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

 

C++

Compiler support

Freestanding and hosted

Language

Standard library

Standard library headers

Named requirements

Feature test macros(C++20)

Language support library

Concepts library(C++20)

Diagnostics library

Memory management library

Metaprogramming library(C++11)

General utilities library

Containers library

Iterators library

Ranges library(C++20)

Algorithms library

Strings library

Text processing library

Numerics library

Date and time library

Input/output library

Filesystem library(C++17)

Concurrency support library(C++11)

Execution control library(C++26)

Technical specifications

Symbols index

External libraries

 

Containers library

node-handle (C++17)

Sequence

array (C++11)

vector

vector<bool>

inplace_vector (C++26)

hive (C++26)

deque

forward_list (C++11)

list

Associative

set

multiset

map

multimap

Unordered associative

unordered_set (C++11)

unordered_multiset (C++11)

unordered_map (C++11)

unordered_multimap (C++11)

Adaptors

stack

queue

priority_queue

flat_set (C++23)

flat_multiset (C++23)

flat_map (C++23)

flat_multimap (C++23)

Views

span (C++20)

mdspan (C++23)

Tables

Iterator invalidation

Member function table

Non-member function table

 

std::array

Member types
Member functions
Element access array::at array::operator[]    array::front array::back array::data Operations array::fill array::swap	Iterators array::beginarray::cbegin array::endarray::cend array::rbeginarray::crbegin    array::rendarray::crend	Capacity array::empty array::size array::max_size
Non-member functions
operator==operator<=> (C++20) get(std::array) swap(std::array) to_array (C++20)	operator|=operator<operator>operator<=operator>= (until C++20)(until C++20)(until C++20)(until C++20)(until C++20)
Helper classes
tuple_size<std::array>
tuple_element<std::array>
Deduction guides(C++17)

 

constexprbool empty()constnoexcept;		(since C++11)

Checks if the container has no elements.

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