|A unary function object type that acts a hash function for a `Key`. It takes a single argument of type `Key` and returns a value of type `std::size_t`.
|A binary function object that implements an equivalence relation on values of type `Key`. A binary function object that induces an equivalence relation on values of type `Key`. It takes two arguments of type `Key` and returns a value of type bool.
The elements are organized into buckets. Keys with the same hash code are stored in the same bucket and elements with equivalent keys are stored next to each other.
Requires:;; If the defaults are used, `hasher`, `key_equal` and `allocator_type` need to be https://en.cppreference.com/w/cpp/named_req/DefaultConstructible[DefaultConstructible^].
Requires:;; If the defaults are used, `hasher`, `key_equal` and `allocator_type` need to be https://en.cppreference.com/w/cpp/named_req/DefaultConstructible[DefaultConstructible^].
Constructs an empty container with at least `n` buckets, using `hf` as the hash function, `eql` as the key equality predicate, `a` as the allocator and a maximum load factor of `1.0` and inserts the elements from `[f, l)` into it.
Requires:;; If the defaults are used, `hasher`, `key_equal` and `allocator_type` need to be https://en.cppreference.com/w/cpp/named_req/DefaultConstructible[DefaultConstructible^].
unordered_multiset(initializer_list<value_type> il,
size_type n = _implementation-defined_,
const hasher& hf = hasher(),
const key_equal& eql = key_equal(),
const allocator_type& a = allocator_type());
----
Constructs an empty container with at least `n` buckets, using `hf` as the hash function, `eql` as the key equality predicate, `a` as the allocator and a maximum load factor of `1.0` and inserts the elements from `il` into it.
Requires:;; If the defaults are used, `hasher`, `key_equal` and `allocator_type` need to be https://en.cppreference.com/w/cpp/named_req/DefaultConstructible[DefaultConstructible^].
Constructs an empty container with at least `n` buckets, using `hf` as the hash function, the default hash function and key equality predicate, `a` as the allocator and a maximum load factor of `1.0`.
Constructs an empty container with at least `n` buckets, using `hf` as the hash function, the default key equality predicate, `a` as the allocator and a maximum load factor of `1.0`.
Constructs an empty container with at least `n` buckets, using `a` as the allocator, with the default hash function and key equality predicate and a maximum load factor of `1.0` and inserts the elements from `[f, l)` into it.
Constructs an empty container with at least `n` buckets, using `hf` as the hash function, `a` as the allocator, with the default key equality predicate and a maximum load factor of `1.0` and inserts the elements from `[f, l)` into it.
The assignment operator. Copies the contained elements, hash function, predicate and maximum load factor but not the allocator.
If `Alloc::propagate_on_container_copy_assignment` exists and `Alloc::propagate_on_container_copy_assignment::value` is `true`, the allocator is overwritten, if not the copied elements are created using the existing allocator.
If `Alloc::propagate_on_container_move_assignment` exists and `Alloc::propagate_on_container_move_assignment::value` is `true`, the allocator is overwritten, if not the moved elements are created using the existing allocator.
Notes:;; On compilers without rvalue references, this is emulated using Boost.Move. Note that on some compilers the copy assignment operator may be used in some circumstances.
Requires:;; `value_type` is https://en.cppreference.com/w/cpp/named_req/CopyInsertable[CopyInsertable^] into the container and https://en.cppreference.com/w/cpp/named_req/CopyAssignable[CopyAssignable^].
Requires:;; `value_type` is https://en.cppreference.com/w/cpp/named_req/EmplaceConstructible[EmplaceConstructible^] into `X` from `args`.
Returns:;; An iterator pointing to the inserted element.
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. +
+
If the compiler doesn't support variadic template arguments or rvalue references, this is emulated for up to `10` arguments, with no support for rvalue references or move semantics. +
Since existing `std::pair` implementations don't support `std::piecewise_construct` this emulates it, but using `boost::unordered::piecewise_construct`.
Requires:;; `value_type` is https://en.cppreference.com/w/cpp/named_req/EmplaceConstructible[EmplaceConstructible^] into `X` from `args`.
Returns:;; An iterator pointing to the inserted element.
Throws:;; If an exception is thrown by an operation other than a call to `hasher` the function has no effect.
Notes:;; 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. +
+
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. +
+
If the compiler doesn't support variadic template arguments or rvalue references, this is emulated for up to 10 arguments, with no support for rvalue references or move semantics. +
Since existing `std::pair` implementations don't support `std::piecewise_construct` this emulates it, but using `boost::unordered::piecewise_construct`.
Requires:;; `value_type` is https://en.cppreference.com/w/cpp/named_req/CopyInsertable[CopyInsertable^].
Returns:;; An iterator pointing to the inserted element.
Throws:;; If an exception is thrown by an operation other than a call to `hasher` the function has no effect.
Notes:;; 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. +
+
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.
Requires:;; `value_type` is https://en.cppreference.com/w/cpp/named_req/MoveInsertable[MoveInsertable^].
Returns:;; An iterator pointing to the inserted element.
Throws:;; If an exception is thrown by an operation other than a call to `hasher` the function has no effect.
Notes:;; 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. +
+
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.
This 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.
Requires:;; `nh` is empty or `nh.get_allocator()` is equal to the container's allocator.
Returns:;; If `nh` was empty, returns `end()`. +
+
Otherwise returns an iterator pointing to the newly inserted element.
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. In C++17 this can be used to insert a node extracted from a compatible `unordered_set`, but that is not supported yet.
Throws:;; If an exception is thrown by an operation other than a call to hasher the function has no effect.
Notes:;; 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. +
+
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. +
+
In C++17 this can be used to insert a node extracted from a compatible `unordered_set`, but that is not supported yet.
Returns:;; The iterator following `position` before the erasure.
Throws:;; Only throws an exception if it is thrown by `hasher` or `key_equal`.
Notes:;; In older versions this could be inefficient because it had to search through several buckets to find the position of the returned iterator. The data structure has been changed so that this is no longer the case, and the alternative erase methods have been deprecated.
This 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.
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.
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.
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.
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.
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.
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 <typename 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.
Returns:;; The number of elements with key equivalent to `k`.
Notes:;; The `template <typename 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.
Returns:;; A boolean indicating whether or not there is an element with key equal to `key` in the container
Notes:;; The `template <typename 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.
Returns:;; A range containing all elements with key equivalent to `k`. If the container doesn't contain any such elements, returns `std::make_pair(b.end(), b.end())`.
Notes:;; The `template <typename 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.
Return `true` if `x.size() == y.size()` and for every element in `x`, there is an element in `y` with the same key, with an equal value (using `operator==` to compare the value types).
Return `false` if `x.size() == y.size()` and for every element in `x`, there is an element in `y` with the same key, with an equal value (using `operator==` to compare the value types).
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.
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.
