NAME

std::array::operator[] - std::array::operator[]

Synopsis

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