std::is_pointer

Defined in header `<type_traits>`
`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.

The behavior of a program that adds specializations for std::is_pointer or std::is_pointer_v is undefined.

Template parameters

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()
{
    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 (*)()>
    );
}

is_member_pointer (C++11)	checks if a type is a pointer to a non-static member function or object (class template)
is_member_object_pointer (C++11)	checks if a type is a pointer to a non-static member object (class template)
is_member_function_pointer (C++11)	checks if a type is a pointer to a non-static member function (class template)
is_array (C++11)	checks if a type is an array type (class template)
is_scalar (C++11)	checks if a type is a scalar type (class template)

Docs

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