std::array<T,N>::operator[]

reference operator[]( size_type pos );		(until C++17)
constexpr reference operator[]( size_type pos );		(since C++17)
const_reference operator[]( size_type pos ) const;		(until C++14)
constexpr const_reference operator[]( size_type pos ) const;		(since C++14)

Returns a reference to the element at specified location pos. No bounds checking is performed.

Parameters

pos

-

position of the element to return

Return value

Reference to the requested element.

Complexity

Constant.

Notes

Unlike std::map::operator[], this operator never inserts a new element into the container. Accessing a nonexistent element through this operator is undefined behavior.

Example

The following code uses operator[] to read from and write to a std::array<int>:

Run this code

#include <array>
#include <iostream>
 
int main()
{
    std::array<int,4> numbers {2, 4, 6, 8};
 
    std::cout << "Second element: " << numbers[1] << '\n';
 
    numbers[0] = 5;
 
    std::cout << "All numbers:";
    for (auto i : numbers) {
        std::cout << ' ' << i;
    }
    std::cout << '\n';
}

Output:

Second element: 4
All numbers: 5 4 6 8

Compiler support
Freestanding and hosted
Language
Standard library headers
Named requirements
Feature test macros (C++20)
Language support library
Concepts library (C++20)
Metaprogramming library (C++11)
Diagnostics library
General utilities library
Strings library
Containers library
Iterators library
Ranges library (C++20)
Algorithms library
Numerics library
Localizations library
Input/output library
Filesystem library (C++17)
Regular expressions library (C++11)
Concurrency support library (C++11)
Technical specifications
Symbols index
External libraries

Sequence
array (C++11)
vector
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
Views
span (C++20)

Member functions
Element access
array::at
array::operator[]
array::front
array::back
array::data
Iterators
array::beginarray::cbegin
array::endarray::cend
array::rbeginarray::crbegin
array::rendarray::crend
Capacity
array::empty
array::size
array::max_size
Modifiers
array::fill
array::swap
Non-member functions
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)