-- data Bool = True | False  deriving Show

und True True = True
und True False = False
und False True = False
und False False = False

data Day = Sun | Mon | Tue | Wed | Thu | Fri | Sat  deriving Show


data PColor = Red | Blue | Yellow  deriving Show

mkColor Red    = Mix 255 0 0
mkColor Blue   = Mix 0 255 0
mkColor Yellow = Mix 0 0 255

data Color = Mix Int Int Int  deriving Show

blend (Mix a b c) (Mix x y z) = Mix (a+x `div` 2) (b+y `div` 2) (c+z `div` 2)

black = Mix 0 0 0
white = Mix 255 255 255

f :: Maybe Int -> Int
f Nothing = 0
f (Just x) = x+3

g (Left str) = length str
g (Right i) = i `div` 2




data Nat = Zero | Succ Nat  deriving Show


plus Zero m = m
plus (Succ n) m = Succ (plus n m)

cti Zero = 0
cti (Succ n) = 1 + cti n

cfi 0 = Zero
cfi n = Succ (cfi (n-1))



data List a = Nil | Cons a (List a)  deriving Show
-- data [a] = [] | (:) a [a]

len Nil = Zero
len (Cons x xs) = Succ (len xs)