std::is_null_pointer
From cppreference.com
                    
                                        
                    
                    
                                                            
                    | Defined in header  <type_traits> | ||
| template< class T > struct is_null_pointer; | (since C++14) | |
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.
| Contents | 
[edit] Template parameters
| T | - | a type to check | 
[edit] Helper variable template
| template< class T > inline constexpr bool is_null_pointer_v = is_null_pointer<T>::value; | (since C++17) | |
Inherited from std::integral_constant
Member constants
| value [static] | true if Tis the type std::nullptr_t (possibly cv-qualified) , false otherwise(public static member constant) | 
Member functions
| operator bool | converts the object to bool, returns value(public member function) | 
| operator() (C++14) | returns value(public member function) | 
Member types
| Type | Definition | 
| value_type | bool | 
| type | std::integral_constant<bool, value> | 
[edit] Possible implementation
| template< class T > struct is_null_pointer : std::is_same<std::nullptr_t, typename std::remove_cv<T>::type> {}; | 
[edit] Notes
std::is_pointer is false for std::nullptr_t because it is not a built-in pointer type.
[edit] Example
Run this code
#include <iostream> #include <type_traits> int main() { std::cout << std::boolalpha << std::is_null_pointer< decltype(nullptr) >::value << ' ' << std::is_null_pointer< int* >::value << '\n' << std::is_pointer< decltype(nullptr) >::value << ' ' << std::is_pointer<int*>::value << '\n'; }
Output:
true false false true
[edit] See also
| (C++11) | checks if a type is void (class template) | 
| (C++11) | checks if a type is an array type (class template) | 
| (C++11) | checks if a type is a pointer type (class template) | 
| (C++11) | checks if a type is an enumeration type (class template) | 
| (C++11) | checks if a type is an union type (class template) | 
| (C++11) | checks if a type is a non-union class type (class template) | 
| (C++11) | checks if a type is a function type (class template) | 
| (C++11) | checks if a type is object type (class template) | 


