18 Jul
2007
18 Jul
'07
8:54 a.m.
Arie Groeneveld wrote:
Ok, so when do I use nub instead of 'map head.group.sort'?
Never. If |nub_sort=map head.group.sort| is applicable, then you are dealing with a member of class Ord, so use the O(n*log n) |nub_sort|. If you want to preserve the relative order of the input list, use something like nub_cache :: Ord a => [a] -> [a] nub_cache = onub Set.empty where onub seen (x:xs) | Set.member x seen = onub seen xs | otherwise = x : onub (Set.insert x seen) xs onub _ _ = [] |nub_cache| also works for infinite lists, btw. /BR -- -- Mirko Rahn -- Tel +49-721 608 7504 -- --- http://liinwww.ira.uka.de/~rahn/ ---