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std::array::at(3)	      C++ Standard Libary	     std::array::at(3)

NAME
       std::array::at -	std::array::at

Synopsis
	  reference at(	size_type pos );			(until C++17)
	  constexpr reference at( size_type pos	);		(since C++17)
	  const_reference at( size_type	pos ) const;		(until C++14)
	  constexpr const_reference at(	size_type pos )	const;	(since C++14)

	  Returns  a  reference	to the element at specified location pos, with
       bounds checking.

	  If pos is not	within the range of the	 container,  an	 exception  of
       type
	  std::out_of_range is thrown.

Parameters
	  pos -	position of the	element	to return

Return value
	  Reference to the requested element.

Exceptions
	  std::out_of_range if !(pos < size()).

Complexity
	  Constant.

Example
       // Run this code

	#include <iostream>
	#include <array>

	int main()
	{
	    std::array<int,6> data = { 1, 2, 4,	5, 5, 6	};

	    // Set element 1
	    data.at(1) = 88;

	    // Read element 2
	    std::cout  <<  "Element  at	 index	2 has value " << data.at(2) <<
       '\n';

	    std::cout << "data size = "	<< data.size() << '\n';

	    try	{
		// Set element 6
		data.at(6) = 666;
	    } catch (std::out_of_range const& exc) {
		std::cout << exc.what()	<< '\n';
	    }

	    // Print final values
	    std::cout << "data:";
	    for	(int elem : data)
		std::cout << " " << elem;
	    std::cout << '\n';
	}

Possible output:
	Element	at index 2 has value 4
	data size = 6
	array::at: __n (which is 6) >= _Nm (which is 6)
	data: 1	88 4 5 5 6

See also
	  operator[] access specified element
	  (C++11)    (public member function)

http://cppreference.com		  2022.07.31		     std::array::at(3)

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