std::array<T,N>::at - cppreference.com (original) (raw)

reference at( size_type pos );	(1)	(since C++11) (constexpr since C++17)
const_reference at( size_type pos ) const;	(2)	(since C++11) (constexpr 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.

[edit] Parameters

pos	-	position of the element to return

[edit] Return value

Reference to the requested element.

[edit] Exceptions

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

[edit] Complexity

Constant.

[edit] Example

#include #include #include #include #include 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 { // Try to set an element at random position >= size() auto moon_phase = [] { return std::chrono::system_clock::now().time_since_epoch().count() % 8; }; data.at(data.size() + moon_phase()) = 13; } catch(const std::out_of_range& ex) { std::cout << ex.what() << '\n'; } // Print final values std::cout << "data:"; for (int elem : data) std::cout << ' ' << elem; std::cout << '\n'; }

Possible output: