Original version

A hardware store

The program determines the price of various configurations of a computer. Two selections must be made when configuring a computer: one for an expansion card and an other for monitor. The slot for an expansion card must contain one of the three options:

• CDROM drive
• Tape drive
• Netword card

The monitor must be either:

• Monochrom
• Color

Questions:

• Are the classes providing the right abstractions?
• Are there ways to eliminate complexity from the program by changing its abstractions?

In reading the program, think about how it may be simplified. Write your own version, compile, and run it. What you gain and what you loose with the new version?

#include <iostream>
using namespace std;

enum CARD       {CDROM, TAPE, NETWORK };
enum MONITOR    { MONO, COLOR };

class Card
{
public:
    virtual int     price() = 0;
    virtual char   *name() = 0;
    virtual int     rebate();
};

class Network : public Card
{
public:
    int     price();
    char   *name();
};

class Tape : public Card
{
public:
    int     price();
    char   *name();
};

class CDRom : public Card
{
public:
    int     price();
    char   *name();
    int     rebate();
};

class Monitor
{
public:
    virtual int     price() = 0;
    virtual char   *name() = 0;
};

class Color : public Monitor
{
public:
    int     price();
    char   *name();
};

class Monochrome : public Monitor
{
public:
    int     price();
    char   *name();
};

int   Card::rebate()  { return 45; }

int   Network::price()    { return 600; }
char *Network::name()     { return "Network"; }

int   CDRom::price()      { return 1500; }
char *CDRom::name()       { return "CDRom"; }
int   CDRom::rebate()     { return 135; }

int   Tape::price()       { return 1000; }
char *Tape::name()        { return "Tape"; }

int   Color::price()      { return 1500; }
char *Color::name()       { return "Color"; }

int   Monochrome::price() { return 500; }
char *Monochrome::name()  { return "Mono"; }

class Computer
{
public:
            Computer( CARD, MONITOR );
           ~Computer();
    int     netPrice();
    void    print();
private:
    Card    *card;
    Monitor *mon;
};

Computer::Computer( CARD c, MONITOR m )
{
    switch( c )
    {
        case NETWORK:   card = new Network;     break;
        case CDROM:     card = new CDRom;       break;
        case TAPE:      card = new Tape;        break;
    }
    switch( m )
    {
        case MONO:      mon = new Monochrome;   break;
        case COLOR:     mon = new Color;        break;
    }
}

Computer::~Computer()
{
    delete card;
    delete mon;
}

int   Computer::netPrice()
{
    return mon->price() + card->price() - card->rebate();
}

void    Computer::print()
{
    cout << "Configuration = " << card->name() 
         << ", "               << mon->name()  
         << ", net price = "   << netPrice() 
         << endl;
}

int main()
{
    Computer nm( NETWORK, MONO );
    Computer cm( CDROM,   MONO );
    Computer tm( TAPE,    MONO );
    Computer nc( NETWORK, COLOR );
    Computer cc( CDROM,   COLOR );
    Computer tc( TAPE,    COLOR );

    nm.print();
    cm.print();
    tm.print();
    nc.print();
    cc.print();
    tc.print();

    return 0;
}