That's pretty cool, but the downsides of switching to RRA are not only about user experience. When the result is 0.0000000..., the calculator cannot decide whet

That's pretty cool, but the downsides of switching to RRA are not only about user experience. When the result is 0.0000000..., the calculator cannot decide whether it's fine to compute the inverse of that number. For instance, 1/(atan(1/5)-atan(1/239)-pi/4) outputs "Can't calculate". Well alright, this is a division by zero. But then you can try 1/(atan(1/5)-atan(1/239)-pi/4+10^(-100000)), and the output is still "Can't calculate" even though it should really be 10^100000.