NAME¶

std::queue - std::queue

Synopsis¶

Defined in header <queue>
template<

class T,
class Container = std::deque<T>

> class queue;

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.

Template parameters¶

The type of the stored elements.
T - The behavior is undefined if T is not the same type as
Container::value_type.
(since C++17)
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:

Container - * back()
* front()
* push_back()
* pop_front()

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¶

constructor constructs the queue
(public member function)
destructor destructs the queue
(public member function)
operator= assigns values to the container adaptor
(public member function)

Element access¶

front access the first element
(public member function)
back access the last element
(public member function)

Capacity¶

empty checks whether the underlying container is empty
(public member function)
size returns the number of elements
(public member function)

Modifiers¶

push inserts element at the end
(public member function)
emplace constructs element in-place at the end
(C++11) (public member function)
pop removes the first element
(public member function)
swap swaps the contents
(C++11) (public member function)

Member objects¶

Container c the underlying container
(protected member object)

Non-member functions¶

operator==
operator!=
operator<
operator<= lexicographically compares the values in the queue
operator> (function template)
operator>=
operator<=>
(C++20)
std::swap(std::queue) specializes the std::swap algorithm
(C++11) (function template)

Helper classes¶

std::uses_allocator<std::queue> specializes the std::uses_allocator type trait
(C++11) (class template specialization)

Deduction guides(since C++17)

See also¶

deque double-ended queue
(class template)