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

void pop_front();

Removes the first element of the container.

If empty() is true, the behavior is undefined.

(until C++26)

If empty() is true:

If the implementation is hardened, a contract violation occurs.
If the implementation is not hardened, the behavior is undefined.

(since C++26)

Iterators and references to the erased element are invalidated. If the element is the last element in the container, the end() iterator is also invalidated. Other references and iterators are not affected.

Complexity

Constant.

Example

#include <deque>
#include <iostream>

int main()
{
    std::deque<char> chars{'A', 'B', 'C', 'D'};
    
    for (; !chars.empty(); chars.pop_front())
        std::cout << "chars.front(): '" << chars.front() << "'\n";
}

Output:

chars.front(): 'A'
chars.front(): 'B'
chars.front(): 'C'
chars.front(): 'D'

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

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

Complexity

Example

See also