How do you expect that your operator= does anything useful if in its body you just do return *this;? You have to assign to the fields of this the fields of rightSide.

But, more importantly, if your class doesn't manage resources that need some particular treatment in case of copy you can just get away with the compiler-provided assignment operator. It simply copies the fields of one instance into the other, which, for a fraction class, seems perfectly fine.

By the way, usually you implement "regular" operators using their compound counterparts; you may want to have a look at the operator overloading FAQ.

How do you expect that your operator= does anything useful if in its body you just do return *this;? You have to assign to the fields of this the fields of rightSide.

But, more importantly, if your class doesn't manage resources that need some particular treatment in case of copy you can just get away with the compiler-provided assignment operator. It simply copies the fields of one instance into the other, which, for a fraction class, seems perfectly fine.

By the way, usually you implement "regular" operators using their compound counterparts; you may want to have a look at the operator overloading FAQ.