[Haskell-cafe] How to improve its performance ?

import Data.List combination :: [a] -> [[a]] combination [] = [[]] combination (x:xs) = (map (x:) (combination xs) )++ (combination xs) samp = [1..100] allTwoGroup = [(x, samp\\x) | x <- combination samp] The above code is used to calculate all the two groups from sample data ? It is very slow ! Sincerely! ----- fac n = let { f = foldr (*) 1 [1..n] } in f -- View this message in context: http://old.nabble.com/How-to-improve-its-performance---tp27940036p27940036.h... Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com.