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)