Chapter 9, Problem 7: OOP By Robert Lafore

Problem Statement:

Start with the COUNTEN2 program in this chapter. It can increment or decrement a
counter, but only using prefix notation. Using inheritance, add the ability to use postfix
notation for both incrementing and decrementing. (See Chapter 8 for a description of
postfix notation.)

Solution:

//Ahmad Furqan

//P9.7

#include <iostream>

#include <conio.h>

using namespace std;

////////////////////////////////////////////////////////////////

class Counter

{

protected: //NOTE: not private

unsigned int count; //count

public:

Counter() : count() //constructor, no args

{ }

Counter(int c) : count(c) //constructor, one arg

{ }

unsigned int get_count() const //return count

{

return count;

}

Counter operator ++ () //incr count (prefix)

{

return Counter(++count);

}

};

////////////////////////////////////////////////////////////////

class CountDn : public Counter

{

public:

CountDn() : Counter() //constructor, no args

{ }

CountDn(int c) : Counter(c) //constructor, 1 arg

{ }

CountDn operator -- () //decr count (prefix)

{

return CountDn(--count);

}

};

////////////////////////////////////////////////////////////////

class Countupdown :public CountDn

{

public:

Countupdown() :CountDn()

{}

Countupdown(int c) :CountDn(c)

{}

Countupdown operator ++(int)

{

return Countupdown(count++);

}

Countupdown operator --(int)

{

return Countupdown(count--);

}

};

////////////////////////////////////////////////////////////////

void main(void)

{

CountDn c1; //class CountDn

CountDn c2(100);

cout << "\nc1 = " << c1.get_count(); //display

cout << "\nc2 = " << c2.get_count(); //display

++c1; ++c1; c1++; //increment c1

cout << "\nc1 = " << c1.get_count(); //display it

--c2; c2--; //decrement c2

cout << "\nc2 = " << c2.get_count(); //display it

CountDn c3 = c2--; //create c3 from c2

cout << "\nc3 = " << c3.get_count(); //display c3

cout << endl;

_getch();

}