We have seen that Prolog can have difficulties with infinite data sets, such as that produced by the clauses

which causes an occur-check problem. In Haskell (Chapter 3), infinite data constructions, such as the foregoing, are possible using delayed evaluation. Does delayed evaluation make sense in Prolog? Can you think of any other ways infinite data structures might be dealt with?

int (0). int (X) - int (Y), X is Y + 1. self-referential terms such as: and with X = [1|X]