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

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

void operator=( const T& value ) const; | (1) |
void operator=( const std::valarray<T>& val_arr ) const; | (2) |
const mask_array& operator=( const mask_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::mask_array to assign

### Return value

1-2) (none)
3) *this

### Example

Run this code

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

    void print(std::valarray<int> const& v)
    {
        for (int e : v)
            std::cout << std::setw(2) << e << ' ';
        std::cout << '\n';
    }

    int main()
    {
        const auto init = {1, 2, 3, 4, 5, 6, 7, 8};
        std::valarray<int> v;

        v = init;
        v[(v % 2) == 0] = 0; // (1)
        print(v);

        v = init;
        v[(v % 2) == 1] = std::valarray<int>{-1, -2, -3, -4}; // (2)
        print(v);

        v = init;
        v[(v % 2) == 0] = v[(v % 2) == 1]; // (3)
        print(v);
    }

Output:

     1  0  3  0  5  0  7  0
    -1  2 -2  4 -3  6 -4  8
     1  1  3  3  5  5  7  7

### 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/mask_array/operator%3D&oldid=120734"