std::array<T,N>::at
From cppreference.com
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.
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 <chrono>
#include <cstddef>
#include <iostream>
#include <array>
#include <stdexcept>
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:
Element at index 2 has value 4
data size = 6
array::at: __n (which is 8) >= _Nm (which is 6)
data: 1 88 4 5 5 6
See also
| access specified element (public member function) |