std::array at() method

since C++17

// Non const version
constexpr reference at( size_type pos );

// Const version
constexpr const_reference at( size_type pos ) const;

since C++14

// Non const version
reference at( size_type pos );

// Const version
constexpr const_reference at( size_type pos ) const;

until C++14

// Non const version
reference at( size_type pos );

// Const version
const_reference at( size_type pos ) const;

Returns a reference

to the element at specified index pos. Bounds checking is performed, exception of type std::out_of_range will be thrown on invalid access.

Parameters

• pos - position of the element to return

Return value

Reference to the requested element.

Exceptions

Throws std::out_of_range if pos >= size().

Complexity

Constant.

Example

Main.cpp

#include <stdexcept>
#include <iostream>
#include <array>
 
int main()
{
	std::array s("message"); // for capacity
 
	s = "abc";
	s.at(2) = 'x'; // ok
	std::cout << s << '\n';
 
	std::cout << "array size = " << s.size() << '\n';
	std::cout << "array capacity = " << s.capacity() << '\n';
 
	try {
		// This will throw since the requested offset
		// is greater than the current size.
		s.at(3) = 'x';
	}
	catch (std::out_of_range const& exc) {
		std::cout << exc.what() << '\n';
	}
}

Possible output

abx
array size = 3
array capacity = 7
basic_array::at