Operator Functions As Class Members Vs. As Friend Functions

• Operator functions
  • Member functions
    • Use this keyword to implicitly get argument
    • Gets left operand for binary operators (like +)
    • Leftmost object must be of same class as operator
  • Non member functions
    • Need parameters for both operands
    • Can have object of different class than operator
    • Must be a friend to access private or protected data
  • Called when
    • Left operand of binary operator of same class
    • Single operand of unitary operator of same class
• Overloaded $<<$ operator
  • Left operand of type ostream &; Such as cout object in cout $<<$ classObject
  • Similarly, overloaded $>>$ needs istream &
  • Thus, both must be non-member functions
• Commutative operators
  • May want + to be commutative; So both "a + b" and "b + a" work
  • Suppose we have two different classes
  • Overloaded operator can only be member function when its class is on left
    • HugeIntClass + Long int
    • Can be member function
  • When other way, need a non-member overload function; Long int + HugeIntClass