calculate dimensions of a circle in c++

[annitaz]

#ifndef CIRCLE_H
#define CIRCLE_H

class Circle {
public:
  //constructors
  Circle();
  Circle(double r);
  //setter
  void setRadius(double r);
  //getter
  double getRadius();
  //calculate the diameter of a circle
  double computeDiameter()const;
  //calculate the area of a circle
  double computeArea()const;
  //calculate the Circumference of a circle
  double computeCircumference()const;
  //checks if radius of circle is bigger
  **bool isBigger(const Circle& other) const;**

private:
  //private data members
  double m_Radius;
};

#endif // CIRCLE_H



#include "circle.h"
#include "math.h"
#include <iostream>
#include <QString>
#include <sstream>
using namespace std;

Circle::Circle()
{
  m_Radius =  0;
}

Circle::Circle(double r)
{
  m_Radius = r;
}

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

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

double Circle::computeDiameter()const{
    return 2* m_Radius;
}

double Circle::computeArea()const {
    return ( m_Radius* m_Radius*M_PI);
}

double Circle::computeCircumference()const {
    return (2* m_Radius*M_PI);
}


#include <iostream>
#include <QTextStream>
#include "circle.h"
using namespace std;

int main(){
    QTextStream cout(stdout);

    Circle c1,c2;     // input
    c1.setRadius(3);
    c2.setRadius(7);

    cout << "Circle with radius " << c1.getRadius() << " has: " << endl;
    cout<< "Diameter " << c1.computeDiameter() << " cm " <<endl;
    cout<< "Area " << c1.computeArea() << " cm" <<endl;
    cout<< "Circumference " << c1.computeCircumference()<< " cm " <<endl<<endl;

    cout << "Circle with radius " << c2.getRadius() << " has: " << endl;
    cout<< "Diameter " << c2.computeDiameter() << " cm " <<endl;
    cout<< "Area " << c2.computeArea() << " cm" <<endl;
    cout<< "Circumference " << c2.computeCircumference()<< " cm " <<endl<<endl;

return 0;
}

The function isBigger() returns true (or false) if the radius of the Circle instance on which the function is invoked is bigger (or smaller) than the radius of the Circle instance passed to the function.: Can someone help me to implement this function?