Can a class member function be invoked without an object?

I was learning the history about Lambda’s in C++ and saw the following code (which is not lambda) but I am surprised how it Works

struct Printer{
void operator() (int x) const{
    std::cout << x << '\n';
 }
};

 int main(){
   std::vector <int> vint;
   //doing it the C++ 03 way
    vint.push_back(1);
    vint.push_back(7);

 std::for_each(vint.begin(),vint.end(), Printer());

}

How is the Printer() call in the for_each function working?

>Solution :

Printer() is an instance of the Printer class. It will result in a temporary object of type Printer which is passed to std::for_each.

This is the object on which operator() is called by std::for_each internally.

Without an object of type Printer, it is not possible to call the operator() member function.