On Sunday 15 May 2011 15:32:03, Herbert Valerio Riedel wrote:
On Thu, 2011-05-12 at 19:31 +0200, Daniel Fischer wrote:
Minor nitpick: instead of doing 'sort . nub', please use 'import qualified Data.Set as S' and do 'S.toAscList . S.fromList'. This should be a lot faster.
Or `map head . group . sort', which may be faster than building an intermediate Set (haven't benchmarked, may be faster, slower or mkae no difference).
if the input list has _many_ duplicates, wouldn't using 'map head . group . sort' require more memory than going the 'toAscList . fromList' way?
Good point. Yes, it would (consider `replicate maxBound 1'). So `map head . group . sort' might be faster for lists with few duplicates, but it has worse worst-case complexity, so it's safer to use `toAscList . fromList'. Even in the where it's slower, it probably wouldn't make too much of a difference.