> You are doing it the wrong way, IMHO. You should introduce \cfracleft and > \cfracright in place of \cfracthree and give visual feedback for the position > of the numerator.
I agree with you but this would be a change in our philosophy of handling optional arguments. We for example already treat optional arguments the way I implemented if for \cfrac for \makebox and \framebox in mathed.
Nevertheless, I think that your solution is more intuitive and I'll implement this instead the next days. \makebox and \framebox will stay as they are because there we have two optional arguments that depend on each other.
thanks and regards Uwe
