std::is_pointer(3)

NAME
std::is_pointer - std::is_pointer

Synopsis
   Defined in header <type_traits>
   template< class T > (since C++11)
   struct is_pointer;
   std::is_pointer is a UnaryTypeTrait.
   Checks whether T is a pointer to object or function (including pointer to void, but
   excluding pointer to member) or a cv-qualified version thereof. Provides the member
   constant value which is equal to true, if T is an object/function pointer type.
   Otherwise, value is equal to false.
   If the program adds specializations for std::is_pointer or std::is_pointer_v, the
   behavior is undefined.

Template parameters
   T - a type to check
   Helper variable template
   template< class T > (since C++17)
   inline constexpr bool is_pointer_v = is_pointer<T>::value; Inherited from std::integral_constant

Member constants
   value true if T is a pointer type, false otherwise
   [static] (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
   Type Definition
   value_type bool
   type std::integral_constant<bool, value>

Possible implementation
   template<class T>
   struct is_pointer : std::false_type {};
   template<class T>
   struct is_pointer<T*> : std::true_type {};
   template<class T>
   struct is_pointer<T* const> : std::true_type {};
   template<class T>
   struct is_pointer<T* volatile> : std::true_type {};
   template<class T>
   struct is_pointer<T* const volatile> : std::true_type {};

Example
// Run this code
 #include <type_traits>
 int main()
 {
     struct A
     {
         int m;
         void f() {}
     };
     int A::*mem_data_ptr = &A::m; // a pointer to member data
     void (A::*mem_fun_ptr)() = &A::f; // a pointer to member function
     static_assert(
            ! std::is_pointer<A>::value
         && ! std::is_pointer_v<A> // same thing as above, but in C++17!
         && ! std::is_pointer<A>() // same as above, using inherited operator bool
         && ! std::is_pointer<A>{} // ditto
         && ! std::is_pointer<A>()() // same as above, using inherited operator()
         && ! std::is_pointer<A>{}() // ditto
         && std::is_pointer_v<A*>
         && std::is_pointer_v<A const* volatile>
         && ! std::is_pointer_v<A&>
         && ! std::is_pointer_v<decltype(mem_data_ptr)>
         && ! std::is_pointer_v<decltype(mem_fun_ptr)>
         && std::is_pointer_v<void*>
         && ! std::is_pointer_v<int>
         && std::is_pointer_v<int*>
         && std::is_pointer_v<int**>
         && ! std::is_pointer_v<int[10]>
         && ! std::is_pointer_v<std::nullptr_t>
         && std::is_pointer_v<void (*)()>
     );
 }

See also
   is_member_pointer checks if a type is a pointer to a non-static member
   (C++11) function or object
                        (class template)
   is_member_object_pointer checks if a type is a pointer to a non-static member
   (C++11) object
                        (class template)
   is_member_function_pointer checks if a type is a pointer to a non-static member
   (C++11) function
                        (class template)
   is_array checks if a type is an array type
   (C++11) (class template)
   is_scalar checks if a type is a scalar type
   (C++11) (class template)