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

 

C++

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Named requirements

Feature test macros (C++20)

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Technical specifications

Symbols index

External libraries

 

Containers library

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array (C++11)

vector

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list

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unordered_set (C++11)

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std::array

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array::at

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array::beginarray::cbegin

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array::rbeginarray::crbegin

array::rendarray::crend

Capacity

array::empty

array::size

array::max_size

Modifiers

array::fill

array::swap

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get

std::swap

to_array (C++20)

operator==operator!=operator<operator>operator<=operator>=operator<=> (until C++20)(until C++20)(until C++20)(until C++20)(until C++20)(C++20)

Helper classes

tuple_size

tuple_element

Deduction guides(C++17)

 

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().

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::array contains any elements:

Run this code

#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

See also

size (C++11)	returns the number of elements (public member function)
empty (C++17)	checks whether the container is empty (function template)