// Written by: Michael Mozer
// Date:  Oct 13 2003
//
// PROGRAM DESCRIPTION
//
// This program lets a user type in number as a radius.
// It then checks if the number is a valid radius.
// If it is, the program calculates
//   1. the circumference of the circle
//   2. the area of the circle
//   3. the surface area of the sphere
//   4. the volume of the sphere
// for that radius and then prints the result to the screen.
// If it is not, the program prints an error message and quits.

#include <iostream.h>

int calculate(double radius,
              double& circumference,
              double& area,
              double& surf_area,
              double& volume);

void main()
{
    double radius,
           circumference,
           area,
           surface_area,
           volume;
    int result;
 
    cout << "Given a radius, this program will compute" << endl;
    cout << "  1. The cicumference of a circle," << endl;
    cout << "  2. The area of a circle," << endl;
    cout << "  3. The surface area of a sphere, and" << endl;
    cout << "  4. The volume of a sphere." << endl;
    cout << endl;
    cout << "Please enter a non-negative number as the radius: ";
    cin >> radius;
 
    result = calculate(radius, circumference, area, surface_area, volume);
    if (result) 
    {
        cout << "Given the radius of " << radius << endl;
        cout << "The circumference of the circle is " << circumference << endl;
        cout << "The area of the circle is " << area << endl;
        cout << "The surface area of the sphere is " << surface_area << endl;
        cout << "The volume of the sphere is " << volume << endl;
        cout << "Good bye." << endl;
    } 
    else 
    {
        cout << "The number you gave is not a valid radius." << endl;
        cout << "A valid radius must be non-negative." << endl;
        cout << "Please try running this program again.  Bye." << endl;
    }
}

// return 1 if the calculation is successful, return 0 otherwise
int calculate(double radius,
			  double& circumference,
			  double& area,
			  double& surface_area,
			  double& volume)
{
    const double PI = 3.14159;
 
    if (radius < 0.0)
        return 0;

    circumference = 2.0 * PI * radius;
    area = PI * radius * radius;
    surface_area = 4.0 * PI * radius * radius;
    volume = (4.0 / 3.0) * PI * radius * radius * radius;
    return 1;
}