What are the pointer-to-member operators ->* and .* in C++?

Question

Yes, I've seen this question and this FAQ, but I still don't understand what ->* and .* mean in C++.
Those pages provide information about the operators (such as overloading), but don't seem to explain well what they are.

What are ->* and .* in C++, and when do you need to use them as compared to -> and .?

Answer 1

I hope this example will clear things for you

//we have a class
struct X
{
   void f() {}
   void g() {}
};

typedef void (X::*pointer)();
//ok, let's take a pointer and assign f to it.
pointer somePointer = &X::f;
//now I want to call somePointer. But for that, I need an object
X x;
//now I call the member function on x like this
(x.*somePointer)(); //will call x.f()
//now, suppose x is not an object but a pointer to object
X* px = new X;
//I want to call the memfun pointer on px. I use ->*
(px ->* somePointer)(); //will call px->f();

Now, you can't use x.somePointer(), or px->somePointer() because there is no such member in class X. For that the special member function pointer call syntax is used... just try a few examples yourself ,you'll get used to it