Basic statistic means in haskell.

gistfile1.txt

harmonicMean :: [Double] -> Double
harmonicMean list = (doubleLength list) / sumo where
	sumo = (sum twisted)
	twisted = (map inv list)

geometricMean :: [Double] -> Double
geometricMean list = (product list) ** (1/(doubleLength list))

arithmeticMean :: [Double] -> Double
arithmeticMean list = (sum list) / (doubleLength list)

quadraticMean :: [Double] -> Double
quadraticMean list = (sqrt quadr) where
	powered = (map pow2 list)
	quadr = (sum powered) / (doubleLength list)


doubleLength (x:xs) = 1.0 + (doubleLength xs)
doubleLength [] = 0.0


-- a na b
power a 1 = a
power a 0 = 1
power a b = a * (power a (b-1))

pow2 x = x*x
inv x = 1/x


mean :: String -> [Double] -> Double
mean variant 
	| variant == "harmonic" = harmonicMean
	| variant == "geometric" = geometricMean
	| variant == "arithmetic" = arithmeticMean
	| variant == "quadratic" = quadraticMean


-- code from the lectures
split :: String -> Char -> [String]
split [] _ = [""]
split (x:xs) c = let rest = split xs c in if x == c then "" : rest else (x : head rest) : tail rest

doubleparse :: String -> Double
doubleparse s = (read s :: Double)


stringToDOubles :: String -> [Double]
stringToDOubles s = (map doubleparse (split s ' '))

makeMean cisla typ = mean typ (stringToDOubles cisla)


main = do
	cisla <- getLine
	typ <- getLine	
	putStrLn (show (makeMean cisla typ))