Can a std::function store pointers to data members?

Question

From cppreference, I found that:

Class template std::function is a general-purpose polymorphic function wrapper. Instances of std::function can store, copy, and invoke any Callable target -- functions, lambda expressions, bind expressions, or other function objects, as well as pointers to member functions and pointers to data members.

I cannot see why a std::function should be able to store such a pointer and I've never heard before about that feature.
Is it really possible, I missed something or that's an error in the documentation?

How should the operator() behave in such a case?
As from the documentation:

Invokes the stored callable function target with the parameters args.

Anyway, there is no stored callable function target to invoke here. Am I wrong?

To be honest, I cannot even figure out what's the right syntax for such a function, otherwise I'd have written an example to test it.
How could the following template be used to define a pointer to data member?

template< class R, class... Args > class function<R(Args...)> 

Answer 1

The effect of a call to the function call operator of std::function<R(ArgTypes...)>:

R operator()(ArgTypes... args) const 

is equivalent to (§ 20.9.11.2.4 [func.wrap.func.inv]/p1):

INVOKE<R>(f, std::forward<ArgTypes>(args)...) 

whose definition includes the following bullet (§ 20.9.2 [func.require]/p1):

Define INVOKE(f, t1, t2, ..., tN) as follows:

[...]

^1.3 — t1.*f when N == 1 and f is a pointer to member data of a class T and t1 is an object of type T or a reference to an object of type T or a reference to an object of a type derived from T;

then, when f is a pointer to a data member stored in an internal invoker of a std::function, then the std::function itself should define a single argument, e.g.:

std::function<int(std::pair<int,int>)> f = &std::pair<int,int>::first;  f(std::make_pair(1, 2)); 

DEMO