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 << "numbers.empty(): " << numbers.empty() << '\n';
std::cout << "no_numbers.empty(): " << no_numbers.empty() << '\n';
}Output:
numbers.empty(): 0 no_numbers.empty(): 1
| returns the number of elements (public member function) |
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