Difference between revisions of "cpp/container/queue"
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Revision as of 23:02, 13 November 2023
| Defined in header <queue>
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| template< class T, |
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The std::queue class is a container adaptor that gives the programmer the functionality of a queue - specifically, a FIFO (first-in, first-out) data structure.
The class template acts as a wrapper to the underlying container - only a specific set of functions is provided. The queue pushes the elements on the back of the underlying container and pops them from the front.
Contents |
Template parameters
| T | - | The type of the stored elements. The behavior is undefined if T is not the same type as Container::value_type.
|
| Container | - | The type of the underlying container to use to store the elements. The container must satisfy the requirements of SequenceContainer. Additionally, it must provide the following functions with the usual semantics:
The standard containers std::deque and std::list satisfy these requirements. |
Member types
| Member type | Definition |
container_type
|
Container
|
value_type
|
Container::value_type
|
size_type
|
Container::size_type |
reference
|
Container::reference
|
const_reference
|
Container::const_reference
|
Member functions
constructs the queue (public member function) | |
destructs the queue (public member function) | |
| assigns values to the container adaptor (public member function) | |
Element access | |
| access the first element (public member function) | |
| access the last element (public member function) | |
Capacity | |
| checks whether the container adaptor is empty (public member function) | |
| returns the number of elements (public member function) | |
Modifiers | |
| inserts element at the end (public member function) | |
| (C++23) |
inserts a range of elements at the end (public member function) |
| (C++11) |
constructs element in-place at the end (public member function) |
| removes the first element (public member function) | |
| (C++11) |
swaps the contents (public member function) |
Member objects | |
| Container c |
the underlying container (protected member object) |
Non-member functions
lexicographically compares the values of two queues (function template) | |
| (C++11) |
specializes the std::swap algorithm (function template) |
Helper classes
| specializes the std::uses_allocator type trait (class template specialization) |
Deduction guides |
(since C++17) |
Notes
| Feature-test macro | Value | Std | Feature |
|---|---|---|---|
__cpp_lib_containers_ranges |
202202L | (C++23) | Ranges construction and insertion for containers |
Defect reports
The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
| DR | Applied to | Behavior as published | Correct behavior |
|---|---|---|---|
| LWG 307 | C++98 | std::queue did not support containers using proxyreference types[1] in place of ( const) value_type&
|
supported |
- ↑ Such as containers similar to std::vector<bool> with additional support of
pop_front(). The resolution of this DR added support of std::vector<bool> for std::stack and std::priority_queue. The changes involvingstd::queueare for maintaining consistency.
See also
| double-ended queue (class template) | |
| doubly-linked list (class template) |
