Is an is_functor C++ trait class possible?

Question

How can I deduce statically if an argument is a C++ function object (functor)?

template 
void test(F f) {}

I tried

Answer 1

template                                 
struct is_functor 
{                                                                   
    typedef char yes[1];                                            
    typedef char no [2];                                            
    template  struct type_check;                     
    template  static yes &chk(type_check*);
    template  static no  &chk(...);                    
    static bool const value = sizeof(chk(nullptr)) == sizeof(yes);     
};

Altered from this answer.

It could be used like...

template
typename std::enable_if::value>::type func()
{
}