# std::indirect_array<T>::operator=

From cppreference.com
< cpp‎ | numeric‎ | valarray‎ | indirect array

void operator=( const T& value ) const; | (1) |
void operator=( const std::valarray <T>& val_arr ) const; | (2) |
const indirect_array& operator=( const indirect_array& other_arr ) const; | (3) |

Assigns values to all referred elements.

1) Assigns value to all of the elements.
2) Assigns the elements of val_arr to the referred to elements of *this.
3) Assigns the selected elements from other_arr to the referred to elements of *this.

### Parameters

value | - | a value to assign to all of the referred elements
val_arr | - | std::valarray to assign
other_arr | - | std::indirect_array to assign

### Return value

1,2) (none)
3) *this

### Example

Run this code

    #include <iomanip>
    #include <iostream>
    #include <numeric>
    #include <valarray>

    void print(int n, std::valarray<int> const& v)
    {
        std::cout << n << ':';
        for (int e : v)
            std::cout << std::setw(3) << e;
        std::cout << '\n';
    }

    int main()
    {
        std::valarray<int> v(8);
        std::iota(std::begin(v), std::end(v), 0);
        print(1, v);

        std::valarray<std::size_t> idx{1, 3, 5, 7};
        const std::indirect_array<int> ia = v[idx];
        // 'ia' refers to v[1], v[3], v[5], v[7]
        ia = -1; // (1), effectively:
                 // v[1] = v[3] = v[5] = v[7] = -1;
        print(2, v);

        ia = /*std::valarray<int>*/{-1, -2, -3, -4}; // (2),
            // effectively: v[1] = -1, v[3] = -2, v[5] = -3, v[7] = -4;
        print(3, v);

        std::valarray<std::size_t> idx2{0, 2, 4, 6};
        const std::indirect_array<int> ia2 = v[idx2];
        // 'ia2' refers to v[0], v[2], v[4], v[6]
        ia = ia2; // (3), effectively:
                  // v[1] = v[0], v[3] = v[2], v[5] = v[4], v[7] = v[6];
        print(4, v);
    }

Output:

    1:  0  1  2  3  4  5  6  7
    2:  0 -1  2 -1  4 -1  6 -1
    3:  0 -1  2 -2  4 -3  6 -4
    4:  0  0  2  2  4  4  6  6

### Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR | Applied to | Behavior as published | Correct behavior
--- | --- | --- | ---
LWG 123 | C++98 | overload (2) was non-const | made const
LWG 253 | C++98 | the copy assignment operator was private | made public
LWG 621 | C++98 | the copy assignment operator was non-const | made const

Retrieved from "https://en.cppreference.com/mwiki/index.php?title=cpp/numeric/valarray/indirect_array/operator%3D&oldid=120735"