Why does operator = return *this?

Question

Say I want to override the operator = so I can do something like

Poly p1;  // an object representing a polynomial
Poly p2;  // another object of the         


        

Answer 1

You return *this so you can write normal compound C++ = statements like:

Poly p1; //an object representing a polynomial
Poly p2;
Poly p2;

// ...

p3 = p2 = p1;  //assigns all the contents of p1 to p2 and then to p3

because that statement is basically:

p3.operator=(p2.operator=(p1));

If p2.operator=(...) didn't return *this you'd have nothing meaningful to pass into p3.operator=(...).