Defined in header <type_traits> | ||
|---|---|---|
template< class T > struct is_pointer; | (since C++11) |
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.
The behavior of a program that adds specializations for is_pointer or is_pointer_v (since C++17) is undefined.
| T | - | a type to check |
template< class T > inline constexpr bool is_pointer_v = is_pointer<T>::value; | (since C++17) |
| value
[static] | true if T is a pointer type, false otherwise (public static member constant) |
| operator bool | converts the object to bool, returns value (public member function) |
| operator()
(C++14) | returns value (public member function) |
| Type | Definition |
|---|---|
value_type | bool |
type | std::integral_constant<bool, value> |
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 {}; |
#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>
);
}|
(C++11) | checks if a type is a pointer to a non-static member function or object (class template) |
|
(C++11) | checks if a type is a pointer to a non-static member object (class template) |
|
(C++11) | checks if a type is a pointer to a non-static member function (class template) |
|
(C++11) | checks if a type is an array type (class template) |
|
(C++11) | checks if a type is a scalar type (class template) |
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https://en.cppreference.com/w/cpp/types/is_pointer