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std::array<T,N>::empty

From cppreference.com
< cpp‎ | container‎ | array
 
 
 
 
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().

Contents

[edit] Parameters

(none)

[edit] Return value

true if the container is empty, false otherwise.

[edit] Complexity

Constant.

[edit] Example

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

[edit] See also

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