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With Comparators
this example from a Well House Consultants training course
More on this [link]
Source code: comparetors.cpp Module: C051
#include <iostream>
using namespace std;

class Computer {
                Computer(float price, int year);
                virtual float getvalue(int inyear) {};
                virtual const char* getkeeper() {};
                Computer* more_valuable(Computer *);
                static Computer* most_valuable(Computer **, int);
                float original; // Original Price
                int o_year; // Purchase year

Computer::Computer(float price, int year) {
        original = price;
        o_year = year;

Computer* Computer::more_valuable(Computer* that) {
        float thisval = this->getvalue(2011);
        float thatval = that->getvalue(2011);
        return thisval > thatval ? this : that;

Computer* Computer::most_valuable(Computer** thems, int num) {
        Computer* sofar = thems[0];
        int i;
        for (i=1; i<num; i++) sofar = sofar->more_valuable(thems[i]);
        return sofar;

class Delegate :public Computer{
                Delegate(float price, int year);
                float getvalue(int yr);
                const char* getkeeper() ;

Delegate::Delegate (float pr, int yr) : Computer (pr, yr) {

float Delegate::getvalue(int inyear) {
        float worth = original - (inyear - o_year) * original / 3.0 ;
        return worth > 0.0 ? worth : 0.0f ;

const char * Delegate::getkeeper() {
        return "Used by anyone!";

class Staff:public Computer {
                Staff(float price, int year);
                Staff(float price, int year, const char* keeper);
                float getvalue(int yr);
                const char* getkeeper() ;
                const char * keeper;


Staff::Staff (float pr, int yr) : Computer (pr, yr) {
        keeper = "Pool System";

Staff::Staff (float pr, int yr, const char* whom) : Computer (pr, yr) {
        keeper = whom;

float Staff::getvalue(int inyear) {
        float worth = original - (inyear - o_year) * original / 10.0 ;
        return worth > 0.0 ? worth : 0.0f ;

const char * Staff::getkeeper() {
        return keeper;

main () {

        Computer* fleet[5];
        fleet[0] = new Staff(1700.0F,2009,"Graham");
        fleet[1] = new Staff(888.0F,2010,"Chris");
        fleet[2] = new Delegate(1700.0F,2009);
        fleet[3] = new Delegate(888.0F,2010);
        fleet[4] = new Staff(1000.0F,2010);
        int fleetsize = 5;
        int i;
        int yr;

        for (yr=2010; yr<2015; yr++) {
        for (i=0; i<fleetsize; i++) {
                float valnow = fleet[i]->getvalue(yr);
                cout << valnow << endl;
                cout << fleet[i]->getkeeper() << endl;
        cout <<endl;

        Computer * is = fleet[1];
        Computer * ers = fleet[3];

// Dymanic or object method - "more" ... runs on one object, given another

        Computer * it = is->more_valuable(ers);
        cout << "More valuable looked after by " << it->getkeeper() << endl;

// Static or class method - "most" runs on class given array or objects

        Computer * jealous = Computer::most_valuable(fleet,fleetsize);
        cout << "Most valuable looked after by " << jealous->getkeeper() << endl;

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