std::array<T,N>::operator[] - cppreference.com (original) (raw)
| 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 location pos.
| If pos < size() is false, the behavior is undefined. | (until C++26) |
|---|---|
| If pos < size() is false: If the implementation is hardened, a contract 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
Unlike std::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 uses operator[] to read from and write to a std::array<int, N>:
#include #include 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'; }
Output:
Second element: 4 All numbers: 5 4 6 8
[edit] See also
| | access specified element with bounds checking (public member function) [edit] | | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |