matoous

permutate :: (Eq a) => [a] -> [[a]]
permutate [] = [[]]
permutate l = [a:x | a <- l, x <- permutate $ filter (\x -> x /= a) l]

matoous

-- Haskell suffix calculator (Polish notation)
import Data.List

suffixCalc :: (Num a, Read a) => String -> a
-- other option is to write this:
-- suffixCalc x = head $ foldl calcFun [] $ words x
suffixCalc = head . foldl calcFun [] . words
  where
    calcFun (a:b:bs) "+" = (a + b):bs
    calcFun (a:b:bs) "-" = (b - a):bs