std::is_pointer - cppreference.com

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`template< class T > struct is_pointer;`		(since C++11)

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

Helper variable template

`template< class T > constexpr bool is_pointer_v = is_pointer<T>::value;`		(since C++17)

Inherited from std::integral_constant

Member constants

true if T is a pointer type, false otherwise
(public static member constant)

Member functions

	converts the object to `bool`, returns `value` (public member function)
	returns `value` (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

#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 (*)()>
    );
}