Imperative, functional, OOP

average.cpp

#define IMPERATIVE

#ifdef IMPERATIVE
#include <iostream>

using namespace std;

int main (int narg, char *varg[]) {
    if (narg != 4) {
        cout << "Usage:\n program_name [number] [number] [number]\n";
        return 0;
    }
    
    cout << "Average:\n" << (atof(varg[1]) + atof(varg[2]) + atof(varg[3]))/3 << "\n";
    return 0;
}
#endif

#ifdef FUNCTIONAL
#include <stdio.h>
#include <stdlib.h>

double sum (double a, double b) {
    return a + b;
}

double divide (double a, double b) {
    return a/b;
}

void print (char *a) {
    cout << a << endl;
}

int main (int narg, char *varg[]) {
    double a = 0, b = 0, c = 0,
        average = 0;
    
    if (narg != 4) {
        print("Usage:" << endl << "program_name [number] [number] [number]" << endl);
        
        return 0;
    }
    
    print(
        "Average: " <<
        divide(
            sum(
                atof(varg[1]),
                sum(
                    atof(varg[2]),
                    atof(varg[3])
                )
            ),
            3
        )
    );
    
    return 0;
}
#endif

#ifdef OOP
#include <iostream>

using namespace std;

class Sum {
    double sum, total;
    
    public:
    
    Sum () {
        sum = 0;
        total = 0;
    }
    
    Sum add (double a) {
        sum += a;
        total++;
        
        return *this;
    }
    
    Sum operator+ (double a) {
        return add(a);
    }
    
    double average () {
        return total ? sum/total : 0;
    }
};

int main (int narg, char *varg[]) {
    Sum sum;
    
    if (narg != 4) {
        cout << "Usage:\nprogram_name [number] [number] [number]\n";
        return 0;
    }
    
    /**
     * Method chaining
     *
     * cout << "Average:\n" << (sum + atof(varg[1]) + atof(varg[2]) + atof(varg[3])).average() << "\n";
     */
    sum.add(atof(varg[1]));
    sum.add(atof(varg[2]));
    sum.add(atof(varg[3]));
    
    cout << "Average:\n" << sum.average() << "\n";
    return 0;
}
#endif