# std::unique_ptr<T,Deleter>::operator[]

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< cpp‎ | memory‎ | unique ptr

T& operator[]( std::size_t i ) const; |  | (since C++11) (constexpr since C++23)

`operator[]` provides access to elements of an array managed by a `unique_ptr`.

The parameter i shall be less than the number of elements in the array; otherwise, the behavior is undefined.

This member function is only provided for specializations for array types.

### Parameters

i | - | the index of the element to be returned

### Return value

Returns the element at index i, i.e. `get()[i]`.

### Example

Run this code

    #include <iostream>
    #include <memory>

    int main()
    {
        const int size = 10;
        std::unique_ptr<int[]> fact(new int[size]);

        for (int i = 0; i < size; ++i)
            fact[i] = (i == 0) ? 1 : i * fact[i - 1];

        for (int i = 0; i < size; ++i)
            std::cout << i << "! = " << fact[i] << '\n';
    }

Output:

    0! = 1
    1! = 1
    2! = 2
    3! = 6
    4! = 24
    5! = 120
    6! = 720
    7! = 5040
    8! = 40320
    9! = 362880

### See also

get | returns a pointer to the managed object (public member function)

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