C++ Operator Overload insertion << and extraction >> operator functions

#include <iostream>
#include <string>
using namespace std;
// declaration section
class Complex/*from w w  w  .  j  a  v  a2  s. c om*/
{
   // prototypes for the overloaded operators
   friend ostream& operator<<(ostream&, const Complex&);
   friend istream& operator>>(istream&, Complex&);
   private:
   double realPart;
   double imaginaryPart;
   public:
   Complex(double real = 0.0, double imag = 0.0)   // inline constructor
   {
      realPart = real;
      imaginaryPart = imag;
   }
};
// overloaded insertion operator function
ostream& operator<<(ostream& out, const Complex& num)
{
   char sign = '+';
   if (num.imaginaryPart < 0)
      sign = '-';
   if (num.realPart == 0 && num.imaginaryPart == 0)
      cout << 0;
   else if (num.imaginaryPart == 0)
      cout << num.realPart;
   else if (num.realPart == 0)
      cout << num.imaginaryPart << 'i';
   else
      cout << num.realPart << ' ' << sign << ' ' << abs(num.imaginaryPart) << 'i';
   return out;
}
// overloaded extraction operator function
istream& operator>>(istream& in, Complex& num)
{
      string temp;
      double value;
      int plusLocation, minusLocation, i_Location;
      in >> value;        // accept the first number
      getline(cin,temp);   // input remaining characters entered, if any
      plusLocation = temp.find('+');   // find whether a + was entered
      minusLocation = temp.find('-');  // find whether a - was entered
      i_Location = temp.find('i');     // find whether an i was entered
      if (plusLocation >= 0 || minusLocation >= 0)
      {
         num.realPart = value;
         if (plusLocation >= 0)
            temp.replace(plusLocation,1," ");
         if (minusLocation >= 0)
            temp.replace(minusLocation,1," ");
         if (i_Location >= 0)
            temp.replace(i_Location,1," ");
         num.imaginaryPart = atof(temp.c_str());   // imaginary part
         if (minusLocation >= 0)
            num.imaginaryPart = -num.imaginaryPart;
      }
      else if (i_Location >= 0)  // only an i follows the first value
      {
            num.realPart = 0.0;
            num.imaginaryPart = value;
      }
      else  // no legitimate characters follow the first number
      {
            num.realPart = value;
            num.imaginaryPart = 0.0;
      }
      return in;
}
int main()
{
         Complex complexOne;
         cout << "Enter a complex number (ex 3.2 + 7.4i): ";
         cin  >> complexOne;   // accept the complex number, using cin
         cout << "The complex number just entered is " << complexOne << endl;
         return 0;
}