std::negation(3)

💅 std::negation(3) — from the C++ Standard Libary 💅

✨ NAME ✨

std::negation — std::negation. That’s literally the name, bestie, no cap. It’s the C++ Standard Libary page for std::negation.

---

🌸 Synopsis 🌸

Defined in header <type_traits>
template< class B >              (since C++17)
struct negation;

okay so std::negation forms the logical negation of the type trait B 💅

The type std::negation<B> is a UnaryTypeTrait with a base characteristic of std::bool_constant<!bool(B::value)>.

🚨 bestie, important: if the program adds specializations for std::negation or std::negation_v, the behavior is undefined. not cute, not iconic, just undefined 😭

---

🦋 Template parameters 🦋

• B — any type such that the expression bool(B::value) is a valid constant expression.

🎀 Helper variable template 🎀

template< class B >                                     (since C++17)
inline constexpr bool negation_v = negation<B>::value;

🫶 Inherited from std::integral_constant 🫶

---

💖 Member constants 💖

• value — true if B has a member ::value that is false when explicitly converted to [static] bool, false otherwise (public static member constant).

---

💅 Member functions 💅

• operator bool — converts the object to bool, returns value (public member function).
• operator() — returns value (C++14) (public member function).

---

🌈 Member types 🌈

• value_type — bool
• type — std::integral_constant<bool, value>

---

✨ Possible implementation ✨

template<class B>
struct negation : std::bool_constant<!bool(B::value)> { };

---

📝 Notes 📝

• Feature-test macro: __cpp_lib_logical_traits — Value: 201510L — Std: (C++17) — Feature: Logical operator type traits

---

💻 Example 💻

Run this code, bestie:

       // Run this code

        #include <iostream>
        #include <type_traits>

        static_assert(
            std::is_same<
                std::bool_constant<false>,
                typename std::negation<std::bool_constant<true>>::type>::value,
            "");
        static_assert(
            std::is_same<
                std::bool_constant<true>,
                typename
       std::negation<std::bool_constant<false>>::type>::value,
            "");

        int main()
        {
            std::cout << std::boolalpha;
            std::cout << std::negation<std::bool_constant<true>>::value <<
       '\n';
            std::cout << std::negation<std::bool_constant<false>>::value <<
       '\n';
        }

📤 Output 📤

false
true

---

👀 See also 👀

• conjunction — variadic logical AND metafunction (C++17) (class template)
• disjunction — variadic logical OR metafunction (C++17) (class template)
• integral_constant — (C++11) (class template)
• bool_constant — compile-time constant of specified type with specified value (C++17) (class template)

---

okay bestie, that’s the whole page 💖 source: http://cppreference.com, version/date stamp: 2024.06.10, and this is std::negation(3) signing off 🎀✨