Calcium is amazing and so is exact real arithmetic or constructive real number, but they all can't avoid practically undecidable inputs. (Algebraic numbers as in Calcium can be made decidable, but they still can take an unreasonable amount of time to compute. Calcium does answer "unknown" for those cases.)
which is pretty darn amazing. pi and e are essentially first class, but a lot of transcendentals aren't. seems like a really neat approach.