constexpr bool empty() const noexcept; | (since C++11) (until C++20) | |
[[nodiscard]] constexpr bool empty() const noexcept; | (since C++20) |
Checks if the container has no elements, i.e. whether begin() == end().
(none).
true if the container is empty, false otherwise.
Constant.
The following code uses empty to check if a std::array contains any elements:
#include <array>
#include <iostream>
int main()
{
std::array<int, 4> numbers {3, 1, 4, 1};
std::array<int, 0> no_numbers;
std::cout << std::boolalpha;
std::cout << "numbers.empty(): " << numbers.empty() << '\n';
std::cout << "no_numbers.empty(): " << no_numbers.empty() << '\n';
}Output:
numbers.empty(): false no_numbers.empty(): true
|
(C++11) | returns the number of elements (public member function) |
|
(C++17) | checks whether the container is empty (function template) |
© cppreference.com
Licensed under the Creative Commons Attribution-ShareAlike Unported License v3.0.
https://en.cppreference.com/w/cpp/container/array/empty