--- Simon Marlow
Ross's point about requiring append to be strict in order to guarantee O(n) toList is a good one. In fact, the current implementation isn't quite correct: either fromList should be strict, or append should check for an empty Many constructor.
That's what exists in the current published version (on my "web page"): fromList guarantees that the Many constructor never has [] as argument. Anyways, 'toList' will still be O(m) where m = number of subtrees. Moreover, I hardly expect more that O(n) empty subtrees in a sequence. So, it is trading off efficiency here for efficiency there. I suspect most haskellers would intuitively expect 'append' to be lazy, so I let myself be convinced by Wolfgang argument. Please let me know if I am wrong. Cheers, JP. __________________________________ Do you Yahoo!? Win a $20,000 Career Makeover at Yahoo! HotJobs http://hotjobs.sweepstakes.yahoo.com/careermakeover