peano.hs

data Nat = Zero | Suc Nat deriving (Show)
data List a = Nil | Cons a (List a) deriving (Show)

addNat :: Nat -> Nat -> Nat
addNat Zero x = x
addNat (Suc x) y = Suc (addNat x y)

mulNat :: Nat -> Nat -> Nat
mulNat Zero _ = Zero
mulNat (Suc x) y = addNat y (mulNat x y)

product' :: List Nat -> Nat
product' Nil = Zero
product' (Cons x Nil) = x
product' (Cons x xs)  = mulNat x (product' xs)

zero = Zero 
one = Suc Zero
two = Suc (Suc Zero)
three = Suc (Suc (Suc Zero))

list = Cons three $ Cons two $ Cons three $ Nil


main = putStrLn "hello, world"