Hello, I was reading about the "Factory Method Pattern" on wikipedia, and noticed that the very first example was written in Haskell. Sweet! http://en.wikipedia.org/wiki/Factory_method_pattern#Haskell Unfortunately, it looks to me like it is missing the 'factory' part. I have attempted to implement something more factory like (see attached). I am wonder what other people think. Is the code on wikipedia really demoing a factory method? Is the code attached any better? Is there an even better what to write this in Haskell? Thanks! - j {-# LANGUAGE ExistentialQuantification #-} import Numeric (showFFloat) -- * A type which can hold different types of pizzas data Pizza = forall a. (PizzaMethods a) => Pizza a -- * A type class with functions common to different types of pizza class (Show a) => PizzaMethods a where price' :: a -> Double -- * Getter functions for the pizza type price :: Pizza -> Double price (Pizza p) = price' p pizzaType :: Pizza -> String pizzaType (Pizza p) = show p -- * Some types of pizza data HamAndMushroom = HamAndMushroom deriving (Read, Show) data Deluxe = Deluxe deriving (Read, Show) data Hawaiin = Hawaiin deriving (Read, Show) -- * Prices of various pizzas instance PizzaMethods HamAndMushroom where price' _ = 8.50 instance PizzaMethods Deluxe where price' _ = 10.50 instance PizzaMethods Hawaiin where price' _ = 11.50 -- * A pizza factory pizzaFactory :: String -> Pizza pizzaFactory pizzaType | pizzaType == "HamAndMushroom" = Pizza HamAndMushroom | pizzaType == "Deluxe" = Pizza Deluxe | pizzaType == "Hawaiin" = Pizza Hawaiin | otherwise = error "We don't serve your kind here." -- * An order at the pizza factory main = let pizza = pizzaFactory "HamAndMushroom" in putStrLn $ "You can get a " ++ pizzaType pizza ++ " for $" ++ showFFloat (Just 2) (price pizza) "."