Let's play Haskell! - #5

store.hs

-- array($year, $model, $price)
-- (Int, String, Int)

type Price = Int
data CarType = Ford | Chevrolet deriving (Show)
data Vehicle = Car Int CarType Price
     | Bicycle Price
     | Motor Price deriving (Show)
data Accessory = SteeringWheel Price | Brake Price deriving (Show)
type Store = [Vehicle]

class Priceable a where
      price :: a -> Price

instance Priceable Vehicle where
         price (Car _ _ p) = p
         price (Bicycle p) = p
         
instance Priceable Accessory where
         price (SteeringWheel p) = p
         price (Brake p)         = p


storePrice :: (Priceable a) => [a] -> Price
storePrice [] = 0
storePrice (p:ps) = price p + storePrice ps

storePrice2 ps = tailStorePrice ps 0

tailStorePrice :: (Priceable a) => [a] -> Price -> Price
tailStorePrice [] pr = pr
tailStorePrice (p:ps) pr = tailStorePrice ps (pr + price p)

storePrice3 ps = foldl (\sum p -> sum + price p) 0 ps


storePrice4 :: (Priceable a) => [a] -> Price
storePrice4 = sum . map price


sampleStore :: Store
sampleStore = [mustang65, corvette63, mustang66, csepel]

sampleAccessories :: [Accessory]
sampleAccessories = [SteeringWheel 12, Brake 23]

mustang65 :: Vehicle
mustang65 = Car 1965 Ford 1111

mustang66 :: Vehicle
mustang66 = Car 1966 Ford 1234

corvette63 :: Vehicle
corvette63 = Car 1963 Chevrolet 2222

csepel :: Vehicle
csepel = Bicycle 12