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

< cpp‎ | container‎ | list

bool empty() const;
 (until C++11)
bool empty() const noexcept;
 (since C++11)
(until C++20)
[[nodiscard]] bool empty() const noexcept;
 (since C++20)

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

Parameters

(none)

Return value

true if the container is empty, false otherwise

Complexity

Constant.

Example

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

#include <list>
#include <iostream>
 
int main()
{
    std::list<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

See also

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