1 // Map implementation -*- C++ -*-
2 
3 // Copyright (C) 2001-2018 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 /*
26  *
27  * Copyright (c) 1994
28  * Hewlett-Packard Company
29  *
30  * Permission to use, copy, modify, distribute and sell this software
31  * and its documentation for any purpose is hereby granted without fee,
32  * provided that the above copyright notice appear in all copies and
33  * that both that copyright notice and this permission notice appear
34  * in supporting documentation.  Hewlett-Packard Company makes no
35  * representations about the suitability of this software for any
36  * purpose.  It is provided "as is" without express or implied warranty.
37  *
38  *
39  * Copyright (c) 1996,1997
40  * Silicon Graphics Computer Systems, Inc.
41  *
42  * Permission to use, copy, modify, distribute and sell this software
43  * and its documentation for any purpose is hereby granted without fee,
44  * provided that the above copyright notice appear in all copies and
45  * that both that copyright notice and this permission notice appear
46  * in supporting documentation.  Silicon Graphics makes no
47  * representations about the suitability of this software for any
48  * purpose.  It is provided "as is" without express or implied warranty.
49  */
50 
51 /** @file bits/stl_map.h
52  *  This is an internal header file, included by other library headers.
53  *  Do not attempt to use it directly. @headername{map}
54  */
55 
56 #ifndef _STL_MAP_H
57 #define _STL_MAP_H 1
58 
59 #include <bits/functexcept.h>
60 #include <bits/concept_check.h>
61 #if __cplusplus >= 201103L
62 #include <initializer_list>
63 #include <tuple>
64 #endif
65 
66 namespace std _GLIBCXX_VISIBILITY(default)
67 {
68 _GLIBCXX_BEGIN_NAMESPACE_VERSION
69 _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
70 
71   template <typename _Key, typename _Tp, typename _Compare, typename _Alloc>
72     class multimap;
73 
74   /**
75    *  @brief A standard container made up of (key,value) pairs, which can be
76    *  retrieved based on a key, in logarithmic time.
77    *
78    *  @ingroup associative_containers
79    *
80    *  @tparam _Key  Type of key objects.
81    *  @tparam  _Tp  Type of mapped objects.
82    *  @tparam _Compare  Comparison function object type, defaults to less<_Key>.
83    *  @tparam _Alloc  Allocator type, defaults to
84    *                  allocator<pair<const _Key, _Tp>.
85    *
86    *  Meets the requirements of a <a href="tables.html#65">container</a>, a
87    *  <a href="tables.html#66">reversible container</a>, and an
88    *  <a href="tables.html#69">associative container</a> (using unique keys).
89    *  For a @c map<Key,T> the key_type is Key, the mapped_type is T, and the
90    *  value_type is std::pair<const Key,T>.
91    *
92    *  Maps support bidirectional iterators.
93    *
94    *  The private tree data is declared exactly the same way for map and
95    *  multimap; the distinction is made entirely in how the tree functions are
96    *  called (*_unique versus *_equal, same as the standard).
97   */
98   template <typename _Key, typename _Tp, typename _Compare = std::less<_Key>,
99 	    typename _Alloc = std::allocator<std::pair<const _Key, _Tp> > >
100     class map
101     {
102     public:
103       typedef _Key					key_type;
104       typedef _Tp					mapped_type;
105       typedef std::pair<const _Key, _Tp>		value_type;
106       typedef _Compare					key_compare;
107       typedef _Alloc					allocator_type;
108 
109     private:
110 #ifdef _GLIBCXX_CONCEPT_CHECKS
111       // concept requirements
112       typedef typename _Alloc::value_type		_Alloc_value_type;
113 # if __cplusplus < 201103L
114       __glibcxx_class_requires(_Tp, _SGIAssignableConcept)
115 # endif
116       __glibcxx_class_requires4(_Compare, bool, _Key, _Key,
117 				_BinaryFunctionConcept)
118       __glibcxx_class_requires2(value_type, _Alloc_value_type, _SameTypeConcept)
119 #endif
120 
121 #if __cplusplus >= 201103L && defined(__STRICT_ANSI__)
122       static_assert(is_same<typename _Alloc::value_type, value_type>::value,
123 	  "std::map must have the same value_type as its allocator");
124 #endif
125 
126     public:
127       class value_compare
128       : public std::binary_function<value_type, value_type, bool>
129       {
130 	friend class map<_Key, _Tp, _Compare, _Alloc>;
131       protected:
132 	_Compare comp;
133 
134 	value_compare(_Compare __c)
135 	: comp(__c) { }
136 
137       public:
138 	bool operator()(const value_type& __x, const value_type& __y) const
139 	{ return comp(__x.first, __y.first); }
140       };
141 
142     private:
143       /// This turns a red-black tree into a [multi]map.
144       typedef typename __gnu_cxx::__alloc_traits<_Alloc>::template
145 	rebind<value_type>::other _Pair_alloc_type;
146 
147       typedef _Rb_tree<key_type, value_type, _Select1st<value_type>,
148 		       key_compare, _Pair_alloc_type> _Rep_type;
149 
150       /// The actual tree structure.
151       _Rep_type _M_t;
152 
153       typedef __gnu_cxx::__alloc_traits<_Pair_alloc_type> _Alloc_traits;
154 
155     public:
156       // many of these are specified differently in ISO, but the following are
157       // "functionally equivalent"
158       typedef typename _Alloc_traits::pointer		 pointer;
159       typedef typename _Alloc_traits::const_pointer	 const_pointer;
160       typedef typename _Alloc_traits::reference		 reference;
161       typedef typename _Alloc_traits::const_reference	 const_reference;
162       typedef typename _Rep_type::iterator		 iterator;
163       typedef typename _Rep_type::const_iterator	 const_iterator;
164       typedef typename _Rep_type::size_type		 size_type;
165       typedef typename _Rep_type::difference_type	 difference_type;
166       typedef typename _Rep_type::reverse_iterator	 reverse_iterator;
167       typedef typename _Rep_type::const_reverse_iterator const_reverse_iterator;
168 
169 #if __cplusplus > 201402L
170       using node_type = typename _Rep_type::node_type;
171       using insert_return_type = typename _Rep_type::insert_return_type;
172 #endif
173 
174       // [23.3.1.1] construct/copy/destroy
175       // (get_allocator() is also listed in this section)
176 
177       /**
178        *  @brief  Default constructor creates no elements.
179        */
180 #if __cplusplus < 201103L
181       map() : _M_t() { }
182 #else
183       map() = default;
184 #endif
185 
186       /**
187        *  @brief  Creates a %map with no elements.
188        *  @param  __comp  A comparison object.
189        *  @param  __a  An allocator object.
190        */
191       explicit
192       map(const _Compare& __comp,
193 	  const allocator_type& __a = allocator_type())
194       : _M_t(__comp, _Pair_alloc_type(__a)) { }
195 
196       /**
197        *  @brief  %Map copy constructor.
198        *
199        *  Whether the allocator is copied depends on the allocator traits.
200        */
201 #if __cplusplus < 201103L
202       map(const map& __x)
203       : _M_t(__x._M_t) { }
204 #else
205       map(const map&) = default;
206 
207       /**
208        *  @brief  %Map move constructor.
209        *
210        *  The newly-created %map contains the exact contents of the moved
211        *  instance. The moved instance is a valid, but unspecified, %map.
212        */
213       map(map&&) = default;
214 
215       /**
216        *  @brief  Builds a %map from an initializer_list.
217        *  @param  __l  An initializer_list.
218        *  @param  __comp  A comparison object.
219        *  @param  __a  An allocator object.
220        *
221        *  Create a %map consisting of copies of the elements in the
222        *  initializer_list @a __l.
223        *  This is linear in N if the range is already sorted, and NlogN
224        *  otherwise (where N is @a __l.size()).
225        */
226       map(initializer_list<value_type> __l,
227 	  const _Compare& __comp = _Compare(),
228 	  const allocator_type& __a = allocator_type())
229       : _M_t(__comp, _Pair_alloc_type(__a))
230       { _M_t._M_insert_unique(__l.begin(), __l.end()); }
231 
232       /// Allocator-extended default constructor.
233       explicit
234       map(const allocator_type& __a)
235       : _M_t(_Compare(), _Pair_alloc_type(__a)) { }
236 
237       /// Allocator-extended copy constructor.
238       map(const map& __m, const allocator_type& __a)
239       : _M_t(__m._M_t, _Pair_alloc_type(__a)) { }
240 
241       /// Allocator-extended move constructor.
242       map(map&& __m, const allocator_type& __a)
243       noexcept(is_nothrow_copy_constructible<_Compare>::value
244 	       && _Alloc_traits::_S_always_equal())
245       : _M_t(std::move(__m._M_t), _Pair_alloc_type(__a)) { }
246 
247       /// Allocator-extended initialier-list constructor.
248       map(initializer_list<value_type> __l, const allocator_type& __a)
249       : _M_t(_Compare(), _Pair_alloc_type(__a))
250       { _M_t._M_insert_unique(__l.begin(), __l.end()); }
251 
252       /// Allocator-extended range constructor.
253       template<typename _InputIterator>
254 	map(_InputIterator __first, _InputIterator __last,
255 	    const allocator_type& __a)
256 	: _M_t(_Compare(), _Pair_alloc_type(__a))
257 	{ _M_t._M_insert_unique(__first, __last); }
258 #endif
259 
260       /**
261        *  @brief  Builds a %map from a range.
262        *  @param  __first  An input iterator.
263        *  @param  __last  An input iterator.
264        *
265        *  Create a %map consisting of copies of the elements from
266        *  [__first,__last).  This is linear in N if the range is
267        *  already sorted, and NlogN otherwise (where N is
268        *  distance(__first,__last)).
269        */
270       template<typename _InputIterator>
271 	map(_InputIterator __first, _InputIterator __last)
272 	: _M_t()
273 	{ _M_t._M_insert_unique(__first, __last); }
274 
275       /**
276        *  @brief  Builds a %map from a range.
277        *  @param  __first  An input iterator.
278        *  @param  __last  An input iterator.
279        *  @param  __comp  A comparison functor.
280        *  @param  __a  An allocator object.
281        *
282        *  Create a %map consisting of copies of the elements from
283        *  [__first,__last).  This is linear in N if the range is
284        *  already sorted, and NlogN otherwise (where N is
285        *  distance(__first,__last)).
286        */
287       template<typename _InputIterator>
288 	map(_InputIterator __first, _InputIterator __last,
289 	    const _Compare& __comp,
290 	    const allocator_type& __a = allocator_type())
291 	: _M_t(__comp, _Pair_alloc_type(__a))
292 	{ _M_t._M_insert_unique(__first, __last); }
293 
294 #if __cplusplus >= 201103L
295       /**
296        *  The dtor only erases the elements, and note that if the elements
297        *  themselves are pointers, the pointed-to memory is not touched in any
298        *  way.  Managing the pointer is the user's responsibility.
299        */
300       ~map() = default;
301 #endif
302 
303       /**
304        *  @brief  %Map assignment operator.
305        *
306        *  Whether the allocator is copied depends on the allocator traits.
307        */
308 #if __cplusplus < 201103L
309       map&
310       operator=(const map& __x)
311       {
312 	_M_t = __x._M_t;
313 	return *this;
314       }
315 #else
316       map&
317       operator=(const map&) = default;
318 
319       /// Move assignment operator.
320       map&
321       operator=(map&&) = default;
322 
323       /**
324        *  @brief  %Map list assignment operator.
325        *  @param  __l  An initializer_list.
326        *
327        *  This function fills a %map with copies of the elements in the
328        *  initializer list @a __l.
329        *
330        *  Note that the assignment completely changes the %map and
331        *  that the resulting %map's size is the same as the number
332        *  of elements assigned.
333        */
334       map&
335       operator=(initializer_list<value_type> __l)
336       {
337 	_M_t._M_assign_unique(__l.begin(), __l.end());
338 	return *this;
339       }
340 #endif
341 
342       /// Get a copy of the memory allocation object.
343       allocator_type
344       get_allocator() const _GLIBCXX_NOEXCEPT
345       { return allocator_type(_M_t.get_allocator()); }
346 
347       // iterators
348       /**
349        *  Returns a read/write iterator that points to the first pair in the
350        *  %map.
351        *  Iteration is done in ascending order according to the keys.
352        */
353       iterator
354       begin() _GLIBCXX_NOEXCEPT
355       { return _M_t.begin(); }
356 
357       /**
358        *  Returns a read-only (constant) iterator that points to the first pair
359        *  in the %map.  Iteration is done in ascending order according to the
360        *  keys.
361        */
362       const_iterator
363       begin() const _GLIBCXX_NOEXCEPT
364       { return _M_t.begin(); }
365 
366       /**
367        *  Returns a read/write iterator that points one past the last
368        *  pair in the %map.  Iteration is done in ascending order
369        *  according to the keys.
370        */
371       iterator
372       end() _GLIBCXX_NOEXCEPT
373       { return _M_t.end(); }
374 
375       /**
376        *  Returns a read-only (constant) iterator that points one past the last
377        *  pair in the %map.  Iteration is done in ascending order according to
378        *  the keys.
379        */
380       const_iterator
381       end() const _GLIBCXX_NOEXCEPT
382       { return _M_t.end(); }
383 
384       /**
385        *  Returns a read/write reverse iterator that points to the last pair in
386        *  the %map.  Iteration is done in descending order according to the
387        *  keys.
388        */
389       reverse_iterator
390       rbegin() _GLIBCXX_NOEXCEPT
391       { return _M_t.rbegin(); }
392 
393       /**
394        *  Returns a read-only (constant) reverse iterator that points to the
395        *  last pair in the %map.  Iteration is done in descending order
396        *  according to the keys.
397        */
398       const_reverse_iterator
399       rbegin() const _GLIBCXX_NOEXCEPT
400       { return _M_t.rbegin(); }
401 
402       /**
403        *  Returns a read/write reverse iterator that points to one before the
404        *  first pair in the %map.  Iteration is done in descending order
405        *  according to the keys.
406        */
407       reverse_iterator
408       rend() _GLIBCXX_NOEXCEPT
409       { return _M_t.rend(); }
410 
411       /**
412        *  Returns a read-only (constant) reverse iterator that points to one
413        *  before the first pair in the %map.  Iteration is done in descending
414        *  order according to the keys.
415        */
416       const_reverse_iterator
417       rend() const _GLIBCXX_NOEXCEPT
418       { return _M_t.rend(); }
419 
420 #if __cplusplus >= 201103L
421       /**
422        *  Returns a read-only (constant) iterator that points to the first pair
423        *  in the %map.  Iteration is done in ascending order according to the
424        *  keys.
425        */
426       const_iterator
427       cbegin() const noexcept
428       { return _M_t.begin(); }
429 
430       /**
431        *  Returns a read-only (constant) iterator that points one past the last
432        *  pair in the %map.  Iteration is done in ascending order according to
433        *  the keys.
434        */
435       const_iterator
436       cend() const noexcept
437       { return _M_t.end(); }
438 
439       /**
440        *  Returns a read-only (constant) reverse iterator that points to the
441        *  last pair in the %map.  Iteration is done in descending order
442        *  according to the keys.
443        */
444       const_reverse_iterator
445       crbegin() const noexcept
446       { return _M_t.rbegin(); }
447 
448       /**
449        *  Returns a read-only (constant) reverse iterator that points to one
450        *  before the first pair in the %map.  Iteration is done in descending
451        *  order according to the keys.
452        */
453       const_reverse_iterator
454       crend() const noexcept
455       { return _M_t.rend(); }
456 #endif
457 
458       // capacity
459       /** Returns true if the %map is empty.  (Thus begin() would equal
460        *  end().)
461       */
462       bool
463       empty() const _GLIBCXX_NOEXCEPT
464       { return _M_t.empty(); }
465 
466       /** Returns the size of the %map.  */
467       size_type
468       size() const _GLIBCXX_NOEXCEPT
469       { return _M_t.size(); }
470 
471       /** Returns the maximum size of the %map.  */
472       size_type
473       max_size() const _GLIBCXX_NOEXCEPT
474       { return _M_t.max_size(); }
475 
476       // [23.3.1.2] element access
477       /**
478        *  @brief  Subscript ( @c [] ) access to %map data.
479        *  @param  __k  The key for which data should be retrieved.
480        *  @return  A reference to the data of the (key,data) %pair.
481        *
482        *  Allows for easy lookup with the subscript ( @c [] )
483        *  operator.  Returns data associated with the key specified in
484        *  subscript.  If the key does not exist, a pair with that key
485        *  is created using default values, which is then returned.
486        *
487        *  Lookup requires logarithmic time.
488        */
489       mapped_type&
490       operator[](const key_type& __k)
491       {
492 	// concept requirements
493 	__glibcxx_function_requires(_DefaultConstructibleConcept<mapped_type>)
494 
495 	iterator __i = lower_bound(__k);
496 	// __i->first is greater than or equivalent to __k.
497 	if (__i == end() || key_comp()(__k, (*__i).first))
498 #if __cplusplus >= 201103L
499 	  __i = _M_t._M_emplace_hint_unique(__i, std::piecewise_construct,
500 					    std::tuple<const key_type&>(__k),
501 					    std::tuple<>());
502 #else
503 	  __i = insert(__i, value_type(__k, mapped_type()));
504 #endif
505 	return (*__i).second;
506       }
507 
508 #if __cplusplus >= 201103L
509       mapped_type&
510       operator[](key_type&& __k)
511       {
512 	// concept requirements
513 	__glibcxx_function_requires(_DefaultConstructibleConcept<mapped_type>)
514 
515 	iterator __i = lower_bound(__k);
516 	// __i->first is greater than or equivalent to __k.
517 	if (__i == end() || key_comp()(__k, (*__i).first))
518 	  __i = _M_t._M_emplace_hint_unique(__i, std::piecewise_construct,
519 					std::forward_as_tuple(std::move(__k)),
520 					std::tuple<>());
521 	return (*__i).second;
522       }
523 #endif
524 
525       // _GLIBCXX_RESOLVE_LIB_DEFECTS
526       // DR 464. Suggestion for new member functions in standard containers.
527       /**
528        *  @brief  Access to %map data.
529        *  @param  __k  The key for which data should be retrieved.
530        *  @return  A reference to the data whose key is equivalent to @a __k, if
531        *           such a data is present in the %map.
532        *  @throw  std::out_of_range  If no such data is present.
533        */
534       mapped_type&
535       at(const key_type& __k)
536       {
537 	iterator __i = lower_bound(__k);
538 	if (__i == end() || key_comp()(__k, (*__i).first))
539 	  __throw_out_of_range(__N("map::at"));
540 	return (*__i).second;
541       }
542 
543       const mapped_type&
544       at(const key_type& __k) const
545       {
546 	const_iterator __i = lower_bound(__k);
547 	if (__i == end() || key_comp()(__k, (*__i).first))
548 	  __throw_out_of_range(__N("map::at"));
549 	return (*__i).second;
550       }
551 
552       // modifiers
553 #if __cplusplus >= 201103L
554       /**
555        *  @brief Attempts to build and insert a std::pair into the %map.
556        *
557        *  @param __args  Arguments used to generate a new pair instance (see
558        *	        std::piecewise_contruct for passing arguments to each
559        *	        part of the pair constructor).
560        *
561        *  @return  A pair, of which the first element is an iterator that points
562        *           to the possibly inserted pair, and the second is a bool that
563        *           is true if the pair was actually inserted.
564        *
565        *  This function attempts to build and insert a (key, value) %pair into
566        *  the %map.
567        *  A %map relies on unique keys and thus a %pair is only inserted if its
568        *  first element (the key) is not already present in the %map.
569        *
570        *  Insertion requires logarithmic time.
571        */
572       template<typename... _Args>
573 	std::pair<iterator, bool>
574 	emplace(_Args&&... __args)
575 	{ return _M_t._M_emplace_unique(std::forward<_Args>(__args)...); }
576 
577       /**
578        *  @brief Attempts to build and insert a std::pair into the %map.
579        *
580        *  @param  __pos  An iterator that serves as a hint as to where the pair
581        *                should be inserted.
582        *  @param  __args  Arguments used to generate a new pair instance (see
583        *	         std::piecewise_contruct for passing arguments to each
584        *	         part of the pair constructor).
585        *  @return An iterator that points to the element with key of the
586        *          std::pair built from @a __args (may or may not be that
587        *          std::pair).
588        *
589        *  This function is not concerned about whether the insertion took place,
590        *  and thus does not return a boolean like the single-argument emplace()
591        *  does.
592        *  Note that the first parameter is only a hint and can potentially
593        *  improve the performance of the insertion process. A bad hint would
594        *  cause no gains in efficiency.
595        *
596        *  See
597        *  https://gcc.gnu.org/onlinedocs/libstdc++/manual/associative.html#containers.associative.insert_hints
598        *  for more on @a hinting.
599        *
600        *  Insertion requires logarithmic time (if the hint is not taken).
601        */
602       template<typename... _Args>
603 	iterator
604 	emplace_hint(const_iterator __pos, _Args&&... __args)
605 	{
606 	  return _M_t._M_emplace_hint_unique(__pos,
607 					     std::forward<_Args>(__args)...);
608 	}
609 #endif
610 
611 #if __cplusplus > 201402L
612       /// Extract a node.
613       node_type
614       extract(const_iterator __pos)
615       {
616 	__glibcxx_assert(__pos != end());
617 	return _M_t.extract(__pos);
618       }
619 
620       /// Extract a node.
621       node_type
622       extract(const key_type& __x)
623       { return _M_t.extract(__x); }
624 
625       /// Re-insert an extracted node.
626       insert_return_type
627       insert(node_type&& __nh)
628       { return _M_t._M_reinsert_node_unique(std::move(__nh)); }
629 
630       /// Re-insert an extracted node.
631       iterator
632       insert(const_iterator __hint, node_type&& __nh)
633       { return _M_t._M_reinsert_node_hint_unique(__hint, std::move(__nh)); }
634 
635       template<typename, typename>
636 	friend class std::_Rb_tree_merge_helper;
637 
638       template<typename _C2>
639 	void
640 	merge(map<_Key, _Tp, _C2, _Alloc>& __source)
641 	{
642 	  using _Merge_helper = _Rb_tree_merge_helper<map, _C2>;
643 	  _M_t._M_merge_unique(_Merge_helper::_S_get_tree(__source));
644 	}
645 
646       template<typename _C2>
647 	void
648 	merge(map<_Key, _Tp, _C2, _Alloc>&& __source)
649 	{ merge(__source); }
650 
651       template<typename _C2>
652 	void
653 	merge(multimap<_Key, _Tp, _C2, _Alloc>& __source)
654 	{
655 	  using _Merge_helper = _Rb_tree_merge_helper<map, _C2>;
656 	  _M_t._M_merge_unique(_Merge_helper::_S_get_tree(__source));
657 	}
658 
659       template<typename _C2>
660 	void
661 	merge(multimap<_Key, _Tp, _C2, _Alloc>&& __source)
662 	{ merge(__source); }
663 #endif // C++17
664 
665 #if __cplusplus > 201402L
666 #define __cpp_lib_map_try_emplace 201411
667       /**
668        *  @brief Attempts to build and insert a std::pair into the %map.
669        *
670        *  @param __k    Key to use for finding a possibly existing pair in
671        *                the map.
672        *  @param __args  Arguments used to generate the .second for a new pair
673        *                instance.
674        *
675        *  @return  A pair, of which the first element is an iterator that points
676        *           to the possibly inserted pair, and the second is a bool that
677        *           is true if the pair was actually inserted.
678        *
679        *  This function attempts to build and insert a (key, value) %pair into
680        *  the %map.
681        *  A %map relies on unique keys and thus a %pair is only inserted if its
682        *  first element (the key) is not already present in the %map.
683        *  If a %pair is not inserted, this function has no effect.
684        *
685        *  Insertion requires logarithmic time.
686        */
687       template <typename... _Args>
688 	pair<iterator, bool>
689 	try_emplace(const key_type& __k, _Args&&... __args)
690 	{
691 	  iterator __i = lower_bound(__k);
692 	  if (__i == end() || key_comp()(__k, (*__i).first))
693 	    {
694 	      __i = emplace_hint(__i, std::piecewise_construct,
695 				 std::forward_as_tuple(__k),
696 				 std::forward_as_tuple(
697 				   std::forward<_Args>(__args)...));
698 	      return {__i, true};
699 	    }
700 	  return {__i, false};
701 	}
702 
703       // move-capable overload
704       template <typename... _Args>
705 	pair<iterator, bool>
706 	try_emplace(key_type&& __k, _Args&&... __args)
707 	{
708 	  iterator __i = lower_bound(__k);
709 	  if (__i == end() || key_comp()(__k, (*__i).first))
710 	    {
711 	      __i = emplace_hint(__i, std::piecewise_construct,
712 				 std::forward_as_tuple(std::move(__k)),
713 				 std::forward_as_tuple(
714 				   std::forward<_Args>(__args)...));
715 	      return {__i, true};
716 	    }
717 	  return {__i, false};
718 	}
719 
720       /**
721        *  @brief Attempts to build and insert a std::pair into the %map.
722        *
723        *  @param  __hint  An iterator that serves as a hint as to where the
724        *                  pair should be inserted.
725        *  @param __k    Key to use for finding a possibly existing pair in
726        *                the map.
727        *  @param __args  Arguments used to generate the .second for a new pair
728        *                instance.
729        *  @return An iterator that points to the element with key of the
730        *          std::pair built from @a __args (may or may not be that
731        *          std::pair).
732        *
733        *  This function is not concerned about whether the insertion took place,
734        *  and thus does not return a boolean like the single-argument
735        *  try_emplace() does. However, if insertion did not take place,
736        *  this function has no effect.
737        *  Note that the first parameter is only a hint and can potentially
738        *  improve the performance of the insertion process. A bad hint would
739        *  cause no gains in efficiency.
740        *
741        *  See
742        *  https://gcc.gnu.org/onlinedocs/libstdc++/manual/associative.html#containers.associative.insert_hints
743        *  for more on @a hinting.
744        *
745        *  Insertion requires logarithmic time (if the hint is not taken).
746        */
747       template <typename... _Args>
748 	iterator
749 	try_emplace(const_iterator __hint, const key_type& __k,
750 		    _Args&&... __args)
751 	{
752 	  iterator __i;
753 	  auto __true_hint = _M_t._M_get_insert_hint_unique_pos(__hint, __k);
754 	  if (__true_hint.second)
755 	    __i = emplace_hint(iterator(__true_hint.second),
756 			       std::piecewise_construct,
757 			       std::forward_as_tuple(__k),
758 			       std::forward_as_tuple(
759 				 std::forward<_Args>(__args)...));
760 	  else
761 	    __i = iterator(__true_hint.first);
762 	  return __i;
763 	}
764 
765       // move-capable overload
766       template <typename... _Args>
767 	iterator
768 	try_emplace(const_iterator __hint, key_type&& __k, _Args&&... __args)
769 	{
770 	  iterator __i;
771 	  auto __true_hint = _M_t._M_get_insert_hint_unique_pos(__hint, __k);
772 	  if (__true_hint.second)
773 	    __i = emplace_hint(iterator(__true_hint.second),
774 			       std::piecewise_construct,
775 			       std::forward_as_tuple(std::move(__k)),
776 			       std::forward_as_tuple(
777 				 std::forward<_Args>(__args)...));
778 	  else
779 	    __i = iterator(__true_hint.first);
780 	  return __i;
781 	}
782 #endif
783 
784       /**
785        *  @brief Attempts to insert a std::pair into the %map.
786        *  @param __x Pair to be inserted (see std::make_pair for easy
787        *	     creation of pairs).
788        *
789        *  @return  A pair, of which the first element is an iterator that
790        *           points to the possibly inserted pair, and the second is
791        *           a bool that is true if the pair was actually inserted.
792        *
793        *  This function attempts to insert a (key, value) %pair into the %map.
794        *  A %map relies on unique keys and thus a %pair is only inserted if its
795        *  first element (the key) is not already present in the %map.
796        *
797        *  Insertion requires logarithmic time.
798        *  @{
799        */
800       std::pair<iterator, bool>
801       insert(const value_type& __x)
802       { return _M_t._M_insert_unique(__x); }
803 
804 #if __cplusplus >= 201103L
805       // _GLIBCXX_RESOLVE_LIB_DEFECTS
806       // 2354. Unnecessary copying when inserting into maps with braced-init
807       std::pair<iterator, bool>
808       insert(value_type&& __x)
809       { return _M_t._M_insert_unique(std::move(__x)); }
810 
811       template<typename _Pair, typename = typename
812 	       std::enable_if<std::is_constructible<value_type,
813 						    _Pair&&>::value>::type>
814 	std::pair<iterator, bool>
815 	insert(_Pair&& __x)
816 	{ return _M_t._M_insert_unique(std::forward<_Pair>(__x)); }
817 #endif
818       // @}
819 
820 #if __cplusplus >= 201103L
821       /**
822        *  @brief Attempts to insert a list of std::pairs into the %map.
823        *  @param  __list  A std::initializer_list<value_type> of pairs to be
824        *                  inserted.
825        *
826        *  Complexity similar to that of the range constructor.
827        */
828       void
829       insert(std::initializer_list<value_type> __list)
830       { insert(__list.begin(), __list.end()); }
831 #endif
832 
833       /**
834        *  @brief Attempts to insert a std::pair into the %map.
835        *  @param  __position  An iterator that serves as a hint as to where the
836        *                    pair should be inserted.
837        *  @param  __x  Pair to be inserted (see std::make_pair for easy creation
838        *               of pairs).
839        *  @return An iterator that points to the element with key of
840        *           @a __x (may or may not be the %pair passed in).
841        *
842 
843        *  This function is not concerned about whether the insertion
844        *  took place, and thus does not return a boolean like the
845        *  single-argument insert() does.  Note that the first
846        *  parameter is only a hint and can potentially improve the
847        *  performance of the insertion process.  A bad hint would
848        *  cause no gains in efficiency.
849        *
850        *  See
851        *  https://gcc.gnu.org/onlinedocs/libstdc++/manual/associative.html#containers.associative.insert_hints
852        *  for more on @a hinting.
853        *
854        *  Insertion requires logarithmic time (if the hint is not taken).
855        *  @{
856        */
857       iterator
858 #if __cplusplus >= 201103L
859       insert(const_iterator __position, const value_type& __x)
860 #else
861       insert(iterator __position, const value_type& __x)
862 #endif
863       { return _M_t._M_insert_unique_(__position, __x); }
864 
865 #if __cplusplus >= 201103L
866       // _GLIBCXX_RESOLVE_LIB_DEFECTS
867       // 2354. Unnecessary copying when inserting into maps with braced-init
868       iterator
869       insert(const_iterator __position, value_type&& __x)
870       { return _M_t._M_insert_unique_(__position, std::move(__x)); }
871 
872       template<typename _Pair, typename = typename
873 	       std::enable_if<std::is_constructible<value_type,
874 						    _Pair&&>::value>::type>
875 	iterator
876 	insert(const_iterator __position, _Pair&& __x)
877 	{ return _M_t._M_insert_unique_(__position,
878 					std::forward<_Pair>(__x)); }
879 #endif
880       // @}
881 
882       /**
883        *  @brief Template function that attempts to insert a range of elements.
884        *  @param  __first  Iterator pointing to the start of the range to be
885        *                   inserted.
886        *  @param  __last  Iterator pointing to the end of the range.
887        *
888        *  Complexity similar to that of the range constructor.
889        */
890       template<typename _InputIterator>
891 	void
892 	insert(_InputIterator __first, _InputIterator __last)
893 	{ _M_t._M_insert_unique(__first, __last); }
894 
895 #if __cplusplus > 201402L
896 #define __cpp_lib_map_insertion 201411
897       /**
898        *  @brief Attempts to insert or assign a std::pair into the %map.
899        *  @param __k    Key to use for finding a possibly existing pair in
900        *                the map.
901        *  @param __obj  Argument used to generate the .second for a pair
902        *                instance.
903        *
904        *  @return  A pair, of which the first element is an iterator that
905        *           points to the possibly inserted pair, and the second is
906        *           a bool that is true if the pair was actually inserted.
907        *
908        *  This function attempts to insert a (key, value) %pair into the %map.
909        *  A %map relies on unique keys and thus a %pair is only inserted if its
910        *  first element (the key) is not already present in the %map.
911        *  If the %pair was already in the %map, the .second of the %pair
912        *  is assigned from __obj.
913        *
914        *  Insertion requires logarithmic time.
915        */
916       template <typename _Obj>
917 	pair<iterator, bool>
918 	insert_or_assign(const key_type& __k, _Obj&& __obj)
919 	{
920 	  iterator __i = lower_bound(__k);
921 	  if (__i == end() || key_comp()(__k, (*__i).first))
922 	    {
923 	      __i = emplace_hint(__i, std::piecewise_construct,
924 				 std::forward_as_tuple(__k),
925 				 std::forward_as_tuple(
926 				   std::forward<_Obj>(__obj)));
927 	      return {__i, true};
928 	    }
929 	  (*__i).second = std::forward<_Obj>(__obj);
930 	  return {__i, false};
931 	}
932 
933       // move-capable overload
934       template <typename _Obj>
935 	pair<iterator, bool>
936 	insert_or_assign(key_type&& __k, _Obj&& __obj)
937 	{
938 	  iterator __i = lower_bound(__k);
939 	  if (__i == end() || key_comp()(__k, (*__i).first))
940 	    {
941 	      __i = emplace_hint(__i, std::piecewise_construct,
942 				 std::forward_as_tuple(std::move(__k)),
943 				 std::forward_as_tuple(
944 				   std::forward<_Obj>(__obj)));
945 	      return {__i, true};
946 	    }
947 	  (*__i).second = std::forward<_Obj>(__obj);
948 	  return {__i, false};
949 	}
950 
951       /**
952        *  @brief Attempts to insert or assign a std::pair into the %map.
953        *  @param  __hint  An iterator that serves as a hint as to where the
954        *                  pair should be inserted.
955        *  @param __k    Key to use for finding a possibly existing pair in
956        *                the map.
957        *  @param __obj  Argument used to generate the .second for a pair
958        *                instance.
959        *
960        *  @return An iterator that points to the element with key of
961        *           @a __x (may or may not be the %pair passed in).
962        *
963        *  This function attempts to insert a (key, value) %pair into the %map.
964        *  A %map relies on unique keys and thus a %pair is only inserted if its
965        *  first element (the key) is not already present in the %map.
966        *  If the %pair was already in the %map, the .second of the %pair
967        *  is assigned from __obj.
968        *
969        *  Insertion requires logarithmic time.
970        */
971       template <typename _Obj>
972 	iterator
973 	insert_or_assign(const_iterator __hint,
974 			 const key_type& __k, _Obj&& __obj)
975 	{
976 	  iterator __i;
977 	  auto __true_hint = _M_t._M_get_insert_hint_unique_pos(__hint, __k);
978 	  if (__true_hint.second)
979 	    {
980 	      return emplace_hint(iterator(__true_hint.second),
981 				  std::piecewise_construct,
982 				  std::forward_as_tuple(__k),
983 				  std::forward_as_tuple(
984 				    std::forward<_Obj>(__obj)));
985 	    }
986 	  __i = iterator(__true_hint.first);
987 	  (*__i).second = std::forward<_Obj>(__obj);
988 	  return __i;
989 	}
990 
991       // move-capable overload
992       template <typename _Obj>
993 	iterator
994 	insert_or_assign(const_iterator __hint, key_type&& __k, _Obj&& __obj)
995 	{
996 	  iterator __i;
997 	  auto __true_hint = _M_t._M_get_insert_hint_unique_pos(__hint, __k);
998 	  if (__true_hint.second)
999 	    {
1000 	      return emplace_hint(iterator(__true_hint.second),
1001 				  std::piecewise_construct,
1002 				  std::forward_as_tuple(std::move(__k)),
1003 				  std::forward_as_tuple(
1004 				    std::forward<_Obj>(__obj)));
1005 	    }
1006 	  __i = iterator(__true_hint.first);
1007 	  (*__i).second = std::forward<_Obj>(__obj);
1008 	  return __i;
1009 	}
1010 #endif
1011 
1012 #if __cplusplus >= 201103L
1013       // _GLIBCXX_RESOLVE_LIB_DEFECTS
1014       // DR 130. Associative erase should return an iterator.
1015       /**
1016        *  @brief Erases an element from a %map.
1017        *  @param  __position  An iterator pointing to the element to be erased.
1018        *  @return An iterator pointing to the element immediately following
1019        *          @a position prior to the element being erased. If no such
1020        *          element exists, end() is returned.
1021        *
1022        *  This function erases an element, pointed to by the given
1023        *  iterator, from a %map.  Note that this function only erases
1024        *  the element, and that if the element is itself a pointer,
1025        *  the pointed-to memory is not touched in any way.  Managing
1026        *  the pointer is the user's responsibility.
1027        *
1028        *  @{
1029        */
1030       iterator
1031       erase(const_iterator __position)
1032       { return _M_t.erase(__position); }
1033 
1034       // LWG 2059
1035       _GLIBCXX_ABI_TAG_CXX11
1036       iterator
1037       erase(iterator __position)
1038       { return _M_t.erase(__position); }
1039       // @}
1040 #else
1041       /**
1042        *  @brief Erases an element from a %map.
1043        *  @param  __position  An iterator pointing to the element to be erased.
1044        *
1045        *  This function erases an element, pointed to by the given
1046        *  iterator, from a %map.  Note that this function only erases
1047        *  the element, and that if the element is itself a pointer,
1048        *  the pointed-to memory is not touched in any way.  Managing
1049        *  the pointer is the user's responsibility.
1050        */
1051       void
1052       erase(iterator __position)
1053       { _M_t.erase(__position); }
1054 #endif
1055 
1056       /**
1057        *  @brief Erases elements according to the provided key.
1058        *  @param  __x  Key of element to be erased.
1059        *  @return  The number of elements erased.
1060        *
1061        *  This function erases all the elements located by the given key from
1062        *  a %map.
1063        *  Note that this function only erases the element, and that if
1064        *  the element is itself a pointer, the pointed-to memory is not touched
1065        *  in any way.  Managing the pointer is the user's responsibility.
1066        */
1067       size_type
1068       erase(const key_type& __x)
1069       { return _M_t.erase(__x); }
1070 
1071 #if __cplusplus >= 201103L
1072       // _GLIBCXX_RESOLVE_LIB_DEFECTS
1073       // DR 130. Associative erase should return an iterator.
1074       /**
1075        *  @brief Erases a [first,last) range of elements from a %map.
1076        *  @param  __first  Iterator pointing to the start of the range to be
1077        *                   erased.
1078        *  @param __last Iterator pointing to the end of the range to
1079        *                be erased.
1080        *  @return The iterator @a __last.
1081        *
1082        *  This function erases a sequence of elements from a %map.
1083        *  Note that this function only erases the element, and that if
1084        *  the element is itself a pointer, the pointed-to memory is not touched
1085        *  in any way.  Managing the pointer is the user's responsibility.
1086        */
1087       iterator
1088       erase(const_iterator __first, const_iterator __last)
1089       { return _M_t.erase(__first, __last); }
1090 #else
1091       /**
1092        *  @brief Erases a [__first,__last) range of elements from a %map.
1093        *  @param  __first  Iterator pointing to the start of the range to be
1094        *                   erased.
1095        *  @param __last Iterator pointing to the end of the range to
1096        *                be erased.
1097        *
1098        *  This function erases a sequence of elements from a %map.
1099        *  Note that this function only erases the element, and that if
1100        *  the element is itself a pointer, the pointed-to memory is not touched
1101        *  in any way.  Managing the pointer is the user's responsibility.
1102        */
1103       void
1104       erase(iterator __first, iterator __last)
1105       { _M_t.erase(__first, __last); }
1106 #endif
1107 
1108       /**
1109        *  @brief  Swaps data with another %map.
1110        *  @param  __x  A %map of the same element and allocator types.
1111        *
1112        *  This exchanges the elements between two maps in constant
1113        *  time.  (It is only swapping a pointer, an integer, and an
1114        *  instance of the @c Compare type (which itself is often
1115        *  stateless and empty), so it should be quite fast.)  Note
1116        *  that the global std::swap() function is specialized such
1117        *  that std::swap(m1,m2) will feed to this function.
1118        *
1119        *  Whether the allocators are swapped depends on the allocator traits.
1120        */
1121       void
1122       swap(map& __x)
1123       _GLIBCXX_NOEXCEPT_IF(__is_nothrow_swappable<_Compare>::value)
1124       { _M_t.swap(__x._M_t); }
1125 
1126       /**
1127        *  Erases all elements in a %map.  Note that this function only
1128        *  erases the elements, and that if the elements themselves are
1129        *  pointers, the pointed-to memory is not touched in any way.
1130        *  Managing the pointer is the user's responsibility.
1131        */
1132       void
1133       clear() _GLIBCXX_NOEXCEPT
1134       { _M_t.clear(); }
1135 
1136       // observers
1137       /**
1138        *  Returns the key comparison object out of which the %map was
1139        *  constructed.
1140        */
1141       key_compare
1142       key_comp() const
1143       { return _M_t.key_comp(); }
1144 
1145       /**
1146        *  Returns a value comparison object, built from the key comparison
1147        *  object out of which the %map was constructed.
1148        */
1149       value_compare
1150       value_comp() const
1151       { return value_compare(_M_t.key_comp()); }
1152 
1153       // [23.3.1.3] map operations
1154 
1155       //@{
1156       /**
1157        *  @brief Tries to locate an element in a %map.
1158        *  @param  __x  Key of (key, value) %pair to be located.
1159        *  @return  Iterator pointing to sought-after element, or end() if not
1160        *           found.
1161        *
1162        *  This function takes a key and tries to locate the element with which
1163        *  the key matches.  If successful the function returns an iterator
1164        *  pointing to the sought after %pair.  If unsuccessful it returns the
1165        *  past-the-end ( @c end() ) iterator.
1166        */
1167 
1168       iterator
1169       find(const key_type& __x)
1170       { return _M_t.find(__x); }
1171 
1172 #if __cplusplus > 201103L
1173       template<typename _Kt>
1174 	auto
1175 	find(const _Kt& __x) -> decltype(_M_t._M_find_tr(__x))
1176 	{ return _M_t._M_find_tr(__x); }
1177 #endif
1178       //@}
1179 
1180       //@{
1181       /**
1182        *  @brief Tries to locate an element in a %map.
1183        *  @param  __x  Key of (key, value) %pair to be located.
1184        *  @return  Read-only (constant) iterator pointing to sought-after
1185        *           element, or end() if not found.
1186        *
1187        *  This function takes a key and tries to locate the element with which
1188        *  the key matches.  If successful the function returns a constant
1189        *  iterator pointing to the sought after %pair. If unsuccessful it
1190        *  returns the past-the-end ( @c end() ) iterator.
1191        */
1192 
1193       const_iterator
1194       find(const key_type& __x) const
1195       { return _M_t.find(__x); }
1196 
1197 #if __cplusplus > 201103L
1198       template<typename _Kt>
1199 	auto
1200 	find(const _Kt& __x) const -> decltype(_M_t._M_find_tr(__x))
1201 	{ return _M_t._M_find_tr(__x); }
1202 #endif
1203       //@}
1204 
1205       //@{
1206       /**
1207        *  @brief  Finds the number of elements with given key.
1208        *  @param  __x  Key of (key, value) pairs to be located.
1209        *  @return  Number of elements with specified key.
1210        *
1211        *  This function only makes sense for multimaps; for map the result will
1212        *  either be 0 (not present) or 1 (present).
1213        */
1214       size_type
1215       count(const key_type& __x) const
1216       { return _M_t.find(__x) == _M_t.end() ? 0 : 1; }
1217 
1218 #if __cplusplus > 201103L
1219       template<typename _Kt>
1220 	auto
1221 	count(const _Kt& __x) const -> decltype(_M_t._M_count_tr(__x))
1222 	{ return _M_t._M_count_tr(__x); }
1223 #endif
1224       //@}
1225 
1226       //@{
1227       /**
1228        *  @brief Finds the beginning of a subsequence matching given key.
1229        *  @param  __x  Key of (key, value) pair to be located.
1230        *  @return  Iterator pointing to first element equal to or greater
1231        *           than key, or end().
1232        *
1233        *  This function returns the first element of a subsequence of elements
1234        *  that matches the given key.  If unsuccessful it returns an iterator
1235        *  pointing to the first element that has a greater value than given key
1236        *  or end() if no such element exists.
1237        */
1238       iterator
1239       lower_bound(const key_type& __x)
1240       { return _M_t.lower_bound(__x); }
1241 
1242 #if __cplusplus > 201103L
1243       template<typename _Kt>
1244 	auto
1245 	lower_bound(const _Kt& __x)
1246 	-> decltype(iterator(_M_t._M_lower_bound_tr(__x)))
1247 	{ return iterator(_M_t._M_lower_bound_tr(__x)); }
1248 #endif
1249       //@}
1250 
1251       //@{
1252       /**
1253        *  @brief Finds the beginning of a subsequence matching given key.
1254        *  @param  __x  Key of (key, value) pair to be located.
1255        *  @return  Read-only (constant) iterator pointing to first element
1256        *           equal to or greater than key, or end().
1257        *
1258        *  This function returns the first element of a subsequence of elements
1259        *  that matches the given key.  If unsuccessful it returns an iterator
1260        *  pointing to the first element that has a greater value than given key
1261        *  or end() if no such element exists.
1262        */
1263       const_iterator
1264       lower_bound(const key_type& __x) const
1265       { return _M_t.lower_bound(__x); }
1266 
1267 #if __cplusplus > 201103L
1268       template<typename _Kt>
1269 	auto
1270 	lower_bound(const _Kt& __x) const
1271 	-> decltype(const_iterator(_M_t._M_lower_bound_tr(__x)))
1272 	{ return const_iterator(_M_t._M_lower_bound_tr(__x)); }
1273 #endif
1274       //@}
1275 
1276       //@{
1277       /**
1278        *  @brief Finds the end of a subsequence matching given key.
1279        *  @param  __x  Key of (key, value) pair to be located.
1280        *  @return Iterator pointing to the first element
1281        *          greater than key, or end().
1282        */
1283       iterator
1284       upper_bound(const key_type& __x)
1285       { return _M_t.upper_bound(__x); }
1286 
1287 #if __cplusplus > 201103L
1288       template<typename _Kt>
1289 	auto
1290 	upper_bound(const _Kt& __x)
1291 	-> decltype(iterator(_M_t._M_upper_bound_tr(__x)))
1292 	{ return iterator(_M_t._M_upper_bound_tr(__x)); }
1293 #endif
1294       //@}
1295 
1296       //@{
1297       /**
1298        *  @brief Finds the end of a subsequence matching given key.
1299        *  @param  __x  Key of (key, value) pair to be located.
1300        *  @return  Read-only (constant) iterator pointing to first iterator
1301        *           greater than key, or end().
1302        */
1303       const_iterator
1304       upper_bound(const key_type& __x) const
1305       { return _M_t.upper_bound(__x); }
1306 
1307 #if __cplusplus > 201103L
1308       template<typename _Kt>
1309 	auto
1310 	upper_bound(const _Kt& __x) const
1311 	-> decltype(const_iterator(_M_t._M_upper_bound_tr(__x)))
1312 	{ return const_iterator(_M_t._M_upper_bound_tr(__x)); }
1313 #endif
1314       //@}
1315 
1316       //@{
1317       /**
1318        *  @brief Finds a subsequence matching given key.
1319        *  @param  __x  Key of (key, value) pairs to be located.
1320        *  @return  Pair of iterators that possibly points to the subsequence
1321        *           matching given key.
1322        *
1323        *  This function is equivalent to
1324        *  @code
1325        *    std::make_pair(c.lower_bound(val),
1326        *                   c.upper_bound(val))
1327        *  @endcode
1328        *  (but is faster than making the calls separately).
1329        *
1330        *  This function probably only makes sense for multimaps.
1331        */
1332       std::pair<iterator, iterator>
1333       equal_range(const key_type& __x)
1334       { return _M_t.equal_range(__x); }
1335 
1336 #if __cplusplus > 201103L
1337       template<typename _Kt>
1338 	auto
1339 	equal_range(const _Kt& __x)
1340 	-> decltype(pair<iterator, iterator>(_M_t._M_equal_range_tr(__x)))
1341 	{ return pair<iterator, iterator>(_M_t._M_equal_range_tr(__x)); }
1342 #endif
1343       //@}
1344 
1345       //@{
1346       /**
1347        *  @brief Finds a subsequence matching given key.
1348        *  @param  __x  Key of (key, value) pairs to be located.
1349        *  @return  Pair of read-only (constant) iterators that possibly points
1350        *           to the subsequence matching given key.
1351        *
1352        *  This function is equivalent to
1353        *  @code
1354        *    std::make_pair(c.lower_bound(val),
1355        *                   c.upper_bound(val))
1356        *  @endcode
1357        *  (but is faster than making the calls separately).
1358        *
1359        *  This function probably only makes sense for multimaps.
1360        */
1361       std::pair<const_iterator, const_iterator>
1362       equal_range(const key_type& __x) const
1363       { return _M_t.equal_range(__x); }
1364 
1365 #if __cplusplus > 201103L
1366       template<typename _Kt>
1367 	auto
1368 	equal_range(const _Kt& __x) const
1369 	-> decltype(pair<const_iterator, const_iterator>(
1370 	      _M_t._M_equal_range_tr(__x)))
1371 	{
1372 	  return pair<const_iterator, const_iterator>(
1373 	      _M_t._M_equal_range_tr(__x));
1374 	}
1375 #endif
1376       //@}
1377 
1378       template<typename _K1, typename _T1, typename _C1, typename _A1>
1379 	friend bool
1380 	operator==(const map<_K1, _T1, _C1, _A1>&,
1381 		   const map<_K1, _T1, _C1, _A1>&);
1382 
1383       template<typename _K1, typename _T1, typename _C1, typename _A1>
1384 	friend bool
1385 	operator<(const map<_K1, _T1, _C1, _A1>&,
1386 		  const map<_K1, _T1, _C1, _A1>&);
1387     };
1388 
1389 
1390 #if __cpp_deduction_guides >= 201606
1391 
1392   template<typename _InputIterator,
1393 	   typename _Compare = less<__iter_key_t<_InputIterator>>,
1394 	   typename _Allocator = allocator<__iter_to_alloc_t<_InputIterator>>,
1395 	   typename = _RequireInputIter<_InputIterator>,
1396 	   typename = _RequireAllocator<_Allocator>>
1397     map(_InputIterator, _InputIterator,
1398 	_Compare = _Compare(), _Allocator = _Allocator())
1399     -> map<__iter_key_t<_InputIterator>, __iter_val_t<_InputIterator>,
1400 	   _Compare, _Allocator>;
1401 
1402   template<typename _Key, typename _Tp, typename _Compare = less<_Key>,
1403 	   typename _Allocator = allocator<pair<const _Key, _Tp>>,
1404 	   typename = _RequireAllocator<_Allocator>>
1405     map(initializer_list<pair<_Key, _Tp>>,
1406 	_Compare = _Compare(), _Allocator = _Allocator())
1407     -> map<_Key, _Tp, _Compare, _Allocator>;
1408 
1409   template <typename _InputIterator, typename _Allocator,
1410 	    typename = _RequireInputIter<_InputIterator>,
1411 	    typename = _RequireAllocator<_Allocator>>
1412     map(_InputIterator, _InputIterator, _Allocator)
1413     -> map<__iter_key_t<_InputIterator>, __iter_val_t<_InputIterator>,
1414 	   less<__iter_key_t<_InputIterator>>, _Allocator>;
1415 
1416   template<typename _Key, typename _Tp, typename _Allocator,
1417 	   typename = _RequireAllocator<_Allocator>>
1418     map(initializer_list<pair<_Key, _Tp>>, _Allocator)
1419     -> map<_Key, _Tp, less<_Key>, _Allocator>;
1420 
1421 #endif
1422 
1423   /**
1424    *  @brief  Map equality comparison.
1425    *  @param  __x  A %map.
1426    *  @param  __y  A %map of the same type as @a x.
1427    *  @return  True iff the size and elements of the maps are equal.
1428    *
1429    *  This is an equivalence relation.  It is linear in the size of the
1430    *  maps.  Maps are considered equivalent if their sizes are equal,
1431    *  and if corresponding elements compare equal.
1432   */
1433   template<typename _Key, typename _Tp, typename _Compare, typename _Alloc>
1434     inline bool
1435     operator==(const map<_Key, _Tp, _Compare, _Alloc>& __x,
1436 	       const map<_Key, _Tp, _Compare, _Alloc>& __y)
1437     { return __x._M_t == __y._M_t; }
1438 
1439   /**
1440    *  @brief  Map ordering relation.
1441    *  @param  __x  A %map.
1442    *  @param  __y  A %map of the same type as @a x.
1443    *  @return  True iff @a x is lexicographically less than @a y.
1444    *
1445    *  This is a total ordering relation.  It is linear in the size of the
1446    *  maps.  The elements must be comparable with @c <.
1447    *
1448    *  See std::lexicographical_compare() for how the determination is made.
1449   */
1450   template<typename _Key, typename _Tp, typename _Compare, typename _Alloc>
1451     inline bool
1452     operator<(const map<_Key, _Tp, _Compare, _Alloc>& __x,
1453 	      const map<_Key, _Tp, _Compare, _Alloc>& __y)
1454     { return __x._M_t < __y._M_t; }
1455 
1456   /// Based on operator==
1457   template<typename _Key, typename _Tp, typename _Compare, typename _Alloc>
1458     inline bool
1459     operator!=(const map<_Key, _Tp, _Compare, _Alloc>& __x,
1460 	       const map<_Key, _Tp, _Compare, _Alloc>& __y)
1461     { return !(__x == __y); }
1462 
1463   /// Based on operator<
1464   template<typename _Key, typename _Tp, typename _Compare, typename _Alloc>
1465     inline bool
1466     operator>(const map<_Key, _Tp, _Compare, _Alloc>& __x,
1467 	      const map<_Key, _Tp, _Compare, _Alloc>& __y)
1468     { return __y < __x; }
1469 
1470   /// Based on operator<
1471   template<typename _Key, typename _Tp, typename _Compare, typename _Alloc>
1472     inline bool
1473     operator<=(const map<_Key, _Tp, _Compare, _Alloc>& __x,
1474 	       const map<_Key, _Tp, _Compare, _Alloc>& __y)
1475     { return !(__y < __x); }
1476 
1477   /// Based on operator<
1478   template<typename _Key, typename _Tp, typename _Compare, typename _Alloc>
1479     inline bool
1480     operator>=(const map<_Key, _Tp, _Compare, _Alloc>& __x,
1481 	       const map<_Key, _Tp, _Compare, _Alloc>& __y)
1482     { return !(__x < __y); }
1483 
1484   /// See std::map::swap().
1485   template<typename _Key, typename _Tp, typename _Compare, typename _Alloc>
1486     inline void
1487     swap(map<_Key, _Tp, _Compare, _Alloc>& __x,
1488 	 map<_Key, _Tp, _Compare, _Alloc>& __y)
1489     _GLIBCXX_NOEXCEPT_IF(noexcept(__x.swap(__y)))
1490     { __x.swap(__y); }
1491 
1492 _GLIBCXX_END_NAMESPACE_CONTAINER
1493 
1494 #if __cplusplus > 201402L
1495   // Allow std::map access to internals of compatible maps.
1496   template<typename _Key, typename _Val, typename _Cmp1, typename _Alloc,
1497 	   typename _Cmp2>
1498     struct
1499     _Rb_tree_merge_helper<_GLIBCXX_STD_C::map<_Key, _Val, _Cmp1, _Alloc>,
1500 			  _Cmp2>
1501     {
1502     private:
1503       friend class _GLIBCXX_STD_C::map<_Key, _Val, _Cmp1, _Alloc>;
1504 
1505       static auto&
1506       _S_get_tree(_GLIBCXX_STD_C::map<_Key, _Val, _Cmp2, _Alloc>& __map)
1507       { return __map._M_t; }
1508 
1509       static auto&
1510       _S_get_tree(_GLIBCXX_STD_C::multimap<_Key, _Val, _Cmp2, _Alloc>& __map)
1511       { return __map._M_t; }
1512     };
1513 #endif // C++17
1514 
1515 _GLIBCXX_END_NAMESPACE_VERSION
1516 } // namespace std
1517 
1518 #endif /* _STL_MAP_H */
1519