You need to be consistent here. In one case you are returning a new object, and in the other you are returning the original object changed. You should almost certainly be returning a new object. If you want a function that returns the same object changed, you would use the augmented assignment (iadd, for example). You are correct that the reflected operator (rmul, below) would return the same thing as the normal operator (here and in most cases), and is often just a call to its non-reflected equivalent.