voidExtended_stack::clear()/*Pre: None.Post: If theExtended_stack is not empty, all entries are removed.*/{ }boolExtended_stack::full() const/*Pre: None.Post: If theExtended_stack is full, true is returned.Otherwise false is returned.*/{ }int Extended_stack::size()const/*Pre: None.Post:Returns the number of entries in the Extended_stack*/{ }