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

 

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std::array

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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
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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)
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reference operator[]( size_type pos );	(1)	(since C++11) (constexpr since C++17)
const_reference operator[]( size_type pos )const;	(2)	(since C++11) (constexpr since C++14)

Returns a reference to the element at specified location pos.

If pos < size() is false, the behavior is undefined.	(until C++26)
If pos < size() is false: If the implementation is hardened, a contract violation occurs. Moreover, if the contract-violation handler returns under “observe” evaluation semantic, the behavior is undefined. If the implementation is not hardened, the behavior is undefined.	(since C++26)

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, unless the implementation is hardened(since C++26).

Example

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

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

See also

at	access specified element with bounds checking (public member function)