If you are making a complex class you should return a complex object, and it should not be the first operand. I mean given z and w two complex number, the instruction z + w should not modify z! Instead, it should be used in an expression like c = z + w , assigning the result of the sum to another complex number c.

The member you need in this class are just Real and Imaginary, that are two double variables holding real and imaginary part of the compex number itself. You don't need to bother about calculating "i" (in fact, you couldn't even if you needed to). You should just append "i" as a char next to the imaginary value when you print the complex number on screen.

Here are examples:

C++ Syntax (Toggle Plain Text)

Complex Complex::operator+(Complex op2) {
	Complex temp;
	temp.Real = Real + op2.Real;
	temp.Imaginary = Imaginary + op2.Imaginary;
	return temp;
}

Complex Complex::operator+(Complex op2) { Complex temp; temp.Real = Real + op2.Real; temp.Imaginary = Imaginary + op2.Imaginary; return temp; }

to overload the operator+, and

C++ Syntax (Toggle Plain Text)

std::ostream& operator<<(std::ostream& lhs, Complex& obj) {
	lhs << "(";
	if(obj.Real>=0) {
		lhs << "+" << obj.Real;
	}
	else {
		lhs << obj.Real;
	}
	if(obj.Imaginary>=0) {
		lhs << " +" << obj.Imaginary << "i";
	}
	else {
		lhs << " " << obj.Imaginary << "i";
	}
	lhs << ")";
	return lhs;
}

std::ostream& operator<<(std::ostream& lhs, Complex& obj) { lhs << "("; if(obj.Real>=0) { lhs << "+" << obj.Real; } else { lhs << obj.Real; } if(obj.Imaginary>=0) { lhs << " +" << obj.Imaginary << "i"; } else { lhs << " " << obj.Imaginary << "i"; } lhs << ")"; return lhs; }

for output purposes.

Last but not least: square root of -1 is not -1.