Thread: arithmetic operator friend functions

i can't quite figure out how the arithmetic operators are supposed to be used, as 2 parameters are being passed in:

Code:

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

class complex
{
private:
    double real; // real part
    double imag; // imaginary part
public:
    complex(double x=0.0, double y=0.0);    
    double magnitude() const; // return magnitude
    double realPart() const; // return real part
    double imagPart() const; // return imaginary part
    
    complex operator- ();

    friend complex operator+ (const complex& lhs, const complex &rhs);
    friend complex operator- (const complex& lhs, const complex &rhs);
    friend complex operator* (const complex& lhs, const complex &rhs);
    friend complex operator/ (const complex& lhs, const complex &rhs);
    friend bool operator== (const complex& lhs, const complex &rhs);
    friend ostream& operator << (ostream& ostr, const complex &x);
    friend istream& operator >> (istream& istr,  complex &x);
};

double complex::magnitude() const
{
    double temp = 0.0;
    temp = (real * real) + (imag * imag);
    temp = sqrt(temp);
}

double complex::realPart() const
{
    return real;
}

double complex::imagPart() const
{
    return imag;
}

complex operator+ (const complex& lhs, const complex &rhs)
{
    return complex(lhs.real - rhs.real, lhs.imag - rhs.imag);
}

complex operator- (const complex& lhs, const complex &rhs)
{
    return complex(lhs.real - rhs.real, lhs.imag - rhs.imag);
}

int main()
{
   // complex number i= 0 + 1i
   complex i(0,1),  z1, z2;

   // input values
   cout << "Enter two complex numbers: ";
   cin >> z1 >> z2;

   cout << "Test the binary arithmetic operators:" << endl;
   cout << " z1 + z2 = " << (z1 + z2) << endl;
   cout << " z1 - z2 = " << (z1 - z2) << endl;
   cout << " z1 * z2 = " << (z1 * z2) << endl;
   cout << " z1 / z2 = " << (z1 / z2) << endl;

   // test relational equality
   if (z1 == z2)
       cout << z1 << " = " << z2 << endl;
   else
       cout << z1 << " != " << z2 << endl;

   // verify that i*i = -1 and that -i*i = 1
   cout << "i*i = " << i*i << endl;
 
   cout << "-i*i = " << -i*i << endl;
   return 0;
}