You might be thinking "what about libraries that require floating-point", and that's a good concern. Luckily in Haskell there's the Num typeclass, so your libraries can let users use whatever fractional number type they'd like.
# where R is some r such that Num r
let huge = <the largest (finite) value in R>
let inf = huge * huge # can't be finite unless you
# truncate or saturate or something
let nan = inf - inf # can't be either of
# infinite (infinitely < +inf and > -inf), or
# finite (catastrophic rounding errors)