Question

Modify the program 7-5 (pr7-5.cpp) on page 425 by performing the following:

1. Add an overloaded constructor that has a parameter for radius. Negative values should result in radius set to 1.0. (see example 7-6 page 427)

2. Add a member function calcCircumference() to compute and return the circle circumference (2 * 3.14 * radius).

3. In main() "circle1" should be instantiated with a value for radius.

// This program uses a constructor to initialize a member variable.

#include <iostream>

#include <cmath>

using namespace std;

// Circle class declaration

class Circle

{ private:

double radius;

   public: // Member function prototypes

Circle();

void setRadius(double);

double calcArea();

};

// Circle member function implementation section

/********************************************

* Circle::Circle *

* This is the constructor. It initializes *

* the radius class member variable. *

********************************************/

Circle::Circle()

{ radius = 1.0;

}

/********************************************

* Circle::setRadius *

* This function validates the value passed *

* to it before assigning it to the radius *

* member variable. *

********************************************/

void Circle::setRadius(double r)

{ if (r >= 0.0)

radius = r;

// else leave it set to its previous value

}

  

/**********************************************

* Circle::calcArea *

* This function calculates and returns the *

* Circle object's area. It does not need any *

* parameters because it can directly access *

* the member variable radius. *

**********************************************/

double Circle::calcArea()

{ return 3.14 * pow(radius, 2);

}

/***************************************

* main *

* The main function creates and uses *

* 2 Circle objects. *

***************************************/

int main()

{

// Define a Circle object. Because the setRadius function

// is never called for it, it will keep the value set

// by the constructor.

Circle circle1;

// Define a second Circle object and set its radius to 2.5

Circle circle2;

circle2.setRadius(2.5);

// Get and display each circle's area

cout << "The area of circle1 is " << circle1.calcArea() << endl;

cout << "The area of circle2 is " << circle2.calcArea() << endl;

return 0;

}

4. In main() add two more output statements for showing the circumference of each of the circles (circle1 and circle2).

Example 7-6 on page 427 shows how to overload constructors.

Save and submit your file as pr7-5_Lab.cpp.

Answer 1

CODE FOR THE FOLLOWING PROGRAM:-

#include <iostream>
#include <cmath>
using namespace std;

// Circle class declaration
    class Circle{ 
        private:
        double radius;
        public: // Member function prototypes

        Circle();
        Circle(double);
        void setRadius(double);
        double calcArea();
        double calcCircumference();
};

// Circle member function implementation section
/********************************************
* Circle::Circle *
* This is the constructor. It initializes *
* the radius class member variable. *
********************************************/

    Circle::Circle()
    { 
        radius = 1.0;
    }

/********************************************
* Circle::Circle(double) *
* This is a parametrized constructor *
* that has a parameter for radius *
********************************************/

    Circle::Circle(double r)
    { 
        if(r<0){
         radius=1.0;   
        }else{
            radius=r;
        }
    }
/********************************************
* Circle::setRadius *
* This function validates the value passed *
* to it before assigning it to the radius *
* member variable. *
********************************************/

    void Circle::setRadius(double r)
    {    
        if (r >= 0.0)
        radius = r;
    // else leave it set to its previous value
}

/**********************************************
* Circle::calcArea *
* This function calculates and returns the *
* Circle object's area. It does not need any *
* parameters because it can directly access *
* the member variable radius. *
**********************************************/

    double Circle::calcArea()
    { 
        return 3.14 * pow(radius, 2);
    }
    
/**********************************************
* Circle::calcCircumference*
* This function calculates and returns the *
* Circle object's circumference. It does not need any *
* parameters because it can directly access *
* the member variable radius. *
**********************************************/
 double Circle::calcCircumference()
    { 
        return 2*3.14*radius;
    }
    
/***************************************
* main *
* The main function creates and uses *
* 2 Circle objects. *
***************************************/

    int main()
    {
    // Define a Circle object. Because the setRadius function
    // is never called for it, it will keep the value set
    // by the constructor.

    Circle circle1;
    // Define a second Circle object and set its radius to 2.5
    Circle circle2(2.5);
    // Get and display each circle's area
    cout << "The area of circle1 is " << circle1.calcArea() << endl;
    cout << "The area of circle2 is " << circle2.calcArea() << endl;
    // Get and display each circle's circumference
    cout << "The circumference of circle1 is " << circle1.calcCircumference() << endl;
    cout << "The circumference of circle2 is " << circle2.calcCircumference() << endl;
    return 0;
}

SCREENSHOT OF THE CODE AND SAMPLE OUTPUT:-

SAMPLE OUTPUT:-

HAPPY LEARNING