std::is_pointer
Defined in header <type_traits> |
||
|---|---|---|
template< class T > struct is_pointer; |
(since C++11) |
Checks whether T is a pointer to object or a pointer to function (but not a pointer to member/member function) or a cv-qualified version thereof. Provides the member constant value which is equal to true, if T is a 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.
Template parameters
| T | - | a type to check |
Helper variable template
template< class T > inline constexpr bool is_pointer_v = is_pointer<T>::value; |
(since C++17) |
Inherited from std::integral_constant
Member constants
|
value
[static]
|
true if T is a pointer type , 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> |
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()
{
class A {};
static_assert(
not std::is_pointer<A>::value
&& not std::is_pointer_v<A> // same thing as above, but in C++17!
&& not std::is_pointer<A>() // same as above, using inherited operator bool
&& not std::is_pointer<A>{} // ditto
&& not std::is_pointer<A>()() // same as above, using inherited operator()
&& not std::is_pointer<A>{}() // ditto
&& std::is_pointer<A *>::value
&& std::is_pointer<A const * volatile>()
&& not std::is_pointer<A &>::value
&& not std::is_pointer<int>::value
&& std::is_pointer<int *>::value
&& std::is_pointer<int **>::value
&& not std::is_pointer<int[10]>::value
&& not std::is_pointer<std::nullptr_t>::value
);
}
See also
|
(C++11)
|
checks if a type is a pointer to an 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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