std::deque<T,Allocator>::pop_front

 

C++

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Freestanding and hosted implementations

Named requirements

Language support library

Concepts library (C++20)

Diagnostics library

Utilities library

Strings library

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Ranges library (C++20)

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Numerics library

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Filesystem library (C++17)

Regular expressions library (C++11)

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Technical Specifications

 

Containers library

array (C++11)

vector

deque

forward_list (C++11)

list

set

multiset

map

multimap

unordered_set (C++11)

unordered_multiset (C++11)

unordered_map (C++11)

unordered_multimap (C++11)

stack

queue

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span (C++20)

 

std::deque

Member functions

deque::deque

deque::~deque

deque::operator=

deque::assign

deque::get_allocator

Element access

deque::at

deque::operator[]

deque::front

deque::back

Iterators

deque::begindeque::cbegin (C++11)

deque::enddeque::cend (C++11)

deque::rbegindeque::crbegin (C++11)

deque::renddeque::crend (C++11)

Capacity

deque::empty

deque::size

deque::max_size

deque::shrink_to_fit

Modifiers

deque::clear

deque::insert

deque::emplace

deque::erase

deque::push_front

deque::emplace_front

deque::pop_front

deque::push_back

deque::emplace_back

deque::pop_back

deque::resize

deque::swap

Non-member functions

std::swap

eraseerase_if (C++20)(C++20)

operator==operator!=operator<operator>operator<=operator>=operator<=> (until C++20)(until C++20)(until C++20)(until C++20)(until C++20)(C++20)

Deduction guides(C++17)

 

void pop_front();

Removes the first element of the container. If there are no elements in the container, the behavior is undefined.

Iterators and references to the erased element are invalidated. It is unspecified whether the past-the-end iterator is invalidated if the element is the last element in the container. Other references and iterators are not affected.	(until C++11)
Iterators and references to the erased element are invalidated. If the element is the last element in the container, the past-the-end iterator is also invalidated. Other references and iterators are not affected.	(since C++11)

Parameters

(none)

Return value

(none)

Complexity

Constant.

Exceptions

Does not throw.

Example

Run this code

#include <deque>
#include <iostream>
 
auto print = [](const auto& con) {
    for (auto const& item : con)
        std::cout << item;
    std::cout << '\n';
};
 
int main() {
    std::deque<char> letters{'A','B','C','D'};
 
    for (char c{letters.back()}; c != 'H' ;) {
        letters.push_back(++c);
        print(letters);
        letters.pop_front();
    }
}

Output:

ABCDE
BCDEF
CDEFG
DEFGH

See also

pop_back	removes the last element (public member function)
push_front	inserts an element to the beginning (public member function)