Hi Wouter,
I just uploaded a fairly unspectacular package Data.Stream to Hackage. It implements quite a few operations on streams (infinite lists), analogous to those defined in Data.List. Sometimes it is just good to know a list is infinite.
What is the advantage of knowing that a list is infinite? Are these versions just identical to the Data.List versions, but you know you won't encounter [] ? If so, I'm not sure there is a pressing need for this. I would have thought a much more common problem is telling the difference between an empty list and a non-empty list, rather than an infinite list and another type of list. I'm not saying that its not useful, I'm just not sure it deserves to be in the base libraries. We could add a multitude of different data types, each of which is "a list by some other name", but we'd probably end up confusing users more than helping them. As a related point, if you do use infinite lists, and are worried that your operations might cause a pattern-match error, Catch will detect this and prove it for you: http://www-users.cs.york.ac.uk/~ndm/catch/ Thanks Neil