[Haskell-beginners] How to show a predicate

Hello all, in my program, I do stuff with predicates (a->Bool). For the most part this representation is just fine, but at the very end I need to convert a resulting predicate into a String so I can write it to a file. Wenn I represent my predicates as Lists or Sets, then this is doable and I am tempted to do it this way. The only other option I could come up with was to have a representation of "everything", which would in my case be large (10^8) but finite. Then I could construct a List or a Set at the very end, as [x | x<-everything, p x] without having explicit sets in the intermediate steps. I cannot see any other option, but I thought I better ask.