> (= doomsday* 1) ; how to represent infinity? 1 will do,
> till Arc gets support.
Arc supports infinity as well as anything that uses ieee floating point. Mzscheme can directly read it with something like:
(= doomsday* +inf.0)
Alternatively, you can divide by 0, if you're sure that the division will happen in float-mode -- division-by-zero is well-defined in ieee floating arithmetic.