[Haskell-cafe] How to improve its performance ?

[zaxis]

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!

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fac n = let {  f = foldr (*) 1 [1..n] } in f 
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