Re: [Haskell-cafe] Set of reals...?

| otherwise = contractSet (contract x0 y0:xs) ys

I think you'll find the original is correct. The first two cases deal with non-overlapping ranges. The only remaining case is overlapping ranges, (partial and full overlap) both these cases are dealt with by contract, and as a result use up both the ranges at the head of both lists, sdo the merged range is prepended to the output list and the tail is calculated by passing the unused tails of both lists to contactSet... Keean.