data Area = Circle Float | Square Float Float
surface :: Area -> Float
surface (Circle r) = pi * r ^ 2
surface (Square l w) = l * w
add :: Int -> Int -> Int
add x y = x + y
fact :: Int -> Int
fact 2 = 2
fact n = n * fact (n-1)
sumL :: [Int] -> Int
sumL x | null x = 0
| not $ null x = head x + sumL (tail x)
sumY :: [Int] -> Int
sumY [] = 0
sumY (x:xs) = x + sumY xs
--for ::
main = do
print (surface $ Circle 10 )
print (surface $ Square 10 5 )
let x = add 1 2
print(x)
print(fact 5)
print(sumL [1,2,3])
print(sumY [1,2,3])
let y = 5
print (y:[1,2,3])
