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

bool empty() const;

(noexcept since C++11)

Checks if the container has no elements, i.e., whether begin() == end().

Return value

true if the container is empty, false otherwise.

Complexity

Constant.

Example

The following code uses empty to check if a std::deque<int> contains any elements:

#include <deque>
#include <iostream>
 
int main()
{
    std::deque<int> numbers;
    std::cout << std::boolalpha;
    std::cout << "Initially, numbers.empty(): " << numbers.empty() << '\n';

    numbers.push_back(42);
    numbers.push_back(13317); 
    std::cout << "After adding elements, numbers.empty(): " << numbers.empty() << '\n';
}

Output:

Initially, numbers.empty(): true
After adding elements, numbers.empty(): false

size	returns the number of elements (public member function)
empty (C++17)	checks whether the container is empty (function template)

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

Return value

Complexity

Example

See also