std::is_null_pointer(3)

🎀 NAME 🎀

hey bestie!! welcome to std::is_null_pointer(3) from the C++ Standard Libary 💖 (yes, that's the manual name, and yes we're obsessed). this page is literally about std::is_null_pointer, no cap.

• std::is_null_pointer — std::is_null_pointer

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✨ Synopsis ✨

Defined in header <type_traits>
template< class T >              (since C++14)
struct is_null_pointer;

std::is_null_pointer is a UnaryTypeTrait.

Checks whether T is the type std::nullptr_t.

Provides the member constant value that is equal to true, if T is the type std::nullptr_t, const std::nullptr_t, volatile std::nullptr_t, or const volatile std::nullptr_t.

Otherwise, value is equal to false.

🚨 bestie warning: if the program adds specializations for std::is_null_pointer or std::is_null_pointer_v (since C++17), the behavior is undefined. do not do that, fr fr.

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🌸 Template parameters 🌸

• T — a type to check

🧚 Helper variable template 🧚

this helper variable template is since C++17, iykyk:

template< class T >
inline constexpr bool is_null_pointer_v = is_null_pointer<T>::value;

💫 Inherited from std::integral_constant 💫

inherited from std::integral_constant — that's the whole vibe.

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💅 Member constants 💅

• value [static] — true if T is the type std::nullptr_t (possibly cv-qualified), false otherwise (public static member constant)

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🦋 Member functions 🦋

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

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🌈 Member types 🌈

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

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🔥 Possible implementation 🔥

template<class T>
struct is_null_pointer : std::is_same<std::nullptr_t,
std::remove_cv_t<T>> {};

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💀 Notes 💀

std::is_pointer is false for std::nullptr_t because it is not a built-in pointer type.

Feature-test macro tea ☕:

• Feature-test macro — __cpp_lib_is_null_pointer
• Value — 201309L
• Std — (C++14)
• Feature — std::is_null_pointer

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🍓 Example 🍓

// Run this code

#include <type_traits>

static_assert(std::is_null_pointer_v<decltype(nullptr)>);
static_assert(!std::is_null_pointer_v<int*>);
static_assert(!std::is_pointer_v<decltype(nullptr)>);
static_assert(std::is_pointer_v<int*>);

int main()
{
}

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👑 See also 👑

• is_void (C++11) — checks if a type is void (class template)
• is_array (C++11) — checks if a type is an array type (class template)
• is_pointer (C++11) — checks if a type is a pointer type (class template)
• is_enum (C++11) — checks if a type is an enumeration type (class template)
• is_union (C++11) — checks if a type is a union type (class template)
• is_class (C++11) — checks if a type is a non-union class type (class template)
• is_function (C++11) — checks if a type is a function type (class template)
• is_object (C++11) — checks if a type is an object type (class template)

kisses bestie 💋 — source: http://cppreference.com, version/date: 2024.06.10, page: std::is_null_pointer(3). bye! 🫶