Operator Overloading newbie question

In my C++ book, I don't understand this particular example demonstrating operator overloading:

Code:

---

ThreeD ThreeD :: operator=(ThreeD &op2) {
x=op2.x;
y=op2.y;
z=op2.z;
return *this;
}

---

What I don't understand is the need to return *this. I know the function is specified as returning an object type 'ThreeD' but isn't that redundant? Would the following achieve the same thing:

Code:

---

void ThreeD :: operator=(ThreeD&op2) {
x=op2.x;
y=op2.y;
z=op2.z;
return;
}

---

no it would not, because it is designed to assign. the = is the assignment operator, so it needs to return a ThreeD object, not void. if it does return void, then there would be no point to the operator.
basically, it will assign like this:

Code:

---

int main() {
        ThreeD object1, object2;
       
        object1 = object2;
       
        return 0;
}

---

returning *this and having the function return a ThreeD object allows you to do this in main.

Ok thanks for your help. I tried it with void and it behaved as predicted. I think the reason why the book used *this was to allow compound assignments like a=b=c=d; to occur.

okay. thanks. :)