给学妹改程序

#include <iostream>
#include <cmath>
using namespace std;
class Complex
{public:
Complex(){real=0;imag=0;}
Complex(double r,double i){real=r;imag=i;}
Complex operator +(Complex &c2);
Complex operator -(Complex &c2);
Complex operator *(Complex &c2);
Complex operator /(Complex &c2);
Complex operator ++();
Complex operator ++(int);
bool operator <(Complex &c2)
{
if(sqrt(real*real+imag*imag)<sqrt(c2.real*c2.real+c2.imag*c2.imag))
return true;
else
return false;
}
bool operator >(Complex &c2)
{
if(sqrt(real*real+imag*imag)>sqrt(c2.real*c2.real+c2.imag*c2.imag))
return true;
else
return false;
}
bool operator == (Complex &c2)
{
if(real == c2.real && imag == c2.imag )
return true;
else
return false;
}
friend ostream & operator <<(ostream &,Complex &);
friend istream & operator >>(istream &,Complex &);
void display();
private:
double real;
double imag;
};
Complex Complex::operator+(Complex &c2)
{
Complex c;
c.real=real+c2.real;
c.imag=imag+c2.imag;
return c;
}
Complex Complex::operator -(Complex &c2)
{
Complex c;
c.real=real-c2.real;
c.imag=imag-c2.imag;
return c;
}
Complex Complex::operator *(Complex &c2)
{
Complex c;
c.real=real*c2.real-imag*c2.imag;
c.imag=imag*c2.real+real*c2.imag;
return c;
}
Complex Complex::operator /(Complex &c2)
{  Complex c;
c.real=(real*c2.real+imag*c2.imag)/(c2.real*c2.real+c2.imag*c2.imag);
c.imag=(imag*c2.real+real*c2.imag)/(c2.real*c2.real+c2.imag*c2.imag);
return c;
}

Complex Complex::operator++(int)
{
Complex c;
c.real=real+1;
return c;
}
Complex Complex::operator ++()
{
real=real+1;
return *this;
}

void compare(Complex c1,Complex c2)
{
if(c1>c2)
{
cout<<c1<<">"<<c2<<endl;
}
else if (c1<c2)
{
cout<<c1<<"<"<<c2<<endl;
}
else if (c1 ==c2)
{
cout<<c1 <<"=="<< c2 <<endl;
}
}

ostream& operator<<(ostream &output,Complex &c)
{
if(c.real == 0 && c.imag == 0)
cout<<"0";
else
{
if(c.imag>=0)
output<<"("<<c.real<<"+"<<c.imag<<"i)";
else
output<<"("<<c.real<<c.imag<<"i)";
}

return output;
}
istream& operator>>(istream & input,Complex &c)
{   cout<<"input real part and imaginary part of complex number:";
input>>c.real>>c.imag;
return input;
}
int main()
{
Complex c1,c2,c3;
cin>>c1>>c2;
c3=c1+c2;
cout<<c1<<"+"<<c2<<"="<<c3<<endl;
c3=c1-c2;
cout<<c1<<"-"<<c2<<"="<<c3<<endl;
c3=c1*c2;
cout<<c1<<"*"<<c2<<"="<<c3<<endl;
c3=c1/c2;
cout<<c1<<"/"<<c2<<"="<<c3<<endl;
cout<<"c1 == "<<c1<<endl;
c1++;
cout<<"c1++ = "<<c1<<endl;

cout<<"c2 == "<<c2<<endl;
++c2;
cout<<"++c2 == "<<c2<<endl;
compare(c1 ,c2);
return 0;
}