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std::is_member_pointer

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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.

Contents

[edit] Template parameters

T - a type to check

[edit] Helper variable template

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

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>

[edit] 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> {};

[edit] 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());
}

[edit] See also

(C++11)
 checks if a type is a pointer type
(class template) [edit]
(C++11)
 checks if a type is a non-static member object pointer
(class template) [edit]
(C++11)
 checks if a type is a non-static member function pointer
(class template) [edit]
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