Question

C++ 8. Circle Class

Write a Circle class that has the following member variables:
• radius: a double
• pi: a double initialized with the value 3.14159

The class should have the following member functions:

• Default Constructor. A default constructor that sets radius to 0.0.
• Constructor. Accepts the radius of the circle as an argument.
• setRadius. A mutator function for the radius variable.
• getRadius. An accessor function for the radius variable.
• getArea. Returns the area of the circle, which is calculated as area = pi * radius * radius
• getDiameter. Returns the diameter of the circle, which is calculated as diameter = radius * 2
• getCircumference. Returns the circumference of the circle, which is calculated as circumference = 2 * pi * radius

Write a program that demonstrates the Circle class by asking the user for the circle’s radius, creating a Circle object, and then reporting the circle’s area, diameter, and circumference.

Answer 1

#include<iostream>

using namespace std;

class Circle {
private:
    double radius;
    double pi = 3.14159;
public:
    Circle() {}
    Circle(double radius);
    void setRadius(double r);
    double getRadius();
    double getDiameter();
    double getArea();
    double getCircumference();
};

Circle::Circle(double radius) : radius(radius) {}

void Circle::setRadius(double r) {
    radius = r;
}

double Circle::getRadius() {
    return radius;
}

double Circle::getArea() {
    return pi * radius * radius;
}

double Circle::getCircumference() {
    return 2 * pi * radius;
}

double Circle::getDiameter() {
    return 2 * radius;
}

int main() {
    double radius;
    cout << "Enter the circle's radius: ";
    cin >> radius;
    Circle c(radius);
    cout << "Radius: " << c.getRadius() << endl;
    cout << "Area : " << c.getArea() << endl;
    cout << "Diameter: " << c.getDiameter() << endl;
    cout << "Circumference: " << c.getCircumference() << endl;
    return 0;
}