std:: is_member_pointer

From cppreference.com
C++
Metaprogramming library
Type traits
Type categories
(C++11)
(C++11)
(C++11)
is_member_pointer
(C++11)
(C++11)
(C++11)
Type properties
(C++11)
(C++11)
(C++11)
(C++11)
(C++14)
(C++11)
(C++17)
(C++23)
(C++11) (deprecated in C++26)
(C++11)
(C++11)
(C++11) ( until C++20* )
(C++11) (deprecated in C++20)
(C++11)
(C++11)
(C++20)
(C++20)
(C++23)
(C++17)
Type trait constants
(C++11) (C++17) (C++11) (C++11)
Metafunctions
(C++17)
(C++17)
(C++17)
Supported operations
Relationships and property queries
Type modifications
Type transformations
(C++11) (deprecated in C++23)
(C++11) (deprecated in C++23)
(C++11)
(C++20)
(C++11)
(C++17)

(C++11)
(C++11)
(C++20)
(C++11)
(C++11) ( until C++20* ) (C++17)
(C++20)
Compile-time rational arithmetic
Compile-time integer sequences
(C++14)
Defined in header <type_traits>
template < class T >
struct is_member_pointer ;
(since C++11)

std::is_member_pointer is a UnaryTypeTrait .

If T is pointer to non-static member object or a pointer to non-static member function, provides the member constant value equal true . For any other type, value is false .

If the program adds specializations for std::is_member_pointer or std::is_member_pointer_v , the behavior is undefined.

Template parameters

T - a type to check

Helper variable template

template < class T >
constexpr bool is_member_pointer_v = is_member_pointer < T > :: value ;
(since C++17)

Inherited from std:: integral_constant

Member constants

value
[static]
true if T is a member 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_member_pointer_helper : std::false_type {};
 
template<class T, class U>
struct is_member_pointer_helper<T U::*> : std::true_type {};
 
template<class T>
struct is_member_pointer : is_member_pointer_helper<typename std::remove_cv<T>::type> {};

Example

Run this code 
#include <cassert>
#include <type_traits>
 
static_assert(!std::is_member_pointer_v<int*>);
 
struct S
{
    int i{42};
    int foo() { return 0xF00; }
};
using mem_int_ptr_t = int S::*;
using mem_fun_ptr_t = int (S::*)();
static_assert(std::is_member_pointer_v<mem_int_ptr_t>);
static_assert(std::is_member_pointer_v<mem_fun_ptr_t>);
 
int main()
{
    S s;
 
    mem_int_ptr_t pm = &S::i;
    assert(s.i == s.*pm);
 
    mem_fun_ptr_t pmf = &S::foo;
    assert((s.*pmf)() == s.foo());
}

See also

(C++11)
checks if a type is a pointer type
(class template)
(C++11)
checks if a type is a non-static member object pointer
(class template)
(C++11)
checks if a type is a non-static member function pointer
(class template)
Retrieved from " https://en.cppreference.com/mwiki/index.php?title=cpp/types/is_member_pointer&oldid=176539 "