26 Aug
2008
26 Aug
'08
9:52 p.m.
Gwern Branwen wrote:
FWIW, when I tested out a number of nub/uniq definitions, the map head version performed the worst, much worse than the O(n^2) one everyone is complaining about. It's a neat definition, but not performant.
When did you try this? IIRC correctly even the old sort was O(n^2), but someone had the sense to replace it a while ago. With ghci now on my machine.. length $ map head $ group $ sort [1..100000] finishes "instantly", but.. length $ nub [1..100000] takes about 90 seconds. Regards -- Adrian Hey