4. Class inheritance

#include <cstdlib>  // Standard General Utilities Library
#include <cstdio>   // Input/Output operations (C)
#include <iostream> // Input/Output stream objects
#include <fstream>  // File input and output
#include <ctime>    // Date and time information
#include <cmath>    // Mathematical operations and transformations
using namespace std;

#define pi 3.14

// Classes
class line {
protected:
    double a;
public:

    line() {a = 1;}
    line(double var1) {a = var1;}
};

class circle: public line {
protected:
    double r;
public:
    double area() {return pi * pow(r, 2);}

    circle():line() {r = a;}
    circle(double var1) {r = var1;}
};

class cylinder: public circle {
private:
    double h;
public:
    void assign(double var1, double var2) {r = var1; h = var2;}
    double volume() {return area() * h;}
    void print() {  cout << "Cylinder information:" << endl;
                    cout << "r = " << r << ", h = " << h << endl;
                    cout << "Volume: " << volume() << endl << endl;}

    cylinder() {h = 1;}
    cylinder(double var1) {h = var1;}
    cylinder(double var1, double var2):circle(var1) {h = var2;}
};

class cone: public circle {
private:
    double h;
public:
    void assign(double var1, double var2) {r = var1; h = var2;}
    double volume() {return 1.0 / 3.0 * area() * h;}
    void print() {  cout << "Cone information:" << endl;
                    cout << "r = " << r << ", h = " << h << endl;
                    cout << "Volume: " << volume() << endl << endl;}

    cone() {h = 1;}
    cone(double var1) {h = var1;}
    cone(double var1, double var2):circle(var1) {h = var2;}
};

class rectangle: public line {
protected:
    double b;
public:
    double area() {return a * b;}

    rectangle():line() {b = 1;}
    rectangle(double var1):line(var1) {b = var1;}
    rectangle(double var1, double var2):line(var1) {b = var2;}
};

class parallelepiped: public rectangle{
private:
    double c;
public:
    double volume() {return area() * c;}
    void print() {  cout << "Parallelepiped rectangle information:" << endl;
                    cout << "a = " << a << ", b = " << b << ", c = " << c << endl;
                    cout << "Volume: " << volume() << endl << endl;}

    parallelepiped():rectangle() {c = 1;}
    parallelepiped(double var1):rectangle(var1) {c = var1;}
    parallelepiped(double var1, double var2):rectangle(var1) {c = var2;}
    parallelepiped(double var1, double var2, double var3):rectangle(var1, var2) {c = var3;}
};

// Main program
int main(int argc, char *argv[]) {

    parallelepiped G(4, 2, 3);
    G.print();

    cylinder R(2, 3);
    R.print();

    cone K(2, 3);
    K.print();

    return 0;
}