This function is not concerned about whether the insertion took place, 
518 * and thus does not return a boolean like the single-argument emplace() 
519 * does. However, if insertion did not take place, 
520 * this function has no effect. 
521 * Note that the first parameter is only a hint and can potentially 
522 * improve the performance of the insertion process. A bad hint would 
523 * cause no gains in efficiency. 
524 * 
525 * See 
526 * https://gcc.gnu.org/onlinedocs/libstdc++/manual/associative.html#containers.associative.insert_hints 
527 * for more on @a hinting. 
528 * 
529 * Insertion requires amortized constant time. 
530 */ 
531 template <typename... _Args> 
532 iterator 
533 try_emplace(const_iterator __hint, const key_type& __k, 
534 _Args&&... __args) 
535 { 
536 iterator __i = find(__k); 
537 if (__i == end()) 
538 __i = emplace_hint(__hint, std::piecewise_construct, 
539 std::forward_as_tuple(__k), 
540 std::forward_as_tuple( 
541 std::forward<_Args>(__args)...)); 
542 return __i; 
543 } 
544 
545 // move-capable overload 
546 template <typename... _Args> 
547 iterator 
548 try_emplace(const_iterator __hint, key_type&& __k, _Args&&... __args) 
549 { 
550 iterator __i = find(__k); 
551 if (__i == end()) 
552 __i = emplace_hint(__hint, std::piecewise_construct, 
553 std::forward_as_tuple(std::move(__k)), 
554 std::forward_as_tuple( 
555 std::forward<_Args>(__args)...)); 
556 return __i; 
557 } 
558#endif // C++17 
559 
560 //@{ 
561 /** 
562 * @brief Attempts to insert a std::pair into the %unordered_map. 
563 
564 * @param __x Pair to be inserted (see std::make_pair for easy 
565 * creation of pairs). 
566 * 
567 * @return A pair, of which the first element is an iterator that  
568 * points to the possibly inserted pair, and the second is  
569 * a bool that is true if the pair was actually inserted. 
570 * 
571 * This function attempts to insert a (key, value) %pair into the 
572 * %unordered_map. An %unordered_map relies on unique keys and thus a 
573 * %pair is only inserted if its first element (the key) is not already 
574 * present in the %unordered_map. 
575 * 
576 * Insertion requires amortized constant time. 
577 */ 
578 std::pair<iterator, bool> 
579 insert(const value_type& __x) 
580 { return _M_h.insert(__x); } 
581 
582 // _GLIBCXX_RESOLVE_LIB_DEFECTS 
583 // 2354. Unnecessary copying when inserting into maps with braced-init 
584 std::pair<iterator, bool> 
585 insert(value_type&& __x) 
586 { return _M_h.insert(std::move(__x)); } 
587 
588 template<typename _Pair> 
589 __enable_if_t<is_constructible<value_type, _Pair&&>::value, 
590 pair<iterator, bool>> 
591 insert(_Pair&& __x) 
592 { return _M_h.emplace(std::forward<_Pair>(__x)); } 
593 //@} 
594 
595 //@{ 
596 /** 
597 * @brief Attempts to insert a std::pair into the %unordered_map. 
598 * @param __hint An iterator that serves as a hint as to where the 
599 * pair should be inserted. 
600 * @param __x Pair to be inserted (see std::make_pair for easy creation 
601 * of pairs). 
602 * @return An iterator that points to the element with key of 
603 * @a __x (may or may not be the %pair passed in). 
604 * 
605 * This function is not concerned about whether the insertion took place, 
606 * and thus does not return a boolean like the single-argument insert() 
607 * does. Note that the first parameter is only a hint and can 
608 * potentially improve the performance of the insertion process. A bad 
609 * hint would cause no gains in efficiency. 
610 * 
611 * See 
612 * https://gcc.gnu.org/onlinedocs/libstdc++/manual/associative.html#containers.associative.insert_hints 
613 * for more on @a hinting. 
614 * 
615 * Insertion requires amortized constant time. 
616 */ 
617 iterator 
618 insert(const_iterator __hint, const value_type& __x) 
619 { return _M_h.insert(__hint, __x); } 
620 
621 // _GLIBCXX_RESOLVE_LIB_DEFECTS 
622 // 2354. Unnecessary copying when inserting into maps with braced-init 
623 iterator 
624 insert(const_iterator __hint, value_type&& __x) 
625 { return _M_h.insert(__hint, std::move(__x)); } 
626 
627 template<typename _Pair> 
628 __enable_if_t<is_constructible<value_type, _Pair&&>::value, iterator> 
629 insert(const_iterator __hint, _Pair&& __x) 
630 { return _M_h.emplace_hint(__hint, std::forward<_Pair>(__x)); } 
631 //@} 
632 
633 /** 
634 * @brief A template function that attempts to insert a range of 
635 * elements. 
636 * @param __first Iterator pointing to the start of the range to be 
637 * inserted. 
638 * @param __last Iterator pointing to the end of the range. 
639 * 
640 * Complexity similar to that of the range constructor. 
641 */ 
642 template<typename _InputIterator> 
643 void 
644 insert(_InputIterator __first, _InputIterator __last) 
645 { _M_h.insert(__first, __last); } 
646 
647 /** 
648 * @brief Attempts to insert a list of elements into the %unordered_map. 
649 * @param __l A std::initializer_list<value_type> of elements 
650 * to be inserted. 
651 * 
652 * Complexity similar to that of the range constructor. 
653 */ 
654 void 
655 insert(initializer_list<value_type> __l) 
656 { _M_h.insert(__l); } 
657 
658 
659#if __cplusplus > 201402L 
660#define __cpp_lib_unordered_map_insertion 201411 // non-standard macro 
661 /** 
662 * @brief Attempts to insert a std::pair into the %unordered_map. 
663 * @param __k Key to use for finding a possibly existing pair in 
664 * the map. 
665 * @param __obj Argument used to generate the .second for a pair  
666 * instance. 
667 * 
668 * @return A pair, of which the first element is an iterator that  
669 * points to the possibly inserted pair, and the second is  
670 * a bool that is true if the pair was actually inserted. 
671 * 
672 * This function attempts to insert a (key, value) %pair into the 
673 * %unordered_map. An %unordered_map relies on unique keys and thus a 
674 * %pair is only inserted if its first element (the key) is not already 
675 * present in the %unordered_map. 
676 * If the %pair was already in the %unordered_map, the .second of  
677 * the %pair is assigned from __obj. 
678 * 
679 * Insertion requires amortized constant time. 
680 */ 
681 template <typename _Obj> 
682 pair<iterator, bool> 
683 insert_or_assign(const key_type& __k, _Obj&& __obj) 
684 { 
685 iterator __i = find(__k); 
686 if (__i == end()) 
687 { 
688 __i = emplace(std::piecewise_construct, 
689 std::forward_as_tuple(__k), 
690 std::forward_as_tuple(std::forward<_Obj>(__obj))) 
691 .first; 
692 return {__i, true}; 
693 } 
694 (*__i).second = std::forward<_Obj>(__obj); 
695 return {__i, false}; 
696 } 
697 
698 // move-capable overload 
699 template <typename _Obj> 
700 pair<iterator, bool> 
701 insert_or_assign(key_type&& __k, _Obj&& __obj) 
702 { 
703 iterator __i = find(__k); 
704 if (__i == end()) 
705 { 
706 __i = emplace(std::piecewise_construct, 
707 std::forward_as_tuple(std::move(__k)), 
708 std::forward_as_tuple(std::forward<_Obj>(__obj))) 
709 .first; 
710 return {__i, true}; 
711 } 
712 (*__i).second = std::forward<_Obj>(__obj); 
713 return {__i, false}; 
714 } 
715 
716 /** 
717 * @brief Attempts to insert a std::pair into the %unordered_map. 
718 * @param __hint An iterator that serves as a hint as to where the 
719 * pair should be inserted. 
720 * @param __k Key to use for finding a possibly existing pair in 
721 * the unordered_map. 
722 * @param __obj Argument used to generate the .second for a pair  
723 * instance. 
724 * @return An iterator that points to the element with key of 
725 * @a __x (may or may not be the %pair passed in). 
726 * 
727 * This function is not concerned about whether the insertion took place, 
728 * and thus does not return a boolean like the single-argument insert() 
729 * does.  
730 * If the %pair was already in the %unordered map, the .second of 
731 * the %pair is assigned from __obj. 
732 * Note that the first parameter is only a hint and can 
733 * potentially improve the performance of the insertion process. A bad 
734 * hint would cause no gains in efficiency. 
735 * 
736 * See 
737 * https://gcc.gnu.org/onlinedocs/libstdc++/manual/associative.html#containers.associative.insert_hints 
738 * for more on @a hinting. 
739 * 
740 * Insertion requires amortized constant time. 
741 */ 
742 template <typename _Obj> 
743 iterator 
744 insert_or_assign(const_iterator __hint, const key_type& __k, 
745 _Obj&& __obj) 
746 { 
747 iterator __i = find(__k); 
748 if (__i == end()) 
749 { 
750 return emplace_hint(__hint, std::piecewise_construct, 
751 std::forward_as_tuple(__k), 
752 std::forward_as_tuple( 
753 std::forward<_Obj>(__obj))); 
754 } 
755 (*__i).second = std::forward<_Obj>(__obj); 
756 return __i; 
757 } 
758 
759 // move-capable overload 
760 template <typename _Obj> 
761 iterator 
762 insert_or_assign(const_iterator __hint, key_type&& __k, _Obj&& __obj) 
763 { 
764 iterator __i = find(__k); 
765 if (__i == end()) 
766 { 
767 return emplace_hint(__hint, std::piecewise_construct, 
768 std::forward_as_tuple(std::move(__k)), 
769 std::forward_as_tuple( 
770 std::forward<_Obj>(__obj))); 
771 } 
772 (*__i).second = std::forward<_Obj>(__obj); 
773 return __i; 
774 } 
775#endif 
776 
777 //@{ 
778 /** 
779 * @brief Erases an element from an %unordered_map. 
780 * @param __position An iterator pointing to the element to be erased. 
781 * @return An iterator pointing to the element immediately following 
782 * @a __position prior to the element being erased. If no such 
783 * element exists, end() is returned. 
784 * 
785 * This function erases an element, pointed to by the given iterator, 
786 * from an %unordered_map. 
787 * Note that this function only erases the element, and that if the 
788 * element is itself a pointer, the pointed-to memory is not touched in 
789 * any way. Managing the pointer is the user's responsibility. 
790 */ 
791 iterator 
792 erase(const_iterator __position) 
793 { return _M_h.erase(__position); } 
794 
795 // LWG 2059. 
796 iterator 
797 erase(iterator __position) 
798 { return _M_h.erase(__position); } 
799 //@} 
800 
801 /** 
802 * @brief Erases elements according to the provided key. 
803 * @param __x Key of element to be erased. 
804 * @return The number of elements erased. 
805 * 
806 * This function erases all the elements located by the given key from 
807 * an %unordered_map. For an %unordered_map the result of this function 
808 * can only be 0 (not present) or 1 (present). 
809 * Note that this function only erases the element, and that if the 
810 * element is itself a pointer, the pointed-to memory is not touched in 
811 * any way. Managing the pointer is the user's responsibility. 
812 */ 
813 size_type 
814 erase(const key_type& __x) 
815 { return _M_h.erase(__x); } 
816 
817 /** 
818 * @brief Erases a [__first,__last) range of elements from an 
819 * %unordered_map. 
820 * @param __first Iterator pointing to the start of the range to be 
821 * erased. 
822 * @param __last Iterator pointing to the end of the range to 
823 * be erased. 
824 * @return The iterator @a __last. 
825 * 
826 * This function erases a sequence of elements from an %unordered_map. 
827 * Note that this function only erases the elements, and that if 
828 * the element is itself a pointer, the pointed-to memory is not touched 
829 * in any way. Managing the pointer is the user's responsibility. 
830 */ 
831 iterator 
832 erase(const_iterator __first, const_iterator __last) 
833 { return _M_h.erase(__first, __last); } 
834 
835 /** 
836 * Erases all elements in an %unordered_map. 
837 * Note that this function only erases the elements, and that if the 
838 * elements themselves are pointers, the pointed-to memory is not touched 
839 * in any way. Managing the pointer is the user's responsibility. 
840 */ 
841 void 
842 clear() noexcept 
843 { _M_h.clear(); } 
844 
845 /** 
846 * @brief Swaps data with another %unordered_map. 
847 * @param __x An %unordered_map of the same element and allocator 
848 * types. 
849 * 
850 * This exchanges the elements between two %unordered_map in constant 
851 * time. 
852 * Note that the global std::swap() function is specialized such that 
853 * std::swap(m1,m2) will feed to this function. 
854 */ 
855 void 
856 swap(unordered_map& __x) 
857 noexcept( noexcept(_M_h.swap(__x._M_h)) ) 
858 { _M_h.swap(__x._M_h); } 
859 
860#if __cplusplus > 201402L 
861 template<typename, typename, typename> 
862 friend class std::_Hash_merge_helper; 
863 
864 template<typename _H2, typename _P2> 
865 void 
866 merge(unordered_map<_Key, _Tp, _H2, _P2, _Alloc>& __source) 
867 { 
868 using _Merge_helper = _Hash_merge_helper<unordered_map, _H2, _P2>; 
869 _M_h._M_merge_unique(_Merge_helper::_S_get_table(__source)); 
870 } 
871 
872 template<typename _H2, typename _P2> 
873 void 
874 merge(unordered_map<_Key, _Tp, _H2, _P2, _Alloc>&& __source) 
875 { merge(__source); } 
876 
877 template<typename _H2, typename _P2> 
878 void 
879 merge(unordered_multimap<_Key, _Tp, _H2, _P2, _Alloc>& __source) 
880 { 
881 using _Merge_helper = _Hash_merge_helper<unordered_map, _H2, _P2>; 
882 _M_h._M_merge_unique(_Merge_helper::_S_get_table(__source)); 
883 } 
884 
885 template<typename _H2, typename _P2> 
886 void 
887 merge(unordered_multimap<_Key, _Tp, _H2, _P2, _Alloc>&& __source) 
888 { merge(__source); } 
889#endif // C++17 
890 
891 // observers. 
892 
893 /// Returns the hash functor object with which the %unordered_map was 
894 /// constructed. 
895 hasher 
896 hash_function() const 
897 { return _M_h.hash_function(); } 
898 
899 /// Returns the key comparison object with which the %unordered_map was 
900 /// constructed. 
901 key_equal 
902 key_eq() const 
903 { return _M_h.key_eq(); } 
904 
905 // lookup. 
906 
907 //@{ 
908 /** 
909 * @brief Tries to locate an element in an %unordered_map. 
910 * @param __x Key to be located. 
911 * @return Iterator pointing to sought-after element, or end() if not 
912 * found. 
913 * 
914 * This function takes a key and tries to locate the element with which 
915 * the key matches. If successful the function returns an iterator 
916 * pointing to the sought after element. If unsuccessful it returns the 
917 * past-the-end ( @c end() ) iterator. 
918 */ 
919 iterator 
920 find(const key_type& __x) 
921 { return _M_h.find(__x); } 
922 
923 const_iterator 
924 find(const key_type& __x) const 
925 { return _M_h.find(__x); } 
926 //@} 
927 
928 /** 
929 * @brief Finds the number of elements. 
930 * @param __x Key to count. 
931 * @return Number of elements with specified key. 
932 * 
933 * This function only makes sense for %unordered_multimap; for 
934 * %unordered_map the result will either be 0 (not present) or 1 
935 * (present). 
936 */ 
937 size_type 
938 count(const key_type& __x) const 
939 { return _M_h.count(__x); } 
940 
941#if __cplusplus > 201703L 
942 /** 
943 * @brief Finds whether an element with the given key exists. 
944 * @param __x Key of elements to be located. 
945 * @return True if there is any element with the specified key. 
946 */ 
947 bool 
948 contains(const key_type& __x) const 
949 { return _M_h.find(__x) != _M_h.end(); } 
950#endif 
951 
952 //@{ 
953 /** 
954 * @brief Finds a subsequence matching given key. 
955 * @param __x Key to be located. 
956 * @return Pair of iterators that possibly points to the subsequence 
957 * matching given key. 
958 * 
959 * This function probably only makes sense for %unordered_multimap. 
960 */ 
961 std::pair<iterator, iterator> 
962 equal_range(const key_type& __x) 
963 { return _M_h.equal_range(__x); } 
964 
965 std::pair<const_iterator, const_iterator> 
966 equal_range(const key_type& __x) const 
967 { return _M_h.equal_range(__x); } 
968 //@} 
969 
970 //@{ 
971 /** 
972 * @brief Subscript ( @c [] ) access to %unordered_map data. 
973 * @param __k The key for which data should be retrieved. 
974 * @return A reference to the data of the (key,data) %pair. 
975 * 
976 * Allows for easy lookup with the subscript ( @c [] )operator. Returns 
977 * data associated with the key specified in subscript. If the key does 
978 * not exist, a pair with that key is created using default values, which 
979 * is then returned. 
980 * 
981 * Lookup requires constant time. 
982 */ 
983 mapped_type& 
984 operator[](const key_type& __k) 
985 { return _M_h[__k]; } 
986 
987 mapped_type& 
988 operator[](key_type&& __k) 
989 { return _M_h[std::move(__k)]; } 
990 //@} 
991 
992 //@{ 
993 /** 
994 * @brief Access to %unordered_map data. 
995 * @param __k The key for which data should be retrieved. 
996 * @return A reference to the data whose key is equal to @a __k, if 
997 * such a data is present in the %unordered_map. 
998 * @throw std::out_of_range If no such data is present. 
999 */ 
1000 mapped_type& 
1001 at(const key_type& __k) 
1002 { return _M_h.at(__k); } 
1003 
1004 const mapped_type& 
1005 at(const key_type& __k) const 
1006 { return _M_h.at(__k); } 
1007 //@} 
1008 
1009 // bucket interface. 
1010 
1011 /// Returns the number of buckets of the %unordered_map. 
1012 size_type 
1013 bucket_count() const noexcept 
1014 { return _M_h.bucket_count(); } 
1015 
1016 /// Returns the maximum number of buckets of the %unordered_map. 
1017 size_type 
1018 max_bucket_count() const noexcept 
1019 { return _M_h.max_bucket_count(); } 
1020 
1021 /* 
1022 * @brief Returns the number of elements in a given bucket. 
1023 * @param __n A bucket index. 
1024 * @return The number of elements in the bucket. 
1025 */ 
1026 size_type 
1027 bucket_size(size_type __n) const 
1028 { return _M_h.bucket_size(__n); } 
1029 
1030 /* 
1031 * @brief Returns the bucket index of a given element. 
1032 * @param __key A key instance. 
1033 * @return The key bucket index. 
1034 */ 
1035 size_type 
1036 bucket(const key_type& __key) const 
1037 { return _M_h.bucket(__key); } 
1038  
1039 /** 
1040 * @brief Returns a read/write iterator pointing to the first bucket 
1041 * element. 
1042 * @param __n The bucket index. 
1043 * @return A read/write local iterator. 
1044 */ 
1045 local_iterator 
1046 begin(size_type __n) 
1047 { return _M_h.begin(__n); } 
1048 
1049 //@{ 
1050 /** 
1051 * @brief Returns a read-only (constant) iterator pointing to the first 
1052 * bucket element. 
1053 * @param __n The bucket index. 
1054 * @return A read-only local iterator. 
1055 */ 
1056 const_local_iterator 
1057 begin(size_type __n) const 
1058 { return _M_h.begin(__n); } 
1059 
1060 const_local_iterator 
1061 cbegin(size_type __n) const 
1062 { return _M_h.cbegin(__n); } 
1063 //@} 
1064 
1065 /** 
1066 * @brief Returns a read/write iterator pointing to one past the last 
1067 * bucket elements. 
1068 * @param __n The bucket index. 
1069 * @return A read/write local iterator. 
1070 */ 
1071 local_iterator 
1072 end(size_type __n) 
1073 { return _M_h.end(__n); } 
1074 
1075 //@{ 
1076 /** 
1077 * @brief Returns a read-only (constant) iterator pointing to one past 
1078 * the last bucket elements. 
1079 * @param __n The bucket index. 
1080 * @return A read-only local iterator. 
1081 */ 
1082 const_local_iterator 
1083 end(size_type __n) const 
1084 { return _M_h.end(__n); } 
1085 
1086 const_local_iterator 
1087 cend(size_type __n) const 
1088 { return _M_h.cend(__n); } 
1089 //@} 
1090 
1091 // hash policy. 
1092 
1093 /// Returns the average number of elements per bucket. 
1094 float 
1095 load_factor() const noexcept 
1096 { return _M_h.load_factor(); } 
1097 
1098 /// Returns a positive number that the %unordered_map tries to keep the 
1099 /// load factor less than or equal to. 
1100 float 
1101 max_load_factor() const noexcept 
1102 { return _M_h.max_load_factor(); } 
1103 
1104 /** 
1105 * @brief Change the %unordered_map maximum load factor. 
1106 * @param __z The new maximum load factor. 
1107 */ 
1108 void 
1109 max_load_factor(float __z) 
1110 { _M_h.max_load_factor(__z); } 
1111 
1112 /** 
1113 * @brief May rehash the %unordered_map. 
1114 * @param __n The new number of buckets. 
1115 * 
1116 * Rehash will occur only if the new number of buckets respect the 
1117 * %unordered_map maximum load factor. 
1118 */ 
1119 void 
1120 rehash(size_type __n) 
1121 { _M_h.rehash(__n); } 
1122 
1123 /** 
1124 * @brief Prepare the %unordered_map for a specified number of 
1125 * elements. 
1126 * @param __n Number of elements required. 
1127 * 
1128 * Same as rehash(ceil(n / max_load_factor())). 
1129 */ 
1130 void 
1131 reserve(size_type __n) 
1132 { _M_h.reserve(__n); } 
1133 
1134 template<typename _Key1, typename _Tp1, typename _Hash1, typename _Pred1, 
1135 typename _Alloc1> 
1136 friend bool 
1137 operator==(const unordered_map<_Key1, _Tp1, _Hash1, _Pred1, _Alloc1>&, 
1138 const unordered_map<_Key1, _Tp1, _Hash1, _Pred1, _Alloc1>&); 
1139 }; 
1140 
1141#if __cpp_deduction_guides >= 201606 
1142 
1143 template<typename _InputIterator, 
1144 typename _Hash = hash<__iter_key_t<_InputIterator>>, 
1145 typename _Pred = equal_to<__iter_key_t<_InputIterator>>, 
1146 typename _Allocator = allocator<__iter_to_alloc_t<_InputIterator>>, 
1147 typename = _RequireInputIter<_InputIterator>, 
1148 typename = _RequireNotAllocatorOrIntegral<_Hash>, 
1149 typename = _RequireNotAllocator<_Pred>, 
1150 typename = _RequireAllocator<_Allocator>> 
1151 unordered_map(_InputIterator, _InputIterator, 
1152 typename unordered_map<int, int>::size_type = {}, 
1153 _Hash = _Hash(), _Pred = _Pred(), _Allocator = _Allocator()) 
1154 -> unordered_map<__iter_key_t<_InputIterator>, 
1155 __iter_val_t<_InputIterator>, 
1156 _Hash, _Pred, _Allocator>; 
1157 
1158 template<typename _Key, typename _Tp, typename _Hash = hash<_Key>, 
1159 typename _Pred = equal_to<_Key>, 
1160 typename _Allocator = allocator<pair<const _Key, _Tp>>, 
1161 typename = _RequireNotAllocatorOrIntegral<_Hash>, 
1162 typename = _RequireNotAllocator<_Pred>, 
1163 typename = _RequireAllocator<_Allocator>> 
1164 unordered_map(initializer_list<pair<_Key, _Tp>>, 
1165 typename unordered_map<int, int>::size_type = {}, 
1166 _Hash = _Hash(), _Pred = _Pred(), _Allocator = _Allocator()) 
1167 -> unordered_map<_Key, _Tp, _Hash, _Pred, _Allocator>; 
1168 
1169 template<typename _InputIterator, typename _Allocator, 
1170 typename = _RequireInputIter<_InputIterator>, 
1171 typename = _RequireAllocator<_Allocator>> 
1172 unordered_map(_InputIterator, _InputIterator, 
1173 typename unordered_map<int, int>::size_type, _Allocator) 
1174 -> unordered_map<__iter_key_t<_InputIterator>, 
1175 __iter_val_t<_InputIterator>, 
1176 hash<__iter_key_t<_InputIterator>>, 
1177 equal_to<__iter_key_t<_InputIterator>>, 
1178 _Allocator>; 
1179 
1180 template<typename _InputIterator, typename _Allocator, 
1181 typename = _RequireInputIter<_InputIterator>, 
1182 typename = _RequireAllocator<_Allocator>> 
1183 unordered_map(_InputIterator, _InputIterator, _Allocator) 
1184 -> unordered_map<__iter_key_t<_InputIterator>, 
1185 __iter_val_t<_InputIterator>, 
1186 hash<__iter_key_t<_InputIterator>>, 
1187 equal_to<__iter_key_t<_InputIterator>>, 
1188 _Allocator>; 
1189 
1190 template<typename _InputIterator, typename _Hash, typename _Allocator, 
1191 typename = _RequireInputIter<_InputIterator>, 
1192 typename = _RequireNotAllocatorOrIntegral<_Hash>, 
1193 typename = _RequireAllocator<_Allocator>> 
1194 unordered_map(_InputIterator, _InputIterator, 
1195 typename unordered_map<int, int>::size_type, 
1196 _Hash, _Allocator) 
1197 -> unordered_map<__iter_key_t<_InputIterator>, 
1198 __iter_val_t<_InputIterator>, _Hash, 
1199 equal_to<__iter_key_t<_InputIterator>>, _Allocator>; 
1200 
1201 template<typename _Key, typename _Tp, typename _Allocator, 
1202 typename = _RequireAllocator<_Allocator>> 
1203 unordered_map(initializer_list<pair<_Key, _Tp>>, 
1204 typename unordered_map<int, int>::size_type, 
1205 _Allocator) 
1206 -> unordered_map<_Key, _Tp, hash<_Key>, equal_to<_Key>, _Allocator>; 
1207 
1208 template<typename _Key, typename _Tp, typename _Allocator, 
1209 typename = _RequireAllocator<_Allocator>> 
1210 unordered_map(initializer_list<pair<_Key, _Tp>>, _Allocator) 
1211 -> unordered_map<_Key, _Tp, hash<_Key>, equal_to<_Key>, _Allocator>; 
1212 
1213 template<typename _Key, typename _Tp, typename _Hash, typename _Allocator, 
1214 typename = _RequireNotAllocatorOrIntegral<_Hash>, 
1215 typename = _RequireAllocator<_Allocator>> 
1216 unordered_map(initializer_list<pair<_Key, _Tp>>, 
1217 typename unordered_map<int, int>::size_type, 
1218 _Hash, _Allocator) 
1219 -> unordered_map<_Key, _Tp, _Hash, equal_to<_Key>, _Allocator>; 
1220 
1221#endif 
1222 
1223 /** 
1224 * @brief A standard container composed of equivalent keys 
1225 * (possibly containing multiple of each key value) that associates 
1226 * values of another type with the keys. 
1227 * 
1228 * @ingroup unordered_associative_containers 
1229 * 
1230 * @tparam _Key Type of key objects. 
1231 * @tparam _Tp Type of mapped objects. 
1232 * @tparam _Hash Hashing function object type, defaults to hash<_Value>. 
1233 * @tparam _Pred Predicate function object type, defaults 
1234 * to equal_to<_Value>. 
1235 * @tparam _Alloc Allocator type, defaults to 
1236 * std::allocator<std::pair<const _Key, _Tp>>. 
1237 * 
1238 * Meets the requirements of a <a href="tables.html#65">container</a>, and 
1239 * <a href="tables.html#xx">unordered associative container</a> 
1240 * 
1241 * The resulting value type of the container is std::pair<const _Key, _Tp>. 
1242 * 
1243 * Base is _Hashtable, dispatched at compile time via template 
1244 * alias __ummap_hashtable. 
1245 */ 
1246 template<typename _Key, typename _Tp, 
1247 typename _Hash = hash<_Key>, 
1248 typename _Pred = equal_to<_Key>, 
1249 typename _Alloc = allocator<std::pair<const _Key, _Tp>>> 
1250 class unordered_multimap 
1251 { 
1252 typedef __ummap_hashtable<_Key, _Tp, _Hash, _Pred, _Alloc> _Hashtable; 
1253 _Hashtable _M_h; 
1254 
1255 public: 
1256 // typedefs: 
1257 //@{ 
1258 /// Public typedefs. 
1259 typedef typename _Hashtable::key_type key_type; 
1260 typedef typename _Hashtable::value_type value_type; 
1261 typedef typename _Hashtable::mapped_type mapped_type; 
1262 typedef typename _Hashtable::hasher hasher; 
1263 typedef typename _Hashtable::key_equal key_equal; 
1264 typedef typename _Hashtable::allocator_type allocator_type; 
1265 //@} 
1266 
1267 //@{ 
1268 /// Iterator-related typedefs. 
1269 typedef typename _Hashtable::pointer pointer; 
1270 typedef typename _Hashtable::const_pointer const_pointer; 
1271 typedef typename _Hashtable::reference reference; 
1272 typedef typename _Hashtable::const_reference const_reference; 
1273 typedef typename _Hashtable::iterator iterator; 
1274 typedef typename _Hashtable::const_iterator const_iterator; 
1275 typedef typename _Hashtable::local_iterator local_iterator; 
1276 typedef typename _Hashtable::const_local_iterator const_local_iterator; 
1277 typedef typename _Hashtable::size_type size_type; 
1278 typedef typename _Hashtable::difference_type difference_type; 
1279 //@} 
1280 
1281#if __cplusplus > 201402L 
1282 using node_type = typename _Hashtable::node_type; 
1283#endif 
1284 
1285 //construct/destroy/copy 
1286 
1287 /// Default constructor. 
1288 unordered_multimap() = default; 
1289 
1290 /** 
1291 * @brief Default constructor creates no elements. 
1292 * @param __n Mnimal initial number of buckets. 
1293 * @param __hf A hash functor. 
1294 * @param __eql A key equality functor. 
1295 * @param __a An allocator object. 
1296 */ 
1297 explicit 
1298 unordered_multimap(size_type __n, 
1299 const hasher& __hf = hasher(), 
1300 const key_equal& __eql = key_equal(), 
1301 const allocator_type& __a = allocator_type()) 
1302 : _M_h(__n, __hf, __eql, __a) 
1303 { } 
1304 
1305 /** 
1306 * @brief Builds an %unordered_multimap from a range. 
1307 * @param __first An input iterator. 
1308 * @param __last An input iterator. 
1309 * @param __n Minimal initial number of buckets. 
1310 * @param __hf A hash functor. 
1311 * @param __eql A key equality functor. 
1312 * @param __a An allocator object. 
1313 * 
1314 * Create an %unordered_multimap consisting of copies of the elements 
1315 * from [__first,__last). This is linear in N (where N is 
1316 * distance(__first,__last)). 
1317 */ 
1318 template<typename _InputIterator> 
1319 unordered_multimap(_InputIterator __first, _InputIterator __last, 
1320 size_type __n = 0, 
1321 const hasher& __hf = hasher(), 
1322 const key_equal& __eql = key_equal(), 
1323 const allocator_type& __a = allocator_type()) 
1324 : _M_h(__first, __last, __n, __hf, __eql, __a) 
1325 { } 
1326 
1327 /// Copy constructor. 
1328 unordered_multimap(const unordered_multimap&) = default; 
1329 
1330 /// Move constructor. 
1331 unordered_multimap(unordered_multimap&&) = default; 
1332 
1333 /** 
1334 * @brief Creates an %unordered_multimap with no elements. 
1335 * @param __a An allocator object. 
1336 */ 
1337 explicit 
1338 unordered_multimap(const allocator_type& __a) 
1339 : _M_h(__a) 
1340 { } 
1341 
1342 /* 
1343 * @brief Copy constructor with allocator argument. 
1344 * @param __uset Input %unordered_multimap to copy. 
1345 * @param __a An allocator object. 
1346 */ 
1347 unordered_multimap(const unordered_multimap& __ummap, 
1348 const allocator_type& __a) 
1349 : _M_h(__ummap._M_h, __a) 
1350 { } 
1351 
1352 /* 
1353 * @brief Move constructor with allocator argument. 
1354 * @param __uset Input %unordered_multimap to move. 
1355 * @param __a An allocator object. 
1356 */ 
1357 unordered_multimap(unordered_multimap&& __ummap, 
1358 const allocator_type& __a) 
1359 : _M_h(std::move(__ummap._M_h), __a) 
1360 { } 
1361 
1362 /** 
1363 * @brief Builds an %unordered_multimap from an initializer_list. 
1364 * @param __l An initializer_list. 
1365 * @param __n Minimal initial number of buckets. 
1366 * @param __hf A hash functor. 
1367 * @param __eql A key equality functor. 
1368 * @param __a An allocator object. 
1369 * 
1370 * Create an %unordered_multimap consisting of copies of the elements in 
1371 * the list. This is linear in N (where N is @a __l.size()). 
1372 */ 
1373 unordered_multimap(initializer_list<value_type> __l, 
1374 size_type __n = 0, 
1375 const hasher& __hf = hasher(), 
1376 const key_equal& __eql = key_equal(), 
1377 const allocator_type& __a = allocator_type()) 
1378 : _M_h(__l, __n, __hf, __eql, __a) 
1379 { } 
1380 
1381 unordered_multimap(size_type __n, const allocator_type& __a) 
1382 : unordered_multimap(__n, hasher(), key_equal(), __a) 
1383 { } 
1384 
1385 unordered_multimap(size_type __n, const hasher& __hf, 
1386 const allocator_type& __a) 
1387 : unordered_multimap(__n, __hf, key_equal(), __a) 
1388 { } 
1389 
1390 template<typename _InputIterator> 
1391 unordered_multimap(_InputIterator __first, _InputIterator __last, 
1392 size_type __n, 
1393 const allocator_type& __a) 
1394 : unordered_multimap(__first, __last, __n, hasher(), key_equal(), __a) 
1395 { } 
1396 
1397 template<typename _InputIterator> 
1398 unordered_multimap(_InputIterator __first, _InputIterator __last, 
1399 size_type __n, const hasher& __hf, 
1400 const allocator_type& __a) 
1401 : unordered_multimap(__first, __last, __n, __hf, key_equal(), __a) 
1402 { } 
1403 
1404 unordered_multimap(initializer_list<value_type> __l, 
1405 size_type __n, 
1406 const allocator_type& __a) 
1407 : unordered_multimap(__l, __n, hasher(), key_equal(), __a) 
1408 { } 
1409 
1410 unordered_multimap(initializer_list<value_type> __l, 
1411 size_type __n, const hasher& __hf, 
1412 const allocator_type& __a) 
1413 : unordered_multimap(__l, __n, __hf, key_equal(), __a) 
1414 { } 
1415 
1416 /// Copy assignment operator. 
1417 unordered_multimap& 
1418 operator=(const unordered_multimap&) = default; 
1419 
1420 /// Move assignment operator. 
1421 unordered_multimap& 
1422 operator=(unordered_multimap&&) = default; 
1423 
1424 /** 
1425 * @brief %Unordered_multimap list assignment operator. 
1426 * @param __l An initializer_list. 
1427 * 
1428 * This function fills an %unordered_multimap with copies of the 
1429 * elements in the initializer list @a __l. 
1430 * 
1431 * Note that the assignment completely changes the %unordered_multimap 
1432 * and that the resulting %unordered_multimap's size is the same as the 
1433 * number of elements assigned. 
1434 */ 
1435 unordered_multimap& 
1436 operator=(initializer_list<value_type> __l) 
1437 { 
1438 _M_h = __l; 
1439 return *this; 
1440 } 
1441 
1442 /// Returns the allocator object used by the %unordered_multimap. 
1443 allocator_type 
1444 get_allocator() const noexcept 
1445 { return _M_h.get_allocator(); } 
1446 
1447 // size and capacity: 
1448 
1449 /// Returns true if the %unordered_multimap is empty. 
1450 _GLIBCXX_NODISCARD bool 
1451 empty() const noexcept 
1452 { return _M_h.empty(); } 
1453 
1454 /// Returns the size of the %unordered_multimap. 
1455 size_type 
1456 size() const noexcept 
1457 { return _M_h.size(); } 
1458 
1459 /// Returns the maximum size of the %unordered_multimap. 
1460 size_type 
1461 max_size() const noexcept 
1462 { return _M_h.max_size(); } 
1463 
1464 // iterators. 
1465 
1466 /** 
1467 * Returns a read/write iterator that points to the first element in the 
1468 * %unordered_multimap. 
1469 */ 
1470 iterator 
1471 begin() noexcept 
1472 { return _M_h.begin(); } 
1473 
1474 //@{ 
1475 /** 
1476 * Returns a read-only (constant) iterator that points to the first 
1477 * element in the %unordered_multimap. 
1478 */ 
1479 const_iterator 
1480 begin() const noexcept 
1481 { return _M_h.begin(); } 
1482 
1483 const_iterator 
1484 cbegin() const noexcept 
1485 { return _M_h.begin(); } 
1486 //@} 
1487 
1488 /** 
1489 * Returns a read/write iterator that points one past the last element in 
1490 * the %unordered_multimap. 
1491 */ 
1492 iterator 
1493 end() noexcept 
1494 { return _M_h.end(); } 
1495 
1496 //@{ 
1497 /** 
1498 * Returns a read-only (constant) iterator that points one past the last 
1499 * element in the %unordered_multimap. 
1500 */ 
1501 const_iterator 
1502 end() const noexcept 
1503 { return _M_h.end(); } 
1504 
1505 const_iterator 
1506 cend() const noexcept 
1507 { return _M_h.end(); } 
1508 //@} 
1509 
1510 // modifiers. 
1511 
1512 /** 
1513 * @brief Attempts to build and insert a std::pair into the 
1514 * %unordered_multimap. 
1515 * 
1516 * @param __args Arguments used to generate a new pair instance (see 
1517 * std::piecewise_contruct for passing arguments to each 
1518 * part of the pair constructor). 
1519 * 
1520 * @return An iterator that points to the inserted pair. 
1521 * 
1522 * This function attempts to build and insert a (key, value) %pair into 
1523 * the %unordered_multimap. 
1524 * 
1525 * Insertion requires amortized constant time. 
1526 */ 
1527 template<typename... _Args> 
1528 iterator 
1529 emplace(_Args&&... __args) 
1530 { return _M_h.emplace(std::forward<_Args>(__args)...); } 
1531 
1532 /** 
1533 * @brief Attempts to build and insert a std::pair into the 
1534 * %unordered_multimap. 
1535 * 
1536 * @param __pos An iterator that serves as a hint as to where the pair 
1537 * should be inserted. 
1538 * @param __args Arguments used to generate a new pair instance (see 
1539 * std::piecewise_contruct for passing arguments to each 
1540 * part of the pair constructor). 
1541 * @return An iterator that points to the element with key of the 
1542 * std::pair built from @a __args. 
1543 * 
1544 * Note that the first parameter is only a hint and can potentially 
1545 * improve the performance of the insertion process. A bad hint would 
1546 * cause no gains in efficiency. 
1547 * 
1548 * See 
1549 * https://gcc.gnu.org/onlinedocs/libstdc++/manual/associative.html#containers.associative.insert_hints 
1550 * for more on @a hinting. 
1551 * 
1552 * Insertion requires amortized constant time. 
1553 */ 
1554 template<typename... _Args> 
1555 iterator 
1556 emplace_hint(const_iterator __pos, _Args&&... __args) 
1557 { return _M_h.emplace_hint(__pos, std::forward<_Args>(__args)...); } 
1558 
1559 //@{ 
1560 /** 
1561 * @brief Inserts a std::pair into the %unordered_multimap. 
1562 * @param __x Pair to be inserted (see std::make_pair for easy 
1563 * creation of pairs). 
1564 * 
1565 * @return An iterator that points to the inserted pair. 
1566 * 
1567 * Insertion requires amortized constant time. 
1568 */ 
1569 iterator 
1570 insert(const value_type& __x) 
1571 { return _M_h.insert(__x); } 
1572 
1573 iterator 
1574 insert(value_type&& __x) 
1575 { return _M_h.insert(std::move(__x)); } 
1576 
1577 template<typename _Pair> 
1578 __enable_if_t<is_constructible<value_type, _Pair&&>::value, iterator> 
1579 insert(_Pair&& __x) 
1580 { return _M_h.emplace(std::forward<_Pair>(__x)); } 
1581 //@} 
1582 
1583 //@{ 
1584 /** 
1585 * @brief Inserts a std::pair into the %unordered_multimap. 
1586 * @param __hint An iterator that serves as a hint as to where the 
1587 * pair should be inserted. 
1588 * @param __x Pair to be inserted (see std::make_pair for easy creation 
1589 * of pairs). 
1590 * @return An iterator that points to the element with key of 
1591 * @a __x (may or may not be the %pair passed in). 
1592 * 
1593 * Note that the first parameter is only a hint and can potentially 
1594 * improve the performance of the insertion process. A bad hint would 
1595 * cause no gains in efficiency. 
1596 * 
1597 * See 
1598 * https://gcc.gnu.org/onlinedocs/libstdc++/manual/associative.html#containers.associative.insert_hints 
1599 * for more on @a hinting. 
1600 * 
1601 * Insertion requires amortized constant time. 
1602 */ 
1603 iterator 
1604 insert(const_iterator __hint, const value_type& __x) 
1605 { return _M_h.insert(__hint, __x); } 
1606 
1607 // _GLIBCXX_RESOLVE_LIB_DEFECTS 
1608 // 2354. Unnecessary copying when inserting into maps with braced-init 
1609 iterator 
1610 insert(const_iterator __hint, value_type&& __x) 
1611 { return _M_h.insert(__hint, std::move(__x)); } 
1612 
1613 template<typename _Pair> 
1614 __enable_if_t<is_constructible<value_type, _Pair&&>::value, iterator> 
1615 insert(const_iterator __hint, _Pair&& __x) 
1616 { return _M_h.emplace_hint(__hint, std::forward<_Pair>(__x)); } 
1617 //@} 
1618 
1619 /** 
1620 * @brief A template function that attempts to insert a range of 
1621 * elements. 
1622 * @param __first Iterator pointing to the start of the range to be 
1623 * inserted. 
1624 * @param __last Iterator pointing to the end of the range. 
1625 * 
1626 * Complexity similar to that of the range constructor. 
1627 */ 
1628 template<typename _InputIterator> 
1629 void 
1630 insert(_InputIterator __first, _InputIterator __last) 
1631 { _M_h.insert(__first, __last); } 
1632 
1633 /** 
1634 * @brief Attempts to insert a list of elements into the 
1635 * %unordered_multimap. 
1636 * @param __l A std::initializer_list<value_type> of elements 
1637 * to be inserted. 
1638 * 
1639 * Complexity similar to that of the range constructor. 
1640 */ 
1641 void 
1642 insert(initializer_list<value_type> __l) 
1643 { _M_h.insert(__l); } 
1644 
1645#if __cplusplus > 201402L 
1646 /// Extract a node. 
1647 node_type 
1648 extract(const_iterator __pos) 
1649 { 
1650 __glibcxx_assert(__pos != end()); 
1651 return _M_h.extract(__pos); 
1652 } 
1653 
1654 /// Extract a node. 
1655 node_type 
1656 extract(const key_type& __key) 
1657 { return _M_h.extract(__key); } 
1658 
1659 /// Re-insert an extracted node. 
1660 iterator 
1661 insert(node_type&& __nh) 
1662 { return _M_h._M_reinsert_node_multi(cend(), std::move(__nh)); } 
1663 
1664 /// Re-insert an extracted node. 
1665 iterator 
1666 insert(const_iterator __hint, node_type&& __nh) 
1667 { return _M_h._M_reinsert_node_multi(__hint, std::move(__nh)); } 
1668#endif // C++17 
1669 
1670 //@{ 
1671 /** 
1672 * @brief Erases an element from an %unordered_multimap. 
1673 * @param __position An iterator pointing to the element to be erased. 
1674 * @return An iterator pointing to the element immediately following 
1675 * @a __position prior to the element being erased. If no such 
1676 * element exists, end() is returned. 
1677 * 
1678 * This function erases an element, pointed to by the given iterator, 
1679 * from an %unordered_multimap. 
1680 * Note that this function only erases the element, and that if the 
1681 * element is itself a pointer, the pointed-to memory is not touched in 
1682 * any way. Managing the pointer is the user's responsibility. 
1683 */ 
1684 iterator 
1685 erase(const_iterator __position) 
1686 { return _M_h.erase(__position); } 
1687 
1688 // LWG 2059. 
1689 iterator 
1690 erase(iterator __position) 
1691 { return _M_h.erase(__position); } 
1692 //@} 
1693 
1694 /** 
1695 * @brief Erases elements according to the provided key. 
1696 * @param __x Key of elements to be erased. 
1697 * @return The number of elements erased. 
1698 * 
1699 * This function erases all the elements located by the given key from 
1700 * an %unordered_multimap. 
1701 * Note that this function only erases the element, and that if the 
1702 * element is itself a pointer, the pointed-to memory is not touched in 
1703 * any way. Managing the pointer is the user's responsibility. 
1704 */ 
1705 size_type 
1706 erase(const key_type& __x) 
1707 { return _M_h.erase(__x); } 
1708 
1709 /** 
1710 * @brief Erases a [__first,__last) range of elements from an 
1711 * %unordered_multimap. 
1712 * @param __first Iterator pointing to the start of the range to be 
1713 * erased. 
1714 * @param __last Iterator pointing to the end of the range to 
1715 * be erased. 
1716 * @return The iterator @a __last. 
1717 * 
1718 * This function erases a sequence of elements from an 
1719 * %unordered_multimap. 
1720 * Note that this function only erases the elements, and that if 
1721 * the element is itself a pointer, the pointed-to memory is not touched 
1722 * in any way. Managing the pointer is the user's responsibility. 
1723 */ 
1724 iterator 
1725 erase(const_iterator __first, const_iterator __last) 
1726 { return _M_h.erase(__first, __last); } 
1727 
1728 /** 
1729 * Erases all elements in an %unordered_multimap. 
1730 * Note that this function only erases the elements, and that if the 
1731 * elements themselves are pointers, the pointed-to memory is not touched 
1732 * in any way. Managing the pointer is the user's responsibility. 
1733 */ 
1734 void 
1735 clear() noexcept 
1736 { _M_h.clear(); } 
1737 
1738 /** 
1739 * @brief Swaps data with another %unordered_multimap. 
1740 * @param __x An %unordered_multimap of the same element and allocator 
1741 * types. 
1742 * 
1743 * This exchanges the elements between two %unordered_multimap in 
1744 * constant time. 
1745 * Note that the global std::swap() function is specialized such that 
1746 * std::swap(m1,m2) will feed to this function. 
1747 */ 
1748 void 
1749 swap(unordered_multimap& __x) 
1750 noexcept( noexcept(_M_h.swap(__x._M_h)) ) 
1751 { _M_h.swap(__x._M_h); } 
1752 
1753#if __cplusplus > 201402L 
1754 template<typename, typename, typename> 
1755 friend class std::_Hash_merge_helper; 
1756 
1757 template<typename _H2, typename _P2> 
1758 void 
1759 merge(unordered_multimap<_Key, _Tp, _H2, _P2, _Alloc>& __source) 
1760 { 
1761 using _Merge_helper 
1762 = _Hash_merge_helper<unordered_multimap, _H2, _P2>; 
1763 _M_h._M_merge_multi(_Merge_helper::_S_get_table(__source)); 
1764 } 
1765 
1766 template<typename _H2, typename _P2> 
1767 void 
1768 merge(unordered_multimap<_Key, _Tp, _H2, _P2, _Alloc>&& __source) 
1769 { merge(__source); } 
1770 
1771 template<typename _H2, typename _P2> 
1772 void 
1773 merge(unordered_map<_Key, _Tp, _H2, _P2, _Alloc>& __source) 
1774 { 
1775 using _Merge_helper 
1776 = _Hash_merge_helper<unordered_multimap, _H2, _P2>; 
1777 _M_h._M_merge_multi(_Merge_helper::_S_get_table(__source)); 
1778 } 
1779 
1780 template<typename _H2, typename _P2> 
1781 void 
1782 merge(unordered_map<_Key, _Tp, _H2, _P2, _Alloc>&& __source) 
1783 { merge(__source); } 
1784#endif // C++17 
1785 
1786 // observers. 
1787 
1788 /// Returns the hash functor object with which the %unordered_multimap 
1789 /// was constructed. 
1790 hasher 
1791 hash_function() const 
1792 { return _M_h.hash_function(); } 
1793 
1794 /// Returns the key comparison object with which the %unordered_multimap 
1795 /// was constructed. 
1796 key_equal 
1797 key_eq() const 
1798 { return _M_h.key_eq(); } 
1799 
1800 // lookup. 
1801 
1802 //@{ 
1803 /** 
1804 * @brief Tries to locate an element in an %unordered_multimap. 
1805 * @param __x Key to be located. 
1806 * @return Iterator pointing to sought-after element, or end() if not 
1807 * found. 
1808 * 
1809 * This function takes a key and tries to locate the element with which 
1810 * the key matches. If successful the function returns an iterator 
1811 * pointing to the sought after element. If unsuccessful it returns the 
1812 * past-the-end ( @c end() ) iterator. 
1813 */ 
1814 iterator 
1815 find(const key_type& __x) 
1816 { return _M_h.find(__x); } 
1817 
1818 const_iterator 
1819 find(const key_type& __x) const 
1820 { return _M_h.find(__x); } 
1821 //@} 
1822 
1823 /** 
1824 * @brief Finds the number of elements. 
1825 * @param __x Key to count. 
1826 * @return Number of elements with specified key. 
1827 */ 
1828 size_type 
1829 count(const key_type& __x) const 
1830 { return _M_h.count(__x); } 
1831 
1832#if __cplusplus > 201703L 
1833 /** 
1834 * @brief Finds whether an element with the given key exists. 
1835 * @param __x Key of elements to be located. 
1836 * @return True if there is any element with the specified key. 
1837 */ 
1838 bool 
1839 contains(const key_type& __x) const 
1840 { return _M_h.find(__x) != _M_h.end(); } 
1841#endif 
1842 
1843 //@{ 
1844 /** 
1845 * @brief Finds a subsequence matching given key. 
1846 * @param __x Key to be located. 
1847 * @return Pair of iterators that possibly points to the subsequence 
1848 * matching given key. 
1849 */ 
1850 std::pair<iterator, iterator> 
1851 equal_range(const key_type& __x) 
1852 { return _M_h.equal_range(__x); } 
1853 
1854 std::pair<const_iterator, const_iterator> 
1855 equal_range(const key_type& __x) const 
1856 { return _M_h.equal_range(__x); } 
1857 //@} 
1858 
1859 // bucket interface. 
1860 
1861 /// Returns the number of buckets of the %unordered_multimap. 
1862 size_type 
1863 bucket_count() const noexcept 
1864 { return _M_h.bucket_count(); } 
1865 
1866 /// Returns the maximum number of buckets of the %unordered_multimap. 
1867 size_type 
1868 max_bucket_count() const noexcept 
1869 { return _M_h.max_bucket_count(); } 
1870 
1871 /* 
1872 * @brief Returns the number of elements in a given bucket. 
1873 * @param __n A bucket index. 
1874 * @return The number of elements in the bucket. 
1875 */ 
1876 size_type 
1877 bucket_size(size_type __n) const 
1878 { return _M_h.bucket_size(__n); } 
1879 
1880 /* 
1881 * @brief Returns the bucket index of a given element. 
1882 * @param __key A key instance. 
1883 * @return The key bucket index. 
1884 */ 
1885 size_type 
1886 bucket(const key_type& __key) const 
1887 { return _M_h.bucket(__key); } 
1888  
1889 /** 
1890 * @brief Returns a read/write iterator pointing to the first bucket 
1891 * element. 
1892 * @param __n The bucket index. 
1893 * @return A read/write local iterator. 
1894 */ 
1895 local_iterator 
1896 begin(size_type __n) 
1897 { return _M_h.begin(__n); } 
1898 
1899 //@{ 
1900 /** 
1901 * @brief Returns a read-only (constant) iterator pointing to the first 
1902 * bucket element. 
1903 * @param __n The bucket index. 
1904 * @return A read-only local iterator. 
1905 */ 
1906 const_local_iterator 
1907 begin(size_type __n) const 
1908 { return _M_h.begin(__n); } 
1909 
1910 const_local_iterator 
1911 cbegin(size_type __n) const 
1912 { return _M_h.cbegin(__n); } 
1913 //@} 
1914 
1915 /** 
1916 * @brief Returns a read/write iterator pointing to one past the last 
1917 * bucket elements. 
1918 * @param __n The bucket index. 
1919 * @return A read/write local iterator. 
1920 */ 
1921 local_iterator 
1922 end(size_type __n) 
1923 { return _M_h.end(__n); } 
1924 
1925 //@{ 
1926 /** 
1927 * @brief Returns a read-only (constant) iterator pointing to one past 
1928 * the last bucket elements. 
1929 * @param __n The bucket index. 
1930 * @return A read-only local iterator. 
1931 */ 
1932 const_local_iterator 
1933 end(size_type __n) const 
1934 { return _M_h.end(__n); } 
1935 
1936 const_local_iterator 
1937 cend(size_type __n) const 
1938 { return _M_h.cend(__n); } 
1939 //@} 
1940 
1941 // hash policy. 
1942 
1943 /// Returns the average number of elements per bucket. 
1944 float 
1945 load_factor() const noexcept 
1946 { return _M_h.load_factor(); } 
1947 
1948 /// Returns a positive number that the %unordered_multimap tries to keep 
1949 /// the load factor less than or equal to. 
1950 float 
1951 max_load_factor() const noexcept 
1952 { return _M_h.max_load_factor(); } 
1953 
1954 /** 
1955 * @brief Change the %unordered_multimap maximum load factor. 
1956 * @param __z The new maximum load factor. 
1957 */ 
1958 void 
1959 max_load_factor(float __z) 
1960 { _M_h.max_load_factor(__z); } 
1961 
1962 /** 
1963 * @brief May rehash the %unordered_multimap. 
1964 * @param __n The new number of buckets. 
1965 * 
1966 * Rehash will occur only if the new number of buckets respect the 
1967 * %unordered_multimap maximum load factor. 
1968 */ 
1969 void 
1970 rehash(size_type __n) 
1971 { _M_h.rehash(__n); } 
1972 
1973 /** 
1974 * @brief Prepare the %unordered_multimap for a specified number of 
1975 * elements. 
1976 * @param __n Number of elements required. 
1977 * 
1978 * Same as rehash(ceil(n / max_load_factor())). 
1979 */ 
1980 void 
1981 reserve(size_type __n) 
1982 { _M_h.reserve(__n); } 
1983 
1984 template<typename _Key1, typename _Tp1, typename _Hash1, typename _Pred1, 
1985 typename _Alloc1> 
1986 friend bool 
1987 operator==(const unordered_multimap<_Key1, _Tp1, 
1988 _Hash1, _Pred1, _Alloc1>&, 
1989 const unordered_multimap<_Key1, _Tp1, 
1990 _Hash1, _Pred1, _Alloc1>&); 
1991 }; 
1992 
1993#if __cpp_deduction_guides >= 201606 
1994 
1995 template<typename _InputIterator, 
1996 typename _Hash = hash<__iter_key_t<_InputIterator>>, 
1997 typename _Pred = equal_to<__iter_key_t<_InputIterator>>, 
1998 typename _Allocator = allocator<__iter_to_alloc_t<_InputIterator>>, 
1999 typename = _RequireInputIter<_InputIterator>, 
2000 typename = _RequireNotAllocatorOrIntegral<_Hash>, 
2001 typename = _RequireNotAllocator<_Pred>, 
2002 typename = _RequireAllocator<_Allocator>> 
2003 unordered_multimap(_InputIterator, _InputIterator, 
2004 unordered_multimap<int, int>::size_type = {}, 
2005 _Hash = _Hash(), _Pred = _Pred(), 
2006 _Allocator = _Allocator()) 
2007 -> unordered_multimap<__iter_key_t<_InputIterator>, 
2008 __iter_val_t<_InputIterator>, _Hash, _Pred, 
2009 _Allocator>; 
2010 
2011 template<typename _Key, typename _Tp, typename _Hash = hash<_Key>, 
2012 typename _Pred = equal_to<_Key>, 
2013 typename _Allocator = allocator<pair<const _Key, _Tp>>, 
2014 typename = _RequireNotAllocatorOrIntegral<_Hash>, 
2015 typename = _RequireNotAllocator<_Pred>, 
2016 typename = _RequireAllocator<_Allocator>> 
2017 unordered_multimap(initializer_list<pair<_Key, _Tp>>, 
2018 unordered_multimap<int, int>::size_type = {}, 
2019 _Hash = _Hash(), _Pred = _Pred(), 
2020 _Allocator = _Allocator()) 
2021 -> unordered_multimap<_Key, _Tp, _Hash, _Pred, _Allocator>; 
2022 
2023 template<typename _InputIterator, typename _Allocator, 
2024 typename = _RequireInputIter<_InputIterator>, 
2025 typename = _RequireAllocator<_Allocator>> 
2026 unordered_multimap(_InputIterator, _InputIterator, 
2027 unordered_multimap<int, int>::size_type, _Allocator) 
2028 -> unordered_multimap<__iter_key_t<_InputIterator>, 
2029 __iter_val_t<_InputIterator>, 
2030 hash<__iter_key_t<_InputIterator>>, 
2031 equal_to<__iter_key_t<_InputIterator>>, _Allocator>; 
2032 
2033 template<typename _InputIterator, typename _Allocator, 
2034 typename = _RequireInputIter<_InputIterator>, 
2035 typename = _RequireAllocator<_Allocator>> 
2036 unordered_multimap(_InputIterator, _InputIterator, _Allocator) 
2037 -> unordered_multimap<__iter_key_t<_InputIterator>, 
2038 __iter_val_t<_InputIterator>, 
2039 hash<__iter_key_t<_InputIterator>>, 
2040 equal_to<__iter_key_t<_InputIterator>>, _Allocator>; 
2041 
2042 template<typename _InputIterator, typename _Hash, typename _Allocator, 
2043 typename = _RequireInputIter<_InputIterator>, 
2044 typename = _RequireNotAllocatorOrIntegral<_Hash>, 
2045 typename = _RequireAllocator<_Allocator>> 
2046 unordered_multimap(_InputIterator, _InputIterator, 
2047 unordered_multimap<int, int>::size_type, _Hash, 
2048 _Allocator) 
2049 -> unordered_multimap<__iter_key_t<_InputIterator>, 
2050 __iter_val_t<_InputIterator>, _Hash, 
2051 equal_to<__iter_key_t<_InputIterator>>, _Allocator>; 
2052 
2053 template<typename _Key, typename _Tp, typename _Allocator, 
2054 typename = _RequireAllocator<_Allocator>> 
2055 unordered_multimap(initializer_list<pair<_Key, _Tp>>, 
2056 unordered_multimap<int, int>::size_type, 
2057 _Allocator) 
2058 -> unordered_multimap<_Key, _Tp, hash<_Key>, equal_to<_Key>, _Allocator>; 
2059 
2060 template<typename _Key, typename _Tp, typename _Allocator, 
2061 typename = _RequireAllocator<_Allocator>> 
2062 unordered_multimap(initializer_list<pair<_Key, _Tp>>, _Allocator) 
2063 -> unordered_multimap<_Key, _Tp, hash<_Key>, equal_to<_Key>, _Allocator>; 
2064 
2065 template<typename _Key, typename _Tp, typename _Hash, typename _Allocator, 
2066 typename = _RequireNotAllocatorOrIntegral<_Hash>, 
2067 typename = _RequireAllocator<_Allocator>> 
2068 unordered_multimap(initializer_list<pair<_Key, _Tp>>, 
2069 unordered_multimap<int, int>::size_type, 
2070 _Hash, _Allocator) 
2071 -> unordered_multimap<_Key, _Tp, _Hash, equal_to<_Key>, _Allocator>; 
2072 
2073#endif 
2074 
2075 template<class _Key, class _Tp, class _Hash, class _Pred, class _Alloc> 
2076 inline void 
2077 swap(unordered_map<_Key, _Tp, _Hash, _Pred, _Alloc>& __x, 
2078 unordered_map<_Key, _Tp, _Hash, _Pred, _Alloc>& __y) 
2079 noexcept(noexcept(__x.swap(__y))) 
2080 { __x.swap(__y); } 
2081 
2082 template<class _Key, class _Tp, class _Hash, class _Pred, class _Alloc> 
2083 inline void 
2084 swap(unordered_multimap<_Key, _Tp, _Hash, _Pred, _Alloc>& __x, 
2085 unordered_multimap<_Key, _Tp, _Hash, _Pred, _Alloc>& __y) 
2086 noexcept(noexcept(__x.swap(__y))) 
2087 { __x.swap(__y); } 
2088 
2089 template<class _Key, class _Tp, class _Hash, class _Pred, class _Alloc> 
2090 inline bool 
2091 operator==(const unordered_map<_Key, _Tp, _Hash, _Pred, _Alloc>& __x, 
2092 const unordered_map<_Key, _Tp, _Hash, _Pred, _Alloc>& __y) 
2093 { return __x._M_h._M_equal(__y._M_h); } 
2094 
2095 template<class _Key, class _Tp, class _Hash, class _Pred, class _Alloc> 
2096 inline bool 
2097 operator!=(const unordered_map<_Key, _Tp, _Hash, _Pred, _Alloc>& __x, 
2098 const unordered_map<_Key, _Tp, _Hash, _Pred, _Alloc>& __y) 
2099 { return !(__x == __y); } 
2100 
2101 template<class _Key, class _Tp, class _Hash, class _Pred, class _Alloc> 
2102 inline bool 
2103 operator==(const unordered_multimap<_Key, _Tp, _Hash, _Pred, _Alloc>& __x, 
2104 const unordered_multimap<_Key, _Tp, _Hash, _Pred, _Alloc>& __y) 
2105 { return __x._M_h._M_equal(__y._M_h); } 
2106 
2107 template<class _Key, class _Tp, class _Hash, class _Pred, class _Alloc> 
2108 inline bool 
2109 operator!=(const unordered_multimap<_Key, _Tp, _Hash, _Pred, _Alloc>& __x, 
2110 const unordered_multimap<_Key, _Tp, _Hash, _Pred, _Alloc>& __y) 
2111 { return !(__x == __y); } 
2112 
2113_GLIBCXX_END_NAMESPACE_CONTAINER 
2114 
2115#if __cplusplus > 201402L 
2116 // Allow std::unordered_map access to internals of compatible maps. 
2117 template<typename _Key, typename _Val, typename _Hash1, typename _Eq1, 
2118 typename _Alloc, typename _Hash2, typename _Eq2> 
2119 struct _Hash_merge_helper< 
2120 _GLIBCXX_STD_C::unordered_map<_Key, _Val, _Hash1, _Eq1, _Alloc>, 
2121 _Hash2, _Eq2> 
2122 { 
2123 private: 
2124 template<typename... _Tp> 
2125 using unordered_map = _GLIBCXX_STD_C::unordered_map<_Tp...>; 
2126 template<typename... _Tp> 
2127 using unordered_multimap = _GLIBCXX_STD_C::unordered_multimap<_Tp...>; 
2128 
2129 friend unordered_map<_Key, _Val, _Hash1, _Eq1, _Alloc>; 
2130 
2131 static auto& 
2132 _S_get_table(unordered_map<_Key, _Val, _Hash2, _Eq2, _Alloc>& __map) 
2133 { return __map._M_h; } 
2134 
2135 static auto& 
2136 _S_get_table(unordered_multimap<_Key, _Val, _Hash2, _Eq2, _Alloc>& __map) 
2137 { return __map._M_h; } 
2138 }; 
2139 
2140 // Allow std::unordered_multimap access to internals of compatible maps. 
2141 template<typename _Key, typename _Val, typename _Hash1, typename _Eq1, 
2142 typename _Alloc, typename _Hash2, typename _Eq2> 
2143 struct _Hash_merge_helper< 
2144 _GLIBCXX_STD_C::unordered_multimap<_Key, _Val, _Hash1, _Eq1, _Alloc>, 
2145 _Hash2, _Eq2> 
2146 { 
2147 private: 
2148 template<typename... _Tp> 
2149 using unordered_map = _GLIBCXX_STD_C::unordered_map<_Tp...>; 
2150 template<typename... _Tp> 
2151 using unordered_multimap = _GLIBCXX_STD_C::unordered_multimap<_Tp...>; 
2152 
2153 friend unordered_multimap<_Key, _Val, _Hash1, _Eq1, _Alloc>; 
2154 
2155 static auto& 
2156 _S_get_table(unordered_map<_Key, _Val, _Hash2, _Eq2, _Alloc>& __map) 
2157 { return __map._M_h; } 
2158 
2159 static auto& 
2160 _S_get_table(unordered_multimap<_Key, _Val, _Hash2, _Eq2, _Alloc>& __map) 
2161 { return __map._M_h; } 
2162 }; 
2163#endif // C++17 
2164 
2165_GLIBCXX_END_NAMESPACE_VERSION 
2166} // namespace std 
2167 
2168#endif /* _UNORDERED_MAP_H */ 
2169