fastfood-hs/app/Main.hs

module Main where

import System.Random
import Data.Time

data Fastfood = Kapsalon
              | Pizza
              | Lasagne
              | Nachos
              | Friet
              | Durum
              deriving (Show, Eq, Ord, Enum, Read, Bounded)

instance Random Fastfood where
    randomR (a, b) g =
        case randomR (fromEnum a, fromEnum b) g of
            (x, g') -> (toEnum x, g')
    random = randomR (minBound, maxBound)

main :: IO ()
main = do
    day <- dayOfWeek . utctDay <$> getCurrentTime -- slight golf optimisation
    case day of
        Tuesday -> print Friet
        _ -> print =<< (randomIO :: IO Fastfood)