std::is_pointer
From cppreference.com
Defined in header <type_traits>
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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.
Contents |
[edit] Template parameters
T | - | a type to check |
[edit] 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
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
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bool |
type
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std::integral_constant<bool, value> |
[edit] 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 {}; |
[edit] 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 (*)()> ); }
[edit] See also
(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) |