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std::mask_array<T>::operator=

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

#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

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