Set - 6

Question 1 :

What do you mean by Stack unwinding?

Answer :

It is a process during exception handling when the destructor is called for all local objects between the place where the exception was thrown and where it is caught.


Question 2 :

Define precondition and post-condition to a member function?

Answer :

Precondition: A precondition is a condition that must be true on entry to a member function. A class is used correctly if preconditions are never false. An operation is not responsible for doing anything sensible if its precondition fails to hold. For example, the interface invariants of stack class say nothing about pushing yet another element on a stack that is already full. We say that isful() is a precondition of the push operation. Post-condition: A post-condition is a condition that must be true on exit from a member function if the precondition was valid on entry to that function. A class is implemented correctly if post-conditions are never false. For example, after pushing an element on the stack, we know that isempty() must necessarily hold. This is a post-condition of the push operation.


Question 3 :

What are the conditions that have to be met for a condition to be an invariant of the class?

Answer :

* The condition should hold at the end of every constructor.
* The condition should hold at the end of every mutator (non-const) operation.


Question 4 :

What is an orthogonal base class? 

Answer :

If two base classes have no overlapping methods or data they are said to be independent of, or orthogonal to each other. Orthogonal in the sense means that two classes operate in different dimensions and do not interfere with each other in any way. The same derived class may inherit such classes with no difficulty.


Question 5 :

What is a node class?

Answer :

A node class is a class that,
* relies on the base class for services and implementation,
* provides a wider interface to the users than its base class,
* relies primarily on virtual functions in its public interface
* depends on all its direct and indirect base class
* can be understood only in the context of the base class
* can be used as base for further derivation
* can be used to create objects.
A node class is a class that has added new services or functionality beyond the services inherited from its base class.