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/ ---
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