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Attempt to "merge" two containers by iterating `source` and extracting any node in `source` that is not contained in `*this` and then inserting it into `*this`.
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:1292
Throws:;; Only throws an exception if it is thrown by `hasher` or `key_equal`. + + In this implementation, this overload doesn't call either function object's methods so it is no throw, but this might not be true in other implementations. Notes:;; This method was implemented because returning an iterator to the next element from erase was expensive, but the container has been redesigned so that is no longer the case. So this method is now deprecated.
抛出：;; 仅当由 `hasher` 或 `key_equal` 抛出异常时才会抛出异常。
在此实现中，此重载不会调用任一函数对象的方法，因此不会抛出异常，但在其他实现中可能并非如此。
备注：;; 之所以实现此方法，是因为从 `erase` 返回下一个元素的迭代器开销较大，但容器已经过重新设计，情况不再如此。因此，此方法现已废弃。
:1297
---
---
swap
交换
```c++ void swap(unordered_map& other) noexcept(boost::allocator_traits<Allocator>::is_always_equal::value && boost::is_nothrow_swappable_v<Hash> && boost::is_nothrow_swappable_v<Pred>); ```
```c++ void swap(unordered_map&amp; other) noexcept(boost::allocator_traits<allocator>::is_always_equal::value &amp;&amp; boost::is_nothrow_swappable_v<hash> &amp;&amp; boost::is_nothrow_swappable_v<pred>); ```</pred></hash></allocator>
Swaps the contents of the container with the parameter.
将容器的内容与参数进行交换。
:1309
If `Allocator::propagate_on_container_swap` is declared and `Allocator::propagate_on_container_swap::value` is `true` then the containers' allocators are swapped. Otherwise, swapping with unequal allocators results in undefined behavior.
如果 `Allocator::propagate_on_container_swap` 已声明且 `Allocator::propagate_on_container_swap::value` 为 `true`，则交换两个容器的分配器。否则，使用不相等的分配器进行交换将导致未定义行为。
Throws:;; Doesn't throw an exception unless it is thrown by the copy constructor or copy assignment operator of `key_equal` or `hasher`. Notes:;; The exception specifications aren't quite the same as the C++11 standard, as the equality predicate and hash function are swapped using their copy constructors.
抛出：;; 除非由 `key_equal` 或 `hasher` 的复制构造函数或复制赋值运算符抛出异常，否则不会抛出异常。
备注：;; 异常规范与 C++11 标准不完全相同，因为相等谓词和哈希函数是通过它们的复制构造函数进行交换的。
:1315
---
---
clear
清空
```c++ void clear(); ```
```c++ void clear(); ```
Erases all elements in the container.
清除容器中的所有元素。
Postconditions:;; `size() == 0` Throws:;; Never throws an exception.
后置条件：;; `size() == 0`抛出：;; 永不抛出异常。
:1328
---
---
merge
合并
```c++ template<class H2, class P2> void merge(unordered_map<Key, T, H2, P2, Allocator>& source); template<class H2, class P2> void merge(unordered_map<Key, T, H2, P2, Allocator>&& source); template<class H2, class P2> void merge(unordered_multimap<Key, T, H2, P2, Allocator>& source); template<class H2, class P2> void merge(unordered_multimap<Key, T, H2, P2, Allocator>&& source); ```
```c++ template<class h2,="" class="" p2=""> void merge(unordered_map<key, t,="" h2,="" p2,="" allocator="">&amp; source); template<class h2,="" class="" p2=""> void merge(unordered_map<key, t,="" h2,="" p2,="" allocator="">&amp;&amp; source); template<class h2,="" class="" p2=""> void merge(unordered_multimap<key, t,="" h2,="" p2,="" allocator="">&amp; source); template<class h2,="" class="" p2=""> void merge(unordered_multimap<key, t,="" h2,="" p2,="" allocator="">&amp;&amp; source); ```</key,></class></key,></class></key,></class></key,></class>
Attempt to "merge" two containers by iterating `source` and extracting any node in `source` that is not contained in `*this` and then inserting it into `*this`.
尝试通过迭代 `source` 并提取 `source` 中不包含在 `*this` 内的任何节点，然后将其插入到 `*this` 中，从而实现两个容器的“合并”。
Because `source` can have a different hash function and key equality predicate, the key of each node in `source` is rehashed using `this\->hash_function()` and then, if required, compared using `this\->key_eq()`.
由于 `source` 可能具有不同的哈希函数和键相等谓词，因此 `source` 中每个节点的键都将使用 `this-&gt;hash_function()` 重新计算哈希值，然后根据需要再使用 `this-&gt;key_eq()` 进行比较。
The behavior of this function is undefined if `this\->get_allocator() != source.get_allocator()`.
如果 `this-&gt;get_allocator() != source.get_allocator()`，则此函数的行为未定义。
This function does not copy or move any elements and instead simply relocates the nodes from `source` into `*this`.
此函数不会复制或移动任何元素，而只是将节点从 `source` 重新定位到 `*this` 中。
Notes:;; + --
注意:;; + --
Pointers and references to transferred elements remain valid.
指向被转移元素的指针和引用保持有效。
Invalidates iterators to transferred elements.
使指向被转移元素的迭代器失效。
Invalidates iterators belonging to `*this`.
使属于 `*this` 的迭代器失效。
Iterators to non-transferred elements in `source` remain valid.
`source` 中未被转移的元素的迭代器保持有效。
--
--
:1363
---
---
Observers
观察器
get_allocator
get_allocator
``` allocator_type get_allocator() const; ```
``` allocator_type get_allocator() const; ```
:1372
---
---
hash_function
哈希函数
English Chinese (Simplified Han script) Actions
```c++ template<class... Args> std::pair<iterator, bool> try_emplace(const key_type& k, Args&&... args); template<class... Args> std::pair<iterator, bool> try_emplace(key_type&& k, Args&&... args); template<class K, class... Args> std::pair<iterator, bool> try_emplace(K&& k, Args&&... args) ```
```c++ template<class... args=""> std::pair<iterator, bool=""> try_emplace(const key_type&amp; k, Args&amp;&amp;... args); template<class... args=""> std::pair<iterator, bool=""> try_emplace(key_type&amp;&amp; k, Args&amp;&amp;... args); template<class k,="" class...="" args=""> std::pair<iterator, bool=""> try_emplace(K&amp;&amp; k, Args&amp;&amp;... args) ```</iterator,></class></iterator,></class...></iterator,></class...>
instead of xref:#unordered_map_emplace[emplace] which simply forwards all arguments to ``value_type``'s constructor.
而不是像 xref:#unordered_map_emplace[emplace] 那样简单地将所有参数转发给 `value_type` 的构造函数。
```c++ template<class... Args> iterator try_emplace(const_iterator hint, const key_type& k, Args&&... args); template<class... Args> iterator try_emplace(const_iterator hint, key_type&& k, Args&&... args); template<class K, class... Args> iterator try_emplace(const_iterator hint, K&& k, Args&&... args); ```
```c++ template<class... args=""> iterator try_emplace(const_iterator hint, const key_type&amp; k, Args&amp;&amp;... args); template<class... args=""> iterator try_emplace(const_iterator hint, key_type&amp;&amp; k, Args&amp;&amp;... args); template<class k,="" class...="" args=""> iterator try_emplace(const_iterator hint, K&amp;&amp; k, Args&amp;&amp;... args); ```</class></class...></class...>
The standard is fairly vague on the meaning of the hint. But the only practical way to use it, and the only way that Boost.Unordered supports is to point to an existing element with the same key.
标准关于 `hint` 的含义表述相当模糊。但唯一实际的使用方式，也是 Boost.Unordered 支持的唯一方式，是将其指向一个具有相同键的已存在元素。
```c++ template<class M> std::pair<iterator, bool> insert_or_assign(const key_type& k, M&& obj); template<class M> std::pair<iterator, bool> insert_or_assign(key_type&& k, M&& obj); template<class K, class M> std::pair<iterator, bool> insert_or_assign(K&& k, M&& obj); ```
```c++ template<class m=""> std::pair<iterator, bool=""> insert_or_assign(const key_type&amp; k, M&amp;&amp; obj); template<class m=""> std::pair<iterator, bool=""> insert_or_assign(key_type&amp;&amp; k, M&amp;&amp; obj); template<class k,="" class="" m=""> std::pair<iterator, bool=""> insert_or_assign(K&amp;&amp; k, M&amp;&amp; obj); ```</iterator,></class></iterator,></class></iterator,></class>
insert_or_assign with Hint
带提示位置的 `insert_or_assign`
```c++ template<class M> iterator insert_or_assign(const_iterator hint, const key_type& k, M&& obj); template<class M> iterator insert_or_assign(const_iterator hint, key_type&& k, M&& obj); template<class K, class M> iterator insert_or_assign(const_iterator hint, K&& k, M&& obj); ```
```c++ template<class m=""> iterator insert_or_assign(const_iterator hint, const key_type&amp; k, M&amp;&amp; obj); template<class m=""> iterator insert_or_assign(const_iterator hint, key_type&amp;&amp; k, M&amp;&amp; obj); template<class k,="" class="" m=""> iterator insert_or_assign(const_iterator hint, K&amp;&amp; k, M&amp;&amp; obj); ```</class></class></class>
```c++ insert_return_type insert(node_type&& nh); ```
```c++ insert_return_type insert(node_type&amp;&amp; nh); ```
If there is already an element in the container with an equivalent key has no effect on `nh` (i.e. `nh` still contains the node.)
如果容器中已存在具有等价键的元素，则对 `nh` 无影响（即 `nh` 仍然包含该节点）。
Returns:;; The number of elements erased. Throws:;; Only throws an exception if it is thrown by `hasher` or `key_equal`. Notes:;; The `template<class K>` overload only participates in overload resolution if `Hash::is_transparent` and `Pred::is_transparent` are valid member typedefs and neither `iterator` nor `const_iterator` are implicitly convertible from `K`. The library assumes that `Hash` is callable with both `K` and `Key` and that `Pred` is transparent. This enables heterogeneous lookup which avoids the cost of instantiating an instance of the `Key` type.
返回：被擦除的元素数量。
抛出：仅当 `hasher` 或 `key_equal` 抛出异常时才会抛出。
注意：`template<class k="">` 重载仅在 `Hash::is_transparent` 和 `Pred::is_transparent` 是有效的成员 typedef，且 `iterator` 和 `const_iterator` 都不能从 `K` 隐式转换时参与重载决议。库假定 `Hash` 可同时使用 `K` 和 `Key` 调用，且 `Pred` 是透明的。这支持了异构查找，从而避免了实例化 `Key` 类型对象的开销。</class>
Returns:;; The iterator following the erased elements - i.e. `last`. Throws:;; Only throws an exception if it is thrown by `hasher` or `key_equal`. + + In this implementation, this overload doesn't call either function object's methods so it is no throw, but this might not be true in other implementations.
返回：被擦除元素之后的迭代器——即 `last`。
抛出：仅当 `hasher` 或 `key_equal` 抛出异常时才会抛出。
在此实现中，此重载不会调用任何函数对象的方法，因此不会抛出异常，但这在其他实现中可能并不成立。
Class Template unordered_map
类模板 unordered_map
:idprefix: unordered_map_
:idprefix: unordered_map_
```c++ void swap(unordered_map& other) noexcept(boost::allocator_traits<Allocator>::is_always_equal::value && boost::is_nothrow_swappable_v<Hash> && boost::is_nothrow_swappable_v<Pred>); ```
```c++ void swap(unordered_map&amp; other) noexcept(boost::allocator_traits<allocator>::is_always_equal::value &amp;&amp; boost::is_nothrow_swappable_v<hash> &amp;&amp; boost::is_nothrow_swappable_v<pred>); ```</pred></hash></allocator>
merge
合并
Attempt to "merge" two containers by iterating `source` and extracting any node in `source` that is not contained in `*this` and then inserting it into `*this`.
尝试通过迭代 `source` 并提取 `source` 中不包含在 `*this` 内的任何节点，然后将其插入到 `*this` 中，从而实现两个容器的“合并”。
Because `source` can have a different hash function and key equality predicate, the key of each node in `source` is rehashed using `this\->hash_function()` and then, if required, compared using `this\->key_eq()`.
由于 `source` 可能具有不同的哈希函数和键相等谓词，因此 `source` 中每个节点的键都将使用 `this-&gt;hash_function()` 重新计算哈希值，然后根据需要再使用 `this-&gt;key_eq()` 进行比较。
Notes:;; + --
注意:;; + --
Invalidates iterators belonging to `*this`.
使属于 `*this` 的迭代器失效。
Iterators to non-transferred elements in `source` remain valid.
`source` 中未被转移的元素的迭代器保持有效。
Returns:;; An iterator pointing to an element with key equivalent to `k`, or `b.end()` if no such element exists. Notes:;; The templated overloads containing `CompatibleKey`, `CompatibleHash` and `CompatiblePredicate` are non-standard extensions which allow you to use a compatible hash function and equality predicate for a key of a different type in order to avoid an expensive type cast. In general, its use is not encouraged and instead the `K` member function templates should be used. + + The `template<class K>` overloads only participate in overload resolution if `Hash::is_transparent` and `Pred::is_transparent` are valid member typedefs. The library assumes that `Hash` is callable with both `K` and `Key` and that `Pred` is transparent. This enables heterogeneous lookup which avoids the cost of instantiating an instance of the `Key` type.
返回：;; 指向键与 `k` 等价之元素的迭代器；若无此元素，则返回 `b.end()`。
备注：;; 包含 `CompatibleKey`、`CompatibleHash` 和 `CompatiblePredicate` 的模板重载属于非标准扩展，允许使用兼容的哈希函数和相等谓词来处理不同类型的键，从而避免昂贵的类型转换。通常不建议使用它们，而应使用 `K` 成员函数模板。
此外，仅当 `Hash::is_transparent` 和 `Pred::is_transparent` 是有效的成员 typedef 时，`template<class k="">` 重载才会参与重载决议。库假定 `Hash` 可同时以 `K` 和 `Key` 类型调用，且 `Pred` 是透明的。这支持了异构查找，从而避免了实例化 `Key` 类型的开销。</class>
```c++ bool contains(const key_type& k) const; template<class K> bool contains(const K& k) const; ```
```c++ bool contains(const key_type&amp; k) const; template<class k=""> bool contains(const K&amp; k) const; ```</class>
```c++ std::pair<iterator, iterator> equal_range(const key_type& k); std::pair<const_iterator, const_iterator> equal_range(const key_type& k) const; template<class K> std::pair<iterator, iterator> equal_range(const K& k); template<class K> std::pair<const_iterator, const_iterator> equal_range(const K& k) const; ```
```c++ std::pair<iterator, iterator=""> equal_range(const key_type&amp; k); std::pair<const_iterator, const_iterator=""> equal_range(const key_type&amp; k) const; template<class k=""> std::pair<iterator, iterator=""> equal_range(const K&amp; k); template<class k=""> std::pair<const_iterator, const_iterator=""> equal_range(const K&amp; k) const; ```</const_iterator,></class></iterator,></class></const_iterator,></iterator,>
```c++ mapped_type& operator[](const key_type& k); mapped_type& operator[](key_type&& k); template<class K> mapped_type& operator[](K&& k); ```
```c++ mapped_type&amp; operator[](const key_type&amp; k); mapped_type&amp; operator[](key_type&amp;&amp; k); template<class k=""> mapped_type&amp; operator[](K&amp;&amp; k); ```</class>
Effects:;; If the container does not already contain an elements with a key equivalent to `k`, inserts the value `std::pair<key_type const, mapped_type>(k, mapped_type())`. Returns:;; A reference to `x.second` where `x` is the element already in the container, or the newly inserted element with a key equivalent to `k`. Throws:;; If an exception is thrown by an operation other than a call to `hasher` the function has no effect. Notes:;; Can invalidate iterators, but only if the insert causes the load factor to be greater to or equal to the maximum load factor. + + Pointers and references to elements are never invalidated. + + The `template<class K>` overload only participates in overload resolution if `Hash::is_transparent` and `Pred::is_transparent` are valid member typedefs. The library assumes that `Hash` is callable with both `K` and `Key` and that `Pred` is transparent. This enables heterogeneous lookup which avoids the cost of instantiating an instance of the `Key` type.
效果：;; 如果容器中尚不存在键与 `k` 等价的元素，则插入值 `std::pair<key_type const,="" mapped_type="">(k, mapped_type())`。
返回：;; 指向 `x.second` 的引用，其中 `x` 是容器中已存在的元素，或者是键与 `k` 等价的新插入元素。
抛出：;; 如果除调用 `hasher` 之外的操作抛出异常，则该函数无效。
备注：;; 可能使迭代器失效，但仅当插入导致负载因子大于或等于最大负载因子时才会发生。
此外，指向元素的指针和引用永远不会失效。
另外，仅当 `Hash::is_transparent` 和 `Pred::is_transparent` 是有效的成员 typedef 时，`template<class k="">` 重载才会参与重载决议。库假定 `Hash` 可同时以 `K` 和 `Key` 类型调用，且 `Pred` 是透明的。这支持了异构查找，从而避免了实例化 `Key` 类型的开销。</class></key_type>
```c++ mapped_type& at(const key_type& k); const mapped_type& at(const key_type& k) const; template<class K> mapped_type& at(const K& k); template<class K> const mapped_type& at(const K& k) const; ```
```c++ mapped_type&amp; at(const key_type&amp; k); const mapped_type&amp; at(const key_type&amp; k) const; template<class k=""> mapped_type&amp; at(const K&amp; k); template<class k=""> const mapped_type&amp; at(const K&amp; k) const; ```</class></class>
Bucket Interface
桶接口
bucket_count
bucket_count
```c++ size_type bucket_count() const noexcept; ```
```c++ size_type bucket_count() const noexcept; ```
max_bucket_count
max_bucket_count

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Translation uploaded
Attempt to "merge" two containers by iterating `source` and extracting any node in `source` that is not contained in `*this` and then inserting it into `*this`.
Attempt to "merge" two containers by iterating `source` and extracting any node in `source` that is not contained in `*this` and then inserting it into `*this`.尝试通过迭代 `source` 并提取 `source` 中不包含在 `*this` 内的任何节点，然后将其插入到 `*this` 中，从而实现两个容器的“合并”。
06/05/2026
User avatar admin

String added in the repository
Attempt to "merge" two containers by iterating `source` and extracting any node in `source` that is not contained in `*this` and then inserting it into `*this`.
Attempt to "merge" two containers by iterating `source` and extracting any node in `source` that is not contained in `*this` and then inserting it into `*this`.
06/05/2026
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Glossary

English Chinese (Simplified Han script)
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String information

Flags
safe-html, strict-same
Unit identifier
55719
Source string location
:1342
String age
06/05/2026
Last updated
06/06/2026
Source string age
06/05/2026
Translation file AsciiDoc file
doc/modules/ROOT/pages/reference/unordered_map_zh_Hans.adoc, string 337