Operator Overloading in a hierarchy

Question 1

When do you use the “using” declaration?

Answer 1

If you want to bring down candidate values in the derived class from the base class with different arguments.

Question 2

What are the absolute member operators within a hierarchy?

Answer 2

1. [ ]
2. =
3. +=
4. ++(prefix)

Question 3

When calling an overloaded assignment operator to kickstart the base class’s assignment operator, what do the following operations do?

1. *this = source_obj;
2. (base)*this = source_obj);

Answer 3

1. Does compile. BUT this is infinitely recursive and will call the derived class’s assignment operator repeatedly.
2. Does not compile. This will have a syntax error because it is trying to type convert without a cast or upcasting. The error is will be “rvalue when expected lvalue” because it will attempt to make a type converted copy with a temporary variable.

Question 4

How do you kickstart a base class’s operator from a derived class that has the same operator implemented?

Answer 4

1. static_cast(*this) = 2nd_operand;
2. base::operator = (2nd_operand);
3. 2nd_operand.operator = (2nd_operand);

Question 5

With FUNCTION overloading in C++, what happens when we have an operator with different arguments in the derived and base class and we try to use the base class’s operator in the derived class?

Answer 5

Syntax error. The compiler will find the operator in the derived class scope and cause an error because the parent’s operator is hidden.

Question 6

What happens when operators of a derived class have the same name operators of their parent’s class?

Answer 6

Operators of a derived class “hide” their parent operators as would be expected with any member functions.

Question 7

How do you call a base class’s member operator in a derived class?

Answer 7

1. base::operator += (2nd_operand);

2. static_cast (*this) = 2nd_operand;

Question 8

What are the non_member operators?

Answer 8

Any operator whose first operand is not an object of the class.

bit shifting operators: <>
conditional operators: , <=, >=, !=, ==
binary arithmetic operators: +, -, ++(postfix), / , %

Question 9

Why is using “friends” for non-member operators okay for object-oriented programming?

Answer 9

Because it allows for direct access of the data members (which should be protected or private) without the use of setters and getters (which is not object-oriented).

Question 10

What is the absolute case to make an operator a non-member?

Answer 10

The first operand is not an object of the class.

Question 11

How do you call a non-member (friend) operator from a base class in a derived class?

Answer 11

friends are not inherited so, to call a non-member friend operator (or use it in some way) of the base class in the derived class you can:

1. use static cast to type convert the operator; operand_1 + static_cast(operand_2);
OR
2. use the operator to act as a wrapper function to call a  member function in the derived class that does the important stuff. Then call the member function.
operand_2.function(operand_1);