difference between global operator and member operator

Question

Is there a difference between defining a global operator that takes two references for a class and defining a member operator that takes only the right operand?

Glob

Answer 1

There is at least one difference. A member operator is subject to access modifiers and can be public, protected or private. A global member variable is not subject to access modifier restrictions.

This is particularly helpful when you want to disable certain operators like assignment

class Foo { 
  ...
private:
  Foo& operator=(const Foo&); 
};

You could achieve the same effect by having a declared only global operator. But it would result in a link error vs. a compile error (nipick: yes it would result in a link error within Foo)