pascal.hs

reduce :: [Int] -> [Int]
reduce (x:rest@(y:z)) = (x + y) : (reduce rest)
reduce _ = []

pascal :: Int -> [Int]
pascal 1 = [1]
pascal 2 = [1,1]
pascal x = [1] ++ reduce (pascal (x - 1)) ++ [1]

center :: Int -> String -> String
center width string =
    let padding = floor (fromIntegral (width - (length string)) / 2)
    in (take padding $ repeat ' ') ++ string

main = do
    putStrLn ""
    putStrLn $ center 40 $ show $ pascal 1
    putStrLn $ center 40 $ show $ pascal 2
    putStrLn $ center 40 $ show $ pascal 3
    putStrLn $ center 40 $ show $ pascal 4
    putStrLn $ center 40 $ show $ pascal 5
    putStrLn $ center 40 $ show $ pascal 6
    putStrLn $ center 40 $ show $ pascal 7