std::mask_array::operator=(3)

🎀 std::mask_array::operator=(3) 🎀

okay bestie, welcome to the C++ Standard Libary page for std::mask_array::operator=(3). This is the assignment operator for a mask_array, and there are three overloads. Let’s get into it ✨

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🎀 NAME 🎀

std::mask_array::operator= — literally std::mask_array::operator=. That’s the name, bestie, no cap 💅

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🌸 Synopsis 🌸

There are three overloads, and yes, all of them are const:

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)

The whole vibe here: assigns values to all referred elements. Overload by overload:

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.

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💖 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.

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🔁 Return value 🔁

• 1,2) — (none). No return, bestie.
• 3) — *this. Yup, it returns itself.

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🧪 Example 🧪

Run this code, bestie:

// 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

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🩹 Defect reports 🩹

okay so these behavior-changing defect reports were applied retroactively to previously published C++ standards — yes, retroactively, bestie:

• DR LWG 123 — applied to C++98; behavior as published: overload (2) was non-const; correct behavior: made const.
• DR LWG 253 — applied to C++98; behavior as published: the copy assignment operator was private; correct behavior: made public.
• DR LWG 621 — applied to C++98; behavior as published: the copy assignment operator was non-const; correct behavior: made const.

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mwah 💋 — footer sign-off time: source http://cppreference.com, version/date 2024.06.10, page std::mask_array::operator=(3). bye bestie, go assign something cute 🫶✨