Peter Verswyvelen wrote: > However, I suspect the experts here will be able to make that much > shorter and more efficient (maybe using Data.Map?)
That makes it difficult to respond. I am definitely not claiming to be an expert. For one thing, my name is not Simon. But I'll say something anyway, fwiw. The problem there is that nub is O(n^2). You're stuck with that if your type is not an instance of Ord (but then you can't use sort, either). When you can assume Ord, the standard solution is, as you suggest, something like: import qualified Data.Map as M import Data.List histogram = M.toList . foldl' (\m x -> M.insertWith' (+) x 1 m) M.empty . M.fromList This should work efficiently, with the right amount of laziness, even for very large lists. Regards, Yitz _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
