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// unordered_map implementation -- C++ -- // Copyright (C) 2010-2018 Free Software Foundation, Inc. // // This file is part of the GNU ISO C++ Library. This library is free // software; you can redistribute it and/or modify it under the // terms of the GNU General Public License as published by the // Free Software Foundation; either version 3, or (at your option) // any later version. // This library is distributed in the hope that it will be useful, // but WITHOUT ANY WARRANTY; without even the implied warranty of // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the // GNU General Public License for more details. // Under Section 7 of GPL version 3, you are granted additional // permissions described in the GCC Runtime Library Exception, version // 3.1, as published by the Free Software Foundation. // You should have received a copy of the GNU General Public License and // a copy of the GCC Runtime Library Exception along with this program; // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see // <http://www.gnu.org/licenses/>. /** @file bits/unordered_map.h * This is an internal header file, included by other library headers. * Do not attempt to use it directly. @headername{unordered_map} / #ifndef _UNORDERED_MAP_H #define _UNORDERED_MAP_H namespace std _GLIBCXX_VISIBILITY(default) { _GLIBCXX_BEGIN_NAMESPACE_VERSION _GLIBCXX_BEGIN_NAMESPACE_CONTAINER /// Base types for unordered_map. template<bool _Cache> using __umap_traits = __detail::_Hashtable_traits<_Cache, false, true>; template<typename _Key, typename _Tp, typename _Hash = hash<_Key>, typename _Pred = std::equal_to<_Key>, typename _Alloc = std::allocator<std::pair<const _Key, _Tp> >, typename _Tr = __umap_traits<__cache_default<_Key, _Hash>::value>> using __umap_hashtable = _Hashtable<_Key, std::pair<const _Key, _Tp>, _Alloc, __detail::_Select1st, _Pred, _Hash, __detail::_Mod_range_hashing, __detail::_Default_ranged_hash, __detail::_Prime_rehash_policy, _Tr>; /// Base types for unordered_multimap. template<bool _Cache> using __ummap_traits = __detail::_Hashtable_traits<_Cache, false, false>; template<typename _Key, typename _Tp, typename _Hash = hash<_Key>, typename _Pred = std::equal_to<_Key>, typename _Alloc = std::allocator<std::pair<const _Key, _Tp> >, typename _Tr = __ummap_traits<__cache_default<_Key, _Hash>::value>> using __ummap_hashtable = _Hashtable<_Key, std::pair<const _Key, _Tp>, _Alloc, __detail::_Select1st, _Pred, _Hash, __detail::_Mod_range_hashing, __detail::_Default_ranged_hash, __detail::_Prime_rehash_policy, _Tr>; template<class _Key, class _Tp, class _Hash, class _Pred, class _Alloc> class unordered_multimap; /* * @brief A standard container composed of unique keys (containing * at most one of each key value) that associates values of another type * with the keys. * * @ingroup unordered_associative_containers * * @tparam _Key Type of key objects. * @tparam _Tp Type of mapped objects. * @tparam _Hash Hashing function object type, defaults to hash<_Value>. * @tparam _Pred Predicate function object type, defaults * to equal_to<_Value>. * @tparam _Alloc Allocator type, defaults to * std::allocator<std::pair<const _Key, _Tp>>. * * Meets the requirements of a <a href="tables.html#65">container</a>, and * <a href="tables.html#xx">unordered associative container</a> * * The resulting value type of the container is std::pair<const _Key, _Tp>. * * Base is _Hashtable, dispatched at compile time via template * alias __umap_hashtable. / template<typename _Key, typename _Tp, typename _Hash = hash<_Key>, typename _Pred = equal_to<_Key>, typename _Alloc = allocator<std::pair<const _Key, _Tp>>> class unordered_map { typedef __umap_hashtable<_Key, _Tp, _Hash, _Pred, _Alloc> _Hashtable; _Hashtable _M_h; public: // typedefs: //@{ /// Public typedefs. typedef typename _Hashtable::key_type key_type; typedef typename _Hashtable::value_type value_type; typedef typename _Hashtable::mapped_type mapped_type; typedef typename _Hashtable::hasher hasher; typedef typename _Hashtable::key_equal key_equal; typedef typename _Hashtable::allocator_type allocator_type; //@} //@{ /// Iterator-related typedefs. typedef typename _Hashtable::pointer pointer; typedef typename _Hashtable::const_pointer const_pointer; typedef typename _Hashtable::reference reference; typedef typename _Hashtable::const_reference const_reference; typedef typename _Hashtable::iterator iterator; typedef typename _Hashtable::const_iterator const_iterator; typedef typename _Hashtable::local_iterator local_iterator; typedef typename _Hashtable::const_local_iterator const_local_iterator; typedef typename _Hashtable::size_type size_type; typedef typename _Hashtable::difference_type difference_type; //@} #if __cplusplus > 201402L using node_type = typename _Hashtable::node_type; using insert_return_type = typename _Hashtable::insert_return_type; #endif //construct/destroy/copy /// Default constructor. unordered_map() = default; /* * @brief Default constructor creates no elements. * @param __n Minimal initial number of buckets. * @param __hf A hash functor. * @param __eql A key equality functor. * @param __a An allocator object. / explicit unordered_map(size_type __n, const hasher& __hf = hasher(), const key_equal& __eql = key_equal(), const allocator_type& __a = allocator_type()) : _M_h(__n, __hf, __eql, __a) { } /* * @brief Builds an %unordered_map from a range. * @param __first An input iterator. * @param __last An input iterator. * @param __n Minimal initial number of buckets. * @param __hf A hash functor. * @param __eql A key equality functor. * @param __a An allocator object. * * Create an %unordered_map consisting of copies of the elements from * [__first,__last). This is linear in N (where N is * distance(__first,__last)). / template<typename _InputIterator> unordered_map(_InputIterator __first, _InputIterator __last, size_type __n = 0, const hasher& __hf = hasher(), const key_equal& __eql = key_equal(), const allocator_type& __a = allocator_type()) : _M_h(__first, __last, __n, __hf, __eql, __a) { } /// Copy constructor. unordered_map(const unordered_map&) = default; /// Move constructor. unordered_map(unordered_map&&) = default; /* * @brief Creates an %unordered_map with no elements. * @param __a An allocator object. / explicit unordered_map(const allocator_type& __a) : _M_h(__a) { } / * @brief Copy constructor with allocator argument. * @param __uset Input %unordered_map to copy. * @param __a An allocator object. / unordered_map(const unordered_map& __umap, const allocator_type& __a) : _M_h(__umap._M_h, __a) { } / * @brief Move constructor with allocator argument. * @param __uset Input %unordered_map to move. * @param __a An allocator object. / unordered_map(unordered_map&& __umap, const allocator_type& __a) : _M_h(std::move(__umap._M_h), __a) { } /* * @brief Builds an %unordered_map from an initializer_list. * @param __l An initializer_list. * @param __n Minimal initial number of buckets. * @param __hf A hash functor. * @param __eql A key equality functor. * @param __a An allocator object. * * Create an %unordered_map consisting of copies of the elements in the * list. This is linear in N (where N is @a __l.size()). / unordered_map(initializer_list<value_type> __l, size_type __n = 0, const hasher& __hf = hasher(), const key_equal& __eql = key_equal(), const allocator_type& __a = allocator_type()) : _M_h(__l, __n, __hf, __eql, __a) { } unordered_map(size_type __n, const allocator_type& __a) : unordered_map(__n, hasher(), key_equal(), __a) { } unordered_map(size_type __n, const hasher& __hf, const allocator_type& __a) : unordered_map(__n, __hf, key_equal(), __a) { } template<typename _InputIterator> unordered_map(_InputIterator __first, _InputIterator __last, size_type __n, const allocator_type& __a) : unordered_map(__first, __last, __n, hasher(), key_equal(), __a) { } template<typename _InputIterator> unordered_map(_InputIterator __first, _InputIterator __last, size_type __n, const hasher& __hf, const allocator_type& __a) : unordered_map(__first, __last, __n, __hf, key_equal(), __a) { } unordered_map(initializer_list<value_type> __l, size_type __n, const allocator_type& __a) : unordered_map(__l, __n, hasher(), key_equal(), __a) { } unordered_map(initializer_list<value_type> __l, size_type __n, const hasher& __hf, const allocator_type& __a) : unordered_map(__l, __n, __hf, key_equal(), __a) { } /// Copy assignment operator. unordered_map& operator=(const unordered_map&) = default; /// Move assignment operator. unordered_map& operator=(unordered_map&&) = default; /* * @brief %Unordered_map list assignment operator. * @param __l An initializer_list. * * This function fills an %unordered_map with copies of the elements in * the initializer list @a __l. * * Note that the assignment completely changes the %unordered_map and * that the resulting %unordered_map's size is the same as the number * of elements assigned. / unordered_map& operator=(initializer_list<value_type> __l) { _M_h = __l; return this; } /// Returns the allocator object used by the %unordered_map. allocator_type get_allocator() const noexcept { return _M_h.get_allocator(); } // size and capacity: /// Returns true if the %unordered_map is empty. bool empty() const noexcept { return _M_h.empty(); } /// Returns the size of the %unordered_map. size_type size() const noexcept { return _M_h.size(); } /// Returns the maximum size of the %unordered_map. size_type max_size() const noexcept { return _M_h.max_size(); } // iterators. /** * Returns a read/write iterator that points to the first element in the * %unordered_map. / iterator begin() noexcept { return _M_h.begin(); } //@{ /* * Returns a read-only (constant) iterator that points to the first * element in the %unordered_map. / const_iterator begin() const noexcept { return _M_h.begin(); } const_iterator cbegin() const noexcept { return _M_h.begin(); } //@} /* * Returns a read/write iterator that points one past the last element in * the %unordered_map. / iterator end() noexcept { return _M_h.end(); } //@{ /* * Returns a read-only (constant) iterator that points one past the last * element in the %unordered_map. / const_iterator end() const noexcept { return _M_h.end(); } const_iterator cend() const noexcept { return _M_h.end(); } //@} // modifiers. /* * @brief Attempts to build and insert a std::pair into the * %unordered_map. * * @param __args Arguments used to generate a new pair instance (see * std::piecewise_contruct for passing arguments to each * part of the pair constructor). * * @return A pair, of which the first element is an iterator that points * to the possibly inserted pair, and the second is a bool that * is true if the pair was actually inserted. * * This function attempts to build and insert a (key, value) %pair into * the %unordered_map. * An %unordered_map relies on unique keys and thus a %pair is only * inserted if its first element (the key) is not already present in the * %unordered_map. * * Insertion requires amortized constant time. / template<typename... _Args> std::pair<iterator, bool> emplace(_Args&&... __args) { return _M_h.emplace(std::forward<_Args>(__args)...); } /* * @brief Attempts to build and insert a std::pair into the * %unordered_map. * * @param __pos An iterator that serves as a hint as to where the pair * should be inserted. * @param __args Arguments used to generate a new pair instance (see * std::piecewise_contruct for passing arguments to each * part of the pair constructor). * @return An iterator that points to the element with key of the * std::pair built from @a __args (may or may not be that * std::pair). * * This function is not concerned about whether the insertion took place, * and thus does not return a boolean like the single-argument emplace() * does. * Note that the first parameter is only a hint and can potentially * improve the performance of the insertion process. A bad hint would * cause no gains in efficiency. * * See * https://gcc.gnu.org/onlinedocs/libstdc++/manual/associative.html#containers.associative.insert_hints * for more on @a hinting. * * Insertion requires amortized constant time. / template<typename... _Args> iterator emplace_hint(const_iterator __pos, _Args&&... __args) { return _M_h.emplace_hint(__pos, std::forward<_Args>(__args)...); } #if __cplusplus > 201402L /// Extract a node. node_type extract(const_iterator __pos) { __glibcxx_assert(__pos != end()); return _M_h.extract(__pos); } /// Extract a node. node_type extract(const key_type& __key) { return _M_h.extract(__key); } /// Re-insert an extracted node. insert_return_type insert(node_type&& __nh) { return _M_h._M_reinsert_node(std::move(__nh)); } /// Re-insert an extracted node. iterator insert(const_iterator, node_type&& __nh) { return _M_h._M_reinsert_node(std::move(__nh)).position; } #define __cpp_lib_unordered_map_try_emplace 201411 /* * @brief Attempts to build and insert a std::pair into the * %unordered_map. * * @param __k Key to use for finding a possibly existing pair in * the unordered_map. * @param __args Arguments used to generate the .second for a * new pair instance. * * @return A pair, of which the first element is an iterator that points * to the possibly inserted pair, and the second is a bool that * is true if the pair was actually inserted. * * This function attempts to build and insert a (key, value) %pair into * the %unordered_map. * An %unordered_map relies on unique keys and thus a %pair is only * inserted if its first element (the key) is not already present in the * %unordered_map. * If a %pair is not inserted, this function has no effect. * * Insertion requires amortized constant time. / template <typename... _Args> pair<iterator, bool> try_emplace(const key_type& __k, _Args&&... __args) { iterator __i = find(__k); if (__i == end()) { __i = emplace(std::piecewise_construct, std::forward_as_tuple(__k), std::forward_as_tuple( std::forward<_Args>(__args)...)) .first; return {__i, true}; } return {__i, false}; } // move-capable overload template <typename... _Args> pair<iterator, bool> try_emplace(key_type&& __k, _Args&&... __args) { iterator __i = find(__k); if (__i == end()) { __i = emplace(std::piecewise_construct, std::forward_as_tuple(std::move(__k)), std::forward_as_tuple( std::forward<_Args>(__args)...)) .first; return {__i, true}; } return {__i, false}; } /* * @brief Attempts to build and insert a std::pair into the * %unordered_map. * * @param __hint An iterator that serves as a hint as to where the pair * should be inserted. * @param __k Key to use for finding a possibly existing pair in * the unordered_map. * @param __args Arguments used to generate the .second for a * new pair instance. * @return An iterator that points to the element with key of the * std::pair built from @a __args (may or may not be that * std::pair). * * This function is not concerned about whether the insertion took place, * and thus does not return a boolean like the single-argument emplace() * does. However, if insertion did not take place, * this function has no effect. * Note that the first parameter is only a hint and can potentially * improve the performance of the insertion process. A bad hint would * cause no gains in efficiency. * * See * https://gcc.gnu.org/onlinedocs/libstdc++/manual/associative.html#containers.associative.insert_hints * for more on @a hinting. * * Insertion requires amortized constant time. / template <typename... _Args> iterator try_emplace(const_iterator __hint, const key_type& __k, _Args&&... __args) { iterator __i = find(__k); if (__i == end()) __i = emplace_hint(__hint, std::piecewise_construct, std::forward_as_tuple(__k), std::forward_as_tuple( std::forward<_Args>(__args)...)); return __i; } // move-capable overload template <typename... _Args> iterator try_emplace(const_iterator __hint, key_type&& __k, _Args&&... __args) { iterator __i = find(__k); if (__i == end()) __i = emplace_hint(__hint, std::piecewise_construct, std::forward_as_tuple(std::move(__k)), std::forward_as_tuple( std::forward<_Args>(__args)...)); return __i; } #endif // C++17 //@{ /* * @brief Attempts to insert a std::pair into the %unordered_map. * @param __x Pair to be inserted (see std::make_pair for easy * creation of pairs). * * @return A pair, of which the first element is an iterator that * points to the possibly inserted pair, and the second is * a bool that is true if the pair was actually inserted. * * This function attempts to insert a (key, value) %pair into the * %unordered_map. An %unordered_map relies on unique keys and thus a * %pair is only inserted if its first element (the key) is not already * present in the %unordered_map. * * Insertion requires amortized constant time. / std::pair<iterator, bool> insert(const value_type& __x) { return _M_h.insert(__x); } // _GLIBCXX_RESOLVE_LIB_DEFECTS // 2354. Unnecessary copying when inserting into maps with braced-init std::pair<iterator, bool> insert(value_type&& __x) { return _M_h.insert(std::move(__x)); } template<typename _Pair> __enable_if_t<is_constructible<value_type, _Pair&&>::value, pair<iterator, bool>> insert(_Pair&& __x) { return _M_h.emplace(std::forward<_Pair>(__x)); } //@} //@{ /* * @brief Attempts to insert a std::pair into the %unordered_map. * @param __hint An iterator that serves as a hint as to where the * pair should be inserted. * @param __x Pair to be inserted (see std::make_pair for easy creation * of pairs). * @return An iterator that points to the element with key of * @a __x (may or may not be the %pair passed in). * * This function is not concerned about whether the insertion took place, * and thus does not return a boolean like the single-argument insert() * does. Note that the first parameter is only a hint and can * potentially improve the performance of the insertion process. A bad * hint would cause no gains in efficiency. * * See * https://gcc.gnu.org/onlinedocs/libstdc++/manual/associative.html#containers.associative.insert_hints * for more on @a hinting. * * Insertion requires amortized constant time. / iterator insert(const_iterator __hint, const value_type& __x) { return _M_h.insert(__hint, __x); } // _GLIBCXX_RESOLVE_LIB_DEFECTS // 2354. Unnecessary copying when inserting into maps with braced-init iterator insert(const_iterator __hint, value_type&& __x) { return _M_h.insert(__hint, std::move(__x)); } template<typename _Pair> __enable_if_t<is_constructible<value_type, _Pair&&>::value, iterator> insert(const_iterator __hint, _Pair&& __x) { return _M_h.emplace_hint(__hint, std::forward<_Pair>(__x)); } //@} /* * @brief A template function that attempts to insert a range of * elements. * @param __first Iterator pointing to the start of the range to be * inserted. * @param __last Iterator pointing to the end of the range. * * Complexity similar to that of the range constructor. / template<typename _InputIterator> void insert(_InputIterator __first, _InputIterator __last) { _M_h.insert(__first, __last); } /* * @brief Attempts to insert a list of elements into the %unordered_map. * @param __l A std::initializer_list<value_type> of elements * to be inserted. * * Complexity similar to that of the range constructor. / void insert(initializer_list<value_type> __l) { _M_h.insert(__l); } #if __cplusplus > 201402L #define __cpp_lib_unordered_map_insertion 201411 /* * @brief Attempts to insert a std::pair into the %unordered_map. * @param __k Key to use for finding a possibly existing pair in * the map. * @param __obj Argument used to generate the .second for a pair * instance. * * @return A pair, of which the first element is an iterator that * points to the possibly inserted pair, and the second is * a bool that is true if the pair was actually inserted. * * This function attempts to insert a (key, value) %pair into the * %unordered_map. An %unordered_map relies on unique keys and thus a * %pair is only inserted if its first element (the key) is not already * present in the %unordered_map. * If the %pair was already in the %unordered_map, the .second of * the %pair is assigned from __obj. * * Insertion requires amortized constant time. / template <typename _Obj> pair<iterator, bool> insert_or_assign(const key_type& __k, _Obj&& __obj) { iterator __i = find(__k); if (__i == end()) { __i = emplace(std::piecewise_construct, std::forward_as_tuple(__k), std::forward_as_tuple(std::forward<_Obj>(__obj))) .first; return {__i, true}; } (__i).second = std::forward<_Obj>(__obj); return {__i, false}; } // move-capable overload template <typename _Obj> pair<iterator, bool> insert_or_assign(key_type&& __k, _Obj&& __obj) { iterator __i = find(__k); if (__i == end()) { __i = emplace(std::piecewise_construct, std::forward_as_tuple(std::move(__k)), std::forward_as_tuple(std::forward<_Obj>(__obj))) .first; return {__i, true}; } (__i).second = std::forward<_Obj>(__obj); return {__i, false}; } /* * @brief Attempts to insert a std::pair into the %unordered_map. * @param __hint An iterator that serves as a hint as to where the * pair should be inserted. * @param __k Key to use for finding a possibly existing pair in * the unordered_map. * @param __obj Argument used to generate the .second for a pair * instance. * @return An iterator that points to the element with key of * @a __x (may or may not be the %pair passed in). * * This function is not concerned about whether the insertion took place, * and thus does not return a boolean like the single-argument insert() * does. * If the %pair was already in the %unordered map, the .second of * the %pair is assigned from __obj. * Note that the first parameter is only a hint and can * potentially improve the performance of the insertion process. A bad * hint would cause no gains in efficiency. * * See * https://gcc.gnu.org/onlinedocs/libstdc++/manual/associative.html#containers.associative.insert_hints * for more on @a hinting. * * Insertion requires amortized constant time. / template <typename _Obj> iterator insert_or_assign(const_iterator __hint, const key_type& __k, _Obj&& __obj) { iterator __i = find(__k); if (__i == end()) { return emplace_hint(__hint, std::piecewise_construct, std::forward_as_tuple(__k), std::forward_as_tuple( std::forward<_Obj>(__obj))); } (__i).second = std::forward<_Obj>(__obj); return __i; } // move-capable overload template <typename _Obj> iterator insert_or_assign(const_iterator __hint, key_type&& __k, _Obj&& __obj) { iterator __i = find(__k); if (__i == end()) { return emplace_hint(__hint, std::piecewise_construct, std::forward_as_tuple(std::move(__k)), std::forward_as_tuple( std::forward<_Obj>(__obj))); } (__i).second = std::forward<_Obj>(__obj); return __i; } #endif //@{ /* * @brief Erases an element from an %unordered_map. * @param __position An iterator pointing to the element to be erased. * @return An iterator pointing to the element immediately following * @a __position prior to the element being erased. If no such * element exists, end() is returned. * * This function erases an element, pointed to by the given iterator, * from an %unordered_map. * Note that this function only erases the element, and that if the * element is itself a pointer, the pointed-to memory is not touched in * any way. Managing the pointer is the user's responsibility. / iterator erase(const_iterator __position) { return _M_h.erase(__position); } // LWG 2059. iterator erase(iterator __position) { return _M_h.erase(__position); } //@} /* * @brief Erases elements according to the provided key. * @param __x Key of element to be erased. * @return The number of elements erased. * * This function erases all the elements located by the given key from * an %unordered_map. For an %unordered_map the result of this function * can only be 0 (not present) or 1 (present). * Note that this function only erases the element, and that if the * element is itself a pointer, the pointed-to memory is not touched in * any way. Managing the pointer is the user's responsibility. / size_type erase(const key_type& __x) { return _M_h.erase(__x); } /* * @brief Erases a [__first,__last) range of elements from an * %unordered_map. * @param __first Iterator pointing to the start of the range to be * erased. * @param __last Iterator pointing to the end of the range to * be erased. * @return The iterator @a __last. * * This function erases a sequence of elements from an %unordered_map. * Note that this function only erases the elements, and that if * the element is itself a pointer, the pointed-to memory is not touched * in any way. Managing the pointer is the user's responsibility. / iterator erase(const_iterator __first, const_iterator __last) { return _M_h.erase(__first, __last); } /* * Erases all elements in an %unordered_map. * Note that this function only erases the elements, and that if the * elements themselves are pointers, the pointed-to memory is not touched * in any way. Managing the pointer is the user's responsibility. / void clear() noexcept { _M_h.clear(); } /* * @brief Swaps data with another %unordered_map. * @param __x An %unordered_map of the same element and allocator * types. * * This exchanges the elements between two %unordered_map in constant * time. * Note that the global std::swap() function is specialized such that * std::swap(m1,m2) will feed to this function. / void swap(unordered_map& __x) noexcept( noexcept(_M_h.swap(__x._M_h)) ) { _M_h.swap(__x._M_h); } #if __cplusplus > 201402L template<typename, typename, typename> friend class std::_Hash_merge_helper; template<typename _H2, typename _P2> void merge(unordered_map<_Key, _Tp, _H2, _P2, _Alloc>& __source) { using _Merge_helper = _Hash_merge_helper<unordered_map, _H2, _P2>; _M_h._M_merge_unique(_Merge_helper::_S_get_table(__source)); } template<typename _H2, typename _P2> void merge(unordered_map<_Key, _Tp, _H2, _P2, _Alloc>&& __source) { merge(__source); } template<typename _H2, typename _P2> void merge(unordered_multimap<_Key, _Tp, _H2, _P2, _Alloc>& __source) { using _Merge_helper = _Hash_merge_helper<unordered_map, _H2, _P2>; _M_h._M_merge_unique(_Merge_helper::_S_get_table(__source)); } template<typename _H2, typename _P2> void merge(unordered_multimap<_Key, _Tp, _H2, _P2, _Alloc>&& __source) { merge(__source); } #endif // C++17 // observers. /// Returns the hash functor object with which the %unordered_map was /// constructed. hasher hash_function() const { return _M_h.hash_function(); } /// Returns the key comparison object with which the %unordered_map was /// constructed. key_equal key_eq() const { return _M_h.key_eq(); } // lookup. //@{ /* * @brief Tries to locate an element in an %unordered_map. * @param __x Key to be located. * @return Iterator pointing to sought-after element, or end() if not * found. * * This function takes a key and tries to locate the element with which * the key matches. If successful the function returns an iterator * pointing to the sought after element. If unsuccessful it returns the * past-the-end ( @c end() ) iterator. / iterator find(const key_type& __x) { return _M_h.find(__x); } const_iterator find(const key_type& __x) const { return _M_h.find(__x); } //@} /* * @brief Finds the number of elements. * @param __x Key to count. * @return Number of elements with specified key. * * This function only makes sense for %unordered_multimap; for * %unordered_map the result will either be 0 (not present) or 1 * (present). / size_type count(const key_type& __x) const { return _M_h.count(__x); } //@{ /* * @brief Finds a subsequence matching given key. * @param __x Key to be located. * @return Pair of iterators that possibly points to the subsequence * matching given key. * * This function probably only makes sense for %unordered_multimap. / std::pair<iterator, iterator> equal_range(const key_type& __x) { return _M_h.equal_range(__x); } std::pair<const_iterator, const_iterator> equal_range(const key_type& __x) const { return _M_h.equal_range(__x); } //@} //@{ /* * @brief Subscript ( @c [] ) access to %unordered_map data. * @param __k The key for which data should be retrieved. * @return A reference to the data of the (key,data) %pair. * * Allows for easy lookup with the subscript ( @c [] )operator. Returns * data associated with the key specified in subscript. If the key does * not exist, a pair with that key is created using default values, which * is then returned. * * Lookup requires constant time. / mapped_type& operator[](const key_type& __k) { return _M_h[__k]; } mapped_type& operator[](key_type&& __k) { return _M_h[std::move(__k)]; } //@} //@{ /* * @brief Access to %unordered_map data. * @param __k The key for which data should be retrieved. * @return A reference to the data whose key is equal to @a __k, if * such a data is present in the %unordered_map. * @throw std::out_of_range If no such data is present. / mapped_type& at(const key_type& __k) { return _M_h.at(__k); } const mapped_type& at(const key_type& __k) const { return _M_h.at(__k); } //@} // bucket interface. /// Returns the number of buckets of the %unordered_map. size_type bucket_count() const noexcept { return _M_h.bucket_count(); } /// Returns the maximum number of buckets of the %unordered_map. size_type max_bucket_count() const noexcept { return _M_h.max_bucket_count(); } / * @brief Returns the number of elements in a given bucket. * @param __n A bucket index. * @return The number of elements in the bucket. / size_type bucket_size(size_type __n) const { return _M_h.bucket_size(__n); } / * @brief Returns the bucket index of a given element. * @param __key A key instance. * @return The key bucket index. / size_type bucket(const key_type& __key) const { return _M_h.bucket(__key); } /* * @brief Returns a read/write iterator pointing to the first bucket * element. * @param __n The bucket index. * @return A read/write local iterator. / local_iterator begin(size_type __n) { return _M_h.begin(__n); } //@{ /* * @brief Returns a read-only (constant) iterator pointing to the first * bucket element. * @param __n The bucket index. * @return A read-only local iterator. / const_local_iterator begin(size_type __n) const { return _M_h.begin(__n); } const_local_iterator cbegin(size_type __n) const { return _M_h.cbegin(__n); } //@} /* * @brief Returns a read/write iterator pointing to one past the last * bucket elements. * @param __n The bucket index. * @return A read/write local iterator. / local_iterator end(size_type __n) { return _M_h.end(__n); } //@{ /* * @brief Returns a read-only (constant) iterator pointing to one past * the last bucket elements. * @param __n The bucket index. * @return A read-only local iterator. / const_local_iterator end(size_type __n) const { return _M_h.end(__n); } const_local_iterator cend(size_type __n) const { return _M_h.cend(__n); } //@} // hash policy. /// Returns the average number of elements per bucket. float load_factor() const noexcept { return _M_h.load_factor(); } /// Returns a positive number that the %unordered_map tries to keep the /// load factor less than or equal to. float max_load_factor() const noexcept { return _M_h.max_load_factor(); } /* * @brief Change the %unordered_map maximum load factor. * @param __z The new maximum load factor. / void max_load_factor(float __z) { _M_h.max_load_factor(__z); } /* * @brief May rehash the %unordered_map. * @param __n The new number of buckets. * * Rehash will occur only if the new number of buckets respect the * %unordered_map maximum load factor. / void rehash(size_type __n) { _M_h.rehash(__n); } /* * @brief Prepare the %unordered_map for a specified number of * elements. * @param __n Number of elements required. * * Same as rehash(ceil(n / max_load_factor())). / void reserve(size_type __n) { _M_h.reserve(__n); } template<typename _Key1, typename _Tp1, typename _Hash1, typename _Pred1, typename _Alloc1> friend bool operator==(const unordered_map<_Key1, _Tp1, _Hash1, _Pred1, _Alloc1>&, const unordered_map<_Key1, _Tp1, _Hash1, _Pred1, _Alloc1>&); }; #if __cpp_deduction_guides >= 201606 template<typename _InputIterator, typename _Hash = hash<__iter_key_t<_InputIterator>>, typename _Pred = equal_to<__iter_key_t<_InputIterator>>, typename _Allocator = allocator<__iter_to_alloc_t<_InputIterator>>, typename = _RequireInputIter<_InputIterator>, typename = _RequireAllocator<_Allocator>> unordered_map(_InputIterator, _InputIterator, typename unordered_map<int, int>::size_type = {}, _Hash = _Hash(), _Pred = _Pred(), _Allocator = _Allocator()) -> unordered_map<__iter_key_t<_InputIterator>, __iter_val_t<_InputIterator>, _Hash, _Pred, _Allocator>; template<typename _Key, typename _Tp, typename _Hash = hash<_Key>, typename _Pred = equal_to<_Key>, typename _Allocator = allocator<pair<const _Key, _Tp>>, typename = _RequireAllocator<_Allocator>> unordered_map(initializer_list<pair<_Key, _Tp>>, typename unordered_map<int, int>::size_type = {}, _Hash = _Hash(), _Pred = _Pred(), _Allocator = _Allocator()) -> unordered_map<_Key, _Tp, _Hash, _Pred, _Allocator>; template<typename _InputIterator, typename _Allocator, typename = _RequireInputIter<_InputIterator>, typename = _RequireAllocator<_Allocator>> unordered_map(_InputIterator, _InputIterator, typename unordered_map<int, int>::size_type, _Allocator) -> unordered_map<__iter_key_t<_InputIterator>, __iter_val_t<_InputIterator>, hash<__iter_key_t<_InputIterator>>, equal_to<__iter_key_t<_InputIterator>>, _Allocator>; template<typename _InputIterator, typename _Allocator, typename = _RequireInputIter<_InputIterator>, typename = _RequireAllocator<_Allocator>> unordered_map(_InputIterator, _InputIterator, _Allocator) -> unordered_map<__iter_key_t<_InputIterator>, __iter_val_t<_InputIterator>, hash<__iter_key_t<_InputIterator>>, equal_to<__iter_key_t<_InputIterator>>, _Allocator>; template<typename _InputIterator, typename _Hash, typename _Allocator, typename = _RequireInputIter<_InputIterator>, typename = _RequireAllocator<_Allocator>> unordered_map(_InputIterator, _InputIterator, typename unordered_map<int, int>::size_type, _Hash, _Allocator) -> unordered_map<__iter_key_t<_InputIterator>, __iter_val_t<_InputIterator>, _Hash, equal_to<__iter_key_t<_InputIterator>>, _Allocator>; template<typename _Key, typename _Tp, typename _Allocator, typename = _RequireAllocator<_Allocator>> unordered_map(initializer_list<pair<_Key, _Tp>>, typename unordered_map<int, int>::size_type, _Allocator) -> unordered_map<_Key, _Tp, hash<_Key>, equal_to<_Key>, _Allocator>; template<typename _Key, typename _Tp, typename _Allocator, typename = _RequireAllocator<_Allocator>> unordered_map(initializer_list<pair<_Key, _Tp>>, _Allocator) -> unordered_map<_Key, _Tp, hash<_Key>, equal_to<_Key>, _Allocator>; template<typename _Key, typename _Tp, typename _Hash, typename _Allocator, typename = _RequireAllocator<_Allocator>> unordered_map(initializer_list<pair<_Key, _Tp>>, typename unordered_map<int, int>::size_type, _Hash, _Allocator) -> unordered_map<_Key, _Tp, _Hash, equal_to<_Key>, _Allocator>; #endif /* * @brief A standard container composed of equivalent keys * (possibly containing multiple of each key value) that associates * values of another type with the keys. * * @ingroup unordered_associative_containers * * @tparam _Key Type of key objects. * @tparam _Tp Type of mapped objects. * @tparam _Hash Hashing function object type, defaults to hash<_Value>. * @tparam _Pred Predicate function object type, defaults * to equal_to<_Value>. * @tparam _Alloc Allocator type, defaults to * std::allocator<std::pair<const _Key, _Tp>>. * * Meets the requirements of a <a href="tables.html#65">container</a>, and * <a href="tables.html#xx">unordered associative container</a> * * The resulting value type of the container is std::pair<const _Key, _Tp>. * * Base is _Hashtable, dispatched at compile time via template * alias __ummap_hashtable. / template<typename _Key, typename _Tp, typename _Hash = hash<_Key>, typename _Pred = equal_to<_Key>, typename _Alloc = allocator<std::pair<const _Key, _Tp>>> class unordered_multimap { typedef __ummap_hashtable<_Key, _Tp, _Hash, _Pred, _Alloc> _Hashtable; _Hashtable _M_h; public: // typedefs: //@{ /// Public typedefs. typedef typename _Hashtable::key_type key_type; typedef typename _Hashtable::value_type value_type; typedef typename _Hashtable::mapped_type mapped_type; typedef typename _Hashtable::hasher hasher; typedef typename _Hashtable::key_equal key_equal; typedef typename _Hashtable::allocator_type allocator_type; //@} //@{ /// Iterator-related typedefs. typedef typename _Hashtable::pointer pointer; typedef typename _Hashtable::const_pointer const_pointer; typedef typename _Hashtable::reference reference; typedef typename _Hashtable::const_reference const_reference; typedef typename _Hashtable::iterator iterator; typedef typename _Hashtable::const_iterator const_iterator; typedef typename _Hashtable::local_iterator local_iterator; typedef typename _Hashtable::const_local_iterator const_local_iterator; typedef typename _Hashtable::size_type size_type; typedef typename _Hashtable::difference_type difference_type; //@} #if __cplusplus > 201402L using node_type = typename _Hashtable::node_type; #endif //construct/destroy/copy /// Default constructor. unordered_multimap() = default; /* * @brief Default constructor creates no elements. * @param __n Mnimal initial number of buckets. * @param __hf A hash functor. * @param __eql A key equality functor. * @param __a An allocator object. / explicit unordered_multimap(size_type __n, const hasher& __hf = hasher(), const key_equal& __eql = key_equal(), const allocator_type& __a = allocator_type()) : _M_h(__n, __hf, __eql, __a) { } /* * @brief Builds an %unordered_multimap from a range. * @param __first An input iterator. * @param __last An input iterator. * @param __n Minimal initial number of buckets. * @param __hf A hash functor. * @param __eql A key equality functor. * @param __a An allocator object. * * Create an %unordered_multimap consisting of copies of the elements * from [__first,__last). This is linear in N (where N is * distance(__first,__last)). / template<typename _InputIterator> unordered_multimap(_InputIterator __first, _InputIterator __last, size_type __n = 0, const hasher& __hf = hasher(), const key_equal& __eql = key_equal(), const allocator_type& __a = allocator_type()) : _M_h(__first, __last, __n, __hf, __eql, __a) { } /// Copy constructor. unordered_multimap(const unordered_multimap&) = default; /// Move constructor. unordered_multimap(unordered_multimap&&) = default; /* * @brief Creates an %unordered_multimap with no elements. * @param __a An allocator object. / explicit unordered_multimap(const allocator_type& __a) : _M_h(__a) { } / * @brief Copy constructor with allocator argument. * @param __uset Input %unordered_multimap to copy. * @param __a An allocator object. / unordered_multimap(const unordered_multimap& __ummap, const allocator_type& __a) : _M_h(__ummap._M_h, __a) { } / * @brief Move constructor with allocator argument. * @param __uset Input %unordered_multimap to move. * @param __a An allocator object. / unordered_multimap(unordered_multimap&& __ummap, const allocator_type& __a) : _M_h(std::move(__ummap._M_h), __a) { } /* * @brief Builds an %unordered_multimap from an initializer_list. * @param __l An initializer_list. * @param __n Minimal initial number of buckets. * @param __hf A hash functor. * @param __eql A key equality functor. * @param __a An allocator object. * * Create an %unordered_multimap consisting of copies of the elements in * the list. This is linear in N (where N is @a __l.size()). / unordered_multimap(initializer_list<value_type> __l, size_type __n = 0, const hasher& __hf = hasher(), const key_equal& __eql = key_equal(), const allocator_type& __a = allocator_type()) : _M_h(__l, __n, __hf, __eql, __a) { } unordered_multimap(size_type __n, const allocator_type& __a) : unordered_multimap(__n, hasher(), key_equal(), __a) { } unordered_multimap(size_type __n, const hasher& __hf, const allocator_type& __a) : unordered_multimap(__n, __hf, key_equal(), __a) { } template<typename _InputIterator> unordered_multimap(_InputIterator __first, _InputIterator __last, size_type __n, const allocator_type& __a) : unordered_multimap(__first, __last, __n, hasher(), key_equal(), __a) { } template<typename _InputIterator> unordered_multimap(_InputIterator __first, _InputIterator __last, size_type __n, const hasher& __hf, const allocator_type& __a) : unordered_multimap(__first, __last, __n, __hf, key_equal(), __a) { } unordered_multimap(initializer_list<value_type> __l, size_type __n, const allocator_type& __a) : unordered_multimap(__l, __n, hasher(), key_equal(), __a) { } unordered_multimap(initializer_list<value_type> __l, size_type __n, const hasher& __hf, const allocator_type& __a) : unordered_multimap(__l, __n, __hf, key_equal(), __a) { } /// Copy assignment operator. unordered_multimap& operator=(const unordered_multimap&) = default; /// Move assignment operator. unordered_multimap& operator=(unordered_multimap&&) = default; /* * @brief %Unordered_multimap list assignment operator. * @param __l An initializer_list. * * This function fills an %unordered_multimap with copies of the * elements in the initializer list @a __l. * * Note that the assignment completely changes the %unordered_multimap * and that the resulting %unordered_multimap's size is the same as the * number of elements assigned. / unordered_multimap& operator=(initializer_list<value_type> __l) { _M_h = __l; return this; } /// Returns the allocator object used by the %unordered_multimap. allocator_type get_allocator() const noexcept { return _M_h.get_allocator(); } // size and capacity: /// Returns true if the %unordered_multimap is empty. bool empty() const noexcept { return _M_h.empty(); } /// Returns the size of the %unordered_multimap. size_type size() const noexcept { return _M_h.size(); } /// Returns the maximum size of the %unordered_multimap. size_type max_size() const noexcept { return _M_h.max_size(); } // iterators. /** * Returns a read/write iterator that points to the first element in the * %unordered_multimap. / iterator begin() noexcept { return _M_h.begin(); } //@{ /* * Returns a read-only (constant) iterator that points to the first * element in the %unordered_multimap. / const_iterator begin() const noexcept { return _M_h.begin(); } const_iterator cbegin() const noexcept { return _M_h.begin(); } //@} /* * Returns a read/write iterator that points one past the last element in * the %unordered_multimap. / iterator end() noexcept { return _M_h.end(); } //@{ /* * Returns a read-only (constant) iterator that points one past the last * element in the %unordered_multimap. / const_iterator end() const noexcept { return _M_h.end(); } const_iterator cend() const noexcept { return _M_h.end(); } //@} // modifiers. /* * @brief Attempts to build and insert a std::pair into the * %unordered_multimap. * * @param __args Arguments used to generate a new pair instance (see * std::piecewise_contruct for passing arguments to each * part of the pair constructor). * * @return An iterator that points to the inserted pair. * * This function attempts to build and insert a (key, value) %pair into * the %unordered_multimap. * * Insertion requires amortized constant time. / template<typename... _Args> iterator emplace(_Args&&... __args) { return _M_h.emplace(std::forward<_Args>(__args)...); } /* * @brief Attempts to build and insert a std::pair into the * %unordered_multimap. * * @param __pos An iterator that serves as a hint as to where the pair * should be inserted. * @param __args Arguments used to generate a new pair instance (see * std::piecewise_contruct for passing arguments to each * part of the pair constructor). * @return An iterator that points to the element with key of the * std::pair built from @a __args. * * Note that the first parameter is only a hint and can potentially * improve the performance of the insertion process. A bad hint would * cause no gains in efficiency. * * See * https://gcc.gnu.org/onlinedocs/libstdc++/manual/associative.html#containers.associative.insert_hints * for more on @a hinting. * * Insertion requires amortized constant time. / template<typename... _Args> iterator emplace_hint(const_iterator __pos, _Args&&... __args) { return _M_h.emplace_hint(__pos, std::forward<_Args>(__args)...); } //@{ /* * @brief Inserts a std::pair into the %unordered_multimap. * @param __x Pair to be inserted (see std::make_pair for easy * creation of pairs). * * @return An iterator that points to the inserted pair. * * Insertion requires amortized constant time. / iterator insert(const value_type& __x) { return _M_h.insert(__x); } iterator insert(value_type&& __x) { return _M_h.insert(std::move(__x)); } template<typename _Pair> __enable_if_t<is_constructible<value_type, _Pair&&>::value, iterator> insert(_Pair&& __x) { return _M_h.emplace(std::forward<_Pair>(__x)); } //@} //@{ /* * @brief Inserts a std::pair into the %unordered_multimap. * @param __hint An iterator that serves as a hint as to where the * pair should be inserted. * @param __x Pair to be inserted (see std::make_pair for easy creation * of pairs). * @return An iterator that points to the element with key of * @a __x (may or may not be the %pair passed in). * * Note that the first parameter is only a hint and can potentially * improve the performance of the insertion process. A bad hint would * cause no gains in efficiency. * * See * https://gcc.gnu.org/onlinedocs/libstdc++/manual/associative.html#containers.associative.insert_hints * for more on @a hinting. * * Insertion requires amortized constant time. / iterator insert(const_iterator __hint, const value_type& __x) { return _M_h.insert(__hint, __x); } // _GLIBCXX_RESOLVE_LIB_DEFECTS // 2354. Unnecessary copying when inserting into maps with braced-init iterator insert(const_iterator __hint, value_type&& __x) { return _M_h.insert(__hint, std::move(__x)); } template<typename _Pair> __enable_if_t<is_constructible<value_type, _Pair&&>::value, iterator> insert(const_iterator __hint, _Pair&& __x) { return _M_h.emplace_hint(__hint, std::forward<_Pair>(__x)); } //@} /* * @brief A template function that attempts to insert a range of * elements. * @param __first Iterator pointing to the start of the range to be * inserted. * @param __last Iterator pointing to the end of the range. * * Complexity similar to that of the range constructor. / template<typename _InputIterator> void insert(_InputIterator __first, _InputIterator __last) { _M_h.insert(__first, __last); } /* * @brief Attempts to insert a list of elements into the * %unordered_multimap. * @param __l A std::initializer_list<value_type> of elements * to be inserted. * * Complexity similar to that of the range constructor. / void insert(initializer_list<value_type> __l) { _M_h.insert(__l); } #if __cplusplus > 201402L /// Extract a node. node_type extract(const_iterator __pos) { __glibcxx_assert(__pos != end()); return _M_h.extract(__pos); } /// Extract a node. node_type extract(const key_type& __key) { return _M_h.extract(__key); } /// Re-insert an extracted node. iterator insert(node_type&& __nh) { return _M_h._M_reinsert_node_multi(cend(), std::move(__nh)); } /// Re-insert an extracted node. iterator insert(const_iterator __hint, node_type&& __nh) { return _M_h._M_reinsert_node_multi(__hint, std::move(__nh)); } #endif // C++17 //@{ /* * @brief Erases an element from an %unordered_multimap. * @param __position An iterator pointing to the element to be erased. * @return An iterator pointing to the element immediately following * @a __position prior to the element being erased. If no such * element exists, end() is returned. * * This function erases an element, pointed to by the given iterator, * from an %unordered_multimap. * Note that this function only erases the element, and that if the * element is itself a pointer, the pointed-to memory is not touched in * any way. Managing the pointer is the user's responsibility. / iterator erase(const_iterator __position) { return _M_h.erase(__position); } // LWG 2059. iterator erase(iterator __position) { return _M_h.erase(__position); } //@} /* * @brief Erases elements according to the provided key. * @param __x Key of elements to be erased. * @return The number of elements erased. * * This function erases all the elements located by the given key from * an %unordered_multimap. * Note that this function only erases the element, and that if the * element is itself a pointer, the pointed-to memory is not touched in * any way. Managing the pointer is the user's responsibility. / size_type erase(const key_type& __x) { return _M_h.erase(__x); } /* * @brief Erases a [__first,__last) range of elements from an * %unordered_multimap. * @param __first Iterator pointing to the start of the range to be * erased. * @param __last Iterator pointing to the end of the range to * be erased. * @return The iterator @a __last. * * This function erases a sequence of elements from an * %unordered_multimap. * Note that this function only erases the elements, and that if * the element is itself a pointer, the pointed-to memory is not touched * in any way. Managing the pointer is the user's responsibility. / iterator erase(const_iterator __first, const_iterator __last) { return _M_h.erase(__first, __last); } /* * Erases all elements in an %unordered_multimap. * Note that this function only erases the elements, and that if the * elements themselves are pointers, the pointed-to memory is not touched * in any way. Managing the pointer is the user's responsibility. / void clear() noexcept { _M_h.clear(); } /* * @brief Swaps data with another %unordered_multimap. * @param __x An %unordered_multimap of the same element and allocator * types. * * This exchanges the elements between two %unordered_multimap in * constant time. * Note that the global std::swap() function is specialized such that * std::swap(m1,m2) will feed to this function. / void swap(unordered_multimap& __x) noexcept( noexcept(_M_h.swap(__x._M_h)) ) { _M_h.swap(__x._M_h); } #if __cplusplus > 201402L template<typename, typename, typename> friend class std::_Hash_merge_helper; template<typename _H2, typename _P2> void merge(unordered_multimap<_Key, _Tp, _H2, _P2, _Alloc>& __source) { using _Merge_helper = _Hash_merge_helper<unordered_multimap, _H2, _P2>; _M_h._M_merge_multi(_Merge_helper::_S_get_table(__source)); } template<typename _H2, typename _P2> void merge(unordered_multimap<_Key, _Tp, _H2, _P2, _Alloc>&& __source) { merge(__source); } template<typename _H2, typename _P2> void merge(unordered_map<_Key, _Tp, _H2, _P2, _Alloc>& __source) { using _Merge_helper = _Hash_merge_helper<unordered_multimap, _H2, _P2>; _M_h._M_merge_multi(_Merge_helper::_S_get_table(__source)); } template<typename _H2, typename _P2> void merge(unordered_map<_Key, _Tp, _H2, _P2, _Alloc>&& __source) { merge(__source); } #endif // C++17 // observers. /// Returns the hash functor object with which the %unordered_multimap /// was constructed. hasher hash_function() const { return _M_h.hash_function(); } /// Returns the key comparison object with which the %unordered_multimap /// was constructed. key_equal key_eq() const { return _M_h.key_eq(); } // lookup. //@{ /* * @brief Tries to locate an element in an %unordered_multimap. * @param __x Key to be located. * @return Iterator pointing to sought-after element, or end() if not * found. * * This function takes a key and tries to locate the element with which * the key matches. If successful the function returns an iterator * pointing to the sought after element. If unsuccessful it returns the * past-the-end ( @c end() ) iterator. / iterator find(const key_type& __x) { return _M_h.find(__x); } const_iterator find(const key_type& __x) const { return _M_h.find(__x); } //@} /* * @brief Finds the number of elements. * @param __x Key to count. * @return Number of elements with specified key. / size_type count(const key_type& __x) const { return _M_h.count(__x); } //@{ /* * @brief Finds a subsequence matching given key. * @param __x Key to be located. * @return Pair of iterators that possibly points to the subsequence * matching given key. / std::pair<iterator, iterator> equal_range(const key_type& __x) { return _M_h.equal_range(__x); } std::pair<const_iterator, const_iterator> equal_range(const key_type& __x) const { return _M_h.equal_range(__x); } //@} // bucket interface. /// Returns the number of buckets of the %unordered_multimap. size_type bucket_count() const noexcept { return _M_h.bucket_count(); } /// Returns the maximum number of buckets of the %unordered_multimap. size_type max_bucket_count() const noexcept { return _M_h.max_bucket_count(); } / * @brief Returns the number of elements in a given bucket. * @param __n A bucket index. * @return The number of elements in the bucket. / size_type bucket_size(size_type __n) const { return _M_h.bucket_size(__n); } / * @brief Returns the bucket index of a given element. * @param __key A key instance. * @return The key bucket index. / size_type bucket(const key_type& __key) const { return _M_h.bucket(__key); } /* * @brief Returns a read/write iterator pointing to the first bucket * element. * @param __n The bucket index. * @return A read/write local iterator. / local_iterator begin(size_type __n) { return _M_h.begin(__n); } //@{ /* * @brief Returns a read-only (constant) iterator pointing to the first * bucket element. * @param __n The bucket index. * @return A read-only local iterator. / const_local_iterator begin(size_type __n) const { return _M_h.begin(__n); } const_local_iterator cbegin(size_type __n) const { return _M_h.cbegin(__n); } //@} /* * @brief Returns a read/write iterator pointing to one past the last * bucket elements. * @param __n The bucket index. * @return A read/write local iterator. / local_iterator end(size_type __n) { return _M_h.end(__n); } //@{ /* * @brief Returns a read-only (constant) iterator pointing to one past * the last bucket elements. * @param __n The bucket index. * @return A read-only local iterator. / const_local_iterator end(size_type __n) const { return _M_h.end(__n); } const_local_iterator cend(size_type __n) const { return _M_h.cend(__n); } //@} // hash policy. /// Returns the average number of elements per bucket. float load_factor() const noexcept { return _M_h.load_factor(); } /// Returns a positive number that the %unordered_multimap tries to keep /// the load factor less than or equal to. float max_load_factor() const noexcept { return _M_h.max_load_factor(); } /* * @brief Change the %unordered_multimap maximum load factor. * @param __z The new maximum load factor. / void max_load_factor(float __z) { _M_h.max_load_factor(__z); } /* * @brief May rehash the %unordered_multimap. * @param __n The new number of buckets. * * Rehash will occur only if the new number of buckets respect the * %unordered_multimap maximum load factor. / void rehash(size_type __n) { _M_h.rehash(__n); } /* * @brief Prepare the %unordered_multimap for a specified number of * elements. * @param __n Number of elements required. * * Same as rehash(ceil(n / max_load_factor())). / void reserve(size_type __n) { _M_h.reserve(__n); } template<typename _Key1, typename _Tp1, typename _Hash1, typename _Pred1, typename _Alloc1> friend bool operator==(const unordered_multimap<_Key1, _Tp1, _Hash1, _Pred1, _Alloc1>&, const unordered_multimap<_Key1, _Tp1, _Hash1, _Pred1, _Alloc1>&); }; #if __cpp_deduction_guides >= 201606 template<typename _InputIterator, typename _Hash = hash<__iter_key_t<_InputIterator>>, typename _Pred = equal_to<__iter_key_t<_InputIterator>>, typename _Allocator = allocator<__iter_to_alloc_t<_InputIterator>>, typename = _RequireInputIter<_InputIterator>, typename = _RequireAllocator<_Allocator>> unordered_multimap(_InputIterator, _InputIterator, unordered_multimap<int, int>::size_type = {}, _Hash = _Hash(), _Pred = _Pred(), _Allocator = _Allocator()) -> unordered_multimap<__iter_key_t<_InputIterator>, __iter_val_t<_InputIterator>, _Hash, _Pred, _Allocator>; template<typename _Key, typename _Tp, typename _Hash = hash<_Key>, typename _Pred = equal_to<_Key>, typename _Allocator = allocator<pair<const _Key, _Tp>>, typename = _RequireAllocator<_Allocator>> unordered_multimap(initializer_list<pair<_Key, _Tp>>, unordered_multimap<int, int>::size_type = {}, _Hash = _Hash(), _Pred = _Pred(), _Allocator = _Allocator()) -> unordered_multimap<_Key, _Tp, _Hash, _Pred, _Allocator>; template<typename _InputIterator, typename _Allocator, typename = _RequireInputIter<_InputIterator>, typename = _RequireAllocator<_Allocator>> unordered_multimap(_InputIterator, _InputIterator, unordered_multimap<int, int>::size_type, _Allocator) -> unordered_multimap<__iter_key_t<_InputIterator>, __iter_val_t<_InputIterator>, hash<__iter_key_t<_InputIterator>>, equal_to<__iter_key_t<_InputIterator>>, _Allocator>; template<typename _InputIterator, typename _Allocator, typename = _RequireInputIter<_InputIterator>, typename = _RequireAllocator<_Allocator>> unordered_multimap(_InputIterator, _InputIterator, _Allocator) -> unordered_multimap<__iter_key_t<_InputIterator>, __iter_val_t<_InputIterator>, hash<__iter_key_t<_InputIterator>>, equal_to<__iter_key_t<_InputIterator>>, _Allocator>; template<typename _InputIterator, typename _Hash, typename _Allocator, typename = _RequireInputIter<_InputIterator>, typename = _RequireAllocator<_Allocator>> unordered_multimap(_InputIterator, _InputIterator, unordered_multimap<int, int>::size_type, _Hash, _Allocator) -> unordered_multimap<__iter_key_t<_InputIterator>, __iter_val_t<_InputIterator>, _Hash, equal_to<__iter_key_t<_InputIterator>>, _Allocator>; template<typename _Key, typename _Tp, typename _Allocator, typename = _RequireAllocator<_Allocator>> unordered_multimap(initializer_list<pair<_Key, _Tp>>, unordered_multimap<int, int>::size_type, _Allocator) -> unordered_multimap<_Key, _Tp, hash<_Key>, equal_to<_Key>, _Allocator>; template<typename _Key, typename _Tp, typename _Allocator, typename = _RequireAllocator<_Allocator>> unordered_multimap(initializer_list<pair<_Key, _Tp>>, _Allocator) -> unordered_multimap<_Key, _Tp, hash<_Key>, equal_to<_Key>, _Allocator>; template<typename _Key, typename _Tp, typename _Hash, typename _Allocator, typename = _RequireAllocator<_Allocator>> unordered_multimap(initializer_list<pair<_Key, _Tp>>, unordered_multimap<int, int>::size_type, _Hash, _Allocator) -> unordered_multimap<_Key, _Tp, _Hash, equal_to<_Key>, _Allocator>; #endif template<class _Key, class _Tp, class _Hash, class _Pred, class _Alloc> inline void swap(unordered_map<_Key, _Tp, _Hash, _Pred, _Alloc>& __x, unordered_map<_Key, _Tp, _Hash, _Pred, _Alloc>& __y) noexcept(noexcept(__x.swap(__y))) { __x.swap(__y); } template<class _Key, class _Tp, class _Hash, class _Pred, class _Alloc> inline void swap(unordered_multimap<_Key, _Tp, _Hash, _Pred, _Alloc>& __x, unordered_multimap<_Key, _Tp, _Hash, _Pred, _Alloc>& __y) noexcept(noexcept(__x.swap(__y))) { __x.swap(__y); } template<class _Key, class _Tp, class _Hash, class _Pred, class _Alloc> inline bool operator==(const unordered_map<_Key, _Tp, _Hash, _Pred, _Alloc>& __x, const unordered_map<_Key, _Tp, _Hash, _Pred, _Alloc>& __y) { return __x._M_h._M_equal(__y._M_h); } template<class _Key, class _Tp, class _Hash, class _Pred, class _Alloc> inline bool operator!=(const unordered_map<_Key, _Tp, _Hash, _Pred, _Alloc>& __x, const unordered_map<_Key, _Tp, _Hash, _Pred, _Alloc>& __y) { return !(__x == __y); } template<class _Key, class _Tp, class _Hash, class _Pred, class _Alloc> inline bool operator==(const unordered_multimap<_Key, _Tp, _Hash, _Pred, _Alloc>& __x, const unordered_multimap<_Key, _Tp, _Hash, _Pred, _Alloc>& __y) { return __x._M_h._M_equal(__y._M_h); } template<class _Key, class _Tp, class _Hash, class _Pred, class _Alloc> inline bool operator!=(const unordered_multimap<_Key, _Tp, _Hash, _Pred, _Alloc>& __x, const unordered_multimap<_Key, _Tp, _Hash, _Pred, _Alloc>& __y) { return !(__x == __y); } _GLIBCXX_END_NAMESPACE_CONTAINER #if __cplusplus > 201402L // Allow std::unordered_map access to internals of compatible maps. template<typename _Key, typename _Val, typename _Hash1, typename _Eq1, typename _Alloc, typename _Hash2, typename _Eq2> struct _Hash_merge_helper< _GLIBCXX_STD_C::unordered_map<_Key, _Val, _Hash1, _Eq1, _Alloc>, _Hash2, _Eq2> { private: template<typename... _Tp> using unordered_map = _GLIBCXX_STD_C::unordered_map<_Tp...>; template<typename... _Tp> using unordered_multimap = _GLIBCXX_STD_C::unordered_multimap<_Tp...>; friend unordered_map<_Key, _Val, _Hash1, _Eq1, _Alloc>; static auto& _S_get_table(unordered_map<_Key, _Val, _Hash2, _Eq2, _Alloc>& __map) { return __map._M_h; } static auto& _S_get_table(unordered_multimap<_Key, _Val, _Hash2, _Eq2, _Alloc>& __map) { return __map._M_h; } }; // Allow std::unordered_multimap access to internals of compatible maps. template<typename _Key, typename _Val, typename _Hash1, typename _Eq1, typename _Alloc, typename _Hash2, typename _Eq2> struct _Hash_merge_helper< _GLIBCXX_STD_C::unordered_multimap<_Key, _Val, _Hash1, _Eq1, _Alloc>, _Hash2, _Eq2> { private: template<typename... _Tp> using unordered_map = _GLIBCXX_STD_C::unordered_map<_Tp...>; template<typename... _Tp> using unordered_multimap = _GLIBCXX_STD_C::unordered_multimap<_Tp...>; friend unordered_multimap<_Key, _Val, _Hash1, _Eq1, _Alloc>; static auto& _S_get_table(unordered_map<_Key, _Val, _Hash2, _Eq2, _Alloc>& __map) { return __map._M_h; } static auto& _S_get_table(unordered_multimap<_Key, _Val, _Hash2, _Eq2, _Alloc>& __map) { return __map._M_h; } }; #endif // C++17 _GLIBCXX_END_NAMESPACE_VERSION } // namespace std #endif / _UNORDERED_MAP_H */ Back

Edit File : unordered_map.h | Size : 73.58 KB

// unordered_map implementation -*- C++ -*-

// Copyright (C) 2010-2018 Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library.  This library is free
// software; you can redistribute it and/or modify it under the
// terms of the GNU General Public License as published by the
// Free Software Foundation; either version 3, or (at your option)
// any later version.

// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

// Under Section 7 of GPL version 3, you are granted additional
// permissions described in the GCC Runtime Library Exception, version
// 3.1, as published by the Free Software Foundation.

// You should have received a copy of the GNU General Public License and
// a copy of the GCC Runtime Library Exception along with this program;
// see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
// <http://www.gnu.org/licenses/>.

/** @file bits/unordered_map.h
 *  This is an internal header file, included by other library headers.
 *  Do not attempt to use it directly. @headername{unordered_map}
 */

#ifndef _UNORDERED_MAP_H
#define _UNORDERED_MAP_H

namespace std _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION
_GLIBCXX_BEGIN_NAMESPACE_CONTAINER

/// Base types for unordered_map.
  template<bool _Cache>
    using __umap_traits = __detail::_Hashtable_traits<_Cache, false, true>;

template<typename _Key,
	   typename _Tp,
	   typename _Hash = hash<_Key>,
	   typename _Pred = std::equal_to<_Key>,
	   typename _Alloc = std::allocator<std::pair<const _Key, _Tp> >,
	   typename _Tr = __umap_traits<__cache_default<_Key, _Hash>::value>>
    using __umap_hashtable = _Hashtable<_Key, std::pair<const _Key, _Tp>,
                                        _Alloc, __detail::_Select1st,
				        _Pred, _Hash,
				        __detail::_Mod_range_hashing,
				        __detail::_Default_ranged_hash,
				        __detail::_Prime_rehash_policy, _Tr>;

/// Base types for unordered_multimap.
  template<bool _Cache>
    using __ummap_traits = __detail::_Hashtable_traits<_Cache, false, false>;

template<typename _Key,
	   typename _Tp,
	   typename _Hash = hash<_Key>,
	   typename _Pred = std::equal_to<_Key>,
	   typename _Alloc = std::allocator<std::pair<const _Key, _Tp> >,
	   typename _Tr = __ummap_traits<__cache_default<_Key, _Hash>::value>>
    using __ummap_hashtable = _Hashtable<_Key, std::pair<const _Key, _Tp>,
					 _Alloc, __detail::_Select1st,
					 _Pred, _Hash,
					 __detail::_Mod_range_hashing,
					 __detail::_Default_ranged_hash,
					 __detail::_Prime_rehash_policy, _Tr>;

template<class _Key, class _Tp, class _Hash, class _Pred, class _Alloc>
    class unordered_multimap;

/**
   *  @brief A standard container composed of unique keys (containing
   *  at most one of each key value) that associates values of another type
   *  with the keys.
   *
   *  @ingroup unordered_associative_containers
   *
   *  @tparam  _Key    Type of key objects.
   *  @tparam  _Tp     Type of mapped objects.
   *  @tparam  _Hash   Hashing function object type, defaults to hash<_Value>.
   *  @tparam  _Pred   Predicate function object type, defaults
   *                   to equal_to<_Value>.
   *  @tparam  _Alloc  Allocator type, defaults to 
   *                   std::allocator<std::pair<const _Key, _Tp>>.
   *
   *  Meets the requirements of a <a href="tables.html#65">container</a>, and
   *  <a href="tables.html#xx">unordered associative container</a>
   *
   * The resulting value type of the container is std::pair<const _Key, _Tp>.
   *
   *  Base is _Hashtable, dispatched at compile time via template
   *  alias __umap_hashtable.
   */
  template<typename _Key, typename _Tp,
	   typename _Hash = hash<_Key>,
	   typename _Pred = equal_to<_Key>,
	   typename _Alloc = allocator<std::pair<const _Key, _Tp>>>
    class unordered_map
    {
      typedef __umap_hashtable<_Key, _Tp, _Hash, _Pred, _Alloc>  _Hashtable;
      _Hashtable _M_h;

public:
      // typedefs:
      //@{
      /// Public typedefs.
      typedef typename _Hashtable::key_type	key_type;
      typedef typename _Hashtable::value_type	value_type;
      typedef typename _Hashtable::mapped_type	mapped_type;
      typedef typename _Hashtable::hasher	hasher;
      typedef typename _Hashtable::key_equal	key_equal;
      typedef typename _Hashtable::allocator_type allocator_type;
      //@}

//@{
      ///  Iterator-related typedefs.
      typedef typename _Hashtable::pointer		pointer;
      typedef typename _Hashtable::const_pointer	const_pointer;
      typedef typename _Hashtable::reference		reference;
      typedef typename _Hashtable::const_reference	const_reference;
      typedef typename _Hashtable::iterator		iterator;
      typedef typename _Hashtable::const_iterator	const_iterator;
      typedef typename _Hashtable::local_iterator	local_iterator;
      typedef typename _Hashtable::const_local_iterator	const_local_iterator;
      typedef typename _Hashtable::size_type		size_type;
      typedef typename _Hashtable::difference_type	difference_type;
      //@}

#if __cplusplus > 201402L
      using node_type = typename _Hashtable::node_type;
      using insert_return_type = typename _Hashtable::insert_return_type;
#endif

//construct/destroy/copy

/// Default constructor.
      unordered_map() = default;

/**
       *  @brief  Default constructor creates no elements.
       *  @param __n  Minimal initial number of buckets.
       *  @param __hf  A hash functor.
       *  @param __eql  A key equality functor.
       *  @param __a  An allocator object.
       */
      explicit
      unordered_map(size_type __n,
		    const hasher& __hf = hasher(),
		    const key_equal& __eql = key_equal(),
		    const allocator_type& __a = allocator_type())
      : _M_h(__n, __hf, __eql, __a)
      { }

/**
       *  @brief  Builds an %unordered_map from a range.
       *  @param  __first  An input iterator.
       *  @param  __last  An input iterator.
       *  @param __n  Minimal initial number of buckets.
       *  @param __hf  A hash functor.
       *  @param __eql  A key equality functor.
       *  @param __a  An allocator object.
       *
       *  Create an %unordered_map consisting of copies of the elements from
       *  [__first,__last).  This is linear in N (where N is
       *  distance(__first,__last)).
       */
      template<typename _InputIterator>
	unordered_map(_InputIterator __first, _InputIterator __last,
		      size_type __n = 0,
		      const hasher& __hf = hasher(),
		      const key_equal& __eql = key_equal(),
		      const allocator_type& __a = allocator_type())
	: _M_h(__first, __last, __n, __hf, __eql, __a)
	{ }

/// Copy constructor.
      unordered_map(const unordered_map&) = default;

/// Move constructor.
      unordered_map(unordered_map&&) = default;

/**
       *  @brief Creates an %unordered_map with no elements.
       *  @param __a An allocator object.
       */
      explicit
      unordered_map(const allocator_type& __a)
	: _M_h(__a)
      { }

/*
       *  @brief Copy constructor with allocator argument.
       * @param  __uset  Input %unordered_map to copy.
       * @param  __a  An allocator object.
       */
      unordered_map(const unordered_map& __umap,
		    const allocator_type& __a)
      : _M_h(__umap._M_h, __a)
      { }

/*
       *  @brief  Move constructor with allocator argument.
       *  @param  __uset Input %unordered_map to move.
       *  @param  __a    An allocator object.
       */
      unordered_map(unordered_map&& __umap,
		    const allocator_type& __a)
      : _M_h(std::move(__umap._M_h), __a)
      { }

/**
       *  @brief  Builds an %unordered_map from an initializer_list.
       *  @param  __l  An initializer_list.
       *  @param __n  Minimal initial number of buckets.
       *  @param __hf  A hash functor.
       *  @param __eql  A key equality functor.
       *  @param  __a  An allocator object.
       *
       *  Create an %unordered_map consisting of copies of the elements in the
       *  list. This is linear in N (where N is @a __l.size()).
       */
      unordered_map(initializer_list<value_type> __l,
		    size_type __n = 0,
		    const hasher& __hf = hasher(),
		    const key_equal& __eql = key_equal(),
		    const allocator_type& __a = allocator_type())
      : _M_h(__l, __n, __hf, __eql, __a)
      { }

unordered_map(size_type __n, const allocator_type& __a)
      : unordered_map(__n, hasher(), key_equal(), __a)
      { }

unordered_map(size_type __n, const hasher& __hf,
		    const allocator_type& __a)
      : unordered_map(__n, __hf, key_equal(), __a)
      { }

template<typename _InputIterator>
	unordered_map(_InputIterator __first, _InputIterator __last,
		      size_type __n,
		      const allocator_type& __a)
	: unordered_map(__first, __last, __n, hasher(), key_equal(), __a)
	{ }

template<typename _InputIterator>
	unordered_map(_InputIterator __first, _InputIterator __last,
		      size_type __n, const hasher& __hf,
		      const allocator_type& __a)
	  : unordered_map(__first, __last, __n, __hf, key_equal(), __a)
	{ }

unordered_map(initializer_list<value_type> __l,
		    size_type __n,
		    const allocator_type& __a)
      : unordered_map(__l, __n, hasher(), key_equal(), __a)
      { }

unordered_map(initializer_list<value_type> __l,
		    size_type __n, const hasher& __hf,
		    const allocator_type& __a)
      : unordered_map(__l, __n, __hf, key_equal(), __a)
      { }

/// Copy assignment operator.
      unordered_map&
      operator=(const unordered_map&) = default;

/// Move assignment operator.
      unordered_map&
      operator=(unordered_map&&) = default;

/**
       *  @brief  %Unordered_map list assignment operator.
       *  @param  __l  An initializer_list.
       *
       *  This function fills an %unordered_map with copies of the elements in
       *  the initializer list @a __l.
       *
       *  Note that the assignment completely changes the %unordered_map and
       *  that the resulting %unordered_map's size is the same as the number
       *  of elements assigned.
       */
      unordered_map&
      operator=(initializer_list<value_type> __l)
      {
	_M_h = __l;
	return *this;
      }

///  Returns the allocator object used by the %unordered_map.
      allocator_type
      get_allocator() const noexcept
      { return _M_h.get_allocator(); }

// size and capacity:

///  Returns true if the %unordered_map is empty.
      bool
      empty() const noexcept
      { return _M_h.empty(); }

///  Returns the size of the %unordered_map.
      size_type
      size() const noexcept
      { return _M_h.size(); }

///  Returns the maximum size of the %unordered_map.
      size_type
      max_size() const noexcept
      { return _M_h.max_size(); }

// iterators.

/**
       *  Returns a read/write iterator that points to the first element in the
       *  %unordered_map.
       */
      iterator
      begin() noexcept
      { return _M_h.begin(); }

//@{
      /**
       *  Returns a read-only (constant) iterator that points to the first
       *  element in the %unordered_map.
       */
      const_iterator
      begin() const noexcept
      { return _M_h.begin(); }

const_iterator
      cbegin() const noexcept
      { return _M_h.begin(); }
      //@}

/**
       *  Returns a read/write iterator that points one past the last element in
       *  the %unordered_map.
       */
      iterator
      end() noexcept
      { return _M_h.end(); }

//@{
      /**
       *  Returns a read-only (constant) iterator that points one past the last
       *  element in the %unordered_map.
       */
      const_iterator
      end() const noexcept
      { return _M_h.end(); }

const_iterator
      cend() const noexcept
      { return _M_h.end(); }
      //@}

// modifiers.

/**
       *  @brief Attempts to build and insert a std::pair into the
       *  %unordered_map.
       *
       *  @param __args  Arguments used to generate a new pair instance (see
       *	        std::piecewise_contruct for passing arguments to each
       *	        part of the pair constructor).
       *
       *  @return  A pair, of which the first element is an iterator that points
       *           to the possibly inserted pair, and the second is a bool that
       *           is true if the pair was actually inserted.
       *
       *  This function attempts to build and insert a (key, value) %pair into
       *  the %unordered_map.
       *  An %unordered_map relies on unique keys and thus a %pair is only
       *  inserted if its first element (the key) is not already present in the
       *  %unordered_map.
       *
       *  Insertion requires amortized constant time.
       */
      template<typename... _Args>
	std::pair<iterator, bool>
	emplace(_Args&&... __args)
	{ return _M_h.emplace(std::forward<_Args>(__args)...); }

/**
       *  @brief Attempts to build and insert a std::pair into the
       *  %unordered_map.
       *
       *  @param  __pos  An iterator that serves as a hint as to where the pair
       *                should be inserted.
       *  @param  __args  Arguments used to generate a new pair instance (see
       *	         std::piecewise_contruct for passing arguments to each
       *	         part of the pair constructor).
       *  @return An iterator that points to the element with key of the
       *          std::pair built from @a __args (may or may not be that
       *          std::pair).
       *
       *  This function is not concerned about whether the insertion took place,
       *  and thus does not return a boolean like the single-argument emplace()
       *  does.
       *  Note that the first parameter is only a hint and can potentially
       *  improve the performance of the insertion process. A bad hint would
       *  cause no gains in efficiency.
       *
       *  See
       *  https://gcc.gnu.org/onlinedocs/libstdc++/manual/associative.html#containers.associative.insert_hints
       *  for more on @a hinting.
       *
       *  Insertion requires amortized constant time.
       */
      template<typename... _Args>
	iterator
	emplace_hint(const_iterator __pos, _Args&&... __args)
	{ return _M_h.emplace_hint(__pos, std::forward<_Args>(__args)...); }

#if __cplusplus > 201402L
      /// Extract a node.
      node_type
      extract(const_iterator __pos)
      {
	__glibcxx_assert(__pos != end());
	return _M_h.extract(__pos);
      }

/// Extract a node.
      node_type
      extract(const key_type& __key)
      { return _M_h.extract(__key); }

/// Re-insert an extracted node.
      insert_return_type
      insert(node_type&& __nh)
      { return _M_h._M_reinsert_node(std::move(__nh)); }

/// Re-insert an extracted node.
      iterator
      insert(const_iterator, node_type&& __nh)
      { return _M_h._M_reinsert_node(std::move(__nh)).position; }

#define __cpp_lib_unordered_map_try_emplace 201411
      /**
       *  @brief Attempts to build and insert a std::pair into the
       *  %unordered_map.
       *
       *  @param __k    Key to use for finding a possibly existing pair in
       *                the unordered_map.
       *  @param __args  Arguments used to generate the .second for a 
       *                new pair instance.
       *
       *  @return  A pair, of which the first element is an iterator that points
       *           to the possibly inserted pair, and the second is a bool that
       *           is true if the pair was actually inserted.
       *
       *  This function attempts to build and insert a (key, value) %pair into
       *  the %unordered_map.
       *  An %unordered_map relies on unique keys and thus a %pair is only
       *  inserted if its first element (the key) is not already present in the
       *  %unordered_map.
       *  If a %pair is not inserted, this function has no effect.
       *
       *  Insertion requires amortized constant time.
       */
      template <typename... _Args>
        pair<iterator, bool>
        try_emplace(const key_type& __k, _Args&&... __args)
        {
          iterator __i = find(__k);
          if (__i == end())
            {
              __i = emplace(std::piecewise_construct,
                            std::forward_as_tuple(__k),
                            std::forward_as_tuple(
                              std::forward<_Args>(__args)...))
                .first;
              return {__i, true};
            }
          return {__i, false};
        }

// move-capable overload
      template <typename... _Args>
        pair<iterator, bool>
        try_emplace(key_type&& __k, _Args&&... __args)
        {
          iterator __i = find(__k);
          if (__i == end())
            {
              __i = emplace(std::piecewise_construct,
                            std::forward_as_tuple(std::move(__k)),
                            std::forward_as_tuple(
                              std::forward<_Args>(__args)...))
                .first;
              return {__i, true};
            }
          return {__i, false};
        }

/**
       *  @brief Attempts to build and insert a std::pair into the
       *  %unordered_map.
       *
       *  @param  __hint  An iterator that serves as a hint as to where the pair
       *                should be inserted.
       *  @param __k    Key to use for finding a possibly existing pair in
       *                the unordered_map.
       *  @param __args  Arguments used to generate the .second for a 
       *                new pair instance.
       *  @return An iterator that points to the element with key of the
       *          std::pair built from @a __args (may or may not be that
       *          std::pair).
       *
       *  This function is not concerned about whether the insertion took place,
       *  and thus does not return a boolean like the single-argument emplace()
       *  does. However, if insertion did not take place,
       *  this function has no effect.
       *  Note that the first parameter is only a hint and can potentially
       *  improve the performance of the insertion process. A bad hint would
       *  cause no gains in efficiency.
       *
       *  See
       *  https://gcc.gnu.org/onlinedocs/libstdc++/manual/associative.html#containers.associative.insert_hints
       *  for more on @a hinting.
       *
       *  Insertion requires amortized constant time.
       */
      template <typename... _Args>
        iterator
        try_emplace(const_iterator __hint, const key_type& __k,
                    _Args&&... __args)
        {
          iterator __i = find(__k);
          if (__i == end())
            __i = emplace_hint(__hint, std::piecewise_construct,
                               std::forward_as_tuple(__k),
                               std::forward_as_tuple(
                                 std::forward<_Args>(__args)...));
          return __i;
        }

// move-capable overload
      template <typename... _Args>
        iterator
        try_emplace(const_iterator __hint, key_type&& __k, _Args&&... __args)
        {
          iterator __i = find(__k);
          if (__i == end())
            __i = emplace_hint(__hint, std::piecewise_construct,
                               std::forward_as_tuple(std::move(__k)),
                               std::forward_as_tuple(
                                 std::forward<_Args>(__args)...));
          return __i;
        }
#endif // C++17

//@{
      /**
       *  @brief Attempts to insert a std::pair into the %unordered_map.

*  @param __x Pair to be inserted (see std::make_pair for easy
       *	     creation of pairs).
       *
       *  @return  A pair, of which the first element is an iterator that 
       *           points to the possibly inserted pair, and the second is 
       *           a bool that is true if the pair was actually inserted.
       *
       *  This function attempts to insert a (key, value) %pair into the
       *  %unordered_map. An %unordered_map relies on unique keys and thus a
       *  %pair is only inserted if its first element (the key) is not already
       *  present in the %unordered_map.
       *
       *  Insertion requires amortized constant time.
       */
      std::pair<iterator, bool>
      insert(const value_type& __x)
      { return _M_h.insert(__x); }

// _GLIBCXX_RESOLVE_LIB_DEFECTS
      // 2354. Unnecessary copying when inserting into maps with braced-init
      std::pair<iterator, bool>
      insert(value_type&& __x)
      { return _M_h.insert(std::move(__x)); }

template<typename _Pair>
	__enable_if_t<is_constructible<value_type, _Pair&&>::value,
		      pair<iterator, bool>>
	insert(_Pair&& __x)
        { return _M_h.emplace(std::forward<_Pair>(__x)); }
      //@}

//@{
      /**
       *  @brief Attempts to insert a std::pair into the %unordered_map.
       *  @param  __hint  An iterator that serves as a hint as to where the
       *                 pair should be inserted.
       *  @param  __x  Pair to be inserted (see std::make_pair for easy creation
       *               of pairs).
       *  @return An iterator that points to the element with key of
       *           @a __x (may or may not be the %pair passed in).
       *
       *  This function is not concerned about whether the insertion took place,
       *  and thus does not return a boolean like the single-argument insert()
       *  does.  Note that the first parameter is only a hint and can
       *  potentially improve the performance of the insertion process.  A bad
       *  hint would cause no gains in efficiency.
       *
       *  See
       *  https://gcc.gnu.org/onlinedocs/libstdc++/manual/associative.html#containers.associative.insert_hints
       *  for more on @a hinting.
       *
       *  Insertion requires amortized constant time.
       */
      iterator
      insert(const_iterator __hint, const value_type& __x)
      { return _M_h.insert(__hint, __x); }

// _GLIBCXX_RESOLVE_LIB_DEFECTS
      // 2354. Unnecessary copying when inserting into maps with braced-init
      iterator
      insert(const_iterator __hint, value_type&& __x)
      { return _M_h.insert(__hint, std::move(__x)); }

template<typename _Pair>
	__enable_if_t<is_constructible<value_type, _Pair&&>::value, iterator>
	insert(const_iterator __hint, _Pair&& __x)
	{ return _M_h.emplace_hint(__hint, std::forward<_Pair>(__x)); }
      //@}

/**
       *  @brief A template function that attempts to insert a range of
       *  elements.
       *  @param  __first  Iterator pointing to the start of the range to be
       *                   inserted.
       *  @param  __last  Iterator pointing to the end of the range.
       *
       *  Complexity similar to that of the range constructor.
       */
      template<typename _InputIterator>
	void
	insert(_InputIterator __first, _InputIterator __last)
	{ _M_h.insert(__first, __last); }

/**
       *  @brief Attempts to insert a list of elements into the %unordered_map.
       *  @param  __l  A std::initializer_list<value_type> of elements
       *               to be inserted.
       *
       *  Complexity similar to that of the range constructor.
       */
      void
      insert(initializer_list<value_type> __l)
      { _M_h.insert(__l); }

#if __cplusplus > 201402L
#define __cpp_lib_unordered_map_insertion 201411
      /**
       *  @brief Attempts to insert a std::pair into the %unordered_map.
       *  @param __k    Key to use for finding a possibly existing pair in
       *                the map.
       *  @param __obj  Argument used to generate the .second for a pair 
       *                instance.
       *
       *  @return  A pair, of which the first element is an iterator that 
       *           points to the possibly inserted pair, and the second is 
       *           a bool that is true if the pair was actually inserted.
       *
       *  This function attempts to insert a (key, value) %pair into the
       *  %unordered_map. An %unordered_map relies on unique keys and thus a
       *  %pair is only inserted if its first element (the key) is not already
       *  present in the %unordered_map.
       *  If the %pair was already in the %unordered_map, the .second of 
       *  the %pair is assigned from __obj.
       *
       *  Insertion requires amortized constant time.
       */
      template <typename _Obj>
        pair<iterator, bool>
        insert_or_assign(const key_type& __k, _Obj&& __obj)
        {
          iterator __i = find(__k);
          if (__i == end())
            {
              __i = emplace(std::piecewise_construct,
                            std::forward_as_tuple(__k),
                            std::forward_as_tuple(std::forward<_Obj>(__obj)))
                .first;
              return {__i, true};
            }
          (*__i).second = std::forward<_Obj>(__obj);
          return {__i, false};
        }

// move-capable overload
      template <typename _Obj>
        pair<iterator, bool>
        insert_or_assign(key_type&& __k, _Obj&& __obj)
        {
          iterator __i = find(__k);
          if (__i == end())
            {
              __i = emplace(std::piecewise_construct,
                            std::forward_as_tuple(std::move(__k)),
                            std::forward_as_tuple(std::forward<_Obj>(__obj)))
                .first;
              return {__i, true};
            }
          (*__i).second = std::forward<_Obj>(__obj);
          return {__i, false};
        }

/**
       *  @brief Attempts to insert a std::pair into the %unordered_map.
       *  @param  __hint  An iterator that serves as a hint as to where the
       *                  pair should be inserted.
       *  @param __k    Key to use for finding a possibly existing pair in
       *                the unordered_map.
       *  @param __obj  Argument used to generate the .second for a pair 
       *                instance.
       *  @return An iterator that points to the element with key of
       *           @a __x (may or may not be the %pair passed in).
       *
       *  This function is not concerned about whether the insertion took place,
       *  and thus does not return a boolean like the single-argument insert()
       *  does.         
       *  If the %pair was already in the %unordered map, the .second of
       *  the %pair is assigned from __obj.
       *  Note that the first parameter is only a hint and can
       *  potentially improve the performance of the insertion process.  A bad
       *  hint would cause no gains in efficiency.
       *
       *  See
       *  https://gcc.gnu.org/onlinedocs/libstdc++/manual/associative.html#containers.associative.insert_hints
       *  for more on @a hinting.
       *
       *  Insertion requires amortized constant time.
       */
      template <typename _Obj>
        iterator
        insert_or_assign(const_iterator __hint, const key_type& __k,
                         _Obj&& __obj)
        {
          iterator __i = find(__k);
          if (__i == end())
            {
              return emplace_hint(__hint, std::piecewise_construct,
                                  std::forward_as_tuple(__k),
                                  std::forward_as_tuple(
                                    std::forward<_Obj>(__obj)));
            }
          (*__i).second = std::forward<_Obj>(__obj);
          return __i;
        }

// move-capable overload
      template <typename _Obj>
        iterator
        insert_or_assign(const_iterator __hint, key_type&& __k, _Obj&& __obj)
        {
          iterator __i = find(__k);
          if (__i == end())
            {
              return emplace_hint(__hint, std::piecewise_construct,
                                  std::forward_as_tuple(std::move(__k)),
                                  std::forward_as_tuple(
                                    std::forward<_Obj>(__obj)));
            }
          (*__i).second = std::forward<_Obj>(__obj);
          return __i;
        }
#endif

//@{
      /**
       *  @brief Erases an element from an %unordered_map.
       *  @param  __position  An iterator pointing to the element to be erased.
       *  @return An iterator pointing to the element immediately following
       *          @a __position prior to the element being erased. If no such
       *          element exists, end() is returned.
       *
       *  This function erases an element, pointed to by the given iterator,
       *  from an %unordered_map.
       *  Note that this function only erases the element, and that if the
       *  element is itself a pointer, the pointed-to memory is not touched in
       *  any way.  Managing the pointer is the user's responsibility.
       */
      iterator
      erase(const_iterator __position)
      { return _M_h.erase(__position); }

// LWG 2059.
      iterator
      erase(iterator __position)
      { return _M_h.erase(__position); }
      //@}

/**
       *  @brief Erases elements according to the provided key.
       *  @param  __x  Key of element to be erased.
       *  @return  The number of elements erased.
       *
       *  This function erases all the elements located by the given key from
       *  an %unordered_map. For an %unordered_map the result of this function
       *  can only be 0 (not present) or 1 (present).
       *  Note that this function only erases the element, and that if the
       *  element is itself a pointer, the pointed-to memory is not touched in
       *  any way.  Managing the pointer is the user's responsibility.
       */
      size_type
      erase(const key_type& __x)
      { return _M_h.erase(__x); }

/**
       *  @brief Erases a [__first,__last) range of elements from an
       *  %unordered_map.
       *  @param  __first  Iterator pointing to the start of the range to be
       *                  erased.
       *  @param __last  Iterator pointing to the end of the range to
       *                be erased.
       *  @return The iterator @a __last.
       *
       *  This function erases a sequence of elements from an %unordered_map.
       *  Note that this function only erases the elements, and that if
       *  the element is itself a pointer, the pointed-to memory is not touched
       *  in any way.  Managing the pointer is the user's responsibility.
       */
      iterator
      erase(const_iterator __first, const_iterator __last)
      { return _M_h.erase(__first, __last); }

/**
       *  Erases all elements in an %unordered_map.
       *  Note that this function only erases the elements, and that if the
       *  elements themselves are pointers, the pointed-to memory is not touched
       *  in any way.  Managing the pointer is the user's responsibility.
       */
      void
      clear() noexcept
      { _M_h.clear(); }

/**
       *  @brief  Swaps data with another %unordered_map.
       *  @param  __x  An %unordered_map of the same element and allocator
       *  types.
       *
       *  This exchanges the elements between two %unordered_map in constant
       *  time.
       *  Note that the global std::swap() function is specialized such that
       *  std::swap(m1,m2) will feed to this function.
       */
      void
      swap(unordered_map& __x)
      noexcept( noexcept(_M_h.swap(__x._M_h)) )
      { _M_h.swap(__x._M_h); }

#if __cplusplus > 201402L
      template<typename, typename, typename>
	friend class std::_Hash_merge_helper;

template<typename _H2, typename _P2>
	void
	merge(unordered_map<_Key, _Tp, _H2, _P2, _Alloc>& __source)
	{
	  using _Merge_helper = _Hash_merge_helper<unordered_map, _H2, _P2>;
	  _M_h._M_merge_unique(_Merge_helper::_S_get_table(__source));
	}

template<typename _H2, typename _P2>
	void
	merge(unordered_map<_Key, _Tp, _H2, _P2, _Alloc>&& __source)
	{ merge(__source); }

template<typename _H2, typename _P2>
	void
	merge(unordered_multimap<_Key, _Tp, _H2, _P2, _Alloc>& __source)
	{
	  using _Merge_helper = _Hash_merge_helper<unordered_map, _H2, _P2>;
	  _M_h._M_merge_unique(_Merge_helper::_S_get_table(__source));
	}

template<typename _H2, typename _P2>
	void
	merge(unordered_multimap<_Key, _Tp, _H2, _P2, _Alloc>&& __source)
	{ merge(__source); }
#endif // C++17

// observers.

///  Returns the hash functor object with which the %unordered_map was
      ///  constructed.
      hasher
      hash_function() const
      { return _M_h.hash_function(); }

///  Returns the key comparison object with which the %unordered_map was
      ///  constructed.
      key_equal
      key_eq() const
      { return _M_h.key_eq(); }

// lookup.

//@{
      /**
       *  @brief Tries to locate an element in an %unordered_map.
       *  @param  __x  Key to be located.
       *  @return  Iterator pointing to sought-after element, or end() if not
       *           found.
       *
       *  This function takes a key and tries to locate the element with which
       *  the key matches.  If successful the function returns an iterator
       *  pointing to the sought after element.  If unsuccessful it returns the
       *  past-the-end ( @c end() ) iterator.
       */
      iterator
      find(const key_type& __x)
      { return _M_h.find(__x); }

const_iterator
      find(const key_type& __x) const
      { return _M_h.find(__x); }
      //@}

/**
       *  @brief  Finds the number of elements.
       *  @param  __x  Key to count.
       *  @return  Number of elements with specified key.
       *
       *  This function only makes sense for %unordered_multimap; for
       *  %unordered_map the result will either be 0 (not present) or 1
       *  (present).
       */
      size_type
      count(const key_type& __x) const
      { return _M_h.count(__x); }

//@{
      /**
       *  @brief Finds a subsequence matching given key.
       *  @param  __x  Key to be located.
       *  @return  Pair of iterators that possibly points to the subsequence
       *           matching given key.
       *
       *  This function probably only makes sense for %unordered_multimap.
       */
      std::pair<iterator, iterator>
      equal_range(const key_type& __x)
      { return _M_h.equal_range(__x); }

std::pair<const_iterator, const_iterator>
      equal_range(const key_type& __x) const
      { return _M_h.equal_range(__x); }
      //@}

//@{
      /**
       *  @brief  Subscript ( @c [] ) access to %unordered_map data.
       *  @param  __k  The key for which data should be retrieved.
       *  @return  A reference to the data of the (key,data) %pair.
       *
       *  Allows for easy lookup with the subscript ( @c [] )operator.  Returns
       *  data associated with the key specified in subscript.  If the key does
       *  not exist, a pair with that key is created using default values, which
       *  is then returned.
       *
       *  Lookup requires constant time.
       */
      mapped_type&
      operator[](const key_type& __k)
      { return _M_h[__k]; }

mapped_type&
      operator[](key_type&& __k)
      { return _M_h[std::move(__k)]; }
      //@}

//@{
      /**
       *  @brief  Access to %unordered_map data.
       *  @param  __k  The key for which data should be retrieved.
       *  @return  A reference to the data whose key is equal to @a __k, if
       *           such a data is present in the %unordered_map.
       *  @throw  std::out_of_range  If no such data is present.
       */
      mapped_type&
      at(const key_type& __k)
      { return _M_h.at(__k); }

const mapped_type&
      at(const key_type& __k) const
      { return _M_h.at(__k); }
      //@}

// bucket interface.

/// Returns the number of buckets of the %unordered_map.
      size_type
      bucket_count() const noexcept
      { return _M_h.bucket_count(); }

/// Returns the maximum number of buckets of the %unordered_map.
      size_type
      max_bucket_count() const noexcept
      { return _M_h.max_bucket_count(); }

/*
       * @brief  Returns the number of elements in a given bucket.
       * @param  __n  A bucket index.
       * @return  The number of elements in the bucket.
       */
      size_type
      bucket_size(size_type __n) const
      { return _M_h.bucket_size(__n); }

/*
       * @brief  Returns the bucket index of a given element.
       * @param  __key  A key instance.
       * @return  The key bucket index.
       */
      size_type
      bucket(const key_type& __key) const
      { return _M_h.bucket(__key); }
      
      /**
       *  @brief  Returns a read/write iterator pointing to the first bucket
       *         element.
       *  @param  __n The bucket index.
       *  @return  A read/write local iterator.
       */
      local_iterator
      begin(size_type __n)
      { return _M_h.begin(__n); }

//@{
      /**
       *  @brief  Returns a read-only (constant) iterator pointing to the first
       *         bucket element.
       *  @param  __n The bucket index.
       *  @return  A read-only local iterator.
       */
      const_local_iterator
      begin(size_type __n) const
      { return _M_h.begin(__n); }

const_local_iterator
      cbegin(size_type __n) const
      { return _M_h.cbegin(__n); }
      //@}

/**
       *  @brief  Returns a read/write iterator pointing to one past the last
       *         bucket elements.
       *  @param  __n The bucket index.
       *  @return  A read/write local iterator.
       */
      local_iterator
      end(size_type __n)
      { return _M_h.end(__n); }

//@{
      /**
       *  @brief  Returns a read-only (constant) iterator pointing to one past
       *         the last bucket elements.
       *  @param  __n The bucket index.
       *  @return  A read-only local iterator.
       */
      const_local_iterator
      end(size_type __n) const
      { return _M_h.end(__n); }

const_local_iterator
      cend(size_type __n) const
      { return _M_h.cend(__n); }
      //@}

// hash policy.

/// Returns the average number of elements per bucket.
      float
      load_factor() const noexcept
      { return _M_h.load_factor(); }

/// Returns a positive number that the %unordered_map tries to keep the
      /// load factor less than or equal to.
      float
      max_load_factor() const noexcept
      { return _M_h.max_load_factor(); }

/**
       *  @brief  Change the %unordered_map maximum load factor.
       *  @param  __z The new maximum load factor.
       */
      void
      max_load_factor(float __z)
      { _M_h.max_load_factor(__z); }

/**
       *  @brief  May rehash the %unordered_map.
       *  @param  __n The new number of buckets.
       *
       *  Rehash will occur only if the new number of buckets respect the
       *  %unordered_map maximum load factor.
       */
      void
      rehash(size_type __n)
      { _M_h.rehash(__n); }

/**
       *  @brief  Prepare the %unordered_map for a specified number of
       *          elements.
       *  @param  __n Number of elements required.
       *
       *  Same as rehash(ceil(n / max_load_factor())).
       */
      void
      reserve(size_type __n)
      { _M_h.reserve(__n); }

template<typename _Key1, typename _Tp1, typename _Hash1, typename _Pred1,
	       typename _Alloc1>
        friend bool
	operator==(const unordered_map<_Key1, _Tp1, _Hash1, _Pred1, _Alloc1>&,
		   const unordered_map<_Key1, _Tp1, _Hash1, _Pred1, _Alloc1>&);
    };

#if __cpp_deduction_guides >= 201606

template<typename _InputIterator,
	   typename _Hash = hash<__iter_key_t<_InputIterator>>,
	   typename _Pred = equal_to<__iter_key_t<_InputIterator>>,
	   typename _Allocator = allocator<__iter_to_alloc_t<_InputIterator>>,
	   typename = _RequireInputIter<_InputIterator>,
	   typename = _RequireAllocator<_Allocator>>
    unordered_map(_InputIterator, _InputIterator,
		  typename unordered_map<int, int>::size_type = {},
		  _Hash = _Hash(), _Pred = _Pred(), _Allocator = _Allocator())
    -> unordered_map<__iter_key_t<_InputIterator>,
		     __iter_val_t<_InputIterator>,
		     _Hash, _Pred, _Allocator>;

template<typename _Key, typename _Tp, typename _Hash = hash<_Key>,
	   typename _Pred = equal_to<_Key>,
	   typename _Allocator = allocator<pair<const _Key, _Tp>>,
	   typename = _RequireAllocator<_Allocator>>
    unordered_map(initializer_list<pair<_Key, _Tp>>,
		  typename unordered_map<int, int>::size_type = {},
		  _Hash = _Hash(), _Pred = _Pred(), _Allocator = _Allocator())
    -> unordered_map<_Key, _Tp, _Hash, _Pred, _Allocator>;

template<typename _InputIterator, typename _Allocator,
	   typename = _RequireInputIter<_InputIterator>,
	   typename = _RequireAllocator<_Allocator>>
    unordered_map(_InputIterator, _InputIterator,
		  typename unordered_map<int, int>::size_type, _Allocator)
    -> unordered_map<__iter_key_t<_InputIterator>,
		     __iter_val_t<_InputIterator>,
		     hash<__iter_key_t<_InputIterator>>,
		     equal_to<__iter_key_t<_InputIterator>>,
		     _Allocator>;

template<typename _InputIterator, typename _Allocator,
	   typename = _RequireInputIter<_InputIterator>,
	   typename = _RequireAllocator<_Allocator>>
    unordered_map(_InputIterator, _InputIterator, _Allocator)
    -> unordered_map<__iter_key_t<_InputIterator>,
		     __iter_val_t<_InputIterator>,
		     hash<__iter_key_t<_InputIterator>>,
		     equal_to<__iter_key_t<_InputIterator>>,
		     _Allocator>;

template<typename _InputIterator, typename _Hash, typename _Allocator,
	   typename = _RequireInputIter<_InputIterator>,
	   typename = _RequireAllocator<_Allocator>>
    unordered_map(_InputIterator, _InputIterator,
		  typename unordered_map<int, int>::size_type,
		  _Hash, _Allocator)
    -> unordered_map<__iter_key_t<_InputIterator>,
		     __iter_val_t<_InputIterator>, _Hash,
		     equal_to<__iter_key_t<_InputIterator>>, _Allocator>;

template<typename _Key, typename _Tp, typename _Allocator,
	   typename = _RequireAllocator<_Allocator>>
    unordered_map(initializer_list<pair<_Key, _Tp>>,
		  typename unordered_map<int, int>::size_type,
		  _Allocator)
    -> unordered_map<_Key, _Tp, hash<_Key>, equal_to<_Key>, _Allocator>;

template<typename _Key, typename _Tp, typename _Allocator,
	   typename = _RequireAllocator<_Allocator>>
    unordered_map(initializer_list<pair<_Key, _Tp>>, _Allocator)
    -> unordered_map<_Key, _Tp, hash<_Key>, equal_to<_Key>, _Allocator>;

template<typename _Key, typename _Tp, typename _Hash, typename _Allocator,
	   typename = _RequireAllocator<_Allocator>>
    unordered_map(initializer_list<pair<_Key, _Tp>>,
		  typename unordered_map<int, int>::size_type,
		  _Hash, _Allocator)
    -> unordered_map<_Key, _Tp, _Hash, equal_to<_Key>, _Allocator>;

#endif

/**
   *  @brief A standard container composed of equivalent keys
   *  (possibly containing multiple of each key value) that associates
   *  values of another type with the keys.
   *
   *  @ingroup unordered_associative_containers
   *
   *  @tparam  _Key    Type of key objects.
   *  @tparam  _Tp     Type of mapped objects.
   *  @tparam  _Hash   Hashing function object type, defaults to hash<_Value>.
   *  @tparam  _Pred   Predicate function object type, defaults
   *                   to equal_to<_Value>.
   *  @tparam  _Alloc  Allocator type, defaults to
   *                   std::allocator<std::pair<const _Key, _Tp>>.
   *
   *  Meets the requirements of a <a href="tables.html#65">container</a>, and
   *  <a href="tables.html#xx">unordered associative container</a>
   *
   * The resulting value type of the container is std::pair<const _Key, _Tp>.
   *
   *  Base is _Hashtable, dispatched at compile time via template
   *  alias __ummap_hashtable.
   */
  template<typename _Key, typename _Tp,
	   typename _Hash = hash<_Key>,
	   typename _Pred = equal_to<_Key>,
	   typename _Alloc = allocator<std::pair<const _Key, _Tp>>>
    class unordered_multimap
    {
      typedef __ummap_hashtable<_Key, _Tp, _Hash, _Pred, _Alloc>  _Hashtable;
      _Hashtable _M_h;

#if __cplusplus > 201402L
      using node_type = typename _Hashtable::node_type;
#endif

//construct/destroy/copy

/// Default constructor.
      unordered_multimap() = default;

/**
       *  @brief  Default constructor creates no elements.
       *  @param __n  Mnimal initial number of buckets.
       *  @param __hf  A hash functor.
       *  @param __eql  A key equality functor.
       *  @param __a  An allocator object.
       */
      explicit
      unordered_multimap(size_type __n,
			 const hasher& __hf = hasher(),
			 const key_equal& __eql = key_equal(),
			 const allocator_type& __a = allocator_type())
      : _M_h(__n, __hf, __eql, __a)
      { }

/**
       *  @brief  Builds an %unordered_multimap from a range.
       *  @param  __first An input iterator.
       *  @param  __last  An input iterator.
       *  @param __n      Minimal initial number of buckets.
       *  @param __hf     A hash functor.
       *  @param __eql    A key equality functor.
       *  @param __a      An allocator object.
       *
       *  Create an %unordered_multimap consisting of copies of the elements
       *  from [__first,__last).  This is linear in N (where N is
       *  distance(__first,__last)).
       */
      template<typename _InputIterator>
	unordered_multimap(_InputIterator __first, _InputIterator __last,
			   size_type __n = 0,
			   const hasher& __hf = hasher(),
			   const key_equal& __eql = key_equal(),
			   const allocator_type& __a = allocator_type())
	: _M_h(__first, __last, __n, __hf, __eql, __a)
	{ }

/// Copy constructor.
      unordered_multimap(const unordered_multimap&) = default;

/// Move constructor.
      unordered_multimap(unordered_multimap&&) = default;

/**
       *  @brief Creates an %unordered_multimap with no elements.
       *  @param __a An allocator object.
       */
      explicit
      unordered_multimap(const allocator_type& __a)
      : _M_h(__a)
      { }

/*
       *  @brief Copy constructor with allocator argument.
       * @param  __uset  Input %unordered_multimap to copy.
       * @param  __a  An allocator object.
       */
      unordered_multimap(const unordered_multimap& __ummap,
			 const allocator_type& __a)
      : _M_h(__ummap._M_h, __a)
      { }

/*
       *  @brief  Move constructor with allocator argument.
       *  @param  __uset Input %unordered_multimap to move.
       *  @param  __a    An allocator object.
       */
      unordered_multimap(unordered_multimap&& __ummap,
			 const allocator_type& __a)
      : _M_h(std::move(__ummap._M_h), __a)
      { }

/**
       *  @brief  Builds an %unordered_multimap from an initializer_list.
       *  @param  __l  An initializer_list.
       *  @param __n  Minimal initial number of buckets.
       *  @param __hf  A hash functor.
       *  @param __eql  A key equality functor.
       *  @param  __a  An allocator object.
       *
       *  Create an %unordered_multimap consisting of copies of the elements in
       *  the list. This is linear in N (where N is @a __l.size()).
       */
      unordered_multimap(initializer_list<value_type> __l,
			 size_type __n = 0,
			 const hasher& __hf = hasher(),
			 const key_equal& __eql = key_equal(),
			 const allocator_type& __a = allocator_type())
      : _M_h(__l, __n, __hf, __eql, __a)
      { }

unordered_multimap(size_type __n, const allocator_type& __a)
      : unordered_multimap(__n, hasher(), key_equal(), __a)
      { }

unordered_multimap(size_type __n, const hasher& __hf,
			 const allocator_type& __a)
      : unordered_multimap(__n, __hf, key_equal(), __a)
      { }

template<typename _InputIterator>
	unordered_multimap(_InputIterator __first, _InputIterator __last,
			   size_type __n,
			   const allocator_type& __a)
	: unordered_multimap(__first, __last, __n, hasher(), key_equal(), __a)
	{ }

template<typename _InputIterator>
	unordered_multimap(_InputIterator __first, _InputIterator __last,
			   size_type __n, const hasher& __hf,
			   const allocator_type& __a)
	: unordered_multimap(__first, __last, __n, __hf, key_equal(), __a)
	{ }

unordered_multimap(initializer_list<value_type> __l,
			 size_type __n,
			 const allocator_type& __a)
      : unordered_multimap(__l, __n, hasher(), key_equal(), __a)
      { }

unordered_multimap(initializer_list<value_type> __l,
			 size_type __n, const hasher& __hf,
			 const allocator_type& __a)
      : unordered_multimap(__l, __n, __hf, key_equal(), __a)
      { }

/// Copy assignment operator.
      unordered_multimap&
      operator=(const unordered_multimap&) = default;

/// Move assignment operator.
      unordered_multimap&
      operator=(unordered_multimap&&) = default;

/**
       *  @brief  %Unordered_multimap list assignment operator.
       *  @param  __l  An initializer_list.
       *
       *  This function fills an %unordered_multimap with copies of the
       *  elements in the initializer list @a __l.
       *
       *  Note that the assignment completely changes the %unordered_multimap
       *  and that the resulting %unordered_multimap's size is the same as the
       *  number of elements assigned.
       */
      unordered_multimap&
      operator=(initializer_list<value_type> __l)
      {
	_M_h = __l;
	return *this;
      }

///  Returns the allocator object used by the %unordered_multimap.
      allocator_type
      get_allocator() const noexcept
      { return _M_h.get_allocator(); }

// size and capacity:

///  Returns true if the %unordered_multimap is empty.
      bool
      empty() const noexcept
      { return _M_h.empty(); }

///  Returns the size of the %unordered_multimap.
      size_type
      size() const noexcept
      { return _M_h.size(); }

///  Returns the maximum size of the %unordered_multimap.
      size_type
      max_size() const noexcept
      { return _M_h.max_size(); }

// iterators.

/**
       *  Returns a read/write iterator that points to the first element in the
       *  %unordered_multimap.
       */
      iterator
      begin() noexcept
      { return _M_h.begin(); }

//@{
      /**
       *  Returns a read-only (constant) iterator that points to the first
       *  element in the %unordered_multimap.
       */
      const_iterator
      begin() const noexcept
      { return _M_h.begin(); }

const_iterator
      cbegin() const noexcept
      { return _M_h.begin(); }
      //@}

/**
       *  Returns a read/write iterator that points one past the last element in
       *  the %unordered_multimap.
       */
      iterator
      end() noexcept
      { return _M_h.end(); }

//@{
      /**
       *  Returns a read-only (constant) iterator that points one past the last
       *  element in the %unordered_multimap.
       */
      const_iterator
      end() const noexcept
      { return _M_h.end(); }

const_iterator
      cend() const noexcept
      { return _M_h.end(); }
      //@}

// modifiers.

/**
       *  @brief Attempts to build and insert a std::pair into the
       *  %unordered_multimap.
       *
       *  @param __args  Arguments used to generate a new pair instance (see
       *	        std::piecewise_contruct for passing arguments to each
       *	        part of the pair constructor).
       *
       *  @return  An iterator that points to the inserted pair.
       *
       *  This function attempts to build and insert a (key, value) %pair into
       *  the %unordered_multimap.
       *
       *  Insertion requires amortized constant time.
       */
      template<typename... _Args>
	iterator
	emplace(_Args&&... __args)
	{ return _M_h.emplace(std::forward<_Args>(__args)...); }

/**
       *  @brief Attempts to build and insert a std::pair into the
       *  %unordered_multimap.
       *
       *  @param  __pos  An iterator that serves as a hint as to where the pair
       *                should be inserted.
       *  @param  __args  Arguments used to generate a new pair instance (see
       *	         std::piecewise_contruct for passing arguments to each
       *	         part of the pair constructor).
       *  @return An iterator that points to the element with key of the
       *          std::pair built from @a __args.
       *
       *  Note that the first parameter is only a hint and can potentially
       *  improve the performance of the insertion process. A bad hint would
       *  cause no gains in efficiency.
       *
       *  See
       *  https://gcc.gnu.org/onlinedocs/libstdc++/manual/associative.html#containers.associative.insert_hints
       *  for more on @a hinting.
       *
       *  Insertion requires amortized constant time.
       */
      template<typename... _Args>
	iterator
	emplace_hint(const_iterator __pos, _Args&&... __args)
	{ return _M_h.emplace_hint(__pos, std::forward<_Args>(__args)...); }

//@{
      /**
       *  @brief Inserts a std::pair into the %unordered_multimap.
       *  @param __x Pair to be inserted (see std::make_pair for easy
       *	     creation of pairs).
       *
       *  @return  An iterator that points to the inserted pair.
       *
       *  Insertion requires amortized constant time.
       */
      iterator
      insert(const value_type& __x)
      { return _M_h.insert(__x); }

iterator
      insert(value_type&& __x)
      { return _M_h.insert(std::move(__x)); }

template<typename _Pair>
	__enable_if_t<is_constructible<value_type, _Pair&&>::value, iterator>
	insert(_Pair&& __x)
        { return _M_h.emplace(std::forward<_Pair>(__x)); }
      //@}

//@{
      /**
       *  @brief Inserts a std::pair into the %unordered_multimap.
       *  @param  __hint  An iterator that serves as a hint as to where the
       *                 pair should be inserted.
       *  @param  __x  Pair to be inserted (see std::make_pair for easy creation
       *               of pairs).
       *  @return An iterator that points to the element with key of
       *           @a __x (may or may not be the %pair passed in).
       *
       *  Note that the first parameter is only a hint and can potentially
       *  improve the performance of the insertion process.  A bad hint would
       *  cause no gains in efficiency.
       *
       *  See
       *  https://gcc.gnu.org/onlinedocs/libstdc++/manual/associative.html#containers.associative.insert_hints
       *  for more on @a hinting.
       *
       *  Insertion requires amortized constant time.
       */
      iterator
      insert(const_iterator __hint, const value_type& __x)
      { return _M_h.insert(__hint, __x); }

template<typename _Pair>
	__enable_if_t<is_constructible<value_type, _Pair&&>::value, iterator>
	insert(const_iterator __hint, _Pair&& __x)
        { return _M_h.emplace_hint(__hint, std::forward<_Pair>(__x)); }
      //@}

/**
       *  @brief Attempts to insert a list of elements into the
       *  %unordered_multimap.
       *  @param  __l  A std::initializer_list<value_type> of elements
       *               to be inserted.
       *
       *  Complexity similar to that of the range constructor.
       */
      void
      insert(initializer_list<value_type> __l)
      { _M_h.insert(__l); }

#if __cplusplus > 201402L
      /// Extract a node.
      node_type
      extract(const_iterator __pos)
      {
	__glibcxx_assert(__pos != end());
	return _M_h.extract(__pos);
      }

/// Extract a node.
      node_type
      extract(const key_type& __key)
      { return _M_h.extract(__key); }

/// Re-insert an extracted node.
      iterator
      insert(node_type&& __nh)
      { return _M_h._M_reinsert_node_multi(cend(), std::move(__nh)); }

/// Re-insert an extracted node.
      iterator
      insert(const_iterator __hint, node_type&& __nh)
      { return _M_h._M_reinsert_node_multi(__hint, std::move(__nh)); }
#endif // C++17

//@{
      /**
       *  @brief Erases an element from an %unordered_multimap.
       *  @param  __position  An iterator pointing to the element to be erased.
       *  @return An iterator pointing to the element immediately following
       *          @a __position prior to the element being erased. If no such
       *          element exists, end() is returned.
       *
       *  This function erases an element, pointed to by the given iterator,
       *  from an %unordered_multimap.
       *  Note that this function only erases the element, and that if the
       *  element is itself a pointer, the pointed-to memory is not touched in
       *  any way.  Managing the pointer is the user's responsibility.
       */
      iterator
      erase(const_iterator __position)
      { return _M_h.erase(__position); }

// LWG 2059.
      iterator
      erase(iterator __position)
      { return _M_h.erase(__position); }
      //@}

/**
       *  @brief Erases elements according to the provided key.
       *  @param  __x  Key of elements to be erased.
       *  @return  The number of elements erased.
       *
       *  This function erases all the elements located by the given key from
       *  an %unordered_multimap.
       *  Note that this function only erases the element, and that if the
       *  element is itself a pointer, the pointed-to memory is not touched in
       *  any way.  Managing the pointer is the user's responsibility.
       */
      size_type
      erase(const key_type& __x)
      { return _M_h.erase(__x); }

/**
       *  @brief Erases a [__first,__last) range of elements from an
       *  %unordered_multimap.
       *  @param  __first  Iterator pointing to the start of the range to be
       *                  erased.
       *  @param __last  Iterator pointing to the end of the range to
       *                be erased.
       *  @return The iterator @a __last.
       *
       *  This function erases a sequence of elements from an
       *  %unordered_multimap.
       *  Note that this function only erases the elements, and that if
       *  the element is itself a pointer, the pointed-to memory is not touched
       *  in any way.  Managing the pointer is the user's responsibility.
       */
      iterator
      erase(const_iterator __first, const_iterator __last)
      { return _M_h.erase(__first, __last); }

/**
       *  Erases all elements in an %unordered_multimap.
       *  Note that this function only erases the elements, and that if the
       *  elements themselves are pointers, the pointed-to memory is not touched
       *  in any way.  Managing the pointer is the user's responsibility.
       */
      void
      clear() noexcept
      { _M_h.clear(); }

/**
       *  @brief  Swaps data with another %unordered_multimap.
       *  @param  __x  An %unordered_multimap of the same element and allocator
       *  types.
       *
       *  This exchanges the elements between two %unordered_multimap in
       *  constant time.
       *  Note that the global std::swap() function is specialized such that
       *  std::swap(m1,m2) will feed to this function.
       */
      void
      swap(unordered_multimap& __x)
      noexcept( noexcept(_M_h.swap(__x._M_h)) )
      { _M_h.swap(__x._M_h); }

#if __cplusplus > 201402L
      template<typename, typename, typename>
	friend class std::_Hash_merge_helper;

template<typename _H2, typename _P2>
	void
	merge(unordered_multimap<_Key, _Tp, _H2, _P2, _Alloc>& __source)
	{
	  using _Merge_helper
	    = _Hash_merge_helper<unordered_multimap, _H2, _P2>;
	  _M_h._M_merge_multi(_Merge_helper::_S_get_table(__source));
	}

template<typename _H2, typename _P2>
	void
	merge(unordered_multimap<_Key, _Tp, _H2, _P2, _Alloc>&& __source)
	{ merge(__source); }

template<typename _H2, typename _P2>
	void
	merge(unordered_map<_Key, _Tp, _H2, _P2, _Alloc>& __source)
	{
	  using _Merge_helper
	    = _Hash_merge_helper<unordered_multimap, _H2, _P2>;
	  _M_h._M_merge_multi(_Merge_helper::_S_get_table(__source));
	}

template<typename _H2, typename _P2>
	void
	merge(unordered_map<_Key, _Tp, _H2, _P2, _Alloc>&& __source)
	{ merge(__source); }
#endif // C++17

// observers.

///  Returns the hash functor object with which the %unordered_multimap
      ///  was constructed.
      hasher
      hash_function() const
      { return _M_h.hash_function(); }

///  Returns the key comparison object with which the %unordered_multimap
      ///  was constructed.
      key_equal
      key_eq() const
      { return _M_h.key_eq(); }

// lookup.

//@{
      /**
       *  @brief Tries to locate an element in an %unordered_multimap.
       *  @param  __x  Key to be located.
       *  @return  Iterator pointing to sought-after element, or end() if not
       *           found.
       *
       *  This function takes a key and tries to locate the element with which
       *  the key matches.  If successful the function returns an iterator
       *  pointing to the sought after element.  If unsuccessful it returns the
       *  past-the-end ( @c end() ) iterator.
       */
      iterator
      find(const key_type& __x)
      { return _M_h.find(__x); }

const_iterator
      find(const key_type& __x) const
      { return _M_h.find(__x); }
      //@}

/**
       *  @brief  Finds the number of elements.
       *  @param  __x  Key to count.
       *  @return  Number of elements with specified key.
       */
      size_type
      count(const key_type& __x) const
      { return _M_h.count(__x); }

//@{
      /**
       *  @brief Finds a subsequence matching given key.
       *  @param  __x  Key to be located.
       *  @return  Pair of iterators that possibly points to the subsequence
       *           matching given key.
       */
      std::pair<iterator, iterator>
      equal_range(const key_type& __x)
      { return _M_h.equal_range(__x); }

std::pair<const_iterator, const_iterator>
      equal_range(const key_type& __x) const
      { return _M_h.equal_range(__x); }
      //@}

// bucket interface.

/// Returns the number of buckets of the %unordered_multimap.
      size_type
      bucket_count() const noexcept
      { return _M_h.bucket_count(); }

/// Returns the maximum number of buckets of the %unordered_multimap.
      size_type
      max_bucket_count() const noexcept
      { return _M_h.max_bucket_count(); }

const_local_iterator
      cbegin(size_type __n) const
      { return _M_h.cbegin(__n); }
      //@}

const_local_iterator
      cend(size_type __n) const
      { return _M_h.cend(__n); }
      //@}

// hash policy.

/// Returns the average number of elements per bucket.
      float
      load_factor() const noexcept
      { return _M_h.load_factor(); }

/// Returns a positive number that the %unordered_multimap tries to keep
      /// the load factor less than or equal to.
      float
      max_load_factor() const noexcept
      { return _M_h.max_load_factor(); }

/**
       *  @brief  Change the %unordered_multimap maximum load factor.
       *  @param  __z The new maximum load factor.
       */
      void
      max_load_factor(float __z)
      { _M_h.max_load_factor(__z); }

/**
       *  @brief  May rehash the %unordered_multimap.
       *  @param  __n The new number of buckets.
       *
       *  Rehash will occur only if the new number of buckets respect the
       *  %unordered_multimap maximum load factor.
       */
      void
      rehash(size_type __n)
      { _M_h.rehash(__n); }

/**
       *  @brief  Prepare the %unordered_multimap for a specified number of
       *          elements.
       *  @param  __n Number of elements required.
       *
       *  Same as rehash(ceil(n / max_load_factor())).
       */
      void
      reserve(size_type __n)
      { _M_h.reserve(__n); }

template<typename _Key1, typename _Tp1, typename _Hash1, typename _Pred1,
	       typename _Alloc1>
        friend bool
	operator==(const unordered_multimap<_Key1, _Tp1,
					    _Hash1, _Pred1, _Alloc1>&,
		   const unordered_multimap<_Key1, _Tp1,
					    _Hash1, _Pred1, _Alloc1>&);
    };

#if __cpp_deduction_guides >= 201606

template<typename _InputIterator,
	   typename _Hash = hash<__iter_key_t<_InputIterator>>,
	   typename _Pred = equal_to<__iter_key_t<_InputIterator>>,
	   typename _Allocator = allocator<__iter_to_alloc_t<_InputIterator>>,
	   typename = _RequireInputIter<_InputIterator>,
	   typename = _RequireAllocator<_Allocator>>
    unordered_multimap(_InputIterator, _InputIterator,
		       unordered_multimap<int, int>::size_type = {},
		       _Hash = _Hash(), _Pred = _Pred(),
		       _Allocator = _Allocator())
    -> unordered_multimap<__iter_key_t<_InputIterator>,
			  __iter_val_t<_InputIterator>, _Hash, _Pred,
			  _Allocator>;

template<typename _Key, typename _Tp, typename _Hash = hash<_Key>,
	   typename _Pred = equal_to<_Key>,
	   typename _Allocator = allocator<pair<const _Key, _Tp>>,
	   typename = _RequireAllocator<_Allocator>>
    unordered_multimap(initializer_list<pair<_Key, _Tp>>,
		       unordered_multimap<int, int>::size_type = {},
		       _Hash = _Hash(), _Pred = _Pred(),
		       _Allocator = _Allocator())
    -> unordered_multimap<_Key, _Tp, _Hash, _Pred, _Allocator>;

template<typename _InputIterator, typename _Allocator,
	   typename = _RequireInputIter<_InputIterator>,
	   typename = _RequireAllocator<_Allocator>>
    unordered_multimap(_InputIterator, _InputIterator,
		       unordered_multimap<int, int>::size_type, _Allocator)
    -> unordered_multimap<__iter_key_t<_InputIterator>,
			  __iter_val_t<_InputIterator>,
			  hash<__iter_key_t<_InputIterator>>,
			  equal_to<__iter_key_t<_InputIterator>>, _Allocator>;

template<typename _InputIterator, typename _Allocator,
	   typename = _RequireInputIter<_InputIterator>,
	   typename = _RequireAllocator<_Allocator>>
    unordered_multimap(_InputIterator, _InputIterator, _Allocator)
    -> unordered_multimap<__iter_key_t<_InputIterator>,
			  __iter_val_t<_InputIterator>,
			  hash<__iter_key_t<_InputIterator>>,
			  equal_to<__iter_key_t<_InputIterator>>, _Allocator>;

template<typename _InputIterator, typename _Hash, typename _Allocator,
	   typename = _RequireInputIter<_InputIterator>,
	   typename = _RequireAllocator<_Allocator>>
    unordered_multimap(_InputIterator, _InputIterator,
		       unordered_multimap<int, int>::size_type, _Hash,
		       _Allocator)
    -> unordered_multimap<__iter_key_t<_InputIterator>,
			  __iter_val_t<_InputIterator>, _Hash,
			  equal_to<__iter_key_t<_InputIterator>>, _Allocator>;

template<typename _Key, typename _Tp, typename _Allocator,
	   typename = _RequireAllocator<_Allocator>>
    unordered_multimap(initializer_list<pair<_Key, _Tp>>,
		       unordered_multimap<int, int>::size_type,
		       _Allocator)
    -> unordered_multimap<_Key, _Tp, hash<_Key>, equal_to<_Key>, _Allocator>;

template<typename _Key, typename _Tp, typename _Allocator,
	   typename = _RequireAllocator<_Allocator>>
    unordered_multimap(initializer_list<pair<_Key, _Tp>>, _Allocator)
    -> unordered_multimap<_Key, _Tp, hash<_Key>, equal_to<_Key>, _Allocator>;

template<typename _Key, typename _Tp, typename _Hash, typename _Allocator,
	   typename = _RequireAllocator<_Allocator>>
    unordered_multimap(initializer_list<pair<_Key, _Tp>>,
		       unordered_multimap<int, int>::size_type,
		       _Hash, _Allocator)
    -> unordered_multimap<_Key, _Tp, _Hash, equal_to<_Key>, _Allocator>;

#endif

template<class _Key, class _Tp, class _Hash, class _Pred, class _Alloc>
    inline void
    swap(unordered_map<_Key, _Tp, _Hash, _Pred, _Alloc>& __x,
	 unordered_map<_Key, _Tp, _Hash, _Pred, _Alloc>& __y)
    noexcept(noexcept(__x.swap(__y)))
    { __x.swap(__y); }

template<class _Key, class _Tp, class _Hash, class _Pred, class _Alloc>
    inline void
    swap(unordered_multimap<_Key, _Tp, _Hash, _Pred, _Alloc>& __x,
	 unordered_multimap<_Key, _Tp, _Hash, _Pred, _Alloc>& __y)
    noexcept(noexcept(__x.swap(__y)))
    { __x.swap(__y); }

template<class _Key, class _Tp, class _Hash, class _Pred, class _Alloc>
    inline bool
    operator==(const unordered_map<_Key, _Tp, _Hash, _Pred, _Alloc>& __x,
	       const unordered_map<_Key, _Tp, _Hash, _Pred, _Alloc>& __y)
    { return __x._M_h._M_equal(__y._M_h); }

template<class _Key, class _Tp, class _Hash, class _Pred, class _Alloc>
    inline bool
    operator!=(const unordered_map<_Key, _Tp, _Hash, _Pred, _Alloc>& __x,
	       const unordered_map<_Key, _Tp, _Hash, _Pred, _Alloc>& __y)
    { return !(__x == __y); }

template<class _Key, class _Tp, class _Hash, class _Pred, class _Alloc>
    inline bool
    operator==(const unordered_multimap<_Key, _Tp, _Hash, _Pred, _Alloc>& __x,
	       const unordered_multimap<_Key, _Tp, _Hash, _Pred, _Alloc>& __y)
    { return __x._M_h._M_equal(__y._M_h); }

template<class _Key, class _Tp, class _Hash, class _Pred, class _Alloc>
    inline bool
    operator!=(const unordered_multimap<_Key, _Tp, _Hash, _Pred, _Alloc>& __x,
	       const unordered_multimap<_Key, _Tp, _Hash, _Pred, _Alloc>& __y)
    { return !(__x == __y); }

_GLIBCXX_END_NAMESPACE_CONTAINER

#if __cplusplus > 201402L
  // Allow std::unordered_map access to internals of compatible maps.
  template<typename _Key, typename _Val, typename _Hash1, typename _Eq1,
	   typename _Alloc, typename _Hash2, typename _Eq2>
    struct _Hash_merge_helper<
      _GLIBCXX_STD_C::unordered_map<_Key, _Val, _Hash1, _Eq1, _Alloc>,
      _Hash2, _Eq2>
    {
    private:
      template<typename... _Tp>
	using unordered_map = _GLIBCXX_STD_C::unordered_map<_Tp...>;
      template<typename... _Tp>
	using unordered_multimap = _GLIBCXX_STD_C::unordered_multimap<_Tp...>;

friend unordered_map<_Key, _Val, _Hash1, _Eq1, _Alloc>;

static auto&
      _S_get_table(unordered_map<_Key, _Val, _Hash2, _Eq2, _Alloc>& __map)
      { return __map._M_h; }

static auto&
      _S_get_table(unordered_multimap<_Key, _Val, _Hash2, _Eq2, _Alloc>& __map)
      { return __map._M_h; }
    };

// Allow std::unordered_multimap access to internals of compatible maps.
  template<typename _Key, typename _Val, typename _Hash1, typename _Eq1,
	   typename _Alloc, typename _Hash2, typename _Eq2>
    struct _Hash_merge_helper<
      _GLIBCXX_STD_C::unordered_multimap<_Key, _Val, _Hash1, _Eq1, _Alloc>,
      _Hash2, _Eq2>
    {
    private:
      template<typename... _Tp>
	using unordered_map = _GLIBCXX_STD_C::unordered_map<_Tp...>;
      template<typename... _Tp>
	using unordered_multimap = _GLIBCXX_STD_C::unordered_multimap<_Tp...>;

friend unordered_multimap<_Key, _Val, _Hash1, _Eq1, _Alloc>;

static auto&
      _S_get_table(unordered_map<_Key, _Val, _Hash2, _Eq2, _Alloc>& __map)
      { return __map._M_h; }

static auto&
      _S_get_table(unordered_multimap<_Key, _Val, _Hash2, _Eq2, _Alloc>& __map)
      { return __map._M_h; }
    };
#endif // C++17

_GLIBCXX_END_NAMESPACE_VERSION
} // namespace std

#endif /* _UNORDERED_MAP_H */

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