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

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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 locationpos.

Ifpos< size() isfalse, the behavior is undefined.

(until C++26)

Ifpos< size() isfalse:

If the implementation ishardened, acontract 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)

[edit]Parameters

pos

position of the element to return

[edit]Return value

Reference to the requested element.

[edit]Complexity

Constant.

[edit]Notes

Unlikestd::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).

[edit]Example

The following code usesoperator[] to read from and write to astd::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';}