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Circle Class - Version 5
version 2: ostream& in showdata(), accessor and mutator functions,
and separate compilation.
version 3: static data member, setCircle, area,
circumference and equal functions
version 4: const, friend functions
version 5: overload operators ==, +, <<
Definition Part
% cat circle.h
#ifndef CIRCLE_H
#define CIRCLE_H
// Circle class definition - file circle.h
class Circle
{
friend double distance( Circle& c
); // friend function
friend ostream&
operator<<(ostream& out, Circle& cc );
public:
Circle();
// default constructor
Circle(int x, int y, double r); // constructor
void showdata(ostream& out) const;
double get_radius() const; // accessor
void set_radius( double r ); //
mutator
void setCircle(int x, int y, double r);
double area() const;
double circumference() const;
bool equal( Circle& c2 ) const;
// operator functions
bool operator==(Circle& c2) const;
Circle operator+(Circle& circle2 ) const;
private:
int xcenter;
int ycenter;
double radius;
static double PI; // static data member
};
#endif // CIRCLE_H
Implementation Part
% cat circle.cpp
#include <iostream>
#include <iomanip>
#include <cmath>
using namespace std;
#include "circle.h" // header file
double Circle::PI = 3.14159; // static data member
// default constructor
Circle::Circle(): xcenter(0), ycenter(0), radius(1.0)
{
// empty body when initialization
// section is used
}
// constructer with parameters for initialization
Circle::Circle(int x, int y, double r): xcenter(x),
ycenter(y),radius(r)
{
// empty body when initialization
// section is used
}
void Circle::showdata( ostream& out ) const
{
out << setiosflags(ios::fixed | ios::showpoint ) << setprecision(2);
out << "The circle is centered at (" << xcenter <<
", "
<< ycenter << ")" <<
endl;
out << "Radius = " << radius << endl;
return;
}
// accessor function
double Circle::get_radius() const
{
return radius;
}
// mutator function
void Circle::set_radius(double r)
{
if( r < 0.0 )
{
cout << "The radius cannot be less than zero." <<
endl;
exit(1);
}
else
radius = r;
}
// setCircle() mutator function
void Circle::setCircle(int x, int y, double r)
{
xcenter = x;
ycenter = y;
radius = r;
}
// area
double Circle::area()const
{
return PI*radius*radius;
}
// circumference
double Circle::circumference()const
{
return 2.0 * PI * radius;
}
// operator functions
// test equality of Circle objects
bool Circle::operator==( Circle& c2 ) const
{
bool eq;
eq = (radius==c2.radius) && (xcenter==c2.xcenter)
&& (ycenter==c2.ycenter);
return eq;
}
// add two Circle objects
Circle Circle::operator+(Circle& circle2 ) const
{
Circle temp; // a tenporary Circle
temp.xcenter = xcenter + circle2.xcenter;
temp.ycenter = ycenter + circle2.ycenter;
temp.radius = sqrt(radius*radius + circle2.radius*circle2.radius);
return temp;
}
// non-member friend functions
// distance to origin
double distance( Circle& c)
{
double dist;
dist = c.xcenter*c.xcenter + c.ycenter*c.ycenter;
return sqrt( dist );
}
// overload <<
ostream& operator<<(ostream& out, Circle& cc)
{
out << "A message from a friend (function):" <<
endl;
out << setiosflags(ios::fixed | ios::showpoint
) << setprecision(2);
out << "The circle is centered at (" << cc.xcenter <<
", "
<< cc.ycenter << ")" <<
endl;
out << "Radius = " << cc.radius << endl;
return out;
}
Driver Program
% cat circ5.cpp
// driver program for Circle class example
#include<iostream>
using namespace std;
#include<fstream>
#include "circle.h" // header file
int main()
{
int new_x, new_y;
double new_r;
// declare Circle objects a and b
Circle a(3, 4, 4.0), b;
// display using << operator
cout << "Circle a: " << endl;
cout << a << endl;
// set new values for b
cout << "Enter new values for xcenter, ycenter, and radius:
";
cin >> new_x >> new_y >> new_r;
b.setCircle(new_x, new_y, new_r);
cout << "New values for Circle b: " << endl;
cout << b << endl;
// check equality with == operator
if ( a == b )
cout << "The circle objects are equal" <<
endl;
else
cout << "The circle objects are NOT equal"
<< endl;
// use operator + function
Circle c;
c = a + b;
cout << "\nSum of circles:\n\n;
cout << c << endl;
cout << "Area of a = " << a.area() <<
endl;
cout << "Area of b = " << b.area() <<
endl;
cout << "Area of c = " << c.area() <<
endl;
return 0;
}
Compile and Execute
% g++ circ5.cpp circle.cpp
% a.out
Circle a:
A message from a friend (function):
The circle is centered at (3, 4)
Radius = 4.00
Enter new values for xcenter, ycenter, and radius: 2 2 2.0
New values for Circle b:
A message from a friend (function):
The circle is centered at (2, 2)
Radius = 2.00
The circle objects are NOT equal
Sum of circles:
A message from a friend (function):
The circle is centered at (5, 6)
Radius = 4.47
Area of a = 50.27
Area of b = 12.57
Area of c = 62.83
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