#include <iostream>
using namespace std;

/**
 * class to implement complex number
 */
class Complex {
	double real, imag;

public:
	/**
	 * default constructor with no argument
	 */
	Complex() : real(0), imag(0) { 
		cout << "call default constructor" << endl; 
	}
	
	/**
	 * copy constructor
	 */
	Complex(const Complex& c) { 
		real = c.real; 
		imag = c.imag; 
	}
	
	/**
	 * constructor with 2 arguments but one is assigned !
	 * declared explicit !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
	 */
	explicit Complex( double r, double i = 0.0) {
		cout << "call constructor with  two arguments: real=" << r
			<< ", imag=" << i << endl; 
		real = r; imag = i; 
	}
  
  	/**
  	 * overloading of addition operator
  	 */
	Complex operator+(const Complex& c) {
		double tmp_real = real + c.real;
		double tmp_imag = imag + c.imag;
		return Complex(tmp_real, tmp_imag);
  	}
  
	bool operator==(Complex rhs) {
		return (real == rhs.real && imag == rhs.imag) ? true : false;
	}
    
	friend ostream& operator<<(ostream& out, Complex& c) {
		out << "(" << c.real << "," << c.imag << ")";
	}
};


int main() {
	Complex one(1);
  	Complex sum;
  	
	cout << one << endl;
	
	// *** explicit *** conversion of 3 into Complex(3, 0)
	sum = one + Complex(3); 
	
	cout << sum << endl;
  
  	// *** explicit *** conversion of 4 into Complex(4, 0)
  	if (sum == Complex(4.0)) {
  		cout << "result is valid" << endl;
  	} else {
  		cout << "error !!!" << endl;
  	}
  	
	return 0;
}