operator overloading

Why?

cout << obj1 << obj2   just like we do cout << i << j;  It is easier than obj1.print();

complex1 + complex2  binary operator...  the alternative is complex1.add(complex2);

complex1 == complex2 operator... the alternative is complex.equal(complex2);

++date, date++ pre and post unary operator

How to do this?

global function

member function

Complex operator-( const Complex & );

Most operators can be implemented with either global or member function, as we do global for + and member for -.

Note that operator << and >> can only be implemented as global friend function.  Why?

Binary operator + example

date1+date2 return temporary date object

use i+j as example, cout << i+j

look into code to see temp is allocated and returned in + operator overloading code

return this for cascading

difference between ++date and date++

can we do (i++)++ ?  why not?

can we do ++(++i) ? why?

Examples:

Complex number class (.cpp .h and main are attached below)

A few notes:

• By looking at the test code, can we figure out what are the constructors?

• How about variable parameters in the constructor?

• >> cin stream extraction operator is tougher to control, what would be a better way to do input?

• considering z = x+y

  • how many operators are there?

  • first one is +, which object is calling + routine?

  • what does it return?

  • second one is =, who is calling =?